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Karlsson, Patrik. "Tribological characterization of selected hard coatings". Thesis, Karlstad University, Faculty of Technology and Science, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-4219.
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Hard coatings are often used for protection of tool surfaces due to coating properties like low friction and high wear resistance. Even though many of the hard coatings have been tested for wear, it is important to try new wear test setups to fully understand tribological mechanisms and the potential of hard coatings. Few experiments have been performed with dual-coated systems where the sliding contact surfaces are coated with the same, or different, hard coating. The dual-coated system could be the solution to many new technical devices and perhaps a further improvement of conventional coated systems.
In this thesis, the wear tests of dual-coated systems were performed in dry reciprocating sliding mode at room temperature. This, quite off the ordinary, wear test setup was performed to study selected hard coatings and set focus on wear mechanisms in forthcoming future surface coating application areas like MEMS and orthopedic implants.
Wear tests of four different PVD hard coatings, CrN, TiAlN, WC/C and diamond-like coating (DLC) were performed in a slider-on-flat-surface (SOFS) tribo-tester with reciprocation sliding mode at room temperature and dry sliding with TiAlN coated counter body. Wear mechanisms and the amount of wear were estimated, by investigation of the wear scars produced in SOFS, by means of scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical profilometer (OP).
Typical wear mechanisms found for coated surfaces in reciprocation sliding contact were crack formation, surface flattening for shorter sliding distance, elongation of surface defects, debris and thin film formation. Two types of film formation were found: tribo-oxidation film and formation of a self-lubrication film. The tribo-oxidation was the most evident for CrN and the formation of a self-lubrication film was revealed for DLC, where smearing of asperities were the initiation of the process. The DLC coatings showed lowest friction coefficient and worn volume of all the selected hard coatings.
Adhesion measurements were performed for all coatings by AFM. Both the unworn and worn surface of each coating were investigated and two coatings, DLC and TiAlN, showed low adhesion forces, which indicated promising properties for small scale devices like MEMS and NEMS with coated, non-sticking, surfaces.
Grundutbildningsprogram: Civilingenjör Bred IngångInriktning: Civilingenjör Maskinteknik och Materialteknik
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Baxi, Juhi Bhaskar. "Tribological characterization of coatings and nanofluids". [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2997.
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Luo, Dabing. "Selection of coatings for tribological applications". Ecully, Ecole centrale de Lyon, 2009. http://www.theses.fr/2009ECDL0017.
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Coatings are often used to reduce friction and protect the substrate surface from wear. However, selecting the appropriate coating from numerous ones for a given tribological application is still complicated because the tribological response of a coating system depends on many factors. The objectives of the thesis are to develop a coating pre-selection tool, and to propose some approaches to evaluate and compare coatings, sequentially to help the coating selection. Based on the study of literature and three different tribological cases, a pre-selection tool is developed by comprehensively considering the requirements and limits of applications and the characteristics of coatings. Two kinds of experiments are carried out to understand the relationships between tribological behaviors and running conditions and coating properties. Pressure sprayed MoS2 coating is investigated under three contact configurations to identify the effect of test conditions on its tribological performance. The coating lifetime can be predicted by relevant dissipated energy master curves. 5 bonded solid lubricant coatings are studied by simple evaluation techniques and fretting tests. The tribological performances of the coatings are closely related to their properties, and the simple evaluation techniques can be used to screen out the poor coatings. The tribological performances of the coatings are evaluated by comparing their dissipated energy – coating lifetime master curves. The best coating can be selected by synthetically comparing the coatings from various aspects in a polar diagramLes revêtements sont souvent utilisés pour réduire le frottement et protéger les surfaces contre l’usure. Cependant, choisir le revêtement approprié pour une application tribologique donnée est toujours compliqué pare que la réponse tribologique d’un système revêtu dépend de beaucoup trop de facteurs. Les objectifs de cette thèse sont de développer un outil de pré-sélection de revêtements, et de proposer quelques approches permettant d’évaluer et de comparer des revêtements. Basé sur l’étude de la littérature et sur trois études de cas tribologiques, un outil de pré-sélection est développé, en considérant tous les aspects des exigences requises et des limites d’application et caractéristiques des revêtements. Deux études expérimentales sont ensuite effectuées. Un revêtement de MoS2 pulvérisé sous pression est examiné dans trois différentes configurations d’essai pour identifier l’effet des conditions d’essai sur sa performance tribologique. La durée de vie de ce revêtement peut être prévue par les courbes maîtresses basées sur l’énergie dissipée. Cinq revêtements de type vernis de glissement sont également étudiés par des techniques simples d’évaluation et par des essais de fretting. Les performances tribologiques de revêtements dépendent de leur propriétés, et les techniques simples dévaluation peuvent être utilisées pour éliminer de mauvais revêtements, lors du processus de choix. Les performances tribologiques des revêtements sont évaluées en comparant les courbes maîtresses reliant durée de vie et énergie dissipée. Le meilleur revêtement peut alors être choisi, en comparant synthétiquement les revêtements selon divers aspects dans un diagramme polaire
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Simonson, William Jeffrey. "Tribological Properties of Mo2N-based Adaptive Coatings". OpenSIUC, 2009. https://opensiuc.lib.siu.edu/theses/15.
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Adaptive coatings are an important development in tribology. These coatings widen the range at which solid lubricants are useful in various environments. In this paper, coatings founded on molybdenum nitride are studied, with a focus on thermal cycling. These coatings were fabricated by unbalanced magnetron sputtering and characterized with techniques including x-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, energy dispersive x-ray spectroscopy (EDS), and pin-on-disk tribometer. The results of two sets of coatings are reported. The first set of coatings is a nanocomposite of Mo2N/MoS2/Me (Me = Ag, Au, Cu). The second is a complex multi-layer system of Mo2N/Ag and a diffusion barrier of TiN which has been etched, then filled and coated with a layer of MoS2. After heating, these compounds produced silver molybdates. The Mo2N/MoS2/Ag nanocomposite shows promise with a 0.02 coefficient of friction at room temperature, while the multi-layer system eventually equilibrated at approximately 0.6. At high temperatures, again the nanocomposite was better, producing a 0.25 frictional coefficient compared to a 0.3 from the multilayer system. These results provide insight into what is needed to achieve thermal cycling.
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Ahmed, Omer. "Tribological and Mechanical properties of Multilayered Coatings". University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1501763970144729.
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Mallia, Bertram. "Novel Nanostructured Coatings for Extreme Tribological Environments". Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491642.
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The degradation of material surfaces is a 'valve' that has limited technological progress through the ages. Today's most challenging environments are those where component surfaces are exposed to the simultaneous or sequential actions of corrosion and mechanical wear. These phenomena can be mitigated by a better understanding of the interactions between the multiple degradation mechanisms and the systematic development of alternative material surfaces. In this work, PVD coatings based on the Fe-Cr-Ni, Cr-Ti, Cr-B-(N) and W-(B) material systems were developed using unbalanced magnetron sputtering and mainly applied to AISI 316L, Ti-6AI-4V and Ortron 90 substrates respectively. For Fe-Cr-Ni and Cr-Ti coatings, post deposition heat treatments were conducted to stimulate the formation of the cr-FeCrNi and Laves Cr2Ti intermetallic phases respectively. In all cases, the morphology, chemical composition, structure, mechanical properties, corrosion behaviour and damage tolerance of the various coated materials were investigated. Special emphasis was placed on the response of the coated materials and uncoated test-pieces to the simultaneous action of corrosion and mechanical wear that resulted from sliding an Ah03 ball against the coated and uncoated materials in a 0.9 wt%NaCI solution. For one case only, W-(B) coated AISI 52100, lubricated rolling/sliding contact durability was assessed. For the corrosion-wear tests, the removal and regeneration of the passive layer (type I corrosion-wear) dominated the material loss. A high coatings hardness for'Fe-Cr-Ni and CrTi coatings was often beneficial to reduce the mechanical wear but the corrosion due to wear frequently remained high. Partial post deposition oxidation of Fe-Cr-Ni coatings was very effective in reducing the latter. Also of importance was the roughening of the Ah03 counterface due to the formation of tribo/transfer films or grain pull out. The material loss for Cr-B-(N) coatings was dominated by a material transfer mechanism and Ah03 grain pull out resulted in high mechanical wear of amorphous Cr-Ti coating. W-(B) coatings generally had low material loss and their crystalline variants displayed a low p.. The latter became inappropriate for conditions which promote high W dissolution. In lubricated rolling/sliding tests W-(B) coated AISI 52100 performance was·dependent on coating crystal structure and boron supersaturation. The crystalline coatings with low boron supersaturation displayed the best rolling/sliding damage resistance.
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Renman, Viktor. "Tribological testing of DLC coatings for automotive applications". Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-177355.
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In this work, the friction and wear behavior of three DLC coatings was evaluated in various conventional and alternative fuels as well as in commercially available formulated engine oils and additive-free synthetic oil. The first DLC has a thin top-coating of hydrogenated amorphous carbon (a-C:H), the second consists of Si-doped DLC (a-C:H:Si) and the third is a W-doped multilayered structure of a-C:H and a-C:H:W. The tribological tests were performed using a ball-on-flat reciprocating rig at low contact pressures. Methods such as white light interferometry (VSI), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), Raman spectroscopy, transmission electron spectroscopy (TEM) and electron spectroscopy for chemical analysis (ESCA/XPS) were used for analyzing and characterizing the coatings and counter surfaces in an effort to gain an understanding of the tribological mechanisms involved.
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Stoyanov, Pantcho. "Micro-tribological performance of metal-doped MoS2 coatings". Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103709.
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The mechanical and tribological properties of pure MoS2, pure Au, Au-MoS2 and Ti-MoS2 coatings were evaluated and examined at a microscopic scale. The metal doped MoS2 coatings had varying metal content, 5-10at% for Ti and 10-90% for Au. Reciprocating sliding wear tests were performed with a range of initial Hertzian contact pressures from 0.41 to 3.5 GPa and in air at two humidity levels (i.e. "low" being 3-5%RH and "high" being 30-40%RH). Titanium and gold were chosen for this study as metal additives due to their positive influence on the mechanical properties of the coating. The friction and wear behavior at the micro-scale were directly compared to tribological properties at the macro-scale, which were performed using an in situ tribometer. Reciprocating micro- and macro- wear tests were performed with spherical diamond tip (with 10 and 50 µm radii) and a sapphire tip (with a radius of 3.175 mm), respectively. The range of initial Hertzian contact pressures for macro-scale (i.e. between 0.41GPa and 1.2GPa) overlapped with that for micro-scale. However, the initial Hertzian contact diameters (2*a) were very different (i.e. 0.8-2.3 µm for micro-scale and 60-180 µm for macro-scale). It was observed that the small addition of Ti or Au to MoS2 improved the microtribological properties (i.e. lower friction and less wear) compared to pure MoS2 coatings. The improved microtribological properties with metal additions were attributed to an increase in the mechanical properties, decrease in adhesion, and a decrease in the interfacial shear strength. In terms of the different length scales, lower steady state friction was observed for macrotribology compared to microtribology. The higher friction at the micro-scale was explained by the greater adhesion effects and additional velocity accommodation modes (e.g. microplowing or plowing). The microplowing or plowing at the microscopic scale was attributed to the tip roughness and the inability to sustain a stable transfer film throughout the tests at high humidity. In addition, using in situ and ex situ techniques, three different stages for solid lubrication were identified based on differences in contact area, tip shapes, and environmental conditions. The first stage has been previously observed with macrotribology on MoS2 coatings at low humidity levels. The second stage, on the other hand, was observed for micro-tribology where the contact size is significantly smaller compared to stage one. The main wear mechanism is still adhesion, but there is also some micro-plowing. The final stage was observed for humid sliding in microtribology, where no transfer films were observed and therefore the main wear mechanism was plowing.Les propriétés mécaniques et tribologiques de revêtements de MoS2 pur, d'Au pur, de Au-MoS2 et de Ti-MoS2 ont été évaluées et examinées à l'échelle microscopique. Les revêtements nanocomposites étudiés contenaient 5-10 % at. de Ti et 10-90 % at. d'Au. Des tests d'usure par glissement alternatif ont été mis en œuvre, l'échelle de pression Hertzienne de contact initiale variant de 0.41 à 3.5 GPa, dans une atmosphère d'air avec deux niveaux d'humidité contrôlée (le niveau le moins élevé se situant entre 3 et 5 % HR et le plus élevé entre 30 et 40 % HR). Pour cette étude, le titane et l'or ont été choisis comme additifs métalliques pour leur influence positive sur les propriétés mécaniques des revêtements. Les comportements de friction et d'usure des revêtements à l'échelle microscopique ont été directement comparés à leurs propriétés tribologiques à l'échelle macroscopique, dont les tests étaient effectués à l'aide d'un tribomètre in situ. Des tests sclérométriques alternatifs ont été réalisés aux échelles microscopiques et macroscopiques avec des pointes de diamant sphérique (10 et 50 µm de rayon) et une pointe de saphir (ayant un rayon de 3.175 mm). La gamme de pression Hertzienne de contact utilisée à l'échelle microscopique (entre 0.41 GPa et 1.2 GPa) était très proche de celle utilisée à l'échelle macroscopique. Cependant, le diamètre de contact Hertzien initial (2*a) était très différent, soit 0.8 – 2.3 µm à l'échelle microscopique et 60 – 180 µm à l'échelle macroscopique. Les résultats montrent que l'ajout de faibles quantités de Ti ou d'Au au MoS2 améliore les propriétés micro-tribologiques (comportements à la friction et à l'usure atténués) en comparaison avec des revêtements de MoS2 pur. L'amélioration des propriétés micro-tribologiques due à l'addition de métaux a été attribuée au renforcement des propriétés mécaniques, une adhésion plus faible et une baisse des contraintes de cisaillement interfaciales. Si l'on compare des tests micro- et macro-tribologiques effectués sur des étendues de longueur variées, ces derniers étaient caractérisés par une friction en régime permanent moins élevée. Le comportement de friction plus accentué dans le cas des tests réalisés à l'échelle microscopique s'explique sur la base d'effets d'adhésion plus importants et des modes additionnels de compensation de vitesse (labourage ou micro-labourage). Les tendances au labourage ou micro-labourage observées à l'échelle microscopique ont été attribuées à la rugosité de la pointe de diamant et à la difficulté de maintenir une couche de film de transfert en place lors de tests effectués dans des conditions d'humidité élevée. L'utilisation de techniques in situ et ex situ a également permis de déterminer trois stades de lubrification solide, en se basant sur des différences observées à la zone de contact, dues aux formes des différentes pointes et aux conditions environnementales appliquées. Le premier stade, avait été identifié auparavant, lors de tests de macro-tribologie sur des revêtements de MoS2, à un niveau d'humidité faible. Par contre, le deuxième stade n'a été observé que lors de tests de micro-tribologie où la taille de la zone de contact était bien plus petite que dans le cas du premier stade. A ce stade, le mécanisme d'usure est principalement relié au comportement d'adhésion du revêtement, avec une influence possible de l'effet de micro-labourage. Le stade final de lubrification a été observé lors de tests de micro-tribologie réalisés dans des conditions d'humidité élevée et caractérisés par l'absence du film de transfert. De cette observation, il a été déduit que le principal mécanisme d'usure du film à ce stade de lubrification correspondait au labourage.
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Simonson, W. Jeffrey. "Tribological properties of Mo₂N-based adaptive coatings /". Available to subscribers only, 2009. http://proquest.umi.com/pqdweb?did=1879993791&sid=2&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Roy, Amit. "Tribological Performance of Polymer Based Self-lubricating Coatings". Thesis, Luleå tekniska universitet, Maskinelement, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75576.
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The thesis comprises the two parts in each chapter: the first part focuses on the development and characterization of polyimide (PI) based composite coatings on a steel substrate. In order to improve the tribological performance of polyimide coatings, the fillers i.e. multi-walled carbon nanotubes (MWCNTs) and Graphene (GP) were added into PI and conducted friction test at elevated temperatures ranging from room temperature (RT) to 200°C. Also, the influence of fillers (MWCNTs and GP) materials into PI coatings surface, mechanical and tribological properties of polyimide composites coatings are measured. The addition of MWCNTs and GP reduces the friction coefficient as well as wear volume at elevated temperatures 50°C, 100°C and sometimes at 150°C. These temperatures play a vital role to form a lubrication layer in the contact interfaces at certain load and operating conditions. In these cases, three weight percentage (3wt%) of MWCNTs and GP into polyimide composites showed low friction and high wear-resistant as compared to other PI composites. Besides, by adding these two fillers into pure PI improved the mechanical properties such as micro-hardness and nanoindentation. The scanning electron microscope (SEM) was used to observe the wear mechanism of the composite coatings worn surfaces. The consequences expose that the fatigue wear mechanisms were predominant in the worn surfaces. Moreover, the thermal study of the polyimide composite coatings was conducted using thermal gravimetric (TG) to analyze the behavior of composite coatings at high temperatures. The results showed that the PI coatings with MWCNTs and GP have high thermal stability at 60% sample residue. In the second part-an epoxy coatings with filler materials e.g. hexagonal boron nitride (h-BN) and expanded graphite (EG) were made and conducted their tribological i.e. friction coefficient and wear performance. Also the perfect mixing ratio 4:1 (80 wt% base epoxy matrix and 20 wt% curing agent) was determined on the basis of stoichiometric ratio to cure the epoxy accurately. Therefore, seven samples with a various weight percentage (wt%) were prepared i.e. pure epoxy, epoxy with 5wt%, 10wt%, 15wt% of h-BN and EG. All the prepared samples ran at two different loading 2 N and 4 N conditions with 5 Hz frequency, 300 rpm and 30 minutes duration. The epoxy with h-BN showed low friction as compared to EG where EG has better wear-resistant behavior than h-BN.
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Boban, Greg. "Tribological Comparison of Traditional and Advanced Firearm Coatings". DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/361.
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The objective of this project is to find which type of coating has the best performance characteristics for finishing firearms. This is accomplished by measuring and comparing several performance characteristics, such as: adhesion, hardness, wear resistance, friction control, and corrosion resistance. Appearance is not a factor since any exterior coating that is flashy can be subdued or camouflaged with special purpose paints, which have proven durable enough for such purposes. Cost will not be a limiting factor for this experiment, but will be discussed in the conclusion as a secondary concern. This data will be used to identify the best coating for steel and aluminum firearm parts. The goal is to lengthen a firearm’s life cycle while increasing performance and reliability by applying the best coating.
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Wu, Jianhui. "Tribological behavior of WC-DLC-WS2 (WCS) nanocomposite coatings". Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1094675462.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xix, 188 p.; also includes graphics. Includes bibliographical references (p. 179-188).
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He, Yang. "Electrodeposition of nickel-based composite coatings for tribological applications". Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/385841/.
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The purpose of this research is to study, evaluate, and compare the different electro deposition processes for producing nickel-based composite coatings for application in tribology, including: Ni/BMA luminescent coating, Ni-P/MoS2 and Ni-P/WS2 self-lubricating coatings. In the first part, a new luminescent Ni coating containing an embedded, blue emitting rare-earth mixed metal oxide (BaMgAl11O17:Eu2+) BAM was electrodeposited successfully from an aqueous electrolyte. Two types of surfactants were utilised to investigate the effective co-deposition of these phosphors into the nickel matrix. The surfactants of non ionic PEG (polyethylene glycol) and cationic CTAB (cetyl trimethylammonium bromide) were observed to increase the phosphor contents in the deposit from zero to 4.6% and 11.5%, respectively. A mixture of these two surfactants produced the highest particle embedded coverage (15.6%). Systematic study of the hardness, corrosion, tribological and luminescent properties of the as-deposited coating was performed before using it for wear sensing. In the second and third parts of this research, a self-lubricating Ni-P/MoS2 composite coating hasbeen designed and deposited on a mild steel substrate by electrodeposition. The effect of current density, electrolyte additive and MoS2 concentration on the structure of the coating have been investigated. The Ni-P/MoS2 coating exhibited a dramatic reduction in friction compared to an electrodeposited Ni-P coating, the coefficient of friction against a bearing steel ball in sliding wear being as low as 0.05. The worn surfaces and the wear debris were characterised by surface analysis techniques. The composite coating showed only slight wear and oxidation compared to the severe wear and oxidation observed in the pure Ni-P coating or the uncoated mild steel substrate. It has been speculated that MoS2 in the coating underwent shear stress-induced reorganization, fragmenting into fine crystallites and ultimately forming a smooth lubricating film. In the final part, Ni-P/WS2 composite coatings have been electrodeposited from an aqueous bath containing suspension of WS2 nanoparticles (80 nm) and their tribological properties have been evaluated by a reciprocating test with bearing steel balls. Increasing the bath temperature did completely eliminate the cracks in coatings by reducing the internal stress and prolonged the duration of the low friction coefficient. By optimizing the combinations of the WS2 and CTAB concentrations in solution, the amount of the WS2 particles incorporated was greatly boosted, demonstrating a highest WS2 content of 4.8 wt%. Significantly, this Ni P/WS2 coating exhibited a greatly lower friction coefficient of 0.17 compared to single Ni-P (0.6).
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Batista, Junia Cristina Avelar. "Promising duplex coatings for tribological applications at elevated temperatures". Universidade Federal de Minas Gerais, 2001. http://hdl.handle.net/1843/BUDB-8DNJCJ.
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The world iron ore production boomed by an expanding steel market forced the producers to seek for larger reserves achieved only through the better understanding of their mineral resources. This is possible through a detailed characterization of the natural resource and of the ores to be exploited. In this study it was performed a detailed mineralogical characterization of the Alegrias mines amphibolitic itabiriteswhich represents 36% of the total resources and more than 20% of Samarcos reserves and are mined either as ore and waste. The first purpose of this study was to identify different types of amphibolitic itabirites based on their chemical and mineralogical characteristics as well as on their performance through laboratory tests that simulate Samarcos production processes. The second purpose was to have amore detailed chemical and mineralogical characterization of the several aliquots coming from the products of the laboratory simulating processes tests. It was identified in Alegrias Mines five visual different amphibolitic itabirites and from each one it was taken 400kg to compose the samples. The samples were submitted to size and chemical analysis, x-Ray diffratometry, infrared spectrometry, thermogravimetry, opticaland scanning electron microscopy, microprobe, grinding, desliming and flotation laboratory tests. The products of these laboratory processes tests were also analyzed. More five tons of each sample was taken in order to produce concentrates to generate pellets to be tested in Pot Grate furnace. The five amphibolitic itabirites are not compact and potentially ore. Their iron content are typical of the poor itabirites (<50%), the LOIs are considered high tenures (>3%), the Al2O3, as well as MnO2 and FeO contents are within the typical values presented by the Alegrias ores. The main iron ore minerals are goethite (botryoidal, massive,pseudomorphs of amphibole, product of the alteration of the magnetite and earthy) and the porous martitic hematite. The iron ore minerals alteration and porosity grades are elevated and the size of their particles variable (from few micrometers to millimeters). The goethites loss their hydroxyl content in an abrupt way and around 315°C. The slimes percentages of these itabirites are high and by their weight and metallic global recoveries numbers they can be classified as potential ores. Simple modifications on the ignition Pot Grate furnace parameters leaded to improvements and to pellets within the required specifications. The five amphibolitic itabirites are suitable to be divided into four different types. The mineralogical association of amphiboles, iron oxides, quartzand carbonates present on the fresh amphibolitic itabirites recently found in Alegrias mines reinforce their origin to be the iron ore formations of the silicate or oxide-silicate facies associated with carbonates impurities or layers.O aumento de produção de minério de ferro, demandada por um mercado siderúrgico aquecido e em franco crescimento, tem levado à necessidade das empresas mineradoras de aumentarem suas reservas através do conhecimento melhor de seu recurso mineral. Isso só é possível através da caracterização detalhada de suas jazidas e dos minérios a serem explotados. Neste trabalho, foi proposto fazer-se umestudo de caracterização mineralógica dos itabiritos anfibolíticos das minas de Alegria, que representam 36% do total dos recursos geológicos da Samarco e cerca de 20% de sua reserva total e que ora são lavrados como minério ora são dispostos como estéril. Os objetivos desse trabalho foram o de identificar diferentes tipos de itabiritoanfibolítico nas minas de Alegria, baseando-se em suas características químicas, mineralógicas e de comportamento em testes que simulam o processo produtivo da Samarco Mineração S.A., além de fazer-se uma caracterização química e mineralógica mais detalhada, de diversas alíquotas provenientes dos testes de laboratório. Para tanto, foram identificadas cinco amostras de itabiritos anfibolíticos visualmente distintos e pertencentes às minas de Alegria 3/4/5, Alegria 1/2/6 eAlegria 9. De cada amostra, foram coletados 400kg para serem submetidos às análises granulométricas, químicas, difratometria de raios-X, espectroscopia no infravermelho, termogravimetria, microscopia óptica, microscopia eletrônica de varredura e microanálise EDS, além de testes de laboratório de moagem, deslamagem e de flotação de bancada cujos produtos foram também analisados. Foram aindaamostradas cerca de cinco toneladas de cada itabirito anfibolítico, para a preparação de concentrados em planta piloto e a geração de pelotas para queima em forno de Pot Grate e determinação de suas principais características. Os cinco itabiritos anfibolíticos estudados não são compactos e, portanto, potencialmente minérios. Seus teores de FeT são típicos de itabiritos pobres (<50%), os de P são relativamente altos (>0,050%), os de PPC são elevados (>3%) e os de Al2O3 MnO2 e FeO estão geralmente dentro da faixa média dos minérios das minas deAlegria. Os principais minerais de ferro são a goethita (botrioidal, maciça, pseudomórfica de anfibólio, produto de alteração da magnetita e terrosa) e a hematita martítica porosa. Os graus de alteração e de porosidade dos minerais de ferro são elevados e o tamanho de suas partículas é bem variado (desde poucos micrometros até milímetros). A desidroxilação das goethitas ocorre de forma relativamente abruptae por volta de 315°C. A porcentagem de lama desses itabiritos é relativamente elevada e suas recuperações em massa e metálicas globais os classificam como potencialmente minérios. Simples modificações nos parâmetros de queima levaram a melhores queimas e a pelotas dentro dos parâmetros de especificação. Para os cinco itabiritos anfibolíticos estudados, propõe-se a formação de quatro tipos diferenciados.A associação mineralógica de anfibólios, óxidos de ferro, quartzo e carbonatos, encontrada nos itabiritos anfibolíticos frescos recém-identificados nos furos de sondagem de Alegria, corroboraram sua origem atribuída a formações ferríferas da fácies silicato ou óxido-silicato, contendo intercalações e impurezas carbonáticas.
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Abdul-Mahdi, F. S. "Tribological characteristics of coatings on aluminium and its alloys". Thesis, Brunel University, 1987. http://bura.brunel.ac.uk/handle/2438/5016.
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Hard anodising on aluminium and its alloys has been widely practised for many years in order to improve the resistance of the otherwise poor wear characteristics of aluminium. In recent years there has been an increasing interest in other treatments and coatings, on both aluminium and other base metals. The aim of this investigation is to explain the tribological performance and wear mechanism(s) of an uncoated aluminium alloy, four anodic coated alloys, and also an electroless nickel alloy. All of the coatings are produced on three different aluminium alloys. The thickness of the anodic films is 30-35 micron, as this thickness falls within the range commonly used by industry. In an endeavour to explain the role of coating thickness on wear life, electroless nickel alloy has been produced in a range of thicknesses of 10, 20 and 30 micron. To evaluate abrasive and adhesive wear, the samples were rubbed against a single point diamond and steel ball, respectively, in a reciprocating movement at room temperature and 65-75% relative humidity, under a wide range of load and sliding distance. Some tests continued to run until a breakdown of the coatings occurred, whilst other tests were interrupted at intermediate stages. This enabled the initiation and propagation of failure mechanisms to be studied. Abrasive wear was performed under dry conditions, whereas, adhesive wear was evaluated under both dry and lubricated conditions. Wear of these coatings was proportional to the applied load and sliding distance, but there was no direct relationship between wear and hardness. The tribological performance of these coatings appears to be dictated by a) the composition of the substrate, b) the chemical and physical nature of the coatings and c) the test conditions. Under boundary lubricated conditions there was a considerable increase in the wear life of the coatings. A three dimensional surface texture is superior to a machined surface, in controlling contact conditions. There is an approximate linear relationship between coating thickness and wear life for electroless nickel alloys. These coatings predominantly fail by adhesion, plastic deformation and brittle fracture. A microscopic model for fracture of brittle materials, under both static and dynamic conditions for abrasive and adhesive wear correlates very well with the behaviour of these coatings. Analytical interpretation of adhesive wear was made by separately calculating the coefficient of wear "K" of the counterbodies. This information enables an improved understanding of the wear test itself to be added to the model of the wear mechanisms involved.
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Beevers, Caroline F. "Structural and tribological properties of TiAlN coatings deposited by CFUBMS". Thesis, University of Salford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395861.
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Lang, Stéphane. "Multifunctional properties of nanostructured ZrO2-based coatings for tribological applications". Université Louis Pasteur (Strasbourg) (1971-2008), 2005. http://www.theses.fr/2005STR13010.
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Les contraintes appliquées aux composants moteurs ont fortement augmentées ces dernières années. Les pièces en contact tribologique doivent résister à de fortes charges, fonctionner avec des carburants à faible lubricité et résister à des chocs thermiques. Dans la dernière décennie, un nouveau type de films minces appelé nanocomposite a été développé. La plupart des investigations ont été réalisées avec des matériaux à base de nitrures ou de carbures. Les oxydes furent moins étudiés en raison de leur fragilité, bien que ces matériaux offrent une résistance à la corrosion et un stabilité thermique. Cette thèse propose une investigation de films nanocomposites à base d'oxydes pour applications tribologiques. Nous avons choisi ZrO2 comme oxyde pour des applications à haute température et le cuivre comme liant pour la ductilité mécanique. Le champ d'application de ce film a été élargi avec l'addition de carbone comme lubrifiant solide. Premièrement, l'énergie des ions et le courant d'ions furent corrélés avec les observations de particules capturées sur des grilles durant le procédé. Cette expérience fut appliquée à la déposition de films ZrO2/Cu. La structure du film fut corrélée aux propriétés mécaniques. Le comportement tribologique de ce film fut investigué dans différents environnements. La résistance à la friction fut testée à l'air (sec et humide) et avec des lubrifiants. Le bombardement ionique durant la pulvérisation réactive fut optimisé en pulsant les cathodes et en appliquant une tension négative au substrat. Dans ces conditions, des particules de 10 nm de diamètre furent capturées. Cette expérience fut vérifiée dans les revêtements ZrO2/Cu avec des particules d'une taille inférieure à 20 nm. La dureté de ZrO2/Cu resta constante jusqu'à 500°C. L'insertion de 35 atomique pourcent de carbone permis d'augmenter la dureté à 30 GPa. Le COF fut réduit à 0. 15. La dureté de ce film fut également stable jusqu'à 500°C. Le film doté de carbone est composé de particules ZrO2 et ZrC insérées dans une matrice de Cu et de carbone amorphe a-C:H. Ce revêtement présente un faible COF (0. 2) en contact tribologique indépendant de l'humidité. La résistance à l'impact de ce film fut assurée jusqu'à de fortes charges pour des durées moyennes et à des faibles charges pour des longues duréesThe loadings applied to engine components are increasing with the demand for more efficient, safer, and environmental friendlier cars. On the opposite to coatings for cutting applications, the future coatings should also protect the counterpart and reduce the friction between the bodies. In the past decade a new type of wear protective films -called nanocomposite coatings- showed promising results in terms of hardness and fracture toughness. Most of the investigations were performed with nitride or carbide-based materials. Oxides were less studied because of their brittleness, but these materials would offer the corrosion and temperature stability required in the future engines. In this work, we proposed an investigation of a nanocomposite coating based on oxides for tribological applications in various environments. We choose ZrO2 as oxide for high temperature applications and copper as surrounding. The properties of this coating were extended with the addition of carbon as solid lubricant material. First, we optimized the pulsed magnetron sputtering for the deposition of nanoparticles. This experience was applied to the deposition of ZrO2/Cu nanocomposite coatings. The Zr-Cu-O-C coatings were optimized for tribological applications under various environments. The film structure was correlated with the mechanical properties. The tribological behavior of this coating was investigated in various environments and wear conditions. The enhanced ion bombardment during the reactive sputtering was obtained by pulsing the cathodes, providing a high sputtering power to the targets, and applying a negative bias to substrate. Using these conditions, 10 nm-particles were captured. This experiment was verified in the ZrO2/Cu coatings with t-ZrO2 particles smaller than 20 nm. The insertion of 35 atomic percent carbon in the nanocomposite structure increased the hardness to 30 GPa and reduced the COF to 0. 15. The hardness of this coating was stable in annealing tests up to 500°C. The structure investigations showed the presence of ZrO2 and ZrC particles inserted in a matrix of copper and a-C:H. This coating presented a low COF independent of the humidity in sliding tests without lubricants. The impact resistance was assured at high loads for medium durations and at low loads for long durations
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Ronkainen, Helena. "Tribological properties of hydrogenated and hydrogen-free diamond-like carbon coatings /". Espoo [Finland] : Technical Research Centre of Finland, 2001. http://www.vtt.fi/inf/pdf/publications/2001/P434.pdf.
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Pai, Anil. "DEVELOPMENT OF TITANIUM NITRIDE/MOLYBDENUM DISULPHIDE COMPOSITE TRIBOLOGICAL COATINGS FOR CRYOCOOLERS". Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2886.
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Hydrogen is a clean and sustainable form of carrier of energy that can be used in mobile and stationary applications. At present hydrogen is produced mostly from fossil sources. Solar photoelectrochemical processes are being developed for hydrogen production. Storing hydrogen can be done in three main ways: in compressed form, liquid form and by chemical bonding. Near term spaceport operations are one of the prominent applications for usage of large quantities of liquid hydrogen as a cryogenic propellant. Efficient storage and transfer of liquid hydrogen is essential for reducing the launch costs. A Two Stage Reverse Turbo Brayton Cycle (RTBC) CryoCooler is being developed at University of Central Florida. The cryocooler will be used for storage and transport of hydrogen in spaceport and space vehicle application. One part in development of the cryocooler is to reduce the friction and wear between mating parts thus increasing its efficiency. Tribological coatings having extremely high hardness, ultra-low coefficient of friction, and high durability at temperatures lower than 60 K are being developed to reduce friction and wear between the mating parts of the cryocooler thus improving its efficiency. Nitrides of high-melting-point metals (e.g. TiN, ZrN) and diamond-like-carbon (DLC) are potential candidates for cryogenic applications as these coatings have shown good friction behavior and wear resistance at cryogenic temperatures. These coatings are known to have coefficient of friction less than 0.1 at room temperature. However, cryogenic environment leads to increase in the coefficient of friction. It is expected that a composite consisting of a base layer of a hard coating covered with layer having an ultra-low coefficient of friction would provide better performance. Extremely hard and extremely low friction coatings of titanium nitride, molybdenum disulphide, TiN/MoS2 bilayer coatings, DLC and DLC/MoS2 bilayer coatings have been chosen for this application. TiN film was deposited by reactive DC magnetron sputtering system from a titanium target and MoS2 film was deposited by RF magnetron sputtering using a MoS2 target. Microwave assisted chemical vapor deposition (MWCVD) technique was used for preparation of DLC coatings. These composite coatings contain a solid lubricating phase and a hard ceramic matrix phase as distinctly segregated phases. These are envisioned as having the desired combination of lubricity and structural integrity. Extremely hard coatings of TiN and DLC were chosen to provide good wear resistance and MoS2 was chosen as the lubricating phase as it provides excellent solid lubricating properties due to its lamellar crystal structure. This thesis presents preparation; characterization (SEM and XRD), microhardness and tribological measurements carried out on TiN and TiN/MoS2 coatings on aluminum and glass substrate at room temperature. It also presents initial development in preparation of DLC coatings.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Gustavsson, Fredrik. "Triboactive Component Coatings : Tribological Testing and Microanalysis of Low-Friction Tribofilms". Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-191223.
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Coatings are often used on critical components in machines and engines to reduce wear and to provide low friction in order to reduce energy losses and the environmental impact. A triboactive coating not only provides this desired performance, it also actively maintains the low friction by a structural or chemical change in a very thin top layer of these already micrometer thin coatings. This so-called tribofilm is often 5-50 nm thick and can be formed either from the coating itself or by a reaction with the counter surface or the surrounding atmosphere, i.e. gas, fuel, oil, etc. The tribofilm will maintain the wanted performance for as long as the system is not chemically disturbed. This thesis provides a detailed overview of the functionality of triboactive low-friction coatings, in many different systems. The majority of the tribofilms discussed, formed in very different environments, are built up by tungsten disulfide (WS2), which is a material similar to graphite, with a lamellar structure where strongly bonded atomic planes may slip over each other almost without resistance. The major difference is that WS2 is an intrinsically triboactive material, while graphite is not. However, graphite and other carbon-based materials can be made triboactive in certain atmospheres or by addition of other elements, such as hydrogen. The remarkable affinity and driving force to form such WS2 low-friction tribofilms, regardless of the initial states of the sulfur and tungsten, and even when the forming elements are present only at ppm levels, is a recurrent observation in the thesis. Addition of an alloying element to sputtered coatings of WS2 can improve its mechanical and frictional properties significantly. Several promising attempts have been made to find good candidates, out of which a few important ones are investigated in this thesis. Their achievable potential in friction reductions is demonstrated. By reducing friction, energy losses can be avoided, which also results in lower particle and exhaust emissions, which directly reduces the environmental impact. Triboactive coatings are shown to be a promising route to significantly improve tribological applications and allow more environmental friendly and energy efficient vehicles.
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Efeoglu, Ihsan. "The mechanical and tribological properties of ceramic sputter ion-plated coatings". Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334034.
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Tu, Wei-Lun Scharf Thomas W. "Processing, structure, and tribological property interrelationships in sputtered nanocrystalline ZnO coatings". [Denton, Tex.] : University of North Texas, 2009. http://digital.library.unt.edu/ark:/67531/metadc12207.
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Paudel, Yadab Kumar. "Tribological properties of adaptive [molybdenum nitride/molybdenum sulfide/silver] nanocomposite coatings /". Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1597633321&sid=7&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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binti, Nik Roseley Nik Roselina. "Fabrication and characterisation of DLC-graphene nanocomposite coatings for tribological application". Thesis, University of Leeds, 2019. http://etheses.whiterose.ac.uk/22712/.
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This work presents the development and characterisation of single and multilayer Diamond-Like Carbon (DLC)-graphene nanoplatelet (GNP) nanocomposite coatings. This study opens up a new challenge in the fabrication of carbon composites using DLC and GNP with enhanced mechanical and tribological properties. The purpose of the composite is to exploit the advantages of the excellent mechanical and tribological properties of graphene that have been reported by many works. The objectives of this thesis are to develop a method to fabricate DLC and GNP nanocomposite coatings, to prepare the nanocomposite coatings and to investigate their physical, mechanical and tribological properties. The fabrication of DLC-GNP nanocomposite coatings was carried out using the combination of spin coating of GNP and DLC deposition using PECVD. The two types of DLC-GNP that have been prepared are single-layer and multilayer. The surface morphology and microstructure of DLC-GNP was characterised using optical microscopy and Scanning Electron Microscopy (SEM). Focused Ion Beam (FIB) SEM was used to observe the layers in the composite and measure the thickness of the multilayer DLC-GNP nanocomposite coating. The coating comprises the interlayer, spin-coated GNP and DLC film. This study shows that an optimised post-treatment is required to substantially improve the adhesion strength of spin-coated GNP and thus that of the whole nanocomposite coating. It was observed that columnar structure was generated in-situ during a wear tests on coatings post-treated for more than 180 minutes. The results were unintentionally found after three hours of sliding test. The columnar structure contributed to the significant reduction of the coefficient of friction (CoF) to 0.06, and the wear rate compared to other samples. According to Raman spectroscopy analysis, both single and multilayer DLC- GNP nanocomposite coatings have typical spectra similar to that of pure DLC. However, DLC-GNP has a broad range of ID/IG ratio values compared to pure DLC due to the dispersion of spin-coated GNP. The observation though cross-section FIB also proved that DLC film covered the spin-coated GNP by creating a bonding layer during DLC film deposition. The multilayer DLC-GNP demonstrated major improvements in adhesion strength of almost doubling the value obtained by single-layer DLC-GNP. The wear resistance also increased remarkably which can be related to the enhancement of adhesion strength. It is proposed that the GNP in the composite is released during the running-in period and acted as a slider between the counterpart and coating.
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Savisalo, Tuukka S. "Enhancing the tribological properties of CrN/NbN nanoscale multilayer PVD coatings". Thesis, Sheffield Hallam University, 2008. http://shura.shu.ac.uk/20329/.
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This research developed a CrN/NbN coating with promising properties for tribological applications where corrosion plays a big role. Building on this knowledge base a novel approach to the surface treatment was selected, in which multiple layers, each chosen for a specific purpose, were optimised to combine the best properties of each. In this approach a careful consideration of macro- and microstructure of each layer is required in order to extract the good properties of each layer while eliminating the negative ones. It was shown in the work that, if such consideration is neglected, a catastrophic failure may follow. For example poor adhesion may cause a total failure of the coating. As the number of layers and interfaces increase a good understanding on the structure and the properties of each layer becomes very important as the number of parameters and possible combinations increase many times. In this whole work the intention was to take a very practical approach to the coating. The objective was to combine different approaches, such as duplex treatments and multi layering and investigate the specific interactions that are not otherwise apparent. The results of this work show that such an approach is viable and should lead to excellent results as long as the wear mechanisms of the coating are understood and the coating is correctly engineered for the application.
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Tu, Wei-Lun. "Processing, Structure, and Tribological Property Interrelationships in Sputtered Nanocrystalline ZnO Coatings". Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc12207/.
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Solid lubricant coatings with controlled microstructures are good candidates in providing lubricity in moving mechanical assembly applications, such as orthopedics and bearing steels. Nanocrystalline ZnO coatings with a layered wurtzite crystal structure have the potential to function as a lubricious material by its defective structure which is controlled by sputter deposition. The interrelationships between sputtered ZnO, its nanocrystalline structure and its lubricity will be discussed in this thesis. The nanocrystalline ZnO coatings were deposited on silicon substrates and Ti alloys by RF magnetron sputtering with different substrate adhesion layers, direct current biases, and temperatures. X-ray diffraction identified that the ZnO (0002) preferred orientation was necessary to achieve low sliding friction and wear along with substrate biasing. In addition, other analyses such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were utilized to study the solid lubrication mechanisms responsible for low friction and wear.
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Repka, Martin. "Research of Coatings of Hydrodynamically Lubricated Sliding Bearings for Combustion Engines". Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-320204.
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Hlavní náplní této dizertační práce je výzkum a vývoj nové povrchové vrstvy pro kluzná ložiska na bázi pevných lubrikantů v polyamid-imidové polymerní matrici se zlepšenými tribologckými vlastnostmi. Podklady pro materiálovou kompozici vzešly z expertízy komerčně dostupného povlaku, respektive jeho povrchovou analýzou v mezných operačních podmínkách. Charakterizace mazného oleje před a po tribotestování společně s detailní povrchovou analýzou dala podmínky pro vznik materiálové formulace. Další část práce se zabývá studiem přípravy a vývojem aplikačního nanášení s přípravou polymerní směsi. Nakonec je popsána studie vlivu sulfidu molybdeničitého a grafitu, jakožto pevných lubrikantů pro zlepšení třecích vlastností a hydroxidu vápenatého pro potenciální zpepšení otěruvzdornosti výsledného povrchu pro palikaci kluzných ložisek.
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Berger, Mattias. "Development and tribological characterisation of magnetron sputtered TiB2 and Cr/CrN coatings". Doctoral thesis, Uppsala universitet, Institutionen för materialvetenskap, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-635.
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The aim of this thesis was to develop wear resistant physical vapour deposited coatings of TiB2 as well as multilayers of Cr/CrN. The correlation between deposition parameters and fundamental coating properties such as microstructure, composition, residual stress and hardness has been investigated. Finally, the influence of these properties on the coating behaviour in tribological applications has been evaluated. It is shown that the use of electron bombardment of the growing coating during d.c. magnetron sputtering is beneficial for the growth of superhard TiB2 coatings. Furthermore, electron bombardment results in TiB2 coatings with significantly lower residual stresses than coatings deposited using ion bombardment. The low stresses in these coatings open up the possibility to deposit thicker PVD coatings, as confirmed in this thesis. In addition, the use of TiB2 coatings in tribological contacts against aluminium proved to be superior to many other commercial coatings used today, with respect to wear resistance, anti galling properties and a low friction. Finally, a model is proposed which explains the observation that the abrasive wear resistance of multilayered Cr/CrN coatings can outperform that of the individual constituents. The model was found to satisfactory predict experimental data.
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Knox, Paul. "Development of high performance tribological coatings for application onto hip joint prostheses". Thesis, University of Wolverhampton, 2010. http://hdl.handle.net/2436/94223.
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In this thesis Graphit-iC™, an amorphous carbon coating developed by Teer Coatings Ltd. was modified and deposited onto CoCr and WHMWPE substrates in order to improve the wear properties. It was identified that depositing a hard coating onto soft substrate would cause high stresses and lead to coating delamination. Consequently the polyethylene substrates were ion implanted with nitrogen to reduce the hardness differential at the substrate-coating boundary. The coating was characterised using a pin on disc method in order to determine wear and friction. Hardness and fatigue was characterised using nano-indentation and the coating adhesion was measured using scratch testing. Application of the coatings resulted in a significant reduction in wear. Wear factors as low as 3.65x10¯18m³/Nm were achieved for coated CoCr substrates compared to 3.53x10¯15m³/Nm reported in the literature for uncoated CoCr. The coating resulted in friction coefficients between 0.12 and 0.19 with hardness ranging from 6.65 and 15.63GPa. Similarly coating UHMWPE resulted in a reduction in the wear factor to less than 9.6x10¯17m³/Nm. It was concluded that the deposition of amorphous carbon coatings can improve wear of hip joint prostheses, although consideration must be made for the adhesion of the coating to the substrate so that it does not contribute to an early failure of the device. Improved adhesion can be achieved by reducing the hardness differential between the coating and adhesion, either through softening the coating or by using interlayers.
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Bello, Jelili Olakunle. "Evaluation and characterisation of the tribological properties of polymeric coatings for downhole application". Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414653.
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Algodi, Samer Jasim Mahmood. "Characterisation, modelling and tribological investigations of nano-structured TiC-based electrical discharge coatings". Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/55168/.
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Electrical discharge coating (EDC) is a surface modification process used to produce hard coatings from a sacrificial powder metallurgy (PM) tool electrode onto a target workpiece. However, the integrity of as-processed EDC surfaces, as reported on in literature, is generally poor, with limited understanding of the fundamental interactions between energy source and workpiece material, and the microstructural development of the surfaces created. This thesis explores, at the nano-scale, the deposition and microstructural development of ED processed cermet coatings. Emphasis is given to TiC-based ED coatings, prepared using a semi-sintered TiC tool electrode. A comprehensive study of TiC/Fe cermet coating microstructural development, as a function of ED processing conditions (current 2 - 19 A; pulse-on time 2 - 64 μs) is presented, using the combined characterisation techniques of scanning electron microscopy (SEM) / energy dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD) and cross-sectional transmission electron microscopy (TEM). The ED coatings were composites in nature, with complex banded nanostructures of TiC grains within an Fe matrix. Preferred TiC/Fe ED coatings on 304-SS, achieved under conditions of low processing energy (10 A current and 8 μs pulse-on time), exhibited low levels of cracks and porosity, with hardness values of ~ 1800 HV. The fraction of energy transferred to the workpiece, Fv, as a consequence of ED sparking, is an important parameter which affects directly individual crater geometry and the microstructural development of the near surface modified layer. Hence, a 2D transient heat transfer model is presented, using finite difference methods, and used to estimate effective values for Fv as a function of processing conditions, and thereby to predict coating layer thicknesses of developed microstructures through appropriate consideration of heat flow into the system. The model is validated against previous work in literature and with experimental observations. The modelling demonstrated a variation of energy transferred to the workpiece, of 17 - 23% for increasing current from 2 - 19 A at fixed pulse-on time of 8 μs; and 7 - 53% for increasing pulse-on time from 2 - 64 μs at fixed current of 10 A. Predictions for heat transfer and the cooling of melt pools, arising from single spark events, compared well with experimental observations for the development of these TiC/Fe cermet microstructures. The cooling phase had two distinct stages, with initial rapid non-uniform cooling within the first ~ 10 - 20 μs leading up to the onset of TiC crystallisation, followed by a more uniform stage of heat loss up to ~ 100 μs, leading up to the onset of Fe matrix solidification. The tribological behaviours of TiC/Fe ED cermet coatings on both HSS and 304-SS substrates were investigated, with reference Cu EDM surfaces. The wear resistance of these cermet coatings, on both substrate types, yielded dry sliding wear resistances up to two orders of magnitude greater than that of the substrate. Further, EDC cermet coatings on HSS were typically 2 - 4 times more wear resistant, depending on loading, than those deposited on 304-SS, with wear performances reflecting the composite nature of the coatings coupled with the mechanical properties of the substrates. Laser surface treatments, used to improve the surface integrity of the as-deposited coatings, through the elimination of cracks and porosity, acted to increase the wear rate for all samples, with the exception of coatings on HSS under conditions of high loading. The general increase in wear rate was attributed to a significant reduction in the proportion of TiC within the ED coatings, after laser treatment, combined with an increase in grain size; whilst improvements to the wear performance of laser treated, cermet coated HSS, under high loading, was attributed to the avoidance of an abrasive wear mechanism.
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Mandal, Paranjayee. "Tribological study of novel metal-doped carbon-based coatings with enhanced thermal stability". Thesis, Sheffield Hallam University, 2015. http://shura.shu.ac.uk/20012/.
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Low friction and high temperature wear resistant PVD coatings are in high demand for use on engine components, which operate in extreme environment. Diamond-like-carbon (DLC) coatings are extensively used for this purpose due to their excellent tribological properties. However, DLC degrades at high temperature and pressure conditions leading to significant increase in friction and wear rate even in the presence of lubricant. To withstand high working temperature and simultaneously maintain improved tribological properties in lubricated condition at ambient and at high temperature, both the transitional metals Mo and W are simultaneously introduced in a carbon-based coating (Mo-W-C) for the first time utilising the benefits of smart material combination and High Power Impulse Magnetron Sputtering (HIPIMS).This research includes development of Mo-W-C coating and investigation of thermal stability and tribological properties at ambient and high temperatures. The as-deposited Mo-W-C coating contains nanocrystalline almost X-ray amorphous structure and show dense microstructure, good adhesion with substrate (Lc -80 N) and high hardness (-17 GPa). During boundary lubricated sliding (commercially available engine oil without friction modifier used as lubricant) at ambient temperature, Mo-W-C coating outperforms commercially available state-of-the-art DLC coatings by providing significantly low friction (u- 0.03 - 0.05) and excellent wear resistance (no measurable wear). When lubricated sliding tests are carried out at 200°C, Mo-W-C coating provides low friction similar to ambient temperature, whereas degradation of DLC coating properties fails to maintain low friction coefficient. A range of surface analyses techniques reveal "in-situ" formation of solid lubricants (WS2 and M0S2) at the tribo-contacts due to tribochemically reactive wear mechanism at ambient and high temperature. Mo-W-C coating reacts with EP additives present in the engine oil during sliding to form WS2 and M0S2. This mechanism is believed to be the key-factor for low friction properties of Mo-W-C coating and presence of graphitic carbon particles further benefits the friction behaviour. It is observed that low friction is achieved mostly due to formation of WS2 at ambient temperature, whereas formation of both WS2 and M0S2 significantly decreases the friction of Mo-W-C coating at high temperature. This further indicates importance of combined Mo and W doping over single-metal doping into carbon-based coatings. Isothermal oxidation tests indicate that Mo-W-C coating preserves it's as-deposited graphitic nature up to 500°C, whereas local delamination of DLC coating leads to substrate exposure and loss of its diamond-like structure at the same temperature. Further, thermo-gravimetric tests confirm excellent thermal stability of Mo-W-C coating compared to DLC. Mo-W-C coating resists oxidation up to ~800°C and no coating delamination is observed due to retained coating integrity and its strong adhesion with substrate. On the other hand, state-of-the-art DLC coating starts to delaminate beyond ~380°C.The test results confirm that Mo-W-C coating sustains high working temperature and simultaneously maintains improved tribological properties during boundary lubricated condition at ambient and high temperature. Thus Mo-W-C coating is a suitable candidate for low friction and high temperature wear resistant applications compared to commercially available state-of-the-art DLC coatings.
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Drahorad, Nicolò. "Quantification of tribological effects in expansion fasteners". Thesis, KTH, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-247902.
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Post-installed anchors for civil construction are elements that ensure the integrity of building structures even under the most severe static, seismic and shock loadings. Despite the high popularity of this technology in construction sites all over the world, the current state of knowledge is limited and there is still a great potential for significant improvements. Specifically, expansion anchors’ mechanism relies purely on friction, therefore being able to manipulate and optimize their tribological behavior is key to meet strict safety regulations and develop outperforming and outlasting design solutions. This research project, conducted at Hilti Corporation in Schaan (Liechtenstein), presents an investigation of several antifriction coating solutions. Laboratory-scale tests have been performed to quantify the different coefficient of friction while, with full-scale standardized tests (anchor set in concrete), it has been possible to evaluate the overall mechanical performances of the specimens. Afterwards, the obtained data have been analyzed with numerical software and the samples have been further investigated with optical microscopy. The outcome of this thesis work is crucial for the development of the next generation of expansion fasteners and gives additional insights for a deeper understanding in the tribology of functional coatings.Eftermonterade fästankare i byggnader säkerställer byggnadsstrukturernas integritet, även under de mest allvarliga statiska, seismiska och chockbelastningar. Trots stor användning och popularitet på byggarbetsplatser över hela världen är det nuvarande kunskapsläget av denna teknik begränsat och det finns en stor potential för betydande förbättringar. Specifikt bygger expansionsankringsmekanismen på ren friktion. Därför är möjligheten att manipulera och optimera fästankarnas tribologiska beteende nyckeln till att uppfylla strikta säkerhetsbestämmelser och kunna utveckla bättre prestanda och designlösningar. Detta forskningsprojekt har utförts på Hilti Corporation i Schaan (Liechtenstein) och presenterar en undersökning av flera antifriktionsbeläggningslösningar. Laboratorieprov har utförts för att kvantifiera olika friktionskoefficienter, och efter fullskaliga standardiserade tester (med fästankare i betong) har det varit möjligt att utvärdera de övergripande mekaniska prestationerna av dessa. Erhållna data har analyserats numerisk och proverna har undersökts ytterligare med optisk mikroskopi. Resultatet av detta examensarbete är viktigt för utvecklingen av nästa generation expansionsfästen och ger även ytterligare insikt och en djupare förståelse av tribologin av funktionella beläggningar.
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Stone, D'Arcy S. "Tribological investigation of nanocomposite thin films of transitional metal nitrides with silver inclusions". OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/768.
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In this tribological study, a temperature dependent inquiry of the changes in chemistry and crystal structure of two selected double metal oxides is undertaken. It is known that chameleon coatings of Mo2N/Ag/MoS2 produce a friction coefficient of 0.1 from wear testing at 600 °C for 300,000 cycles. The low friction is attributed to the formation of silver molybdates layers, a lubricious double-metal oxide, in the coating. Double-metal oxides consisting of a group 6 transitional metal and silver (silver molybdate (Ag2Mo2O7) and silver tungstate (Ag2WO4)) were used for this investigation. Thin films and powders were investigated using high temperature x-ray diffraction, high-temperature Raman spectroscopy and differential scanning calorimetry in tandem with sliding tests from 25 to 600 °C. Our results were compared to external ab-initio molecular dynamic simulations performed elsewhere to qualify experimental results. The layered atomic structure of silver molybdate facilitates sliding, resulting in a low coefficient of friction (<0.2) from 300-500 °C. Unlike Ag2Mo2O7, however, Ag2WO4 does not possess a layered atomic structure and produced coefficients of friction (>0.4) in all temperature ranges between room temperature and 500 °C. Applying the knowledge gained from prior studies of the intrinsic properties of double metal oxides of group 6, chameleon coatings consisting of group 5 transitional metal nitrides (vanadium nitride, niobium nitride, and tantalum nitride) with silver inclusions were created using unbalanced magnetron sputtering to investigate their potential application as adaptive, friction reducing coatings. The coatings were tribotested against a Si3N4 counterface in the 22 to 1000 °C temperature range. In-situ Raman Spectroscopy measurements were taken during heating and wear testing at 700 °C to identify the evolution of phases in the coatings' surfaces and in the wear track. The chemical and structural properties of the coatings were also characterized before and after wear testing using x-ray diffraction. At higher temperatures, oxygen, silver and the transition metals react on the surface to form potentially lubricious double oxide phases (silver vanadate, silver niobate and silver tantalate). All coatings performed similarly up to 750 °C. The VN/Ag coating, however, had a lower coefficient of friction at 750 °C comparatively to TaN/Ag and NbN/Ag, likely due to its reported lower melting temperature (450 °C) and its layered crystal structure.
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Fallqvist, Mikael. "Microstructural, Mechanical and Tribological Characterisation of CVD and PVD Coatings for Metal Cutting Applications". Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-172364.
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The present thesis focuses on characterisation of microstructure and the resulting mechanical and tribological properties of CVD and PVD coatings used in metal cutting applications. These thin and hard coatings are designed to improve the tribological performance of cutting tools which in metal cutting operations may result in improved cutting performance, lower energy consumption, lower production costs and lower impact on the environment. In order to increase the understanding of the tribological behaviour of the coating systems a number of friction and wear tests have been performed and evaluated by post-test microscopy and surface analysis. Much of the work has focused on coating cohesive and adhesive strength, surface fatigue resistance, abrasive wear resistance and friction and wear behaviour under sliding contact and metal cutting conditions. The results show that the CVD deposition of accurate crystallographic phases, e.g. α-Al2O3 rather than κ-Al2O3, textures and multilayer structures can increase the wear resistance of Al2O3. However, the characteristics of the interfaces, e.g. topography as well as interfacial porosity, have a strong impact on coating adhesion and consequently on the resulting properties. Through the deposition of well designed bonding and template layer structures the above problems may be eliminated. Also, the presence of macro-particles in PVD coatings may have a significant impact on the interfacial adhesive strength, increasing the tendency to coating spalling and lowering the surface fatigue resistance, as well as increasing the friction in sliding contacts. Finally, the CVD-Al2O3 coating topography influences the contact conditions in sliding as well as in metal cutting. In summary, the work illuminates the importance of understanding the relationships between deposition process parameters, composition and microstructure, resulting properties and tribological performance of CVD and PVD coatings and how this knowledge can be used to develop the coating materials of tomorrow.
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Singh, Harpal. "An Investigation of Material Properties and Tribological Performance of Magnetron Sputtered Thin Film Coatings". University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1449850005.
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Jang, Dong-Seob. "Tribological behavior of soft metallic coatings on hard substrates for low load sliding applications /". The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487857546385896.
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Ascroft, Helen Louise. "Tribological evaluation of lubricant coatings in high speed and dry machining of aluminium alloys". Thesis, University of Birmingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.694638.
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Torkashvand, Kaveh. "Tribological behaviour ofHVAF-sprayed WC-based coatings: : Role of process variables and binder chemistry". Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-17484.
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Tungsten carbide (WC) based metallic matrix coatings sprayed using high velocity air fuel (HVAF) technique have attracted increasing attention as they show excellent tribological performance in various wear conditions. In the HVAF method, particles’ in-flight temperature and velocity can be influenced by the process variables including nozzle configuration as well as feedstock particle size range. On the other hand, the chemistry of metallic binder can also play a key role in determining both properties and performance of these coatings. In this thesis, characteristics and tribological behaviour of HVAF-sprayed WC-based coatings were investigated employing four different nozzle configurations (4L2, 4L4, 5L2and 5L4), and three different feedstock particle sizes of WC-CoCr feedstock powder (5/20, 5/30 and 15/45 μm). Also, characteristics and performance of coatings processed with four different WC-based feedstocks comprising alternative binders to traditionally used CoCr (namely CoCr, NiMoCrFeCo,FeNiCrMoCu and FeCrAl) were investigated. Characteristics of the coatings were explored by conducting scanning electron microscopy observations, microindentation testing and X-ray diffraction analysis. Performance of the coatings was evaluated by conducting sliding wear, dry jet erosion wear and sand rubber wheel abrasion wear testing. Moreover, material removal mechanisms in the coatings subjected to the above tests were investigated through post wear analysis. X-ray diffraction analysis showed that no considerable phase change compared to the starting feedstock was observed in any of the coatings sprayed by HVAF technique. It was revealed that decrease in powder particle size range can result in an improvement in microstructural characteristics, such as homogeneity and density, as well as hardness of the coatings. Besides, it can lead to a substantial improvement in wear performance of the coatings. It was shown that using various nozzle configurations does not result in any considerable change in characteristics or performance of the HVAF-sprayed WC-CoCr coatings. It was further shown that, by decreasing particle sizes from coarse to medium or fine, a significant difference can be observed. While wear mechanisms for medium and fine feedstock coatings were dominated by ploughing and fracture of individual carbide grains, for the coarse feedstock coatings ploughing and grooving along with the local removal of coating material were observed. Hardness values for all the four coatings with different binder chemistries were in a narrow range of 1100 – 1300 HV0.3. WC-NiMoCrFeCo and WC-FeNiCrMoCu coatings showed better or comparable sliding wear performance compared to WC-CoCr coating (as reference). WC-FeNiCrMoCu and WC-FeCrAl coatings showed comparable performance under erosion conditions while all the three binder alternatives yielded slightly inferior coating performance under abrasion wear, compared to the reference coating. While ploughing was the common wear mechanism in all the four coatings, pitting was noted in coatings with CoCr and FeNiCrMoCu binders in case of sliding wear.Populärvetenskaplig Sammanfattning Cermet-beläggningar består av WC-partiklar inbäddade i ett metallbindemedel,sprutat med High Velocity Air Fuel (HVAF) uppvisar utmärkt tribologiskprestanda under olika slitage förhållanden. Med HVAF-tekniken kan partiklarnasflygtemperatur och hastighet påverkas av konfigurationen av den utrustning somanvänds såväl som partikelstorleksintervallet för råmaterialet. Därtill kan kemin hos det metalliska bindemedlet spela en nyckelroll för beläggningarnas egenskaper och prestanda. I denna avhandling undersöktes egenskaper och tribologiskt beteende hos HVAF-besprutade WC-baserade beläggningar. Undersökningen gjordes genom att använda fyra olika uppsättningar av ändra sprutparametrar förHVAF-processen där fyra olika munstyckskonfigurationer (4L2, 4L4, 5L2 och5L4) och tre olika partikelstorleksintervaller av WC-CoCr råvarupulver (5/20,5/30 och 15/45 μm). Studieegenskaper och prestanda för alla deponerade beläggningar, påverkan av processvariabler (olika munstyckskonfigurationer och olika partikelstorlekar) undersöktes. Dessutom undersöktes egenskaper och prestanda för tre olika WC-baserade råvaror med alternativa bindemedel till CoCr (NiMoCrFeCo, FeNiCrMoCu och FeCrAl) och jämfördes med WC-CoCrbeläggningsom referens. Beläggningens egenskaper undersöktes genom att genomföra SEM-analys, mikroindragningstest och röntgenanalys. Beläggningens prestanda utvärderades genom att utföra glidförslitning, erosionsslitage under torra förhållanden och test med torr sand/gummihjulanordning. Vidare undersöktes mekanismer för materialavlägsning i beläggningarna med ovanstående tester genom analys efter slitage. Ingen avsevärd fasförändring observerades för alla beläggningar som besprutades med HVAF-teknik. Det avslöjades att minskning av pulvrets genomsnittliga partikelstorlek resulterade i en förbättring av mikrostrukturella egenskaper, såsom homogenitet och densitet, samt beläggningarnas hårdhetsvärde. Dessutom leder det till en avsevärd förbättring av beläggningens slitageförmåga. Det visades att användning av olika munstycken till HVAF-processen inte resulterar i en avsevärd förändring i egenskaper eller prestanda hos WC-CoCr-beläggningarna. När det gäller förslitningsmekanismer visades det att genom att minska partikelstorleken från grov till medium eller fin sågs en avsevärd skillnad. För beläggningar besprutade med fina och medelstora partiklar dominerades förslitningsmekanismer av plöjningsslitage och sprickor av enskilda hårdmetallkorn. För grova beläggningar observerades plöjningsslitage och spårning tillsammans med avlägsnande av material. Ingen signifikant skillnad i mikrostruktur eller fasförändring observerades i alla beläggningar med alternativa bindemedel såväl som WC-CoCr som referensbeläggning. Hårdhetsvärdet för alla de fyra beläggningarna låg inom x intervallet 1100 - 1300 HV0.3. NiMoCrFeCo och FeNiCrMoCu visade bättre eller jämförbar glidförmåga med referensbeläggningen. FeNiCrMoCu och FeCrAl visade jämförbara prestanda under erosionsförhållanden och alla de tre undersökta beläggningsmaterialen visade något sämre prestanda under nötningsslitage jämfört med referensbeläggningen. Medan plöjningsslitage var den vanliga förslitningsmekanismen i alla de fyra beläggningarna noterades gropning i beläggningarna CoCr och FeNiCrMoCu vid glidförslitning.
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Binfield, Mark L. "A tribological study of a detonation gun coating of tungsten carbide for use in a subsea gate valve". Thesis, Brunel University, 1995. http://bura.brunel.ac.uk/handle/2438/6363.
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Detonation gun coatings of tungsten carbide have been widely recognised as one of the most effective anti-wear coatings for oilfield applications. However, very little fundamental tribological information exists for the material, which hinders coating development and the evolution of correct specifications. This study redresses this problem by conducting adhesive, abrasive and erosive tests upon the coating and relating the findings to the coated microstructure. The intention has been to simulate the in-service behaviour of parallel gate valves, which are used primarily to control flow in remote locations where reliability and freedom from maintenance are essential. Although problems with such valves are rare, costs associated with replacement are exceptionally high and therefore a high research priority has been placed on valves of this type. Currently, new designs of valve are tested using a pipe loop rig at BP Research Centre. However, such tests are both expensive and time consuming and with the increasing desire to bring products to market more quickly an alternative is sought. Probably, the area offering most scope for improvement is in material specification of the sealing surfaces and this work sets out to produce a first stage selection procedure for candidate materials. Uniquely, the study has taken one component, systematically categorised its failure mechanisms using non-destructive replication techniques and then reproduced them in the laboratory. The failure analysis has pointed to three-body abrasion, erosion and adhesion being the dominant failure modes and therefore, a suite of tribo-test methods have been developed to replicate them These are namely reciprocating diamond-on-flat, slurry erosion and reciprocating pin-on-plate tests. The material studied was a proprietary detonation gun coating of tungsten carbide, LW45, which is currently the most popular seal facing material specified for gate valves. A conformal contact geometry was chosen for the reciprocating pin-on-plate tests and problems with alignment were overcome by using a pre-test running-in procedure with 1 μm metallographic paste. Wear of LW45 occurring during the pin-on-plate test was not affected by test speed over the range selected, but was highly dependent upon load. Four different categories ranging from minimal wear to catastrophic wear have been identified. Extensive post test analysis using optical and scanning electron microscopy has further classified the failure that occurs into two groups, termed mild and severe. In the mild regime wear occurs by preferential removal of the binder phase, which is minimised on further sliding by protruding carbide particles. Eventually sufficient binder is removed for carbide fall-out to occur, upon which the cycle is repeated. A greater wear volume is produced by the severe wear mechanism which is caused by the interlinking of cracks present within the microstructure of the coating. To ensure operation in the mild regime, continuous sliding under operating pressures of above 7.84 MPa should be avoided. Abrasive wear simulated by the diamond-on-flat test increased with load. However, the failure mechanisms produced were independent of load and consist of a combination of plastic deformation and brittle fracture with plastic deformation representing the rate controlling step in the wear process. Slurry erosion tests have shown that LW45 wears by a brittle erosive mechanism and is therefore best able to resist erosion at low impingement angles. The volume loss per particle impact for LW45 is proportional to the kinetic energy of the impinging particles. The failure mechanism involved the growth of cracks in the microstructure by a fatigue action eventually leading to crack interlinking and material fall out. For all wear conditions, it is suggested that the removal of microcracking from the coating microstructure will lead to significant improvements in wear performance. A simplified design guide has been produced that gives a weighted importance to the various failure modes attributable to the respective tests. A significant improvement in performance was recorded by LW45 in comparison to typical substrate materials such as AISI 410 and Ferralium F255 stainless steels.
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Mudhivarthi, Subrahmanya. "Dry Sliding Tribological Characteristics of Hard, Flat Materials with Low Surface Roughness". [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000197.
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Berger, Mattias. "Development and tribological characterisation of magnetron sputtered TiB2 and Cr/CrN coatings". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-4990-5/.
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Stallard, Joanne. "The tribological behaviour of three carbon-based coatings, tested in air, water and oil environments". Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420358.
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Bajwa, Rizwan. "Electroplated composite coatings with incorporated nano particles for tribological systems with the focus on water lubrication". Thesis, Bournemouth University, 2016. http://eprints.bournemouth.ac.uk/24757/.
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Increasing demand of water-lubricated mechanical components or systems requires the development of novel materials with better wear or corrosion performance in the adjoining water environment. This applies to broad oceanic applications, for example, marine vessels, conventional power plants, tidal and wave energy systems and other water-lubricated industrial bearings. The current research project aims to evaluate the feasibility of the electrodeposited Ni–based nanocomposite coatings for water-lubricated tribological systems. The tribological behaviour of newly developed nanocomposite coatings is assessed under immersed water lubrication. For this reason test rig modification is deployed, to allow tribometer (TE92) to accommodate water lubrication facility to replicate water-lubricated contacts. In this research tribological performance of electrodeposited nanocomposite coatings incorporating different nanoparticles, including Al2O3, SiC and ZrO2 are presented. Tribological performance experiments were conducted using modified ball-on-disc assembly with three ball system using TE92 Rotary Tribo-meter (Phoenix Tribology). The electrodeposition setup is installed for nanocomposite coatings. Different characterization tools including SEM, XRD, EDS and 3D surface profiling are used for nanocomposite coating investigations and to identify the optimized parameters for coatings in terms of tribological performance under water lubrication. Overall, the addition of nanoparticles into a nickel matrix shows improvements in tribological properties than conventional pure nickel coatings. The specific wear rate is reduced almost 30% and corrosion resistance property enhanced nearly double in nickel composite of silicon carbide and alumina coatings respectively. All the coatings are mainly consisted of dispersive part of surface energy indicating covalent bonding between surface and liquids.
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Wassborg, Pär. "Tribological evaluation of the contact between upper compression ring and cylinder liner with different surface coatings". Thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-45454.
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The constant pursuit in the automotive industry to increase the engines performance, new solutions are always developed and tested to reduce the friction and increase the efficiency in the engine. One component that contributes to friction losses is the piston ring pack where the top compression stands for up to 40 %. This master thesis collaborated with Scania’s material science department Basic engine and covers the friction and wear of four different materials on the cylinder liner surface against the top compression ring.The four tested materials were grey cast iron with different honing quality and three atmospheric plasma sprayed coatings with titanium oxide, chromium oxide and Metco’s mixture F2071 which is a stainless steel mixed with a ceramic. A martensitic steel piston ring with a chromium coated sliding surface was used for all the testing in the Cameron-Plint TE77 test-rig. This is a pin-on-disc test method and the parameters used for testing is set to replicate the environment the ring is exposed to at the top dead centre.The test-rig has been in Scania’s possession for a long time and has not always given a satisfying result. An uneven contact between the ring and liner has been a problem resulting in only worn edges of the liner specimen. The piston ring holder was therefore redesigned to be able to adjust the radius of the ring. This allowed a good conformability between the ring and liner to be obtained.The tested materials were evaluated according to friction and wear. Friction was measured with the test-rig and the wear was calculated with surface profiles that were measured before and after testing. Worn surfaces were studied in a SEM to verify which wear mechanism that was active. The changes of the surfaces was studied with the use of following surface parameters Ra, Rk, Rpk, Rvk and if there was a connection between these parameters and friction and wear coefficient.Independent of honing quality showed the grey cast iron lowest friction coefficient just under 0.13, the F2071 liner showed a friction coefficient just above 0.13. Both oxide layers showed similar friction where the chromium oxide had a friction just below 0.15 and the titanium oxide lay just above 0.15. Lowest wear coefficient had the chromium oxide followed by F2071, titanium oxide and the bad honed grey cast iron. These three liners showed almost the exact same wear coefficient. Worst wear coefficient had the grey cast iron with a good honing quality. A mild abrasive wear mechanism was active during the wear test and vague wear marks was found on the surface. There is no connection between wear coefficient and friction and the change in surface roughness during the test does not affect the friction.
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Ageh, Victor. "Processing, Structure and Tribological Property Relations of Ternary Zn-Ti-O and Quaternary Zn-Ti-Zr-O Nanocrystalline Coatings". Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699894/.
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Conventional liquid lubricants are faced with limitations under extreme cyclic operating conditions, such as in applications that require lubrication when changing from atmospheric pressure to ultrahigh vacuum and ambient air to dry nitrogen (e.g., satellite components), and room to elevated (>500°C) temperatures (e.g., aerospace bearings). Alternatively, solid lubricant coatings can be used in conditions where synthetic liquid lubricants and greases are not applicable; however, individual solid lubricant phases usually perform best only for a limited range of operating conditions. Therefore, solid lubricants that can adequately perform over a wider range of environmental conditions are needed, especially during thermal cycling with temperatures exceeding 500°C. One potential material class investigated in this dissertation is lubricious oxides, because unlike other solid lubricant coatings they are typically thermodynamically stable in air and at elevated temperatures. While past studies have been focused on binary metal oxide coatings, such as ZnO, there have been very few ternary oxide and no reported quaternary oxide investigations. The premise behind the addition of the third and fourth refractory metals Ti and Zr is to increase the number of hard and wear resistant phases while maintaining solid lubrication with ZnO. Therefore, the major focus of this dissertation is to investigate the processing-structure-tribological property relations of composite ZnO, TiO2 and ZrO2 phases that form ternary (ZnTi)xOy and quaternary (ZnTiZr)xOy nanocrystalline coatings. The coatings were processed by atomic layer deposition (ALD) using a selective variation of ALD parameters. The growth structure and chemical composition of as-deposited and ex situ annealed ternary and quaternary oxide coatings were studied by combined x-ray diffraction/focused ion beam microscopy/cross-sectional transmission electron microscopy, and x-ray photoelectron spectroscopy/Auger electron spectroscopy, respectively. It was determined that the structure varied from purely nanocrystalline (ternary oxides) to composite amorphous/nanocrystalline (quaternary oxides) depending on ALD parameters and annealing temperatures. In particular, the ZnTiO3 ilmenite phase with (104) textured nanocolumnar grains, exhibiting high stacking fault/partial dislocation densities >1012/cm2, was responsible for the excellent tribological behavior. Steady-state sliding friction coefficients down to 0.12 in humid air and 0.2 in dry nitrogen were measured along with sliding and fretting wear factors in the range of 10-6 to 10-7 mm3/N·m, even after ex situ annealing to 550°C. Additionally, the quaternary oxide phase Zn(Ti,Zr)O3 in solid solution exhibited a low fretting wear rate of 1x10-6 mm3/N·m. In contrast, certain phases, such as Zn2TiO4 cubic spinel, that form at annealing temperatures >550°C were responsible for high friction and wear. Mechanistic studies using the above techniques revealed low friction and wear-reducing surfaces and subsurfaces were due to different velocity accommodation modes (VAM). In the case of the ternary system, sliding-induced plastic deformation was possible when ZnTiO3 (104) stacking faults, bordered by partial dislocations, serve as a pathway for the dislocations to glide parallel to the sliding direction and hence achieve low friction and wear via an intrafilm shear VAM. It was evident that the individual nanocolumnar ZnTiO3 grains were plastically sheared as opposed to being fractured during wear. Conversely for the quaternary system, an interfacial sliding VAM between the counterface and a mechanically mixed layer (tribofilm) composed of the refined coating and counterface material, that also served as a source for the formation of cylindrical rolls, was responsible for wear reduction. Therefore, these lubricious oxides are a potential candidate for solid lubrication at high temperatures (up to 550 °C) and in space environments.
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Ghasemi, Hamid-Reza M. R. "Fundamental studies of the tribological behavior of thin polymeric coatings in fretting contact using infrared and photo/video techniques". Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/39591.
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Direct measurements of surface temperatures produced during fretting contact are an unknown area in the discipline of tribology; in addition, the possible effects of such temperatures on the behavior of protective anti-fretting coatings (e.g., polymeric) have never been investigated. An oscillating contact device was designed and built to study fretting contact behavior in tribological processes. The contact geometry consisted of a stationary spherical test specimen loaded against a vibrating sapphire disk driven by an electromagnetic shaker. Surface temperatures generated by frictional heating were measured during fretting contact using an infrared microscope. A photo/video technique was developed to view the fretting contact interface during an experiment and to measure the size and distribution of real area(s) of contact. The effects of size and distribution of the areas on the experimental surface temperatures for polymer-coated steel spheres-on- sapphire were investigated. Archard's theoretical model was also modified to account for multiple contact areas, and the calculated surface temperatures were compared to the experimental results.
Polymeric coatings - including polystyrene (PS), polymethylmethacrylate (PMMA), polysulfone (PSO), polyvinylchloride (PVC), and polyvinylidenechloride (PVDC) were studied at a given load (20 N), frequency (150 Hz), amplitude (100 JLm), and film thickness (55 p.m). The surface temperatures generated were generally low and below the glass transition temperatures of the rigid polymers studied. The magnitude of the surface temperatures was found to be particularly dependent on the size and distribution of real area(s) of contact. The most extensive studies were performed using polystyrene coatings. Effects of load, frequency, amplitude, and film thickness on surface temperature rise and the size and distributions of real area of contact were examined. In addition, uncoated steel specimens were studied under various loads and fretting amplitudes. The observed formation of iron oxide at low surface temperature (60°C) tribologica1 experiments was explained in terms of exoelectron emission.
There were considerable differences observed in the behavior of polymeric coatings under various fretting conditions. The fretting behavior of the coatings was explained in terms of mechanical and thermo-elastic effects. Thermo-elastic predictions of size distributions of real contact areas (patches) showed good agreement with the observed photo/video studies. A mechanism was proposed for tribological behavior and fretting protection of polystyrene coatings.Ph. D.
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Mahmoudi, Behzad. "Investigation the Effect of Tribological Coatings: WC/a-C:H and Black Oxide on Micropitting Behavior of SAE52100 Bearing Steel". University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1444838738.
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Chun-ChuanLin y 林俊全. "Tribological performance of W-Ti coatings". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/54001762975316556501.
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碩士國立成功大學
機械工程學系碩博士班
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The TiN/TiWN/W-Ti multilayer coatings were deposited on the high speed steel substrate by closed field unbalanced magnetron sputtering system. The coatings were deposited with different tungsten and titanium ratios on the surface. The main purpose of this study is to research the mechanical and tribological properties and cutting performance of the TiN/TiWN/W-Ti multilayer before and after high thermal oxidation. The experiment was divided into two stages. In first stage, The effect of the mechanical properties of tungsten, titanium and tungsten nitride coatings were deposited on TiN coating. In second stage, The effect of the mechanical properties of oxidation treatment at 500 ℃ and 600 ℃. Finally, the cutting performance of the optimal coatings were understood in the turning and micro-drilling tests. The results reveal that the highest nano hardness of 35.2 GPa and the micro hardness of Hv0.011545 have the best wear resistance were performed by the W-Ti coatings with the titanium of at.5 %. the hardness and tribological properties decreased of W-Ti05 coating after 500 ℃ and 600 ℃ one hour oxidation treatment. In actually turning and micro-drilling tests, the W-Ti05 coatings will be deposited on cutting tools can be reduced about 48 % and 58 %, respectively.
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Santos, Rúben. "Tribological Characterization of Self-Lubricated Coatings". Dissertação, 2013. http://hdl.handle.net/10216/73856.
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