Дисертації: "Laser surfaces treatment"

1

Katakam, Shravana K. "Laser Surface Treatment of Amorphous Metals." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500194/.

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Amorphous materials are used as soft magnetic materials and also as surface coatings to improve the surface properties. Furthermore, the nanocrystalline materials derived from their amorphous precursors show superior soft magnetic properties than amorphous counter parts for transformer core applications. In the present work, laser based processing of amorphous materials will be presented. Conventionally, the nanocrystalline materials are synthesized by furnace heat treatment of amorphous precursors. Fe-based amorphous/nanocrystalline materials due to their low cost and superior magnetic properties are the most widely used soft magnetic materials. However, achieving nanocrystalline microstructure in Fe-Si-B ternary system becomes very difficult owing its rapid growth rate at higher temperatures and sluggish diffusion at low temperature annealing. Hence, nanocrystallization in this system is achieved by using alloying additions (Cu and Nb) in the ternary Fe-Si-B system. Thus, increasing the cost and also resulting in reduction of saturation magnetization. laser processing technique is used to achieve extremely fine nanocrystalline microstructure in Fe-Si-B amorphous precursor. Microstructure-magnetic Property-laser processing co-relationship has been established for Fe-Si-B ternary system using analytical techniques. Laser processing improved the magnetic properties with significant increase in saturation magnetization and near zero coercivity values. Amorphous materials exhibit excellent corrosion resistance by virtue of their atomic structure. Fe-based amorphous materials are economical and due to their ease of processing are of potential interest to synthesize as coatings materials for wear and corrosion resistance applications. Fe-Cr-Mo-Y-C-B amorphous system was used to develop thick coatings on 4130 Steel substrate and the corrosion resistance of the amorphous coatings was improved. It is also shown that the mode of corrosion depends on the laser processing conditions. The microstructure evolution and the corrosion mechanisms operating are evaluated using post processing and post corrosion analysis.

2

Dolan, Jeffrey Alan. "Characterization of Laser Modified Surfaces for Wood Adhesion." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/64352.

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The controlled degradation of wood surfaces with infrared light from a CO2 pulsed laser facilitated adhesion without the use of additional resins. Laser modification creates a surface phenomenon that physically and chemically alters the natural biopolymer organization of lignocellulosic materials in a way that promotes adhesion when hot pressed using typical industrial equipment. Laser optimization was determined through mechanical and microscopic observation. It was determined that a mild level of laser surface modification (scale of 30 W/mm2) resulted in the highest bond-line strength. The large spot size of the laser beam resulted in evenly modified surfaces. Surface analysis revealed that laser modification changed native wood morphology, hydrolyzed and vaporized hemicellulose, and enriched the surface with cellulose II and lignin. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR) was used to analyze the bulk of the laser material. This experiment revealed a change in the hydroxyl region related to hydrogen bonding conformations between wood polymers, mainly cellulose. X-ray photoelectron spectroscopy (XPS) provided an elemental composition of the top 5 nanometers of the surface, which resulted in increased carbon-carbon/carbon-hydrogen linkages and decreased oxygen containing bonds due to laser ablation. Static acid-base contact angle analysis was conducted using three probe liquids to find the Lewis acid, Lewis base, and dispersion components of the top nanometer of surface chemistry. Contact angle analysis revealed laser modified samples had a surface free energy that remained similar to the control wood sample. In addition, the dispersion component of the surface free energy increased due to laser ablation while acid-base components were reduced. Atomic force microscopy (AFM) visually displays a reduction in surface roughness due to the laser technique. An additional set of experiments like thermal gravimetric analysis, thermal pre and post treatments, and heated ATR FTIR and XPS support findings which require more investigation into this adhesion phenomenon.
Master of Science

3

Belaud, Vanessa. "Structuration de surfaces au moyen d'un traitement laser femtoseconde : applications à la fonctionnalisation de surface du polypropylène en vue de sa métallisation." Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0003/document.

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Ce présent travail de thèse porte sur l’étude du potentiel d’un traitement de surface par laser femtoseconde comme étape de substitution aux traitements réalisés actuellement lors de la métallisation de polymère. Pour cela, l’étude des modifications chimiques et morphologiques induites par traitement laser femtoseconde ainsi que leurs influences respectives sur les propriétés d’adhérences et de mouillabilités de la surface polypropylène sont présentées. Une revue bibliographique met en évidence la faisabilité d’une modification contrôlée de la surface du polypropylène après traitement laser femtoseconde. De plus, ces modifications engendrent une évolution démontrée des propriétés de mouillage qui peuvent répondre à certaines demandes industrielles. Après traitement laser femtoseconde, la surface traitée répond de différentes manières à la sollicitation en fonction de ses propriétés intrinsèques. Les expériences d’impacts localisés et de surfaces nous ont conduits à observer trois stades de modifications topographiques pour les conditions étudiées : un phénomène d’incubation, d’accumulation et d’ablation. Ce dernier a fait l’objet d’une étude plus approfondie. De manière générale, on observe deux régimes d’ablation linéaires pour l’ensemble des densités de puissance étudiées lorsque l’on étudie la profondeur d’ablation en fonction du nombre d’impulsion et le volume d’ablation en fonction de la densité de puissance cumulée. Enfin, nous montrons que les liaisons présentes en surface après traitement sont dépendantes de deux facteurs ; la densité de puissance cumulée utilisée et l’environnement de travail. Sachant que les modifications topographiques obtenues sont de types multi-échelles, les résultats ont été analysés sur la base des modèles de Wenzel (1936) et de Cassie-Baxter (1944) relatifs à la théorie du mouillage de surfaces rugueuses. Les résultats expérimentaux et leurs corrélations avec les paramètres de rugosités 3D calculés à différentes échelles ont été traités par une analyse statistique. On observe alors un comportement mixte avec un contact intime de la goutte sur les sommets des aspérités (modèle de Wenzel) et un contact hétérogène (airpolypropylène) à une échelle mésoscopique (état « fakir » décrit par le modèle de Cassie-Baxter). Toutefois, la situation où la goute repose sur le sommet des structures (CB) n’est pas toujours stable. Nous avons étudié la transition de l’état CB à l’état W par des expériences d’évaporation. On observe que cette transition est fortement dépendante de la chimie de surface dont la contribution est prépondérante sur les propriétés d’adhérence métal/PP. En contrôlant cette propriété, il est alors possible de répondre à une problématique industrielle de galvanoplastie (adhérence augmenté par le traitement laser) ou d’électroformage (adhérence faible permettant une réplication de bonne qualité des motifs)
This work presents the potential of a femtosecond laser surface treatment as an alternative step of pretreatments during the metallization of polymer. To do this, the study of chemical and morphological modification induced by femtosecond laser treatment and their respective influences on the properties of adhesion and wettability of polypropylene surface are presented. A literature review highlights the feasibility of a controlled surface modification after femtosecond laser treatment of polypropylene (PP). In addition, it is known that these modifications changes the wetting properties and can be used to meet industrial applications development. After femtosecond laser treatment, the treated surface responds to the solicitation with different morphological comportment according to its intrinsic properties. Experiences of localized impacts and surfaces us to observe three stages of topographic changes to the conditions studied: an incubation phenomenon of accumulation and ablation. The ablation phenomenon is further study. Generally, two linear ablation regime is observed for all power densities examined when considering the depth of ablation as a function of the pulse number and the ablation volume according to the accumulated power density. Finally, we show that the bonds present on the surface after treatment are dependent on two factors: the accumulated power density used and the working environment. Knowing that topographic obtained is multi-scales, the results were analyzed on the basis of models Wenzel (W)(1936) and Cassie–Baxter (CB) (1944) which explain the theory of wetting of rough surfaces. The experimental results and their correlations with 3D roughness parameters calculated at different scales were treated by statistical analysis. We observe a mixed model behavior with intimate contact of the drop on the tops of the asperities (Wenzel model) and a heterogeneous contact (air - PP) in a mesoscopic scale (state " fakir " described by the Cassie -Baxter model). However, this situation where the drop sits on the top of asperities (CB) is not always the most stable. We have studied the transition between the CB state and the W state by evaporation experiments. It is observed that this transition is strongly dependent on the surface chemistry whose contribution is much greater than the adhesion properties metal / PP. If controlling this property, it is possible to obtain two industrial applications: electroplating (increased adhesion by laser treatment) or electroforming (low adherence to replicate the topography)

4

Rezai, Bidakhavidi Caminde. "Nouvelles solutions de préparation et d'activation des surfaces : assemblages époxy-fonte." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCA021/document.

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Les revêtements organiques déposés en surface de tuyaux en fonte ductile ont pour vocation d’assurer une protection (notamment la résistance chimique, la tenue à la corrosion) vis-à-vis des effluents agressifs transportés. Pour assurer l’adhérence entre le revêtement (époxy) et son substrat, une préparation de surface est souvent nécessaire. Parmi les procédés conventionnels, le grenaillage est la solution la plus utilisée. Simple à mettre en œuvre et d’efficacité prouvée, il permet d’assurer le décapage de la surface tout en générant une rugosité adaptée. Si la solution est approuvée, des questions subsistent néanmoins quant à l’influence respective de la topographie et de la physico-chimie des surfaces. De plus, encouragées par les nouvelles réglementations environnementales, de nouvelles techniques de préparation de surface se développent.Le travail présenté s’est alors attaché à évaluer l’effet de nouvelles techniques de préparation comme le laser de structuration et le jet d’eau à ultra haute pression à comparer à d’autres procédés conventionnels tels que le brossage et le sablage. Ces nouvelles alternatives vont permettre alors de mieux comprendre l’influence du décapage et de la rugosité de surface avant la mise en peinture.Enfin, les différents résultats obtenus ont été alors spécifiquement analysés pour permettre la compréhension des phénomènes ou mécanismes d’adhésion se produisant à l’interface du couple époxy/substrat, d’un point de vue mécanique et physico-chimique. Divers moyens d’analyses ont alors pu être mis en œuvre pour caractériser les surfaces d’un point de vue morphologique (ratio de surface) et chimique (spectroscopies Raman et photoélectronique à rayons X (XPS)) pour évaluer la tenue interfaciale (test de traction adhérence)
Organic coatings applied on the surface of cast iron pipes ensure very good chemical and anti-corrosion protection against aggressive effluents. To improve adherence between coating (epoxy) and substrate, a surface preparation is required. Among conventional processes shot blasting has emerged as the most efficient and cheapest solution for ensuring stripping while generating adapted roughness. However, as it may enhance both mechanical anchorage and chemical bonding a better understanding of these phenomena should be developed. Besides new eco-friendly alternatives were investigated.Indeed, new techniques were evaluated, i.e. laser structuring and an ultra-high pressure water jet whose major benefits are understanding the effect of ablation and surface roughness prior to applying a coating. Moreover, two other conventional processes (sand blasting and brushing) were introduced to obtain a various roughness.Results obtained were then analyzed to further understand bonding mechanisms at the interface.Several processes were then implemented to evaluate the surface morphology as well as the surface chemistry (spectroscopy Raman and XPS) correlated to the adhesion mechanisms

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Pacquentin, Wilfried. "Contribution à l'étude des propriétés physico-chimiques des surfaces modifiées par traitement laser : application à l'amélioration de la résistance à la corrosion localisée des aciers inoxydables." Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00676332.

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Les matériaux métalliques sont utilisés dans des conditions de plus en plus sévères et doivent présenter une parfaite intégrité sur des périodes de plus en plus longues. L'objectif de ce travail de thèse est d'évaluer le potentiel d'un traitement de refusion laser pour améliorer la résistance à la corrosion d'un acier inoxydable de type 304L ; l'utilisation du laser dans le domaine des traitements de surface constituant un procédé en pleine évolution à cause des changements récents dans la technologie des lasers. Dans le cadre de ce travail, le choix du laser s'est porté sur un laser nano-impulsionnel à fibre dopée ytterbium dont les caractéristiques permettent la fusion quasi-instantanée sur quelques microns de la surface traitée, immédiatement suivie d'une solidification ultra-rapide avec des vitesses de refroidissement pouvant atteindre 1011 K/s. La combinaison de ces processus favorise l'élimination des défauts surfaciques, la formation de phases hors équilibre, la ségrégation d'éléments chimiques et la formation d'une nouvelle couche d'oxyde dont les propriétés sont gouvernées par les paramètres laser. Afin de les corréler avec la réactivité électrochimique de la surface, l'influence de deux paramètres laser sur les propriétés physico-chimiques de la surface a été étudiée : la puissance du laser et le taux de recouvrement des impacts laser. Pour clarifier ces relations, la résistance à la corrosion par piqûration des surfaces traitées a été déterminée par des tests électrochimiques. Pour des paramètres laser spécifiques, le potentiel de piqûration d'un acier inoxydable de type 304L augmente de plus de 500 mV traduisant ainsi une meilleure tenue à la corrosion localisée en milieu chloruré. L'interdépendance des différents phénomènes résultant du traitement laser a rendu complexe la hiérarchisation de leur effet sur la sensibilité de l'alliage testé. Cependant, il a été montré que la nature de l'oxyde thermique formé au cours de la refusion laser et ses défauts sont du premier ordre pour l'amorçage des piqûres.

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Abang, mahmod Dayang Salyani Binti. "Sintering of Zirconium Diboride-Silicon Carbide (ZrB2-SIC) and Titanium Dibor'ide-Silicon Carbide (TiB2-SIC) Ceramic Composites and Laser Surface Treatment : Application in Low Temperature Protonic Ceramic Fuel Cells (LTPCFCs)." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0074/document.

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Le frittage et le traitement par laser sont des techniques remarquables, couramment utilisées dans de nombreux domaines d’applications du fait des qualités qu’ils confèrent aux surfaces traitées. Ces technologies permettent de substantielles économies d’énergie comparée aux traitements de surfaces conventionnels. Le chauffage est par ailleurs, strictement localisé à la zone choisie. Notre recherche a pour objectif de développer une fine couche de verre de silice à la surface de céramiques poreusescomposites : le diborure de zirconium-carbure de silicium (ZrB2-SiC) et le diborure de titane-carbure de silicium (TiB2-SiC) frittées avec une porosité contrôlée d’environ 30%. La principale application de ces matériaux concerne les piles à combustibles protoniques fonctionnant à basse température (de type LTPCFCs). Les poudres ZrB2-SiC et TiB2-SiC sont soigneusement mélangées et pressées à froid dans un moule à la pression de 40 MPa. Le frittage naturel est conduit dans un four à 1900 et 2100 °C durant 2,5 heures, sous atmosphère contrôlée d’argon. Après polissage, le traitement de surface est effectué par laser verre-ytterbium. Les paramètres du traitement ont été optimisés (puissance et trajet du faisceau laser, temps de traitement, atmosphère) et ont permit d’obtenir une couche superficielle d’un verre à forte conduction protonique, sans affecter la structure et la composition des couches situées au-dessous de la surface. Les échantillons ont été caractérisés en utilisant les méthodes classiques : EDS, XRD, MEB, microscopie optique. Les meilleurs résultats ont été obtenus avec des échantillons de composition 61 mol. % ZrB2-SiC et 61 mol. % TiB2-SiC traités thermiquement a 1900 °C. La porosité obtenue, de l’ordre de 30%, assure une bonne circulation des gaz. La couche de verre produite sur le composite ZrB2-SiC, d’une épaisseur moyenne de 8 μm, est continue et exempte demacro fissuration. Une microfissuration est cependant détectée par MEB aux plus forts grossissements. Les essais ont été conduits à plus haute température de frittage (2100 °C) et avec des compositions différentes dans le but d’améliorer les propriétés du substrat. ZrB2-SiC. A la composition de 80 mol. % ZrB2-SiC les analyses révèlent la présence de cristaux de forme cuboïdale, attribuée à la formation de carbure de bore B4C dont la formation est admise par l’analyse thermodynamique. Les essais sur le composite ZrB2-SiC conduisent à l’apparition de bulles et de défauts dans la couche de verre. Une optimisation des conditions de traitement sera nécessaire pour contrôler ce phénomène. Cette étude démontre qu’il est possible de développer des couches poreuses de matériaux céramiques de type ZrB2-SiC, et de former à leur surface une couche de verre dense et exempte de fissuration par traitement laser. Les propriétés générales de cette couche permettent d’envisager une utilisation comme électrolyte solide dans les piles à combustibles de type LTPCFCs
Sintering and laser are a remarkable technology with a broad range of applications especially material processing. It offers a wide variety of desired surface properties depending on the type of usage. Sintering allows high reliability and repeatability to the large mass production. Laser benefits in the aspect of energy saving compared to conventional surface heat treatment due to the heating is restricted and localized only to the required area. Therefore, this research aims to develop a silica-glass-layer onto a porous non-oxide, Zirconium Diboride-Silicon Carbide (ZrB2-SiC) and Titanium Diboride-Silicon Carbide (TiB2-SiC) ceramic composites by sintering and laser surface treatment for potential application in the Low-Temperature Protonic Fuel Cells (LTPCFCs). ZrB2-SiC and TiB2-SiC mixed powders at different composition were cold-pressed around 40 MPa under ambient environment. Next, the composites were pressureless sintered at 1900 °C and 2100 °C for 2.5 h dwell time under argon atmosphere, respectively. The pressureless sintering was conducted by Nabertherm furnace and followed by surface treatment via an ytterbium fibre laser (Yb). Anew round spiral laser pattern was inspired, designed and scanned onto the surface of pellets to obtain a smooth glass surface layer that acted as proton-conducting (electrolyte) while preserving the beneath structures of laser-treated pellets that served as an electrode. Characterization techniques such as Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-Ray Spectroscopy (EDS) and X-ray Diffraction (XRD) were performed accordingly onto the samples. Pressureless sintering of 61 mol.% ZrB2-SiC and 61 mol.% TiB2-SiC pellets at 1900 °C exhibited ca. 29% porosity. The resulting porosity was in the best range of effectiveness for gas diffusion. SEM micrographs revealed the formation of semiglassy layer on the surface of sintered 61 mol.% ZrB2-SiC pellets. The bulk structures remained unaffected and unoxidized. SEM micrographs and EDS patterns displayed thatsilica (SiO2) at a thickness of 8 μm, presence on the surface of ZrB2-SiC structures. It demonstrated that the surface treatment by Yb-fibre laser on sintered ZrB2-SiC ceramic composites at 1900 °C had accomplished. The laser surface treatment was ineffective for TiB2-SiC pellets due to several bubbles formation and crack deflection. Nevertheless, at higher magnification of the SEM for laser-treated ZrB2-SiC ceramic composites, cracks were observed. Therefore, the pressureless sintering at high temperature was conducted to improve the ZrB2-SiC structural properties. Sintering at 2100 °C had demonstrated increment of density and at 80 mol.% ZrB2-SiC sintered pellet unpredictably exhibited the presence of boron carbide (B4C) compounds. SEM micrographs revealed the dark cuboidal shapes and XRD patterns identified as B4C peaks. The reactions of B4C formation were proposed andsupported by thermodynamic analysis. In conclusion, the present research had developed a glassy layer on the surface of ZrB2-SiC ceramic composites which has potential in the application of LTPCFCs. It proved that B4C was possible to be developed by pressureless sintering at 2100 °C and it might assist in developing better morphology for ZrB2-SiC ceramic composites

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Perrin, Thibaut. "Elaboration et caractérisation de revêtements base Ni, obtenus par projection, pour outils de coupe agricoles." Thesis, Troyes, 2021. http://www.theses.fr/2021TROY0016.

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Sous l’impulsion du développement technologique et démographique, les exploitations agricoles ont évolué et les équipements agricoles se sont perfectionnés. Les machines sont fortement sollicitées, ainsi la durabilité des outils de coupe étant des pièces d’usure est devenue un enjeu stratégique. L’application d’un revêtement Cermet (céramique-metal) est alors largement utilisée industriellement, notamment par projection flamme-poudre. Dans une optique d’amélioration de la performance des outils, cette étude vise à augmenter la résistance de ce revêtement. La technologie de rechargement laser, qui permet d’appliquer des revêtements à forte teneur en carbure dans une matrice nickel, présente un fort potentiel. Un comparatif est réalisé entre les deux technologiques de dépôt, puis, une étude paramétrique est menée sur la poudre appliquée par rechargement laser. Les effets de la composition de la matrice, de la densité apparente de la poudre de carbure de tungstène, de sa proportion massique et de sa granulométrie sur les propriétés physico – chimiques, mécaniques, tribologiques et fonctionnelles des revêtements sont étudiés. Le laser prévient la décarburation, affine la microstructure et favorise la précipitation de phases intermétalliques par rapport à la flamme sans amélioration claire de la résistance du dépôt. L’étude paramétrique a montré que l’utilisation d’une poudre de carbure dense et dure, une teneur massique en carbure de 50 % et une granulométrie fine améliore la résistance du revêtement lors des essais de frottement et de coupe
Driven by technological and demographic development, farms have evolved and agricultural equipment has improved. The machines are heavily used and maintenance operations are limited. As cutting tools are wearing parts, their durability has become a strategic issue. The application of Cermet composite coating is then widely used industrially, in particular by flame-powder spraying. To improve the performance of the tools, this study aims to increase the resistance of this coating to the degradation mechanisms. The laser cladding technology which can applying coatings with high carbide content has great potential. A comparison is made between the two deposition technologies, then a parametric study is carried out on the powder applied by laser cladding. The effect of the composition of the NiCrBSi matrix, the bulk density of the tungsten carbide powder, its mass ratio and its particle size are studied on the physicochemical, mechanical, tribological and functional properties of the coatings. Laser technology prevents carbide decarburization, refines the matrix structure and promotes intermetallic phase precipitation over flame - powder spraying without a clear improvement in deposit strength. The parametric study showed that the use of a dense and hard carbide powder, a carbide mass content of 50% and a fine particle size improves the resistance of the coating during friction and cutting tests

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Sexton, Cornelius Leo. "Rapid Alloy Scanning by laser cladding." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320605.

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Primartomo, A. "Laser surface treatment using customised heat source profiles." Thesis, Loughborough University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429008.

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Ng, Chi-Ho. "Laser surface modification of NiTi for medical applications." Thesis, University of Chester, 2017. http://hdl.handle.net/10034/620830.

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Regarding the higher demand of the total joint replacement (TJR) and revision surgeries in recent years, an implant material should provide much longer lifetime without failure. Nickel titanium (NiTi) is the most popular shape memory alloy in the industry, especially in medical devices due to its unique mechanical properties such as pseudo-elasticity, damping capacity, shape memory and good biocompatibility. However, concerns of nickel ion release of this alloy still exist if it is implanted for a prolonged period of time. Nickel is well known for the possibility of causing allergic response and degeneration of muscle tissue as well as being carcinogenic for the human body beyond a certain threshold. Therefore, drastically improving the surface properties (e.g. wear resistance) of NiTi is a vital step for its adoption as orthopaedic implants. To overcome the above-mentioned risks, different surface treatment techniques have been proposed and investigated, such as Physical Vapour Deposition (PVD), Chemical Vapour Deposition (CVD), ion implantation, plasma spraying, etc. Yet all of these techniques have similar limitations such as high treatment temperature, poor metallurgical bonding between coated film and substrate, and lower flexibility and efficiency. As a result, laser gas nitriding would be an ideal treatment method as it could overcome these drawbacks. Moreover, the shape memory effect and pseudo-elasticity of NiTi from a reversible phase transformation between the martensitic phase and the austenitic phase are very sensitive to heat. Hence, NiTi implant is subjected to the following provisions of the thermo-mechanical treatment process, and this implant provides desired characteristics. It is important to suggest a surface treatment, which would not disturb the original build-in properties. As a result, the low-temperature methods for substrate have to be employed on the surface of NiTi. This present study aims to investigate the feasibility of applying diffusion laser gas nitriding technique to improve the wettability and wear resistance of NiTi as well as establish the optimization technique. The current report summaries the result of laser nitrided NiTi by continuous-wave (CW) fibre laser in nitrogen environment. The microstructure, surface morphology, wettability, wear resistance of the coating layer has been analysed using scanning electron microscopy (SEM), X-ray diffractometry (XRD), sessile drop technique, 3-D profile measurement and reciprocating wear test. The resulting surface layer is free of cracks, and the wetting behaviour is better than the bare NiTi. The wear resistance of the optimised nitride sample with different hatch patterns is also evaluated using reciprocating wear testing against ultra-high-molecular-weight polyethylene (UHMWPE) in Hanks’ solution. The results indicate that the wear rates of the nitride samples and the UHMWPE counter-part were both significantly reduced. It is concluded that the diffusion laser gas nitriding is a potential low-temperature treatment technique to improve the surface properties of NiTi. This technique can be applied to a femoral head or a bone fixation plates with relatively large surface area and movable components.

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Yang, Wen Fu. "Laser cladding surface treatment for enhancement of mechanical properties." Thesis, Peninsula Technikon, 2003. http://hdl.handle.net/20.500.11838/1267.

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Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 2003
Systematic laser cladding experiments were performed using a mixture of a Nickel base alloy powder mixed with tungsten carbide powder (percentage contents of tungsten carbide from 10% to 40%) on EN8 steel substrate with pre-placed powder method. Laser cladding of the Nickel base alloy powder + 50% tungsten carbide powder on EN9 steel substrate was performed with powder injection method as well. A Finite Element Method for calculating the surface temperature distribution was used to help prediction of temperature distribution laser cladding results. Composition of cladding materials was designed; a sticking agent was chosen for the pre-placed powder method. Clad coatings were obtained for different process parameters for laser cladding, and a detailed study of the affects of these parameters has been carried out. The characteristic microstructure and properties of the clad layers and interface were investigated by using an optical microscope, a micro hardness tester and a makeshift wear test. A comprehensive review is presented on the dilution of the coating and the typical problems experienced with the coating substrate interface. The results show that microstructure of clad layers comprise three zones: the cladding layer, bonding zone and heat-affected zone. The results showed that tungsten carbide particles increased the hardness and wear resistance as expected. Wear resistance of laser cladding coating is 3.5 times than that of substrate. The micro hardness range of the cladding layer is from RV 981.5 to RV 1187, which is 2-3 times than that of substrate. The micro hardness varies from cladding coating to transition layer then to heat affected zone and substrate along a gradient.

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Shukla, Pratik P. "Viability and characterization of the laser surface treatment of engineering ceramics." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8426.

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Laser surface treatment of engineering ceramics offers various advantages in comparison with conventional processing techniques and much research has been conducted to develop applications. Even so, there still remains a considerable gap in knowledge that needs to be filled to establish the process. By employing a fibre laser for the first time to process silicon nitride (Si3N4) and zirconia (ZrO2) engineering ceramics, a comparison with the CO2 and a Nd:YAG lasers was conducted to provide fundamental understanding of various aspects of the laser beam-material interaction. Changes in the morphology, microstructure, surface finish, fracture toughness parameter (K1c) were investigated, followed by thermal finite element modelling (FEM) of the laser surface treatment and the phase transformation of the two ceramics, as well as the effects of the fibre laser beam parameter - brightness (radiance). Fibre and CO2 laser surface treatment of both Si3N4 and ZrO2 engineering ceramics was performed by using various processing gases. Changes in the surface roughness, material removal, surface morphology and microstructure were observed. But the effect was particularly more remarkable when applying the reactive gases with both lasers and less significant when using the inert gases. Microcracking was also observed when the reactive gases were applied. This was due to an exothermic reaction produced during the laser-ceramic interaction which would have resulted to an increased surface temperature leading to thermal shocks. Moreover, the composition of the ceramics was modified with both laser irradiated surfaces as the ZrO2 transformed to zirconia carbides (ZrC) and Si3N4 to silicon dioxide (SiO2) respectively. The most appropriate equation identified for the determination of the fracture toughness parameter K1c of the as-received, CO2 and the fibre laser surface treated Si3N4 and ZrO2 was K1c=0.016 (E/Hv) 1/2 (P/c3/2). Surfaces of both ceramics treated with CO2 and the fibre laser irradiation produced an increased K1c under the measured conditions, but with different effects. The CO2 laser surface treatment produced a thicker and softer layer whereas the fibre laser surface treatment increased the hardness by only 4%. This is inconsiderable but a reduction in the crack lengths increased the K1c value under the applied conditions. This was through a possible transformation hardening which occurred within both engineering ceramics. Experimental findings validated the generated thermal FEM of the CO2 and the fibre laser surface treatment and showed good agreement. However, a temperature difference was found between the CO2 and fibre laser surface treatment due to the difference in absorption of the near infra-red (NIR) wavelength of the fibre laser being higher than the mid infra-red (MIR) wavelength of the CO2 laser. This in turn, generated a larger interaction zone on the surface that was not induced further into the bulk, as was the case with the fibre laser irradiation. The MIR wavelength is therefore suitable for Viability and Characterization of the Laser Surface Treatment of Engineering Ceramics 3 the surface processing of mainly oxide ceramics and surface treatments which do not require deep penetration. Phase transformation of the two ceramics occurred at various stages during the fibre laser surface treatment. The ZrO2 was transformed from the monoclinic (M) state to a mixture of tetragonal + cubic (T+C) during fibre laser irradiation and from T+C to T and then a partially liquid (L) phase followed by a possible reverse transformation to the M state during solidification. The Si3N4 transformed to a mixture of α-phase and β-phase (α→ α+β) followed by α+β and fully transforms from α+β → β-phase. What is more, is a comparison of the fibre laser-beam brightness parameter with that of the Nd:YAG laser. In particular, physical and microstructural changes due to the difference in the laser-beam brightness were observed. This research has identified the broader effects of various laser processing conditions, as well as characterization techniques, assessment and identification of a method to determine the K1c and the thermal FEM of laser surface treated engineering ceramics. Also, the contributions of laser-beam brightness as a parameter of laser processing and the influence thereof on the engineering ceramics have been identified from a fundamental viewpoint. The findings of this research can now be adopted to develop ceramic fuel cell joining techniques and applications where laser beam surface modification and characterization of engineering ceramics are necessary.

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Chan, Weng Kin. "Effect of heat treatment and laser surface treatment on the corrosion behavior of stainless steels." Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2493669.

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Wellburn, Daniel. "Circular laser beam intensity profile shaping for uniform surface treatments." Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533912.

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15

Suggs, Allison Elizabeth. "Kr-F laser surface treatment of poly(methyl methacrylate), glycol-modified poly(ethylene terephthalate), and polytetrafluoroethylene for enhanced adhesion of Escherichia Coli K-12." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/35182.

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Environmental response as determined by the cell-polymer interaction stands as the greatest restriction to the implementation of new polymeric materials. Cell-polymer interactions are most influenced by substrate surface free energy, surface chemistry, topography, and rigidity[1]. Alteration of these properties through surface treatment has become a common approach to attain the desired cellular interaction. This study investigates Kr-F excimer laser(248 nm) surface modification of poly(methyl methacrylate), glycol-modified poly(ethylene terephthalate), and polytetrafluoroethylene and its effect on the adhesion of Escherichia Coli K-12 bacteria. These three polymers were chosen for their very different mechanisms of ablation as well as their range of surface free energies and bacterial responses[2-4]. Polymers were ablated using a pulsed Kr-F excimer laser with a dose of 3.3x 10-9 W/cm2 per pulse. This high level of UV radiation was sufficient to cause significant surface damage on both PMMA and PTFE. PETG showed some signs of wavering in the surface and material removal was confirmed through optical microscopy. Due to the extensive damage associated with ablation, a much lower-powered, continuous beam Kr-F laser was used for contact angle samples. It delivered a dose of 1.27 W/cm2. Contact angle measurements were then taken which showed dose-dependent surface free energy in all three polymers. Following ablation, bacterial adhesion to PETG was improved two-fold, while it decreased in both PTFE and PMMA. Surface chemistry analysis supported the idea that the ablation occurred through chain scission, since there were no new surface groups created. There were significan texture modifications observed in PTFE and PMMA whicle PETG demonstrated the rolling structure characteristic of polyesters following laser ablation described in Wefers et al [4] and Hopp et al [5]. Contact angle measurements showed a correlation between radiation dose and surface free energy of all three polymers.
Master of Science

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Waugh, David G. "Laser surface treatment of nylon 6,6 for the modification of wettability characteristics and subsequent enhancement of osteoblast cell response." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6591.

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The control of cell adhesion to synthetic polymers is a key factor in tissue engineering, resting on the ability to direct specific cell types to adhere and proliferate in order to stimulate tissue reconstruction. But often the surface properties are compromised for the sake of the bulk properties, leading to surfaces that do not support sufficiently the level of bioactivity required and accordingly the polymeric biomaterial will fail clinically. Laser treatment offers a unique means of enhancing the osteoblast cell response of the surface of a polymeric biomaterial, whilst keeping the already sufficient bulk properties intact. To this end, infra-red (IR) and ultraviolet (UV) lasers have been employed to modify the wettability characteristics of nylon 6,6, as wetting is often the primary factor dictating the adhesion and bonding potential of materials, as a route to enhancing the surface in terms of osteoblast cell response. What is more, modifying wettability characteristics in this way is a highly attractive means of estimating the biofunctionality of a polymer. IR (CO2) and UV (F2 and KrF excimer) lasers were employed to carry out two different processes: laser whole area irradiative processing and laser-induced patterning. With both CO2 and the excimer lasers changes in the wettability characteristics could be effected with subsequent enhancement of osteoblast cell response. This was also the case with both laser-induced patterning and laser whole area irradiative processing. Essentially, an approach has been established whereby the osteoblast cell response on the surfaces of laser treated nylon 6,6 can be predicted through the laser-induced wettability characteristics modification, particularly for the laser whole area irradiative processed nylon 6,6. This ultimately allows one to determine the osteoblast cell response of the laser surface treated nylon 6,6 surfaces directly from the laser operating parameters. In concurrence with established wetting theory the laser whole area irradiative processing of the nylon 6,6 surfaces caused increased surface roughness, increased surface oxygen content, increased polar component, γP , and increased total surface energy, γT ; thereby generating surfaces displaying reduced contact angle, θ, making the nylon 6,6 surfaces more hydrophilic. The laser-induced patterned samples differed from current theory insofar as the nylon 6,6 surfaces became less hydrophilic due to an increase in θ despite an increase in surface roughness, an increase in surface oxygen content, an increase in γP and an increase in γT . This phenomena can be explained by the transition in wetting regimes from a Wenzel regime to a mixed-state wetting regime. Nevertheless, collation of the wettability characteristics results revealed that θ was a strong correlative decreasing function of both γP and γT , indicating that surface energy played a large role in determining the wetting nature of the nylon 6,6. It was found that for all laser whole area irradiative processed nylon 6,6 surfaces the osteoblast cell response was an increasing correlative and therefore predictive function of θ and was a decreasing function of γP . To an extent, the surface oxygen content and surface roughness could be used indirectly to foretell the osteoblast cell response of the nylon 6,6 surfaces. This is on account of the CO2 and KrF excimer laser whole area irradiative processing bringing about increased surface toxicity, which above a certain level hindered the osteoblast cell response. For the laser-induced patterned nylon 6,6 samples there did not appear to be any particular correlative trend between the modified surface parameters and osteoblast cell response. This can be accounted for by the transition in wetting regimes. Another important factor is that cell morphologies were modulated over all samples which suggests that varying surface parameters on account of laser surface treatment gave rise to variations in cell signaling. It was determined that θ, γP and γT all had very strong correlative relationships with the cytotoxicity. The cytotoxicity reduced upon an increase in θ until a minimum constant was achieved, whereas the cytotoxicity remained constant at low γP and γT until a point at which the cytotoxicity began to increase. These results are noteworthy as they allow one to deduce that, with constant cytotoxicity levels, the osteoblast cell response appeared to be modulated by the wettability characteristics. But once the cytotoxicity increased, the toxicity began to dominate and so negated the identified positive wettability characteristic correlations with osteoblast cell response. Practically, the surface roughness and surface oxygen content could be implemented indirectly to estimate the cytotoxicity. Increase in cytotoxicity was the result of the laser processing with higher fluences generating excessive melting. As a result of this, it is possible to deduce that there was a maximum threshold fluence, beyond which the toxicity of the nylon 6,6 began to dominate, giving rise to a less enhanced osteoblast cell response. On account of the correlative trends which have been identified between the laser surface treatment, wettability characteristics and osteoblast cell response of nylon 6,6 it is likely for one to have the ability to estimate the osteoblast cell response in vitro. This is significant as it indicates that laser surface modification of polymeric materials could have tremendous potential for application within the field of regenerative medicine.

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Jeng, Jeng-Ywan. "Computer controlled laser surface treatments of stainless steels for improved corrosion resistance." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250360.

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Källgren, Rasmus. "Influence of level of cellulose oxidation and surface treatment on the adhesion between cellulose beads." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276412.

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With the growing impact of climate change on both political decisions and how companies develop their products, it is increasingly important to find environmentally friendly alternatives to fossil-based materials. One of the more interesting materials in this respect is cellulose, which is the world's most naturally occurring polymer and can be used in a variety of applications. One way to modify the fibers and to change their properties is to use a method called Layer-by-Layer (LbL) treatment where two polymers of opposite charge are alternately adsorbed to the fiber surface. Another possibility is to oxidize the cellulose in the fibers to obtain a higher charge. This means that the fibers can adsorb a higher amount of cationic additives and that the fibers swell more which means that they are plasticized and can create stronger joints between the fiber surfaces in the dry state, which results in stronger dry fiber networks. However, wood-based fibers are small and inhomogeneous, both chemically and morphologically, which means that it is necessary to use model systems to be able to clarify, in detail, how treated and untreated surfaces interact with each other at a molecular level. One model system that can be used to investigate how cellulose fibers are affected by coating using the LbL method is to use spherical beads made from regenerated cellulose. In the present work, these beads were treated with polyallylamine hydrochloride (PAH) and hylauronic acid (HA) as well as with PAH and alginate (Alg) before being allowed to dry together and then subjected to tensile testing to clarify the adhesion between the surfaces. The beads were treated with five and ten bi-layers of these polymers, respectively, and then dried together on an AKD-coated surface, to avoid adhesion to the underlying surface, to examine the adhesion between the beads. The adhesion increased when treated with LbL and became higher upon adsorption of multiple layers of polyelectrolytes and the Alg / PAH system showed the greatest increase. Ten-layer samples of Alg / PAH were also tested after a solution of calcium chloride was added during drying, resulting in poorer adhesion between the beads.
Med klimatfrågans växande inverkan på både politiska beslut och hur företagen utvecklar sina produkter så läggs det allt större vikt vid att hitta miljövänliga alternativ till fossilbaserade material. Ett av de mer intressanta materialen är cellulosa vilket är världens mest naturligt förekommande polymer och som kan användas i en rad olika tillämpningar. Ett sätt att modifiera fibrerna och att ändra deras egenskaper är att använda sig av en metod som kalls Layer-by-layer (LbL) behandling där två polymerer mot motsatt laddning växelvis adsorberas till fiberytan. En annan möjlighet är att oxidera cellulosan i fibrerna så att de erhåller de en högre laddning. Detta innebär dels att fibrerna kan adsorbera en högre mängd katjoniska tillsatskemikalier samt att fibrerna sväller mera vilket innebär att de plasticeras och kan skapa starkare fogar mellan fiberytorna i torrt tillstånd vilket resulterar i starkare torra fibernätverk. Vedbaserade fibrer är dock små och inhomogena såväl kemiskt som morfologiskt vilket innebär att det är nödvändigt att använda modellsystem för att kunna klarlägga, i detalj, hur behandlade och icke behandlade ytor växelverkar med varandra på en molekylär nivå. Ett modellsystem som kan användas för att undersöka hur cellulosafibrer påverkas av att beläggas med hjälp av LbL metoden är att använda sig av sfäriska kulor tillverkade från regenererad cellulosa. I föreliggande arbete behandlades dessa kulor med polyallylaminhydroklorid (PAH) och hylauronsyra (HA) samt med PAH och alginat (Alg) innan de tilläts torka ihop och därefter utsattes för dragprovning för att klarlägga adhesionen mellan ytorna. Kulorna behandlades med fem respektive tio bilager av dessa polymerer och torkades sedan ihop på en AKD-belagd yta, för att undvika adhesion till den underliggande ytan, för att undersöka adhesionen mellan kulorna. Adhesionen ökade när de behandlades med LbL och blev högre vid adsorption av flera lager polyelektrolyter och systemet med Alg/PAH resulterade i den största ökningen. Prover med tio lager av Alg/PAH testades även efter att en lösning av kalciumklorid tillsattes under torkningen vilket resulterade i en sämre adhesion mellan kulorna.

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Elkandari, Bader M. H. M. "Excimer laser surface melting treatment on 7075-T6 aluminium alloy for improved corrosion resistance." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/excimer-laser-surface-melting-treatment-on-7075t6-aluminium-alloy-for-improved-corrosion-resistance(c2da3b82-eeb5-4eae-a1dc-e4aefba18c62).html.

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High strength 7xxx aluminium alloys are used extensively in the aerospace industry because the alloys offer excellent mechanical properties. Unfortunately, the alloys can suffer localised corrosion due to the presence of large intermetallic particles at the alloy surface that are aligned in the rolling direction. Laser surface melting (LSM) techniques offer the potential to reduce and/or to eliminate the intermetallic phases from the surface of the alloy without affecting the alloy matrix.The present study concerns the application of LSM using an excimer laser to enhance the corrosion resistance of AA 7075-T6 aluminium alloy. The initial stage of the project was aimed at optimising the laser conditions for production of a uniform microstructure, with the increase in the corrosion resistance of the alloy being determined by potentiodynamic polarization measurements in sodium chloride solution. Low and high laser energy densities were used with a different number of pulses per unit area to treat the alloy surface, which were achieved by changing both the laser fluence and the pulse repetition frequency. A laser fluence of 3.3 J/cm2 with 80 pulses was subsequently selected as the optimum condition to treat the surface of the alloy. The composition and microstructure of the alloy before and after LSM treatment, and following corrosion tests, were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD).After the laser treatment, the surface and the cross-sections of the alloy showed a significant reduction in the number of large intermetallic particles and a relatively homogenous melted layer was generated that provided significant improvement in the resistance of the alloy against corrosion, as assessed by several corrosion test methods, including exfoliation corrosion (EXCO) tests. However, delamination of the melted layer was observed after extended testing in the EXCO solution which is possibly related to the formation of bands of fine magnesium and zinc-rich precipitates within the melted layer. Therefore, anodising in sulphuric acid was applied to the LSM alloy, in order to further increase the corrosion resistance and to protect the laser treated layer from delamination by generating a thin oxide film over the LSM layer. The results revealed that the anodic treatment increased the resistance of the alloy to exfoliation attack.

20

Zhang, Bo Kai. "A study on nanocomposite hydroxyapatite coatings on Ti6Al4V fabricated by electrophoretic deposition and laser surface treatment." Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2493696.

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OLIVEIRA, FELIPE de. "Estudo de camadas finas tratadas por laser em anéis de pistão." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10048.

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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Domfang, Ngnekou Julius-Noël. "Étude expérimentale de la tenue en fatigue de l’alliage AlSi10Mg élaboré par fusion laser de lit de poudre Influence of as-built surface and heat treatment on the fatigue resistance of Additively Layer Manufacturing (ALM) AlSi10Mg alloy Fatigue resistance of selectively laser melted aluminum alloy under T6 heat treatment Fatigue properties of AlSi10Mg produced by Additive Layer Manufacturing." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2019. http://www.theses.fr/2019ESMA0015.

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Ce travail montre l'impact des défauts et de la microstructure sur la limite de fatigue de l’AlSi10Mg de fabrication additive (FA). Les échantillons d’étude sont fabriqués suivant trois orientations (0 °, 45 ° et 90 °) ; les surfaces d’étude sont usinées ou brutes de fabrication. Les éprouvettes sont étudiées avec ou sans traitement thermique T6. Avant toute chose, le matériau est d’abord caractérisé en lien avec les paramètres du procédé à l’aide de plusieurs moyens (microscopie, microtomographie). Du point de la fatigue, les courbes S-N sont établies avant et après T6, principalement à R = -1 en sollicitation uniaxiale. Pour toutes les éprouvettes d’étude, l’analyse des faciès montre que ce sont toujours les défauts qui sont à l’origine de la rupture par fatigue. Ainsi, un critère est appliqué pour définir ces défauts critiques (type, taille morphologie et position) et la limite de fatigue est systématiquement analysée via les diagrammes de Kitagawa. Le rôle de la direction de construction sur la tenue en fatigue est étudié, avant et après traitement thermique T6, tant pour les surfaces usinées que brutes de fabrication. À cet effet, un scénario basé sur la taille caractéristique des grains est proposé pour expliquer les effets d’orientation post-T6. La contribution de la structure de précipitation est également étudiée ; ainsi que le rôle des défauts (type, taille, morphologie et position) sur la limite de fatigue à différents états microstructuraux : avant et après T6. Afin de comprendre les mécanismes d’endommagement par fatigue en surface, la méthode des répliques est déployée sur une éprouvette polie. Dans ce cadre, une loi de propagation des fissures naturelles, c'est-à-dire qu'elles sont dues à un défaut hérité du procédé, est identifiée. Elle permet de séparer les phases d’amorçage et de propagation, alimentant ainsi les discussions sur les phénomènes d’amorçage en présence de défauts. Par ailleurs, quelques critères de fatigue sont également discutés et l’approche Defect Stress Gradient (DSG) est adaptée au matériau d’étude en tenant compte de la taille des grains cristallographiques. Pour les sections utiles brutes de fabrication, le rôle du mode de suppression des supports fabrication sur l’amorçage des fissures de fatigue est étudié ; la définition de la notion de taille de défauts en présence de la rugosité, à l’échelle de l’ondulation de surface, est abordée. Sachant que l’amorçage peut avoir lieu sur une ondulation de surface ou sur un défaut isolé (porosité ou défaut de fusion), une méthode expérimentale est proposée pour analyser la compétition entre ces facteurs. Dans un contexte de développement industriel, l’influence sur la limite de fatigue des paramètres de procédé relatifs au laser (vitesse de balayage, puissance et distance de hachure), au lit de poudre (composition chimique, taille des particules, épaisseur du lit) est étudiée, en vue d’alimenter les discussions vers l’optimisation du procédé du point de vue de la tenue en fatigue
This work shows the impact of defects and microstructure on the fatigue limit of AlSi10Mg produced by Additive Layer Manufacturing (ALM). Samples are produced according to three orientations with respect to the construction plate (0 °, 45 ° and 90 °); the studied surfaces are machined or left as-built (AB) in the gauge section. The specimens are studied with or without T6 heat treatment. The study surfaces are machined or as built. Some specimens are subjected to T6 heat treatment. Before any others study, the material is characterized in connection with the process parameters through several techniques (microscopes and 3D X-ray microtomography). Regarding the fatigue, the S-N curves are established before and after T6, mainly at R = -1 under uniaxial loading. For all the fatigue test specimens, fracture surfaces analysis shows that it is always a defect that cause fatigue failure. Thus, a criterion is applied to define these critical defects (type, size morphology and position) and the fatigue limit is analyzed through the Kitagawa type diagrams. The role of the building direction on the fatigue strength is studied, before and after T6 heat treatment, for both machined and as-built surfaces. For this purpose, a sketch based on the characteristic grain size is proposed to explain post-T6 orientation effects. The contribution of the precipitation structure is also studied; as well as the role of defects (type, size, morphology and position) on the fatigue limit at different microstructural states: before and after T6. In order to understand the surface fatigue damage mechanisms, the replica method is used on a polished specimen. In this context, a propagation law of natural cracks, that is to say due to a defect inherited from the process, is identified. It makes it possible to separate the initiation and propagation phases, thus feeding the discussions on the phenomena of priming in the presence of defects. In addition, some fatigue criteria are also discussed and the Defect Stress Gradient (DSG) approach is adapted to the studied material, by taking into account the size of the crystallographic grains. In the specific case of specimens with as-built useful sections, the role of the process of suppression of the building supports on the initiation of fatigue cracks is studied; the definition of the concept of defect size in the presence of roughness, at the scale of the surface undulation, is discussed. Knowing that initiation can occurs on a surface undulation or on an isolated defect (porosity or lack-of-fusion), an experimental method is proposed to analyze the competition between these factors. In a context of industrial development, the influence on the fatigue limit of the process parameters, related to the laser (scanning speed, power and hatching distance), or powder bed (chemical composition, particle size, bed thickness) is studied, in order to feed the discussions towards the process optimization regarding the fatigue strength

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Kitwiroon, Nutthida. "Treatment of surface boundary layer parameters for modelling air quality in urban regions." Thesis, University of Hertfordshire, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431958.

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Harder, Sergej [Verfasser]. "Near-infrared laser surface treatment of milled CFRP aircraft structures for bonded repair applications / Sergej Harder." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2020. http://d-nb.info/1222589230/34.

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Soares, Evaldo Julio Ferreira. "Tratamento superficial a laser dos aços AISI 1045 e AISI 4340 : transformações microestruturais e propriedades." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263557.

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Orientador: Maria Clara Filippini Ierardi
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: A melhoria nas propriedades superficiais dos materiais tem sido buscada incessantemente pelas indústrias de transformação. A utilização do laser para tratamento térmico e refusão, entre outros processos, tem possibilitado grandes avanços nesta área. Muito se tem trabalhado na determinação dos parâmetros operacionais do laser e a resultante destas influências sobre as propriedades dos materiais. Os objetivos deste trabalho são estudar os efeitos destes parâmetros operacionais sobre a profundidade da camada superficial e a caracterização microestrutural das amostras submetidas a tratamento térmico a laser. Foram feitos experimentos usando os aços AISI 1045 e AISI 4340, a partir de amostras recozidas, temperadas e nitretadas. Foi utilizado um laser de CO2, pertencente ao LNLS, com potência nominal de 1 kW, desfocado em 2 mm, velocidade de deslocamento do feixe variando de 3000 a 10000 mm/min. Os resultados confirmam o laser como um instrumento eficaz na aplicação dos tratamentos superficiais. Para o aço AISI 1045, verifica-se que as amostras nitretadas apresentam maior profundidade da poça resultante após tratamento a laser. Já para o aço AISI 4340 as amostras endurecidas são as que se apresentam com maiores profundidades de poça. Para ambos os casos, as amostras recozidas apresentam os menores valores de profundidade da poça. Os ensaios de corrosão demonstram, com exceção das amostras nitretadas, uma tendência de elevação na nobreza do potencial eletroquímico do material. Quanto à resistência ao desgaste, com exceção das amostras nitretadas, do aço AISI 4340, todas as amostras apresentaram melhora após submetidas aos tratamentos propostos
Abstract: The industry development during last decades has allowed significant improvements concerning materials surface properties. Laser application for thermal treatment and remelting has also permitted important advances in this area. A lot of work has been spent in order to understand the influence of the operational laser parameters on the products¿ performance. The main objective of this study is to examine the effects of such parameters on the surface layer depth and on the typical microstructural arrangement of the treated samples. Thus, experiments were carried out using the steels AISI 1045 and AISI 4340, which were annealed, tempered and nitrated. Further, It was used a CO2¿s laser equipment, with nominal power of 1kW (defocusing of 2mm) and scan speed varying from 3000 mm/min to 10000 mm/min. The results confirmed the laser as an effective technique for surface treatments application. For steel AISI 1045, it was verified that nitrated samples presented the deepest liquid pool as consequence of the laser treatment. However, for steel AISI 4340, the hardened samples presented the deepest liquid pool. In both cases the annealed samples presented the lowest values concerning such parameter. The corrosion tests demonstrated that, except for the nitrated samples, a tendency of electrochemical potential increasing could be observed for all other studied conditions. Concerning wear resistance, excepting steel AISI 4340 nitrated samples, the others shown an improvement after the proposed treatment
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica

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Sreekanth, Suhas. "Laser-Directed Energy Deposition : Influence of Process Parameters and Heat-Treatments." Licentiate thesis, Högskolan Väst, Avdelningen för svetsteknologi (SV), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-15767.

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Laser-Directed Energy Deposition (L-DED), an Additive Manufacturing (AM) processused for the fabrication of parts in a layer-wise approach has displayed an immense potential over the last decade. The aerospace industry stands as the primary beneficiary due to the L-DED process capability to build near-net-shape components with minimal tooling and thereby producing minimum wastage because of reduced machining. The widespread use of Alloy 718 in the aero-engine application has prompted huge research interest in the development of L-DED processing of this superalloy. AM processes are hindered by low build rates and high cycle times which directly affects the process costs. To overcome these issues, the present work focusses on obtaining high deposition rates through a high material feed. Studying the influence of process parameters during the L-DED process is of prime importance as they determine the performance of in-service structures. In the present work, process parameters such as laser power, scanning speed, feed rate and stand-offdistances are varied and their influence on geometry and microstructure of Alloy 718 single-track deposits are analyzed. The geometry of deposits is measured in terms of height, width and depth; and the powder capture efficiency is determined by measuring areas of deposition and dilution. The microstructure of the deposits shows a column ardendritic structure in the middle and bottom region of the deposits and equiaxed grains in the top region. Nb-rich segregation involving laves and NbC phases, typical of Alloy718 is found in the interdendritic regions and grain boundaries. The segregation increases along the height of the deposit with the bottom region having the least and the top region showing the highest concentration of Nb-rich phases due to the variation in cooling rates. A high laser power (1600 W – 2000 W) and a high scanning speed (1100 mm/min) are found to be the preferable processing conditions for minimizing segregation. Another approach to minimize segregation is by performing post-build heat treatments. The solution treatment (954 °C/1 hr) and double aging (718 °C/8 hr + 621 °C/ 8 hr) standardized for the wrought form of Alloy 718 is applied to as-built deposits which showed a reduction in segregation due to the dissolution of Nb-rich phases. Upon solution treatment, this reduction is accompanied by precipitation of the delta phase, found predominantly in top and bottom regions and sparsely in the middle region of the deposit.

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Shimizu, Yu. "Bioactive effects of strontium loading on micro/nano surface Ti6Al4V components fabricated by selective laser melting." Kyoto University, 2020. http://hdl.handle.net/2433/253206.

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Monjarret, Ronan. "The multi-layer shallow water model with free surface : treatment of the open boundaries." Toulouse 3, 2014. http://www.theses.fr/2014TOU30334.

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This PhD dissertation, conducted as a collaboration between the SHOM and the University of Toulouse, deals with improving the treatment of open boundary conditions, for the multi-layer shallow water model with free surface. One of the main difficulties with such an objective is the determination of the modes associated to the internal surfaces liquid/liquid: the baroclinic modes. The work of this thesis focusses on two axes: The first one concerns the eigenstructure of the differential operator, associated to the general model. This allows to insure conditions of hyperbolicity and local wellposedness of the system of equations. This axis is divided in two chapters. The analysis of the two-layer model is performed in the first chapter: the calculus are exact and it is proved the gap is important compared with the single-layer model. The model with n layers, n _ 3, is studied in the second chapter: the main difficulty of these equations is the number of parameters, which obliges to concede assumptions. A new conservative multi-layer model is introduced and analyzed. The second axis deals with practical treatment of the open boundary conditions. The conditional local well-posedness of the initial-boundary value problem is proved. Afterwards, the boundary conditions are clarified for a general domain and a particular one: a rectangle. Comparison of the errors is performed between the single-layer model and the two and four-layer models, with two test case: the propagation of a gravity wave and a barotropic vortex.

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Leong, Hoi San. "Effect of corrosion inhibitor and laser surface treatment on corrosion behavior of steel used in chilling system." Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2550589.

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Kriebel, Mariano. "Effect of Er,Cr:YSGG and diode laser treatment on surface properties of 3Y-TZP for dental applications." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275049945.

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Girault, Marie. "Etude d'un plasma généré lors d'un traitement de surface métallique par ablation laser dans l'air : caractérisations du rayonnement et des nanoparticules induits." Thesis, Dijon, 2015. http://www.theses.fr/2015DIJOS028/document.

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L’interaction d’un faisceau laser de courte durée d’impulsion sur des matériaux tels que l’aluminium, le fer ou le titane est caractérisée par la présence d’une plume très énergétique et fortement ionisée (plasma). L'objectif de cette étude est de comprendre les mécanismes mis en jeu dans le plasma, créé lors de l'interaction laser-cible, qui conduisent à la formation de nanoparticules.Nous souhaitons étudier de façon générale la dynamique d’expansion dans l’air de la plume formée par un laser Nd :YAG déclenché de courte durée d’impulsion pour préciser les conditions de formation de ces particules et leurs caractéristiques morphologiques et structurales. Ainsi, ce travail se décompose en deux parties. Dans une première partie, nous présentons la caractérisation expérimentale de l’expansion de la plume dans l’air. Le rayonnement induit par le plasma permet d’extraire ses caractéristiques. Deux méthodes complémentaires ont été utilisées : la spectrométrie qui permet de faire une analyse physique du plasma et l’imagerie spectrale qui permet une analyse morphologique. La seconde partie est consacrée à la caractérisation des particules formées dans les mêmes conditions opératoires. Dans le but d’analyser les particules le plus proche de leur milieu de formation, une analyse « en vol » de la distribution en taille des particules est mise en œuvre par granulométrie EEPS. Cette expérience est préparatoire à une analyse par diffusion des rayons X aux petits angles (S.A.X.S.) sous atmosphère contrôlée, qui permet d’étudier l’influence de l’oxygène sur la taille et la morphologie des particules formées
The interaction of a laser beam of short pulse duration with metallic materials such as aluminum, iron or titanium is characterized by the presence of a high energy and strongly ionized plume (plasma). The aim of this study is to understand the mechanisms involved in plasma, created when laser-target interaction, which lead to the formation of nanoparticles. We would generally consider the dynamic expansion in the air of the plasma plume formed with a nanosecond Nd:YAG laser to specify the conditions of formation of these particles and their morphological and structural characteristics. Thus, this work is divided onto two parts. In the first part, we present the experimental characterization of the expansion of the plume in the air. The radiation induced by plasma allows to extracting the plasma characteristics. Two complementary methods were used: atomic spectrometry which allows to doing a physical analysis of plasma and spectral fast imagery to obtain a morphological analysis. The second part is devoted to the characterization of particles formed in the same operating conditions. In order to analyzing the particles as close to their formation environment, an analysis “in flight” of particle size distribution is implemented by EEPS granulometry. This experiment is preparatory at an analysis by in-situ Small-Angle X-ray Scattering (S.A.X.S.) under a controlled atmosphere, which allows to studying the influence of oxygen on the size and the morphology of the particles

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NOGUEIRA, ALESSANDRO F. "Texturização em superfícies de titânio grau 2 irradiadas com laser de pulsos ultracurtos." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23740.

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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Sgura, Ricardo. "Tratamento de superfície de porcelanas dentárias pela irradiação com laser de CO2." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/23/23140/tde-10092013-201616/.

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Este estudo teve como objetivo testar o laser de CO2 como um agente de tratamento de superfície de porcelanas dentárias. Material e Métodos: O estudo foi dividido em duas etapas: na primeira etapa, discos de porcelana (3,5 mm diam. x 2,0 mm espess.) das marcas VM7, VM9 e VM13 (VITA) foram sinterizados e tiveram uma de suas faces asperizadas por uma ponta diamantada 2134F para acabamento. Os espécimes foram então divididos em grupos de acordo com os seguintes tratamentos: nenhum (C), auto-glaze em forno (G) e irradiação com laser (L) de CO2 (Coherent, = 10,6 m, 35 W) de forma contínua com 40, 45 ou 50 W/cm2 nos tempos de 3, 4 ou 5 minutos (n=7). Nesta primeira etapa, as caracterizações das amostras constaram de: difratometria por raios-X, diferença de cor (Easyshade VITA), rugosidade superficial (Surftest 301, Mitutoyo) e análise visual por meio de esteromicroscopia e MEV. Um espécime de VM9 de cada grupo foi polido e levado a um exame por microscopia de força atômica (MFA). A segunda etapa consistiu na sinterização de discos das três porcelanas nas mesmas dimensões da etapa anterior, porém submetidos a um polimento de uma das superfícies com soluções diamantadas de granulação decrescente até 1 m. Os grupos testados foram os mesmos da primeira etapa, com exceção dos grupos irradiados com 40W/cm2. As caracterizações que se seguiram foram (n=10): microdureza Vickers, tenacidade à fratura, porosidade superficial, razão de contraste (RC) e capacidade de mascaramento (CM). Resultados: A rugosidade de espécimes asperizados foi diminuída pela aplicação do laser nas irradiâncias de 45 e 50 W/cm2, similar ao auto-glaze em forno, sem alteração de cor perceptível para a quase totalidade dos grupos irradiados. Houve um aumento do conteúdo cristalino das porcelanas VM9 e VM13 após a irradiação com o laser. As micrografias (MEV) demonstraram padrão de superfície homogêneo para os espécimes dos grupos irradiados a 50 W/cm2 e G. Os resultados da segunda etapa apontaram para alterações na microdureza e tenacidade à fratura na dependência da marca comercial e das irradiâncias estudadas. Quanto à porosidade, as porcelanas VM7 e VM13 apresentaram um aumento na fração volumétrica de poros, enquanto a porcelana VM9 irradiada apresentou-se semelhante a G. As médias de RC e CM indicaram um aumento na opacidade das porcelanas VM7 e VM13 irradiadas com o laser. Conclusão: Em condições específicas, o laser de CO2 é capaz de produzir uma lisura de superfície semelhante ao auto-glaze, com pequenas alterações nos aspectos ópticos e mecânicos. As diferentes marcas comerciais de porcelana apresentaram comportamentos distintos em relação aos tratamentos aplicados.
Glazing porcelain is an important procedure in dentistry that leads to surface smoothness, to less plaque accumulation and to brightness, especially after a chair side adjustment. Despite a good absorption of CO2 laser wavelength by dental porcelain it has not yet been tested as an alternative to oven glaze. Aim: This study tested CO2 laser as a heat source in surface treatment of dental porcelains. Material and Methods: This study was divided in two stages: at the first stage porcelain discs (VM7, VM9, VM13 VITA; 3.5 diam. x 2.0 mm thickness) were sintered, machined and had one of their sides grounded by a diamond bur (2134F KG Sorensen) simulating a chair side adjustment in clinical office. Specimens were then divided into groups according to treatment: no treatment (C); auto-glazed in conventional furnace (G) and submitted to CO2 continuous laser irradiation (Coherent, = 10.6 m; output power = 35 W, 0.5 cm laser beam) in 40, 45 or 50 W/cm2 for 3, 4 or 5 minutes (n=7). Specimens were supported by a ceramic refractory. At this first stage, the characterization consisted of X-ray diffraction (RU-200B, Rigaku), color difference (E) (Easyshade VITA), roughness (Surftest 301, Mitutoyo) and analysis of images achieved by stereomicroscopy (SZ61, Olympus) and SEM (Stereoscan 440, LEO). A VM9 specimen of each group had one of their side polished and was submitted to atomic force microscopy (AFM) Nanoscope IIIA (Veeco). In the second stage discs with the same dimension described above were sintered and polished with diamond solutions (Ecomet 3; 1 m). The same groups were tested except 40W/cm2 irradiance. Specimens were submitted to the following characterizations (n=10): Vickers microhardness test, fracture toughness by indentation fracture (HMV, Shimadzu), surface porosity (HMV, Image J software), contrast ratio (CR) and masking ability (MA) (CM-3770d, Konica Minolta). Results from both stages were submitted to one-way-ANOVA or Kruskall-Wallis test. A post-hoc Tukey test was applied when necessary ( = 0.05). Results: Ground specimens showed a reduction in roughness after laser irradiation (45 and 50 W/cm2), comparable to oven-glazed specimens with almost no color change. SEM images presented similarity between a irradiated group (50W/cm2) and G. AFM test revealed the formation of long rounded peaks and long valleys after laser exposition. Second stage results pointed to changes in microhardness and fracture toughness of irradiated specimens depending on the porcelain and irradiance tested. Regarding porosity, after laser exposition, porcelain VM7 and VM13 presented an increase in pores (area fraction) for the majority of groups while VM9 porcelain didnt show any increase in porosity after laser incidence. CR and MA means pointed to an increase in porcelain opacity to irradiated specimens of VM7 and VM13. Conclusion: Under specific conditions CO2 laser was able to produce a surface smoothness similar to auto-glaze, despite punctual changes in some optical and mechanical properties. The different brands presented distinct effects after laser heat treatment.

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Carvalho, Lisiane Rocha Azevedo de 1985. "Gradiente de rigidez na superfície de peças de Ti através da obtenção de ligas Ti-Nb por laser : Stiffness gradient Ti parts obtained by laser surface alloying with Nb." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265960.

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Orientador: João Batista Fogagnolo
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Titânio e suas ligas são amplamente utilizados como biomateriais devido a propriedades como alta resistência específica, alta resistência à corrosão e baixo módulo de elasticidade. As ligas de titânio apresentam diferentes estruturas cristalinas, as quais possuem diferentes módulos de elasticidade. Esta característica permite que o módulo de elasticidade seja manipulado através do controle da composição química da peça, o que por sua vez possibilita a fabricação de peças com gradientes de rigidez, abrindo-se um amplo campo de pesquisa e novas aplicações. Este trabalho utiliza a técnica de modificação superficial por laser e adição de nióbio com o objetivo de obter peças de titânio com revestimentos constituídos por fases com menores módulos de elasticidade, ou seja, peças com revestimentos menos rígidos que o substrato. Inicialmente foram caracterizados cordões isolados obtidos com diferentes densidades de energia do feixe de laser, através da variação da potência, do diâmetro e da velocidade de varredura do feixe de laser. Nos cordões isolados, observou-se que a potência do feixe de laser é o parâmetro de maior influência e que densidades de energia intermediárias possibilitaram obter cordões com zonas fundidas com dimensões e formato adequados para a posterior etapa de obtenção de recobrimento contínuo por sobreposição de cordões. As composições dos cordões isolados, apesar de apresentar heterogeneidade, permitiram a estabilização da fase ?. No entanto, uma fração significativa dos cordões apresentou também a fase ? com microestrutura dendrítica, indicando que essa fase foi resultado da solidificação, o que pode ter ocorrido pela contaminação por oxigênio, que é um forte estabilizador dessa fase. Dessa forma, mesmo com a formação da fase ?, não se observou uma redução do módulo de elasticidade. Em todos os casos, a dureza apresentou um significativo aumento, também devido a forte contaminação por oxigênio. A formação de revestimentos contínuos foi obtida através da sobreposição de 50% da largura dos cordões. Os revestimentos contínuos assim obtidos apresentaram segregação de soluto, com fase ? estabilizada nas regiões com maiores teores de nióbio e agulhas de martensita nas regiões com menores teores de nióbio. A contaminação por oxigênio foi reduzida em comparação com os cordões isolados. Os revestimentos contínuos apresentaram aumento de dureza e diminuição do módulo de elasticidade, conforme o objetivo proposto
Abstract: Titanium and its alloys are commonly used as biomaterials due to their properties as high specific strength, high corrosion resistance and low elastic modulus. Titanium alloys show differents crystalline structures, which have different elastic modulus. This characteristic allows the manipulation of the elastic modulus through chemical composition control, which allows the manufacture of pieces with stiffness gradients, spreading a large research field and new applications. This work use the laser surface alloying technique with addition of niobium powder to obtain titanium pieces with coatings composed by phases with lower elastic modulus, in other words, pieces with coatings less stiff than the substrate. Firstly, isolated tracks obtained by different beam laser energy densities, by varying laser beam power, diameter and scan speed were characterized. In this case, the laser beam power was the most important parameter and the intermediaries energy densities allowed to obtain tracks with melted zones with dimensions and shape suitable to obtain a continuous coating by overlapping tracks. The isolated tracks compositions, despite their chemical heterogeneities, showed the stabilization of the ? phase. However, a significant fraction of tracks showed also ? phase with dendritic microstructure, indicating that this phase was the result of solidification, which may have occurred due oxygen contamination, which is a strong ? stabilizer element. Thus, despite the stabilization of the ? phase, a reduction in elastic modulus was not observed. In all the cases the hardness showed a significant increase, also because of the high contamination by oxygen. The continuous coating formation was obtained by overlapping 50% of the tracks width. The continuous coatings obtained showed solution segregation, with ? phase stabilized in the regions with higher niobium content and needle like traces of martensite in the regions with less niobium content. The oxygen contamination was reduced in comparison with isolated tracks. The continuous coatings showed high hardness with a decrease of the elastic modulus, in accordance with the proposed objective
Mestrado
Materiais e Processos de Fabricação
Mestra em Engenharia Mecânica

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Bobb, Julian A. "LASER SYNTHESIS OF NANOMATERIALS INCORPORATED WITHIN HIGH SURFACE AREA MATERIALS: APPLICATIONS FOR HETEROGENEOUS CATALYSIS, WATER TREATMENT, AND PHOTOTHERMAL ENERGY CONVERSION." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5693.

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Chemical methods are generally used for the synthesis of active nanoparticles (metals, semi-metals, metal oxides, and etc) supported on high surface area materials. Chemical methods involve using strong solvents, harmful gases (H2 & CO), and high temperature techniques such as high boiling solvents, calcination and pyrolysis. The main drawbacks of using this approach, is the prevalence of chemical agents on nanomaterials which tends to negate its applications. Alternatively, photochemical and photothermal methods are widely being considered for the synthesis and design of nanomaterials. For these studies, the active nanomaterials incorporated within high surface area materials were prepared by the laser vaporization-controlled condensation (LVCC) technique or by the laser irradiation in solution (LIS) technique. The LVCC technique involves the irradiation of a solid target at the focal point of a laser beam (532 nm, 30 Hz) by the Nd: YAG laser inside a chamber that is sandwiched between two steel plates in the presence of high purity He. Whereas, the LIS technique involves the laser irradiation of chemical precursors in aqueous solvents using an unfocused beam. The LVCC technique was used for the preparation of carbonaceous and N-doped carbonaceous TiO2 support materials from MIL-125(Ti) and NH2-MIL-125(Ti) metal organic frameworks, Ge and GeO2 nanostructures, GeOx/PRGO nanocomposite, and the Fe3O4/PRGO nanocomposite. On the other hand, Pd supported on MIL-125(Ti) and NH2-MIL-125(Ti) nanocatalysts, GeO2/RGO, and the poly(ethylene glycol methacrylate-co-bisacrylamide) hydrogels were all prepared by the LIS technique.

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Santos, Douglas dos [UNESP]. "Caracterização microestrutural e mecânica do aço 300m tratado termoquimicamente a plasma e a laser." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/148806.

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O aço 300M surgiu como uma melhoria do aço de alta resistência SAE 4340, este foi desenvolvido para adquirir melhor tenacidade e soldabilidade em aplicações que exigem melhores propriedades mecânicas, foram feitas pequenas alterações nos elementos de liga como a adição de vanádio e elevação no teor de silício. Este trabalho realizou tratamentos de superfície de nitretação a Plasma e de carbonetação a Laser na superfície de um aço 300M com estrutura bainítica. A microestrutura bainítica foi obtida por resfriamento isotérmico na temperatura de 300°C durante 60 minutos, a partir da região de austenitização, elevando a dureza de 380 para 474 HV. O tratamento de superfície de carbonetação, utilizando um laser de CO2 de baixa potência (125 W) utilizou como revestimento negro de fumo, com objetivo de adicionar carbono e criar uma camada protetora. O tratamento de superfície por nitretação a plasma ocorreu na temperatura de 500ºC durante 3 horas, em uma atmosfera com mistura de gases N2 e H2. As amostras foram caracterizadas por microscopia óptica. Foram analisadas as espessuras da camada de compostos formada na superfície, em torno de 20 μm, e da zona termicamente afetada pelo calor (ZTA), em torno de 45 μm, para tratamento a laser. Pelo tratamento de nitretação, a camada formada na superfície do aço, apresentou uma região branca com aproximadamente 3 μm e uma camada de difusão atômica endurecida com cerca de 20 μm. As propriedades mecânicas foram avaliadas por meio de ensaios de tração e fadiga uniaxial. Os resultados mostraram que o comportamento mecânico em tração foi fortemente afetado pela microestrutura bainítica, aumentando os níveis do limite de escoamento e de resistência. Estas propriedades em tracão não foram afetadas pelos tratamentos de superfície. No desempenho da vida em fadiga, o tratamento de superfície a plasma apresentou melhor comportamento, melhorando significativamente as propriedades em fadiga.
300M steel was developed from high-strength steel SAE 4340, the goal of this improvement was get better toughness and weldability in applications requiring improved mechanical properties; with small changes in alloy elements, addition of vanadium and especially the silicon content. This work uses low-power laser CO2 (125 W) for introducing carbon into the surface of 300M steel with bainitic structure. The bainitic microstructure was obtained by isothermal cooling at 300 °C for 60 minutes after austenitizing at 850 ºC for 30 minutes; this heat treatment increased the hardness of 360 HV for 474 HV. The CO2 laser parameters as resolution and power were kept constant and the speed is varied. It was used as carbon black coating to better the absorption of light laser. Treatment plasma nitriding surface was at a temperature of 500° C for 3 hours in atmosphere having a gas mixture N2 e H2. The samples were characterized by optical microscopy. They were analyzed thicknesses of the layers formed on the surface around 20 μm, and the heat affected zone (HAZ) about 45 μm, for laser treatment. To nitriding treatment, the layer formed on the surface of the steel showed a white area of approximately 3 μm and 20 μm near HAZ. The mechanical properties were analyzed using tensile and fatigue tests. The results showed that the mechanical properties in tensile tests was strongly affected by the bainitic microstructure. The steel that received the nitriding surface plasma treatment showed better fatigue behavior.

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Aravamudhan, Boopa Nandhini. "Study of the Effect of Laser Shock Peening on Corrosion Behavior of Aluminum Alloy 7075." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535374351540327.

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AGUIAR, AMANDA A. "Avaliação do recobrimento biomimético em compósitos de alumina-zircônia texturizadas superficialmente com laser de femtossegundo." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10203.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Robles, Fábio Renato Pereira. "Avaliação da resistência à tração da dentina bovina irradiada com laser de Er:YAG combinada a diferentes tratamentos. Análise das superfícies pela microscopia eletrônica de varredura." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/23/23134/tde-01042009-172347/.

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Diante dos avanços científicos da odontologia visando o selamento perfeito das cavidades com adesão, desenvolvimento de materiais, técnicas e maior compreensão das características do substrato dental, a tecnologia a laser de Er:YAG (2,94 mm) apresenta-se como recurso eficiente para o tratamento superficial da dentina, isoladamente ou em associação ao condicionamento ácido, em baixa densidade de energia. Para obtenção de uma zona microrretentiva (camada híbrida, tags e microtags) mais uniforme e evitarem-se aspectos críticos de adesão como o colapso da trama protéica, sua remoção pela desproteinização com hipoclorito de sódio (NaOCl) tem sido proposta. O presente estudo teve por objetivo pesquisar a interação de diferentes tratamentos superficiais em dentina bovina (condicionamento ácido convencional, laser de Er:YAG e desproteinização), avaliar a resistência adesiva à tração utilizando-se um sistema adesivo à base de acetona, e analisar as superfícies dentinárias submetidas a estes diferentes tratamentos em microscopia eletrônica de varredura (MEV). Verificou-se que o laser de Er:YAG em baixa densidade de energia (19,29 J / cm2, a 60 mJ e 2 Hz) pôde influenciar positivamente na resistência adesiva da dentina, comparando-se ao condicionamento ácido convencional. A associação laser e ácido no tratamento de superfície dentinária aumentou a resistência adesiva independente de ter-se realizado ou não a desproteinização. A observação em MEV das superfícies dentinárias tratadas com o laser de Er:YAG seguido da desproteinização com NaOCl revelou aspecto morfológico microrretentivo, embora o comportamento adesivo tenha produzido baixos valores de resistência à tração.
Under scientific improvements in dentistry towards the perfect cavity sealing and adhesion, the development of materials, techniques and the better understanding of dental substrate features, the Er:YAG laser (2,94 mm) technology plays a role as an efficient tool in dentin surface treatment, performed in low energy density, whether isolated or in association with acid etching. In order to obtain a more uniform mircro-retentive zone (hybrid layer, tags and microtags) and to avoid the critical aspects on adhesion such as the collagenous demineralized zone collapse, it has been proposed the removal of this collagenous zone with the sodium hypochlorite (NaOCl) protein depletion technique. The aim of the present study was to evaluate the interaction of these surface treatments in bovine dentin (conventional acid etching. Er:YAG laser and protein depletion), to measure the tensile bond strength of the treated dentin surfaces, by using an acetone-based adhesive system and to observe the dentin surfaces under scanning electron microscopy analysis (SEM). The results showed that Er:YAG laser performed in low energy density (19,29 J / cm2, at 60 mJ and 2 Hz) could positively influence in dentin tensile strength, as good as conventional acid etching. The laser / acid association in dentin treatment increased tensile bond strength whether had it been performed the NaOCl protein depletion or not. SEM observation of Er:YAG dentin treated surfaces followed by NaOCl had shown a morphologic micro-retentive pattern; however, its tensile bond strength values came out to be low.

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Piecha, Julita. "Segregation of ions in surface layer of the LiNbO3 single crystal induced by proton exchange reaction and by thermal treatment." Doctoral thesis, Katowice : Uniwersytet Śląski, 2016. http://hdl.handle.net/20.500.12128/713.

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Niobian litu to ferroelektryczny kryształ otrzymywany metodą Czochralskiego, wykazuje on strukturę romboedryczną z grupą przestrzenną R3c. Charakteryzuje się wysokimi wartościami temperatury Curie (TC≈1120 °C) oraz temperatury topnienia (Tm≈1230 °C). Celem moich badań było określenie wpływu reakcji protonizacji oraz redukcji na segregację jonów litu w warstwie powierzchniowej kongruentnego LiNbO3. Wysoką mobilność jonów litu w warstwie powierzchniowej oraz ich migrację z wnętrza kryształu ku jego powierzchni wykorzystano w procesie wymiany jonowej Li+/H+. Reakcję wymiany protonowej prowadzono w specjalnie skompletowanej aparaturze chemicznej objętej patentem. Wpływ reakcji protonizacji, przeprowadzonej w środowisku stężonego HNO3(V) przedstawiono w formie profili głębokościowych SIMS. Na podstawie analizy danych ICP-OES określono stężenie jonów litu i niobu znajdujących się w roztworze kwasu, w którym prowadzono reakcję. Badaniami XRD potwierdzono strukturę czystego niobianu litu, natomiast próbka protonizowana, HxLi1-xNbO3, wykazała strukturę jednoskośną. Badania elektryczne wykazały wpływ procesu protonizacji na obniżenie wartości energii aktywacji modyfikowanych próbek. Wykorzystując technikę Brillouin’owskiego rozpraszania światła wyznaczono temperaturę Curie TC=1120 °C, oraz wykazano wpływ protonizowanej warstwy powierzchniowej na badania objętościowe. Próbkę czystego LiNbO3 poddano analizie XPS (w RT oraz w zakresie temperatur od 300 do 900 °C) celem określenia jej składu chemicznego. Zaobserwowano znaczny niedobór jonów litu zarówno w warstwie powierzchniowej [Li]/[Nb]=0.04 oraz na krawędzi przełomu kryształu [Li]/[Nb]=0.67. Różnice otrzymanych wartości stosunku [Li]/[Nb], względem wartości literaturowych, mogą świadczyć o istnieniu bardziej złożonych form zdefektowania, np. ścieżek łatwej dyfuzji, a nie tylko defektów punktowych. Niewielka stabilność jonów litu i brak jednorodności w warstwie powierzchniowej próbek poddanych obróbce termicznej w redukującej atmosferze potwierdzono przy użyciu technik: XPS, TGA, efuzji, SIMS, ICP-OES oraz XRD. Analiza XPS ukazała brak stanu Li 1s w warstwie powierzchniowej w przedziale 300–500 °C, uwidocznił się on w T=700 °C. Badania TGA ukazały ubytek masy oraz zmianę transparentności analizowanego materiału. Efuzja prowadzona w temperaturach 800 i 900 °C umożliwiła identyfikację uwolnionych z próbki gazowych produktów, np. Li2O i O2. Mapy SIMS przedstawiły niehomogeniczny rozkład litu i niobu w warstwie powierzchniowej. Uzyskane wyniki pozwoliły na wyznaczenie wartości oraz zmian w stosunku [Li]/[Nb] na profilach głębokościowych dla 750, 850 i 950 °C. Dyfuzja jonów Li została potwierdzona. Warunki formowania HxLi1-xNbO3 zostały określone.

41

SILVA, LUCIANA V. da. "Estudos dos mecanismos envolvidos em processos de endurecimento superficial a laser de ligas a base de aluminio." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9634.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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SILVA, EDMARA M. R. da. "Estudo dos mecanismos envolvidos no processo de endurecimento superficial a laser de ligas metalicas." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10934.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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Nascimento, Alex Maia do. "Obtenção por tratamento a laser e caracterização de composito superficial em aços inoxidaveis duplex fundidos." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263555.

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Orientador: Maria Clara Filippini Ierardi
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Neste trabalho estudaram-se as relações de orientação entre a austenita e ferrita de três aços inoxidáveis duplex fundidos, ASTM A890 1A, 3A e 6A, na condição solubilizada. Logo após, tratamentos superficiais de refusão a laser simples (RL) e com injeção simultânea de partículas cerâmicas (RLI) foram realizados sobre as ligas. As mudanças microestruturais e os efeitos dos tratamentos sobre as propriedades de dureza, resistência ao desgaste e à corrosão das ligas foram analisadas. As mudanças microestruturais foram caracterizadas por microscopia ótica, microscopia eletrônica de varredura com detectores de EDAX e EBSD acoplados, difração de raios-X e microdureza Vickers. Realizaram-se ensaios de desgaste do tipo pino sobre disco sobre as três ligas, nas condições superficiais: inicial, RL e RLI. A análise do comportamento corrosivo das ligas, antes e após os tratamentos a laser, foi realizada usando-se ensaios de polarização em solução de 0,5M de H2SO4 + 0,5M de NaCl na temperatura ambiente. Os resultados obtidos mostraram que as ligas na condição inicial apresentaram a existência de relações de orientação preferenciais entre a austenita e a ferrita, próxima aos modelos teóricos de Greninger-Troiano, Kurdjumov-Sachs e Bain. As superfícies tratadas por laser, apresentaram mudanças microestruturais significativas, as quais produziram durezas e resistências ao desgaste superiores as da condição inicial, e com a manutenção da elevada resistência à corrosão típica dos aços inoxidáveis duplex
Abstract: In this work was studied the orientation relations between austenite and ferrite in three cast duplex stainless steels, ASTM A890 1A, 3A, 6A on solution treatment. After that, simple laser surface remelting (LR) and laser melt injection (LMI) treatments were carried out on the alloys. The microstructural changes and the effects of laser treatments on hardness, wear resistance and corrosion resistance properties were analyzed. The microstructural changes were investigated by means of optical microscopy, scanning electron microscopy with integrated EDS and EBSD systems, X-ray diffraction and Vickers microhardness. The wear properties were measured by pin-on-disc tests on the three alloys in all different conditions : initial, LR and LMI. In order to analyze the corrosive behavior of the alloys before and after the treatments, polarization tests were carried out in the 0,5M de H2SO4 + 0,5M de NaCl solution at room temperature. The results obtained showed that the austenite and ferrite of alloys in the initial condition have orientation relations close to Greninger-Troiano, Kurdjumov-Sachs and Bain theoritical models. However, the laser treated surfaces showed accentuated microstructural changes and the microhardness and wear resistance were increased in comparing with the wear of the substrate. The three alloys in all conditions showed an excellent corrosion resistance what it is typical for the duplex stainless steels
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica

44

Gouton, Lucille. "Formation par traitement de surface par laser d’une couche de chromine sur un alliage base nickel pour limiter le relâchement des cations en circuit primaire." Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0034/document.

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Le contexte industriel de cette étude est la modification de surface de l’alliage 690(60%Ni, 30%Cr, 10%Fe) utilisé dans la fabrication de tubes de générateurs de vapeur.L’objectif de ce travail de thèse est donc de former, par traitement de fusion par laser nanopulsé, une couche de Cr2O3 étanche au relâchement du nickel. Pour maîtriser la formation decette couche, il est primordial de déterminer les paramètres opératoires influant sur lespropriétés de cette couche. L’objectif scientifique est alors d’expliquer les phénomènesintervenant pendant et après l’impulsion laser au niveau de l’extrême surface.Suite à une étude paramétrique détaillée, un traitement de fusion superficielle par laser nanopulsé a permis d’obtenir un fort rapport Cr/Ni en surface et une couche d’oxyde dense etcontinue. Afin de vérifier l’efficacité du traitement, des coupons traités ont été introduits dansune boucle simulant le milieu primaire.Des expériences et des calculs ont été mis en oeuvre pour tenter d’expliquer l’enrichissementen chrome de la surface à l’aide de ce procédé. Les résultats expliquent l’enrichissement enchrome jusqu’à la solidification du bain liquide en surface qui précède la formation du Cr2O3favorisée par la forte affinité du chrome avec l’oxygène et la grande stabilité de l’oxyde Cr2O3
Alloy 690 (60%Ni, 30%Cr, 10%Fe) is mainly used in primary circuit pipes fornuclear power plants.The aim of this thesis is to form a Cr2O3 layer, using laser surface melting, with the objective ofcreating a chromium-rich oxide layer. In order to optimize the treatment, it was first important todetermine parameters influence on the layer oxide properties then, with the objective of adeeper understanding of mechanisms involved, to address thermo-physical phenomenaoccurring during and after the laser pulse striking the upper surface.A deep parametric study first enabled to find an optimized laser surface treatment whichproduces chromium enrichment of the upper surface and a dense and continuous oxide layer.This treatment has been applied on samples, set in a primary medium simulation loop.Experiments and calculations were carried out to provide understanding of surface chromiumenrichment by laser process. The results were shown to explain chromium enrichment until meltpool solidification occurred on the upper surface, assumingly just before chromium oxideformation. This was also promoted by a high affinity with oxygen and a higher stability of Cr2O3oxide compared with other potential oxide formation

45

Kříž, Daniel. "Studium vlivu velikosti svazku na hloubku prokalení materiálu 42CrMo4 při laserovém kalení." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231069.

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This master thesis is focused on surface hardening by using disk laser. Ten samples made of 42CrMo4 steel were hardened at varying speeds of quenching and diameter of the laser beam. The theoretical part initially describes the types of lasers. Further it describes methods of surface hardness processing such as kinds of hardening and chemical-thermal treatment, followed by description of the used material. Images of macrostructure, microstructure and compared values of hardness of single samples are evaluated in the experimental part. The thesis subsequently contains a technical-economic evaluation. Appropriate parameters for surface laser hardening are evaluated in the conclusion.

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Telang, Abhishek. "A Study of the Effects of Mechanical Surface Treatments on Residual Stresses, Microstructure and Stress Corrosion Cracking Behavior of Alloy 600." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447070304.

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47

PIERETTI, EURICO F. "Biomêcanica aplicada na avaliação de propriedades de implantes ortopédicos metálicos tratados por feixe laser." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27881.

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A marcação por feixe laser em superfícies é utilizada para assegurar a identificação e a rastreabilidade em biomateriais. A texturização via feixe laser confere maior aderência às superfícies dos dispositivos médicos implantáveis. Este trabalho teve o objetivo de avaliar o comportamento da superfície do aço inoxidável austenítico ABNT NBR ISO 5832-1 submetido à marcação e texturização com feixe laser de fibra óptica, alterando-se a frequência dos pulsos; frente ao seu comportamento biomecânico, por meio de: ensaios de resistência à tração, fadiga e desgaste; verificar a susceptibilidade à corrosão localizada, por ensaios eletroquímicos em solução que simula os fluidos corpóreos; e caracterizar a sua microestrutura. Os tratamentos alteraram a rugosidade e a dureza dos biomateriais em função do aumento da frequência dos pulsos. A microestrutura e composição química das superfícies sofreram mudanças que afetaram diretamente a camada passiva dos aços inoxidáveis. Este efeito foi comprovado com o uso de SVET, XPS e caracterização de propriedades eletrônicas do filme passivo. Os dois tipos de tratamentos implicaram em aumento de susceptibilidade magnética das superfícies. Os parâmetros utilizados para as marcações e texturizações não causaram diminuição na viabilidade celular, de modo que não apresentou citotoxicidade mesmo após incubação prolongada. Este biomaterial mostrou-se adequado perante os ensaios biomecânicos, uma vez que os tratamentos a laser, nas condições utilizadas, não induziram a formação de tensões superficiais de magnitude capaz de levar à fratura por fadiga, indicando vida em fadiga infinita; tampouco se pôde relacionar a região de fratura por tração com as marcações a laser. O volume de desgaste diminuiu em função do aumento da dureza produzido pela elevação da frequência do pulso nas texturizações. O caráter visual das marcações e texturizações por feixe laser foi assegurado após a maioria dos ensaios realizados.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

48

Sharma, Anurag. "Effects of Advanced Surface Treatments on Microstructure, Residual Stress and Corrosion-Fatigue Behavior of Aluminum Alloy 7075-T6." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin162765884039947.

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49

中本, 剛., Takeshi NAKAMOTO, 英二社本, Eiji SHAMOTO, 義丈山崎, Yoshitake YAMAZAKI, 洋一白形 та Youichi SHIRAKATA. "レーザー焼結によるホウ化チタン砥石の開発 (ホウ化チタン成膜と研削性能の基礎研究)". 日本機械学会, 2006. http://hdl.handle.net/2237/9004.

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50

Silva, Beatriz Togoro Ferreira da. "Efeito da largura temporal de pulso do Laser de Er:YAG em zircônia pré-sinterizada." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/23/23134/tde-19012016-160857/.

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Este estudo se propôs a analisar os efeitos das diferentes larguras temporais de pulso do laser de Er:YAG na rugosidade superficial, na perda de volume do material e na altura do degrau formado em uma Y-TZP (Yttrium-stabilized Tetragonal Zirconia Polycrystal) pré-sinterizada. Foram utilizados 5 blocos de Y-TZP pré-sinterizados destinados ao uso CAD/CAM que foram seccionados, obtendo-se 63 espécimes padronizados. Em seguida, esses espécimes foram lixados com uma sequência decrescente de lixas para padronização da superfície. Os grupos experimentais foram compostos a partir de 1 fator de variação - o tratamento de superfície. Os espécimes foram irradiados com o laser de Er:YAG (Fidelis III Fotona, Eslovênia) - 2,94 ?m, 100 mJ, 15,87J/cm2, 10 Hz, 1W, 7 mm, 60% água/40% ar. Assim formaram-se 7 grupos experimentais (n=9): G1 (50 ?s); G2 (100 ?s); G3 (300 ?s); G4 (600 ?s); G5 (1000 ?s); G6 (Abrasão triboquímica com partículas de 30 ?m); G7 (Sem tratamento). Após os tratamentos de superfície, os espécimes foram sinterizados em forno específico, de acordo com as recomendações do fabricante. Foram capturadas imagens em Microscópio Confocal a Laser 3D de cada espécime e avaliadas por meio de um software. A análise dos grupos irradiados revelou um aumento da rugosidade nos grupos G1, G2, G3 e G4 quando comparados aos grupos G6 e G7. O grupo G5 apresentou superfície totalmente plana e desfavorável para retenção. No que se refere à perda de volume e formação de degrau, os grupos G1, G2 e G3 demonstraram grande perda de volume e grande altura de degrau formado, o que pode levar a uma desadaptação da peça protética. No grupo G4 foram observados valores de rugosidade satisfatórios com pouca perda de volume e pequena altura de degrau formado, semelhante ao que foi notado para a abrasão trioboquímica (G6), podendo ser indicada para tratamento de superfície de Y-TZP pré-sinterizada. A irradiação com o laser de Er:YAG promoveu um padrão morfológico com muitas irregularidades, característico de ablação para os grupos G1, G2, G3 e G4 e, para todos os protocolos utilizados, não foi observada a presença de trincas ou carbonização. Sugere-se que a largura temporal de 600 ?s (G4) seja a mais indicada como alternativa para tratamento de superfície, objetivando a criação de micro-retenções superficiais, com pouca perda de volume de material e que, ao mesmo tempo, não provoque danos à estrutura da cerâmica policristalina.
This study evaluated the effects of different Er:YAG laser pulse width protocols on surface roughness, loss of volume of the material and the step height formed of pre-sintered Yttrium-stabilized tetragonal Zirconia Polycrystal (Y-TZP) by three-dimensional profilometric assessment. Blocks of pre-sintered Y-TZP were cut providing 63 standard 5mm thick samples which were divided by surface treatment, as follows (n=9): G1 (50?s); G2 (100?s); G3 (300?s); G4 (600?s); G5 (1000?s); G6 (tribochemical silica coating); G7 (Untreated). Laser settings: The Er:YAG laser (Fidelis III; Fotona, Ljubljana, Slovenia) 100mJ, 15,87J/cm2, 10Hz, 1W, (60%) and air (40%) cooling. After treated or not, samples were sintered according to the manufacturer\'s recommendations. Roughness, volume loss and step and were analyzed by 3D profilometric assessment with confocal laser microscopy. Irradiated groups showed an increased roughness in the groups G1, G2, G3 and G4 when compared to G6 and G7 groups. The G5 group showed a completely flat and unfavorable surface for retention. The groups G1, G2 and G3 shown great loss of volume and the step height formed, which can lead to a gap on the crowns. In G4 were observed satisfactory roughness with little loss of volume and the step height formed similar to G6. Irrespective of laser protocol, any of the specimens showed presence of cracks and carbonization. It is suggested that the pulse width 600?s (G4) is the most suitable pulse width protocol as an alternative surface treatment, promoting micro-retention, with little loss of volume of material, comparable to gold standard treatment.

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