Dissertations / Theses: 'Laser Metal Deposition (LMD)'

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Byseke, David, and Alexander Thunell. "Automatic monitoring and control of Laser Metal Deposition Process." Thesis, Högskolan Väst, Avdelningen för Industriell ekonomi, Elektro- och Maskinteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-16745.

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Laser metal deposition is an additive manufacturing technique that enables the manufacturing or repair of high-quality metal parts by building fine layers one at a time. To get a stable process with a low number of flaws and irregularities the process needs a fully operational and functioning control system. At PTC in Trollhättan, a production research facility that is a department of University West, several experiments have previously been conducted with an LMD machine. The main objective of this thesis is to deliver input from available methods for automatic control and monitoring of the LMD process. The available methods are explained in the report and previous experiments that have been conducted have been documented in this thesis. Another objective of the thesis is to develop a prototype for monitoring and control of the process. Previous work has mainly used a visual-based control system that has used CMOS-, CCD-, or an infrared camera. Pyrometers and structured light scanning have also been used. Non-optical methods such as acoustical sensors and thermocouples have also been used for monitoring and control. With the gathered information about the available control methods, a prototype has been developed to automatically control the LMD machine located at PTC. The control uses a CMOS camera to gather live imaging from the machine in order to adjust machine parameters, in real-time, to automatically control the process. The different parameters have a strong correlation to the final machine output and are also explained in the thesis. The prototype and the gathering of data from the process have been made using Labview as an image-processing software. An evaluation of the developed prototype has been made and the different control methods have been discussed. The developed prototype measures the melt pool by using an algorithm that counts the number of pixels in the melt pool. However, further research needs to be made to determine if the measured width correlates with the actual width of the cladded string.

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Säger, Florian. "A Feasibility Study of an Automated Repair Process using Laser Metal Deposition (LMD) with a Machine Integrated Component Measuring Solutio." Thesis, KTH, Industriell produktion, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-248022.

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The repair of worn or damaged components is becoming more attractive to manufacturers, since it enables them to save resources, like raw material and energy. With that costs can be reduced, and profit can be maximised. When enabling the re-use of components, the lifetime of a component can be extended, which leads to improved sustainability measures. However, repair is not applied widely, mainly because costs of repairing are overreaching the costs of purchasing a new component. One of the biggest expense factors of repairing a metal component is the labourintense part of identifying and quantifying worn or damages areas with the use of various external measurement systems. An automated measuring process would reduce application cost significantly and allow the applications to less cost intense component. To automate the repair process, in a one-machine solution, it is prerequisite that a measuring device is included in the machine enclosure. For that, different measuring solutions are being assessed towards applicability on the “Trumpf TruLaser Cell 3000 Series”. A machine that uses the Laser Metal Deposition (LMD) technology to print, respectively weld, metal on a target surface. After a theoretical analysis of different solutions, the most sufficient solution is being validated by applying to the machine. During the validation a surface models from a test-component is generated. The result is used to determine the capability of detecting worn areas by doing an automated target-actual comparison with a specialised CAM program. By verifying the capability of detecting worn areas and executing a successful repair, the fundamentals of a fully automated repair process can be proven as possible in a one-machine solution. Tillverkare har börjat se stora möjligheter i att reparera slitna eller skadade komponenter som ett sätt att spara resurser, så som råmaterial och energi. Med den besparingen minskar kostnaderna och vinsten kan således maximeras. Reparation möjliggör även återanvändning av komponenter, vilket förlänger komponentens livslängd och leder till förbättrade hållbarhetsåtgärder. Dock tillämpas reparation inte i någon stor utsträckning i nuläget, främst eftersom kostnaderna för reparation överstiger kostnaderna för att köpa en ny komponent. En av de största kostnaderna för att reparera en metallkomponent är att identifiera och kvantifiera slitna eller skadade områden med hjälp av olika externa mätsystem, som är en väldigt arbetsintensiv process. En automatiserad mätprocess skulle minska avsökningskostnaden avsevärt och således reducera den totala kostnaden för komponenten. För att möjliggöra en automatiserad reparationsprocess i en enda maskinlösning är det en förutsättning att en mätanordning ingår i maskinhöljet. Därför har olika mätningslösningar utvärderats med avseende på användbarhet i "TRUMPF TruLaser Cell 3000 Series", vilket är en maskin som använder Laser Metall Deposition-teknik (LMD-teknik) för att skriva ut och svetsa metall på en definierad yta. En teoretisk analys av olika lösningar har utförts, där den teoretiskt mest lämpliga lösningen validerades genom att appliceras till maskinen. Valideringen genererade en modell av ytan av en testkomponent. Sedan utfördes en automatiserad, målrelaterad jämförelse med ett specialiserat CAM-program baserat på modellresultatet, för att bestämma möjligheten att upptäcka slitna områden. Genom att verifiera förmågan att upptäcka slitna områden samt genomförandet av en lyckad reparation kan grunden för en helt automatiserad reparationsprocess bevisas som möjlig i en enda maskinlösning. Das reparieren von abgenutzten oder beschädigten Komponenten wird immer attraktiver für Hersteller. Es ermöglicht es Ressourcen einzusparen wie beispielsweise Rohmaterial und Energie, was die Lebenszeit einer Komponente verlängert und damit die Nachhaltigkeit verbessert. Allerdings ist Reparieren nach wie vor nicht weit verbreitet, hauptsächlich dadurch bedingt, dass die Reparaturkosten die Kosten für eine neue Komponente übersteigen. Einer der größten Kostenfaktoren des reparieren einer Metallkomponente ist der Arbeitsintensive Teil der Identifizierung und Quantifizierung des abgenutzten oder beschädigten Bereichs mit verschiedensten externen Vermessung Systemen. Ein automatisierter Vermessungsprozess würde die Kosten signifikant reduzieren und neue Applikationen ermöglichen. Das automatisieren der gesamte Prozesskette – in einer Single-Maschinenlösung – erfordert, dass eine Messeinrichtung im Bearbeitungsraum der Maschine angebracht wird. Dafür werden verschiedene Lösungen nach Anwendbarkeit an der Trumpf Laser Cell 3000 Serie hin beurteilt. Eine Maschine, welche Laser Metal Deposition (LMD) als Technologie anwendet um Material auf Oberflächen aufzubringen. Nach einer theoretischen Analyse verschiedener Lösungen wird die beste Lösung va durch anbringen an die Maschine validiert. Bei der Validierung wird ein Oberflächenmodel erzeugt. Das Ergebnis wird dann genutzt um die Fähigkeit zu belegen, dass beschädigte Stellen, durch einen Soll-Ist-Vergleich in einem speziellen CAM Programm, automatisch detektiert werden können. Basierend auf diesem Beleg und mit dem Ergebnis eine Komponente erfolgreich reparieren zu können, gilt die These eines automatisierten Reparaturprozesses in einer Single-Maschinenlösung als beweisen.

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Makiewicz, Kurt Timothy. "Development of Simultaneous Transformation Kinetics Microstructure Model with Application to Laser Metal Deposited Ti-6Al-4V and Alloy 718." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366023857.

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Morville, Simon. "Modélisation multiphysique du procédé de Fabrication Directe par Projection Laser en vue d'améliorer l'état de surface final." Lorient, 2012. http://www.theses.fr/2012LORIS280.

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Molina, Griggs Alejandro José. "Laser Metal Powder Deposition of Austenitic Stainless Steel on Spheroidal Graphite Cast Iron : A corrosion resistant coating for the Food & Beverage Industry." Thesis, Högskolan Väst, Avdelningen för svetsteknologi (SV), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-13016.

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Spheroidal graphite cast iron is a material widely used in the industry for the manufacturing of all kind of covers and protective casings thanks to its good combination of mechanical properties, processability and cost. When cast iron components are put into service in corrosive environments the most common approach to protect the components is painting them. The protective painting has been found to flake off with time when aggressive washing procedures, such as the ones used in the Food & Beverage industry, are applied several times. In this project, the coating of cast iron with a corrosion resistant AISI 316L stainless steel by Laser Metal Powder Deposition has been studied as an alternative protection against corrosion. Several samples with different combinations of substrate preparation, number of layers and surface conditions were produced and analysed by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, wash down tests and salt spray chamber corrosion tests. Main results show that the diffusion of carbon from the carbon-rich cast iron to the stainless steel coating, which would have a negative effect on the corrosion resistant properties, was significantly low as a result of the low penetration and dilution achieved during the laser metal powder deposition process. The deposited stainless steel coatings successfully protected the substrate during the corrosion tests and the integrity of the coatings is not expected to fail during the washing producers applied in the industry.

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Conti, Alfredo. "Tecniche della manifattura additiva - applicazioni in ambito aeronautico e aerospaziale." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13306/.

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Il potenziale delle nuove tecnologie digitali applicate al settore industriale ha consentito di ridurre enormemente la durata dei cicli produttivi grazie alla rapida gestione di quantità di dati sempre più considerevoli attraverso l’introduzione delle Macchine a Controllo Numerico (Computer Numerical Control – CNC). Nel corso delle ultime tre decadi, l’industria manifatturiera ha subito notevoli e sostanziali cambiamenti grazie ad una sempre più forte connessione con il mondo dell’informatica. La più grande rivoluzione in tale ambito è stata segnata dall’avvento della Manifattura Additiva (Additive Manufacturing - AM), conosciuta sotto diversi nomi, tra i quali Prototipazione Rapida (Rapid Prototyping), Manifattura Rapida (Rapid Manufacturing) o Libera Fabbricazione di Forme (Free Form Fabrication). Materia di ricerca e sviluppo sin dalla fine degli anni ’80, la Manifattura Additiva consente la creazione di elementi fisici tridimensionali partendo da modelli CAD attraverso la sovrapposizione successiva di materiale strato per strato (layer by layer), offrendo i benefici di una elevata flessibilità geometrica degli elaborati, altrimenti irraggiungibile attraverso le tradizionali tecniche di Manifattura Sottrattiva operanti per asportazione di materiale. In seguito ad intensive ricerche, progressi significativi sono stati fatti nello sviluppo e nella commercializzazione di nuovi ed innovativi processi AM.

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Linney, Rachel E. "The laser powered pyrolysis of metal deposition precursors." Thesis, University of Leicester, 1993. http://hdl.handle.net/2381/33788.

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Pereira, M. F. V. T., M. Williams, and R. Bruwer. "Rapid die manufacturing using direct laser metal deposition." Journal for New Generation Sciences, Vol 7, Issue 3: Central University of Technology, Free State, Bloemfontein, 2009. http://hdl.handle.net/11462/542.

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Published Article Global issues such as energy and climate changes have impacted on both the automotive and aerospace industries, forcing them to adopt measures to produce products that consume fewer combustibles and emit less carbon dioxide. Making vehicles lighter is one of the logical ways of reducing fuel consumption. The need for light components, able to fulfil technical and quality specifications, led to market growth for tooling that is able to mass produce parts using manufacturing processes such as high pressure die casting. Competitive pressures to reduce the lead time required for tooling-up has also increased dramatically. For this reason research into various methods, techniques and approaches to tool manufacture is being undertaken globally. This paper highlights the work undertaken at the CSIR on the issue of rapid die manufacturing through the application and evaluation of a rapid prototyping technique and coating technologies applied to die components of a high pressure casting die for the production of aluminium components. Criteria for determining suitability were developed against which the technique was evaluated that included time, cost and life-expectancy. Results of accelerated testing procedures to evaluate the die material produced by the rapid prototyping technique and surface coatings and treatments of die materials for their resistance to washout, erosion, heat checking and corrosion in a high pressure die casting environment, are presented. The outcomes of this research will be used for further development and application of specific techniques, design principles and criteria for this approach.

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Garner, Simon. "Laser ultrasonic testing for on-line inspection of laser metal deposition." Thesis, Swansea University, 2015. https://cronfa.swan.ac.uk/Record/cronfa42997.

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Heralic, Almir. "Towards full Automation of Robotized Laser Metal-wire Deposition." Licentiate thesis, University West, Department of Engineering Science, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-2148.

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Metal wire deposition by means of robotized laser welding offers great saving potentials, i.e. reduced costs and reduced lead times, in many different applications, such as fabrication of complex components, repair or modification of high-value components, rapid prototyping and low volume production, especially if the process can be automated. Metal deposition is a layered manufacturing technique that builds metal structures by melting metal wire into beads which are deposited side by side and layer upon layer. This thesis presents a system for on-line monitoring and control of robotized laser metal wire deposition (RLMwD). The task is to ensure a stable deposition process with correct geometrical profile of the resulting geometry and sound metallurgical properties. Issues regarding sensor calibration, system identification and control design are discussed. The suggested controller maintains a constant bead height and width throughout the deposition process. It is evaluated through real experiments, however, limited to straight line deposition experiments. Solutions towards a more general controller, i.e. one that can handle different deposition paths, are suggested.A method is also proposed on how an operator can use different sensor information for process understanding, process development and for manual on-line control. The strategies are evaluated through different deposition tasks and considered materials are tool steel and Ti-6Al-4V. The developed monitoring system enables an operator to control the process at a safe distance from the hazardous laser beam.The results obtained in this work indicate promising steps towards full automation of the RLMwD process, i.e. without human intervention and for arbitrary deposition paths. RMS

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Farrell, Ian Laurence. "Growth of Metal-Nitride Thin Films by Pulsed Laser Deposition." Thesis, University of Canterbury. Physics and Astronomy, 2010. http://hdl.handle.net/10092/5011.

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The growth of thin-film metal nitride materials from elemental metal targets by plasma-assisted pulsed laser deposition (PLD) has been explored and analysed. A new UHV PLD growth system has been installed and assembled and its system elements were calibrated. A series of GaN thin films have been grown to calibrate the system. In-situ RHEED indicated that the films were single crystal and that growth proceeded in a three-dimensional fashion. SEM images showed heavy particulation of film surfaces that was not in evidence for later refractory metal nitride films. This may be connected to the fact that Ga targets were liquid while refractory metals were solid. Most GaN films were not continuous due to insufficient laser fluence. Continuous films did not exhibit photoluminescence. HfN films have been grown by PLD for the first time. Films grown have been shown to have high reflectivity in the visible region and low resistivity. These factors, along with their crystal structure, make them suitable candidates to be used as back-contacts in GaN LEDs and could also serve as buffer layers to enable the integration of GaN and Si technologies. Growth factors affecting the films’ final properties have been investigated. Nitrogen pressure, within the operating range of the plasma source, has been shown to have little effect on HfN films. Substrate temperature has been demonstrated to have more influence on the films’ properties, with 500 °C being established as optimum. ZrN films have also been grown by PLD. Early results indicated that they exhibit reflectivities 50 % ± 5 % lower than those of HfN. However, further growth and characterisation would be required in order to establish this as a fundamental property of ZrN as nitride targets were mostly used in ZrN production. Single-crystal epitaxial GdN and SmN films have been produced by PLD. This represents an improvement in the existing quality of GdN films reported in the literature, which are mostly polycrystalline. In the case of SmN, these are the first epitaxial films of this material to be grown. Film quality has been monitored in-situ by RHEED which has allowed growth to be tailored to produce ever-higher crystal quality. Post-growth analyses by collaborators was also of assistance in improving film growth. Substrate temperatures and nitrogen plasma parameters have been adjusted to find optimum values for each. In addition, laser fluence has been altered to minimise the presence of metal particulates in the films, which interfere with magnetic measurements carried out in analyses. Capping layers of Cr, YSZ or AlN have been deposited on the GdN and SmN prior to removal from vacuum to prevent their degradation upon exposure to atmospheric water vapour. The caps have been steadily improved over the course of this work, extending the lifetime of the nitride films in ambient. However, they remain volatile and this may persist since water vapour can enter the film at the edge regardless of capping quality. Optical transmission has shown an onset of absorption at 1.3 eV for GdN and 1.0 eV for SmN.

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Touzé, Stéphane. "Laser Metal Deposition of Aluminium-Copper alloys for Repair applications." Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0025.

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Ce travail de thèse vise à démontrer la faisabilité de la réparation de pièces de fonderie à haute performance et haute valeur ajoutée faites d’un alliage aluminiumcuivre en utilisant un procédé de fabrication additive métallique par projection de poudre avec fusion laser dénommé Laser Metal Deposition. Ces alliages présentent notamment une faible soudabilité et ne peuvent donc être réparés de façon fiable par des procédés traditionnels de soudage à l’arc. Afin de permettre l’utilisation de ce procédé innovant pour la réparation de pièces en alliage Al-Cu, des difficultés majeures ont dû être levées en ce qui concerne notamment la coulabilité des poudres Al-Cu et leur comportement en fusion et en solidification, ainsi que la méthodologie de réparation pour effectuer l’opération de façon fiable et efficace. Des travaux expérimentaux, théoriques et numériques ont permis d’élucider ces aspects et in fine de permettre l’utilisation de ce matériau avec ce procédé de fabrication additive. Une méthode de réparation comprenant un algorithme de segmentation robuste a également été développée et mise en oeuvre afin d’automatiser le processus de réparation en permettant la génération de trajectoire sur la base de mesures 3D in-situ. Des réparations de pièces de fonderie en aluminium-cuivre ont ainsi pu être effectuées avec le procédé Laser Metal Deposition, et les analyses métallographiques montrent que les rechargements effectués avec ce procédé offrent une microstructure très fine avec un taux de ségrégation chimique limité et peu de fissuration à chaud The present thesis aims at demonstrating the feasibility of repairing high performance castings made of an aluminiumcopper alloy using the Laser Metal Deposition metal additive manufacturing process. These alloys present a low weldability and thus cannot be reliably repaired with manual arc-welding processes. To instead use this innovative additive manufacturing process for repair applications and thereby improve upon current methods, major challenges had to be overcome regarding the flowability and solidification behavior of this aluminium alloy powder as well as the overall methodology to reliably and efficiently perform the repair operation. Experimental, theoretical and numerical studies allowed to elucidate some of these aspects and eventually enabled the use of a 224.0 casting aluminium alloy with the Laser Metal Deposition metal additive manufacturing process. A repair methodology including a robust segmentation algorithm was also developped to automate the repair process and permit the generation of toolpaths based on raw in-situ 3D scanning measurements. Repairs of high performance aluminium-copper castings were carried out successfully as no major lack of fusion, bonding or cracking defects were observed. A metallographic analysis showed that the aluminium deposits obtained by Laser Metal Deposition generally offer a refined microstructure with limited solute segregation and hot cracking

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Shah, Kamran. "Laser direct metal deposition of dissimilar and functionally graded alloys." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/laser-direct-metal-deposition-of-dissimilar-and-functionally-graded-alloys(baa5f8fd-cead-4047-afbf-860844b501d8).html.

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The challenges in the deposition of dissimilar materials are mainly related to the large differences in the physical and chemical properties of the deposited and substrate materials. These differences readily cause residual stresses and intermetallic phases. This has led to the development of functionally graded materials which exhibit spatial variation in composition. Laser direct metal deposition due to its flexibility, it offers wide variety of dissimilar and functionally graded materials deposition. Despite considerable advances in process optimization, there is a rather limited understanding of the role of metallurgical factors in the laser deposition of dissimilar and functionally graded alloys. The aim of this work is to understand and explain mechanisms occurring in diode laser deposition of dissimilar materials and functionally graded materials. The first part of this work addressed diode laser deposition of Inconel 718 nickel alloy to Ti-6Al-4V titanium alloy. Here, the effect of laser pulse parameters and powder mass flow rates on the stress formation and cracking has evaluated by experiment and numerical techniques. Results showed that the clad thickness was an important factor affecting the cracking behaviour. In the second part of this study, an image analysis technique has been developed to measure the surface disturbance and the melt pool cross section size during laser direct metal deposition of Inconel 718 on a Ti-6Al-4V thin wall. It was noted that under tested conditions the overall melt pool area increased with the increase in powder flow rate; the powder carrier gas flow rates also seemed to play important roles in determining the melt pool size. In the third part of this study, a parametric study on the development of Inconel 718 and Stainless steel 316L continuously graded structure has been carried out. Results suggested that microstructure and other mechanical properties can be selectively controlled across the deposited wall. The results presented in this dissertation can be used as a metallurgical basis for further development of dissimilar and functionally graded manufacturing using LDMD technique, guiding future manufacturing engineers to produce structurally sound and microstructurally desirable laser deposited samples.

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Kulish, Aleksandr. "Etude paramétrique d’un procédé d’impression 3D (LMD) en vue d’optimiser l’intégrité matière : Application à l’alliage maraging 1.2709." Thesis, Lyon, 2022. http://www.theses.fr/2022LYSEE001.

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La thèse de doctorat présentée dans ce travail est consacrée à une méthode innovante de production de moules d'injection plastique. Cette méthode combine la technologie additive laser, notamment le rechargement par injection coaxiale de poudre (LMD) et la technique de traitement laser visant à réduire les contraintes résiduelles. Par conséquent, l'objectif principal du présent travail est d'optimiser et d'analyser la méthode de fabrication proposée en ce qui concerne les propriétés finales des pièces déposées. L'étude paramétrique de LMD des "simples cordons", des structures de type "mur" et des "cubes" a été réalisée. La LMD d'échantillons cubiques a été analysée en fonction de la densité, des contraintes résiduelles et de la microstructure afin d’obtenir les paramètres optimaux de LMD. Les paramètres optimaux de LMD ont été vérifiés lors du dépôt à long terme d'échantillons cubiques et cylindriques en une seule et plusieurs fois. La tenue en fatigue ainsi que la densité, la microdureté et la microstructure ont ensuite été évaluées. La simulation numérique a également été réalisée pour prédire les champs thermiques générés pendant le procédé LMD. Enfin, cette thèse comprend l'étude numérique et expérimentale du processus de traitement laser (de détentionnement) visant à réduire les contraintes résiduelles et à éviter les post-traitements durables tels que le vieillissement The PhD thesis presented in this work is dedicated to the innovative method of plastic injection mould production. This method combines laser additive technology, namely, the Laser Metal Deposition (LMD) and technique of laser treatment aiming to reduce the residual stresses. Therefore, the main objective of the present work is to optimize and analyze the proposed fabrication method regarding the final properties of deposited parts. The parametrical study of “single-bead”, multi-bead “wall” and multi-bead “cube” LMD has been carried out. The LMD of cubic specimens has been analyzed with respect to the density, residual stresses and microstructure in order to find the optimal deposition parameters. The optimal LMD parameters have been verified during the longtime deposition of cubic and cylindrical specimens in a single operating session and after multiple pauses. The fatigue resistance as well as the density, microhardness and microstructure were then evaluated. The numerical simulation has been also performed to predict the thermal fields generated during LMD. Finally, this thesis includes the numerical and experimental study of laser treatment process aiming to reduce the residual stresses and avoid the possible long-lasting post-treatment such as aging

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Grindeland, Andreas. "Improved inert gas protection - for laser weld and metal deposition processes." Thesis, KTH, Industriell produktion, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-40433.

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The purpose of this thesis was to create a requirement specification for a shielding gas chamber for laser welding and/or laser metal deposition. This to improve the understanding of requirements that are needed for a chamber being able to be used in full production at Volvo Aero, Trollhättan. During welding in Titanium it is very important to protect welding areas from oxygen. The idea of using a chamber instead of local shielding is not new. However, when there are many welds to be performed in the same operation and/or the access to shield the weld (or rootside of weld) is difficult it might be advantages to use a chamber. For metal deposition it is even more difficult (and thereby costly) to use local shielding.The information and results have been gathered from daily interviews with operators and engineers with experience of welding and metal deposition. Internal documents, literature and participating in the manufacturing process have also contributed.The conclusion of the work led up to a list of requirements for a shielding gas chamber that will be used when welding or metal deposition are performed on components for the aerospace industry. It is not the design of the chamber that has been achieved with this work; it is the requirement for the chamber that will influence the design of the shielding gas chamber.During this work it was clear that some parts were more important than others: How to realize an oxygen free atmosphere Temperature in the chamber Materials for the chamberThe difficult part of finding essential information was the fact that nothing was found if any other company uses the same welding technology along with the material used.The combination of flexibility, high temperature resistance and transparency properties reduce the number of avalible materials to choose from to build a chamber. However, the result that the temperature reached inside the chamber was lower than expected made it possible for more materials to meet the requirements.

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Zekovic, Srdja. "Numerical simulation and experimental investigation of laser-based direct metal deposition." Ann Arbor, Mich. : ProQuest, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3207912.

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Thesis (Ph.D. in Mechanical Engineering)--S.M.U. Title from PDF title page (viewed July 20, 2007). Source: Dissertation Abstracts International, Volume: 67-02, Section: B, page: 1125. Adviser: Radovan Kovasevic. Includes bibliographical references.

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Medrano, Téllez Alexis G. "Fibre laser metal deposition with wire : parameters study and temperature control." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/12812/.

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This research addresses the development of a laser metal deposition process with wire feeding and melt pool temperature control. The system consists of a2 kW fibre laser, a CNC table, a wire feeder and a temperature monitoring and control system. A study of the influence of the main parameters on the process and on the deposited bead geometry was performed. The parameters analysed were: laser power, traverse speed and wire feed rate. As a result of this study, a process window was established for metal deposition of stainless steel 308LSi (wire) on stainless steel 304 (plate). The influence of the parameters on the bead geometry (height and width) was analysed applying the Design of Experiments methodology, using a full factorial design 3k. The results are presented, together with important practical considerations for laser metal deposition with wire. A closed-loop temperature control system was developed: it controls the melt pool temperature by means of modifying the laser power. The melt pool temperature was measured by a two-colour pyrometer, whereas a single-colour pyrometer was used for monitoring the workpiece (upper layer) temperature. A model of the melt pool was derived from a heat balance equation. It was then utilized for the design of the controller in the discrete domain, using the root locus method. The control algorithm was developed in LabVIEW software and executed in a computer. The control system was implemented successfully and was utilized to build single-bead walls and cylinders of stainless steel 308LSi. The study performed on the parameters and the developed temperature controller proved to be very effective tools to facilitate the transition to the deposition of titanium alloy Ti-6A1-4V, requiring only minimum adaptations. Single-bead walls and cylinders were also built in this material. Stable and smooth metal deposition was achieved for both materials. During the experiments, several strategies for the automation of wire metal deposition of multilayered structures were developed. Finally, mechanical tests were performed. The mechanical properties of the deposited materials are comparable to those in wrought (annealed) condition and to similar alloys made by laser powder deposition systems. The system developed in this work provides a means to perform stable and smooth wire metal deposition, achieving good mechanical properties. It also facilitates the transition to deposit different materials. It has a flexible structure and can be expanded or adapted to be used in other wire metal deposition systems.

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Syed, Waheed Ul Haq. "Combined wire and powder deposition for laser direct metal additive manufacturing." Thesis, University of Manchester, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556499.

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Ibarra, Medina Juansethi Ramses. "Development and application of a CFD model of laser metal deposition." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/development-and-application-of-a-cfd-model-of-laser-metal-deposition(d74829d8-c4b9-40f1-b80f-cbdc456ffaf5).html.

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Laser metal deposition is one of the most versatile methods in the expanding field of additive manufacturing. Its outstanding advantage is its capability to process a variety of metallic materials for the freeform fabrication of objects having sound mechanical properties. The process is used in applications of rapid manufacturing, components repair and surface coating. During recent years, modelling has been increasingly used to study and improve the laser metal deposition process. However, most models have focused on analysing individual stages of the deposition process and thus have not thoroughly dealt with the occurrence of mutually-influencing phenomena. This work presents a new numerical model that, starting from the simulation of powder particles in the deposition head, integrates the important phenomena and interactions that govern the dynamics of a powder stream and a deposition melt pool, within a single model for the first time.The resulting model is comprehensive enough to allow the prediction of the morphology of deposited tracks and structures and the heat flows during their creation; as well as the flexibility to simulate, in principle, any deposition shape. The model has been demonstrated using the settings of an actual laser metal deposition system, and has been applied to study clad formation in the deposition of single tracks, layers, walls and simple three-dimensional structures. Moreover, the model has been used to study the formation of irregularities and excessive mass deposition. A new sensor-less deposition control technique based on the simulation and testing of different deposition strategies prior to actual deposition, is proposed. As a demonstration of this control technique, the model has also been used to study the case where excessive deposition develops at intersecting or cornered tracks. Improved deposition strategies have been tested using the model and applied to real deposits. A two fold improvement in layer height control has been achieved in the case of cornered layers.The outcome of the work presented in this thesis can be applied in further studies and prediction of laser deposited shapes for real applications. Furthermore, it can be potentially used for improvement of the laser metal deposition technology through the simulation of deposition strategies prior to actual processing.

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Hussein, Nur Izan Syahriah. "Direct metal deposition of Waspaloy wire using laser and arc heat sources." Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523507.

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Pinkerton, Andrew J. "A mathematical and experimental investigation of thin wall Laser Direct Metal Deposition." Thesis, University of Manchester, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488244.

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Yang, Yu. "On-line inspection and thermal properties comparison for laser deposition process." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/Yang_09007dcc803bca12.pdf.

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Thesis (M.S.)--University of Missouri--Rolla, 2007. Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 6, 2007) Includes bibliographical references.

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Mendelsberg, Rueben Joseph. "Photoluminescence of ZnO Grown by Eclipse Pulsed Laser deposition." Thesis, University of Canterbury. Physics and Astronomy, 2009. http://hdl.handle.net/10092/3052.

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ZnO thin films and nanostructures were grown by eclipse pulsed laser deposition (EPLD) for the first time. On bare sapphire held at 600 °C, a complex nanostructured surface was formed when ablating a metallic Zn target in an oxygen ambient. Nanorods grown by a vapor-solid mechanism clumped together in well separated, micron-sized regions. Nanoscale pyramids with 6 fold symmetry formed between the nanorod clumps by vapor-liquid-solid growth. Strong photoluminescence (PL) was observed from the EPLD grown samples, an order of magnitude stronger than PLD grown nanorods formed under similar growth conditions. Low temperature PL was dominated by the I₇ exciton, which still has an unknown origin. Excitation intensity dependence of I₇ was drastically different than the rest of the nearby excitonic features, behavior which has not been previously reported for bound excitons in ZnO. I₇ also showed large, seemingly random variations in intensity across the surface of each sample compared to the other nearby recombinations, suggesting a structural connection. Introduction of a buffer layer had a profound effect on the morphology and PL from EPLD grown ZnO from a metallic Zn target. Pt has a high melting temperature, which helped suppress the vapor-liquid-solid nanostructure growth resulting in thin-film formation. For standard PLD, the ZnO film showed large grains separated by cracks on the surface. Due to the reduced growth rate in the EPLD geometry, the ZnO layer had a high density of nanoscale pores, reminiscent of the porous Pt buffer layer. Strong PL emission, which was dominated by I₇, was observed from the ZnO/Pt/Al₂O₃ which showed unusual blue/violet emission when the EPLD geometry was used for growth. Thin ZnO buffer layers deposited at reduced temperature also had a profound effect on EPLD grown ZnO, resulting in a random array of nanorods with alignment which was dependent on the growth temperature of the buffer layer. Buffer layers offer another dimension in the control over epitaxial structures and show large potential for EPLD growth of ZnO. Pb was the dominant impurity in the Zn targets used for EPLD growth, hinting at a Pb-related origin for the I7 peak. To explore this idea, hydrothermally grown bulk ZnO was ion-implanted with Pb and then annealed in oxygen at 600 °C to repair damage to the crystal. PL emission intensity was substantially reduced in the Pb-implanted ZnO but the line widths were preserved. No evidence of an I₇ feature was seen for Pb concentrations of up to 0.10%, three orders of magnitude higher than the expected level in the EPLD grown ZnO. However, this does not rule out a Pb-related complex as the origin of I₇ since Pb has complicated interactions with the impurities and native defects in ZnO. Instead of I₇, other sharp excitonic features were observed near the band edge. A bound exciton with a localization energy of 12.4 ± 0.2 meV was observed in the Pb-implanted samples and was attributed to neutral interstitial Pb donors. Pb-implantation produced a clear PL signature which is unique enough to unambiguously detect its presence in ZnO. EPLD also proved successful at depositing oxides of the noble metals. Ir, Pt, Pd, and Ru targets were ablated in oxygen and argon ambients and films were collected on room temperature substrates. Growth in argon resulted in pure metal while oxidized layers were obtained in oxygen. This was clearly evident by the semiconductor-like transmission spectra observed for the oxidized samples. The high fluence used for these growths promoted the oxidation of these resilient metals while the shadow mask blocked most of the molten particulates generated by the high fluence. EPLD is an excellent way to produce oxides from metallic targets, a technique which should be explored in more detail for many material systems.

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Tal, Amir. "THREE-DIMENSIONAL MICRON-SCALE METAL PHOTONIC CRYSTALS VIA MULTI-PHOTON DIRECT LASER WRITING AND ELECTROLESS METAL DEPOSITION." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3889.

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Three-dimensional (3D) metal photonic crystals (MPCs) can exhibit interesting electromagnetic properties such as ultra-wide photonic or "plasmonic" band gaps, selectively tailored thermal emission, extrinsically modified absorption, and negative refractive index. Yet, optical-wavelength 3D MPCs remain relatively unexplored due to the challenges posed by their fabrication. This work explores the use of multi-photon direct laser writing (DLW) coupled with electroless metallization as a means for preparing MPCs. Multi-photon DLW was used to prepare polymeric photonic crystal (PC) templates having a targeted micron-scale structure and form. MPCs were then created by metallizing the polymeric PCs via wet-chemical electroless deposition. The electromagnetic properties of the polymeric PCs and the metallized structures were characterized using Fourier transform infrared spectroscopy. It is shown that metallization transforms the optical properties of the structures from those of conventional 3D dielectric PCs to those consistent with 3D MPCs that exhibit ultra-wide photonic band gaps. These data demonstrate that multi-photon DLW followed by electroless deposition provides a viable and highly flexible route to MPCs, opening a new path to metal photonic materials and devices. M.S. Optics and Photonics Optics and Photonics Optics MS

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Yarrapareddy, Eswar. "Development of slurry erosion resistant materials by laser-based direct metal deposition process." Ann Arbor, Mich. : ProQuest, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3258777.

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Thesis (Ph.D. in Mechanical Engineering)--S.M.U., 2007. Title from PDF title page (viewed Mar. 18, 2008). Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1898. Adviser: Radovan Kovacevic. Includes bibliographical references.

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Ahsan, Muhammad Naveed. "Modelling and analysis of laser direct metal deposition of Ti-6Al-4V alloy." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/modelling-and-analysis-of-laser-direct-metal-deposition-of-ti6al4v-alloy(e56c53a4-ca76-4870-89df-b34390b6697a).html.

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A major strength of the laser direct metal deposition (LDMD) rapid manufacturing technique is its ability to manufacture freeform shapes, to directly create different surface coatings on a part, and to produce parts from graded porous to fully dense solid structures. This technique is gaining popularity in the fields of aerospace and biomedical manufacture due to its flexibility and cost effectiveness. Surface coating and repair are its biggest application in industry. Previous models of surface layer coating predicted heat flow in the substrate and the resulting temperature distributions successfully, however layer geometry predictions were absent or incomplete. Here, an analytical modelling method of surface layer coating has been presented which accounts for track interactions and uses a novel powder mass affinity factor in multiple track laser direct metal deposition. The model has been validated by a series of surface layer coating experiments using Ti-6Al-4V alloy. Surface layer characteristics in terms of layer profile, layer thickness and layer roughness have been compared. The model is, then, extended from multiple tracks to multilayer structure fabrication. The multilayer porous structures have been fabricated by using the laser in continuous-wave and pulsed-wave modes for potential use in biomedical applications. In the second part of the work, a coupled analytical-numerical solution has been developed for the single track deposition model described earlier. Laser direct metal deposition is a complex process involving multiple interdependent processes which can be best simulated using a fully coupled mass-energy balance solution and the model removes the shortcoming of previous models where energy and mass balance equations are solved in a decoupled manner. The model has been applied to find out temperature distributions, track profile and microstructure scale, its experimental validation makes it convincing. The model is quite efficient as compared to finite element methods and a useful industrial aid for selecting the parameters to use for laser direct metal deposition when separate geometric and microstructural outcomes are required. In the third part of the work, a comparative study of LDMD characteristics using GA (gas-atomised) and PREP (plasma rotating electrode process) Ti-6Al-4V powders has been presented. The LDMD characteristics in terms of geometric dimensions, surface finish, microstructure, micro hardness and any defects such as intralayer porosity are compared and it is concluded that PREP powder deposition has some potential benefits when high value components are to be built, for example, aerospace applications. This study has also exposed the scientific understanding on the causes of intralayer porosity generation behaviour in laser direct metal deposition. To minimize the intralayer porosity, optimum combinations of processing parameters/ conditions and characteristics of the initial powder, have been proposed for practical engineering applications.

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MURER, MAURO. "Computational Fluid Dynamics simulations of Laser Metal Deposition process exploring open source software." Doctoral thesis, Università degli studi di Pavia, 2021. http://hdl.handle.net/11571/1447833.

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Laser Metal Deposition (LMD) is an innovative technology adopted in Additive Manufacturing (AM) processes and its use is becoming more and more popular in various application fields, such as part manufacturing, repair, and prototype fabrication. This technique is capable of creating several layers of solidified material, by the simultaneous delivery of metal powders and the laser beam, and offers an effective way to produce complicated geometries thanks to its high flexibility. However, complex physical phenomena occur during the additive process, which have a great impact on the success of the process, and many of these have yet to be fully understood. With the aim of shedding light on these aspects, a detailed numerical study, focused on LMD technology, will be conducted using three-dimensional models based on Com- putational Fluid Dynamics (CFD). The particle flow problem regarding the coupling between the fluid phase (i.e., the carrier gas) and the solid phase (i.e., a metallic material powder) is first investigated using OpenFOAM, an open source software widely used in the CFD community. In particular, two different numerical approaches are investigated: the first approach is based on an Eulerian method to describe the carrier gas flow combined with a Lagrangian method to describe the particle flow (LE method), and the second approach is based on a pure Eulerian method to model both the carrier gas and the particle flow (EE method). Simulations results show the main features of the two approaches considered in terms of reliability in reproducing the key geometrical and physical features of the LMD process, together with a comparison with experimental evidences. On the other hand, the thermal problem, that describes the interaction between particles flow and the laser beam, play a crucial role and cannot be neglected. For this purpose, the time-dependent Navier-Stokes equations for incompressible flows are coupled with the energy equation in order to represent the temperature field, whereas the Lagrangian description of the particle dynamic is enriched accounting the thermal evolution, and the consequent phase changing of the metallic powder due to the particle-laser interaction. This model is developed in a C++ in-house code using the open source Finite Element library deal.II and it is validated through consolidated results available in the literature. Furthermore, different schemes able to solve the Navier-Stokes equations, coupled with the heat transfer equation, are implemented and compared, so as to prove both accuracy and efficiency. Then, with the aim of investigating the LMD process in detail, and in particular the thermal behaviour of the powder exiting from the nozzle, a sensitivity analysis is performed in terms of the parameters most meaningful from a technological viewpoint, i.e., the nozzle inclination, the carrier gas and powder flow rate, and the laser power. The results of such an analysis show that it is possible to predict both the configuration and the energy distribution that character- izes the flow of the powder leaving the nozzle until it reaches the substrate. In particular, the influence of both laser power and nozzle geometry to phase change conditions of powder flux are analyzed in order to improve the set up of the printing process, which can lead to increased productivity and less material waste.

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Konrad, Chad E. "Analysis of heat transfer in subcooled metal powder subjected to pulsed laser heating." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4300.

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Thesis (M.S.)--University of Missouri-Columbia, 2005. The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (July 14, 2006) Includes bibliographical references.

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Segerstark, Andreas. "Laser Metal Deposition using Alloy 718 Powder : Influence of Process Parameters on Material Characteristics." Doctoral thesis, Högskolan Väst, Avdelningen för svetsteknologi (SV), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-11842.

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Additive manufacturing (AM) is a general name used for manufacturing methods which have the capabilities of producing components directly from 3D computeraided design (CAD) data by adding material layer-by-layer until a final componentis achieved. Included here are powder bed technologies, laminated object manufacturing and deposition technologies. The latter technology is used in this study. Laser Metal Powder Deposition (LMPD) is an AM method which builds components by fusing metallic powder together with a metallic substrate, using a laser as energy source. The powder is supplied to the melt-pool, which is created by the laser, through a powder nozzle which can be lateral or coaxial. Both the powder nozzle and laser are mounted on a guiding system, normally a computer numerical control (CNC) machine or a robot. LMPD has lately gained attentionas a manufacturing method which can add features to semi-finished components or as a repair method. LMPD introduce a low heat input compared to conventional arc welding methods and is therefore well suited in, for instance, repair of sensitive parts where too much heating compromises the integrity of the part. The main part of this study has been focused on correlating the main process parameters to effects found in the material which in this project is the superalloy Alloy 718. It has been found that the most influential process parameters are the laser power, scanning speed, powder feeding rate and powder standoff distance.These process parameters have a significant effect on the temperature history ofthe material which, among others, affects the grain structure, phase transformation, and cracking susceptibility of the material. To further understand the effects found in the material, temperature measurements has been conducted using a temperature measurement method developed and evaluated in this project. This method utilizes a thin stainless steel sheet to shield the thermocouple from the laser light. This has proved to reduce the influence of the laser energy absorbed by the thermocouples.

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Melo, Leonardo de. "Powder jet particle density distribution analysis and qualification for the laser metal deposition process." reponame:Repositório Institucional da UFSC, 2015. https://repositorio.ufsc.br/xmlui/handle/123456789/171441.

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2015. Made available in DSpace on 2016-12-13T03:03:04Z (GMT). No. of bitstreams: 1 340514.pdf: 4063742 bytes, checksum: 6a2f911982008b177bc31b52c459c372 (MD5) Previous issue date: 2015 Abstract: The quality of the Laser Metal Deposition process depends on several factors and components. One of them and also one of the most important is the powder jet. Regular monitoring of the different variables involved on the powder jet need to be performed in order to assure the demanded high stability and quality standards of the produced coating layers. This monitoring is done through process monitoring techniques, where the powder jet is illuminated from the side, by a laser line, and recorded by a coaxially aligned camera through the powder feed nozzle. Symmetry, geometry and position of different levels of the powder jet can be analyzed through relevant algorithms. They also provide calculations of the particle density distribution the recorded images. The spatial particle density distribution of the powder jet can be calculated by superimposing individual levels along the jet. The measurement and monitoring principle was successfully tested with various nozzles and powder properties, making it possible to fully characterize a powder jet. A qualidade do processo de deposição de metais a laser depende de diversos fatores e componentes. Um dos componentes mais importantes é o fluxo de pó metálico. É necessário o monitoramento contínuo das diferentes variáveis e parâmetros que influenciam no fluxo de pó para se garantir os altos padrões de qualidade e estabilidade requeridos nas peças produzidas. Este monitoramento é realizado através de técnicas de controle de processos, onde o fluxo de pó metálico é iluminado lateralmente, por um laser de iluminação em formato de linha, e gravado por uma câmera coaxial ao bocal alimentador de pó. Simetria, geometria e posição de diferentes níveis do fluxo de pó podem ser analisados através de algoritmos relevantes. Tais algoritmos tornam possíveis também cálculos da distribuição das partículas no fluxo, através da sobreposição de imagens de todos os frames gravados no vídeo em cada nível do fluxo de pó. O processo de medição e análise foi testado com sucesso em diferentes bocais alimentadores de pó e com diferentes materiais e parâmetros do fluxo, tornando possível sua caracterização e qualificação.

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Lundkvist, Jennifer. "CFD Simulation of Fluid Flow During Laser Metal Wire Deposition using OpenFOAM : 3D printing." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-74476.

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The focus of this work was to simulate the fluid flow within a melt pool geometry, during an additive manufacturing process, implementing the CFD software OpenFOAM version 1806. Two separate models were created and run during this work, the first using a temperature mapping from a finite element (FE) model and the second being a free-standing model with Gaussian distributed laser beam striking down on the top surface. Both models were run with the standard solver icoReactingMultiphaseInterFoam, being a multiphase solver, with phase transition possibilities. Addition of gas particles was carried out during post-processing and these were to visualise the imperfections caused by melting metal alloys in a 3D printing case. During comparison of the movement of the free-standing model, using a moving laser beam, to the mapped temperature FE model, it was revealed that the fluid flow in the molten pool was heavily influenced by the pressure introduced by the laser beam. No streamlines were found that would indicate entrapment of gas particles during solidification. Fokuset på detta arbete var att simulera vätskeflöde i en smältpool-geometri, under en additiv-tillverkningsprocess. Detta implementerades med hjälp av CFD-mjukvaran OpenFOAM, version 1806. Två separata modeller skapades och simulerades under arbetets gång. Den första modellen kördes med hjälp av en mappning av temperaturfältet från finita-element-modellen (FE-modellen) och den andra modellen var en fristående modell tillsammans med en Gaussisk distribuerad laserstråle riktad ned på översta ytan. Båda simuleringarna använde sig av standardlösaren icoReactingMultiphaseInterFoam, vilket är en multifas-lösare, med möjlighet till fasövergångar. Tillägg av gaspartiklar utfördes under post-processing och dessa var för att visualisera porer som kan uppstå under smältning av metall-legering i en 3D-utskrivningsprocess. Vid jämförelse av den fristående modellen, som implementerade en rörlig laserstråle, till den mappade FE-modellen, uppdagades det att vätskeflödet i smältpoolen influerades starkt av trycket som orsakades av lasern. Inga strömlinjer tydde på en inkapsling av gaspartiklar under stelning.

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Swan, Lindsay Jane. "Characterization of residual stress driven deformation in terms of build height for thin walled laser metal deposition (Ti6AI4V) components." Thesis, Nelson Mandela University, 2018. http://hdl.handle.net/10948/23537.

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Ti6Al4V is the most commonly used of the titanium alloys and is known for its high strength to weight ratio and superb corrosion resistance compared to conventional steels. Ti6Al4V is used in applications in the aerospace, biomedical, automotive, power generation and oil and gas fields. Laser metal deposition (LMD) is an additive manufacturing (AM) platform used to build 3-D metal shapes. LMD is one of the most researched topics within the laser processing field currently and is advancing continuously. The rapid growth in the AM field is driven by market demands to reduce manufacturing costs, shorter lead times and an increasing demand for customized products. One of the major challenges facing the production of Ti6Al4V components using LMD is the high resultant residual stresses, limiting build size due to delamination or distortion. At the commencement of this study, little data pertaining to the residual stress build up in larger LMD components was available. This research was conducted to create an understanding of the relationship between build height and surface residual stresses and how they influence the dimensional stability of a part. Additionally, the relationship between build height and static mechanical properties was analysed. The effects of laser power, scanning speed and powder mass flow rate on the deposition layer were evaluated. The number of defects and the deposition build height were evaluated to determine the optimum process parameters for multi-layer components. An increase in laser power resulted in an increase in build height for the parameter window selected for the study. Similarly, an increase in build height was observed with an increase in powder mass flow rate, while an increase in scanning speed resulted in a decrease in build height. As laser power and scanning speed had inverse effects on the build height, heat input was evaluated to determine the optimum combination of the 2 parameters. Multilayer samples were produced with a laser power setting of 1900 W, a scanning speed of 0.01 m/s and a powder mass flow rate of 8 g/min. Fully dense components were produced with no notable defects. These components were analysed to reveal the relationship between build height and surface residual stresses and showed that the minimum residual stress observed in a component was related to an actual height from the base and was not affected by the build height of the sample. Maximum residual stresses were observed closest to the base of the cylinder and the stresses were larger in larger samples for both hoop and longitudinal surface residual stress. The micro-hardness of the samples increased as build height increased. The tensile strength remained within constant range between 1080 MPa and 1050 MPa for all samples successfully tested. Brittle failures were observed on the upper sections of the larger samples, attributed to the high micro-hardness observed in these areas. The study successfully evaluated the relationship between build height and surface residual stresses as well as build height and static mechanical properties thereby increasing the knowledge within this field.

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Engblom, Eyvind. "Effect of oxygen concentration in build chamber during laser metal deposition of Ti-64 wire." Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230638.

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Additive manufacturing of titanium and other metals is a rapidly growing field that could potentially improve component manufacturing through optimization of geometries, less material waste and fewer process steps. Although powder-based additive manufacturing processes have so far been predominant, methods using a wire as feedstock has gained popularity due to faster deposition rates and lower porosity in deposited material. The titanium alloy Ti-6Al-4V accounts for the majority of aerospace titanium alloy consumption and as titanium is a precious and expensive resource, reducing material waste is an important factor. Laser metal deposition with wire (LMD-w) is currently used in production at GKN Aerospace in Trolhättan. One important process parameter is the oxygen level in the chamber during deposition as titanium is highly reactive with oxygen at process temperatures. Oxygen enrichment of titanium can cause embrittlement and reduced fatigue life due to formation of alpha-case, an oxygen enriched region directly beneath the surface. The oxygen level in the chamber is controlled through extensive use of protective inert gas which is a costly and time-consuming practice. The objective of this thesis was to study how elevated oxygen levels in the chamber would affect surface oxidation, chemical composition, tensile properties and microstructure. Two different sample geometries were built with Ti-6Al-4V wire at an oxygen level of 100, 500 and 850 ppm. The subsequent analysis was based around microstructural features, alpha-case formation, chemical composition in surface layers, and tensile tests. Results showed that elevated oxygen levels in the build chamber did not degrade the chemical composition or tensile properties with regard to aerospace specifications. However, significant layers of alpha-case were found in all samples indicating that subsequent processing such as machining or etching is needed.

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Josse, François. "Apport à la compréhension et à la simulation numérique du procédé Laser Metal Deposition – poudre." Thesis, Ecully, Ecole centrale de Lyon, 2022. http://www.theses.fr/2022ECDL0025.

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La fabrication additive offre des libertés de conception et d’utilisation accrues grâce à l’obtention de pièces couche par couche à partir d’un modèle CAO. La réparation de pièces, le prototypage et l’ajout de fonctionnalités sont à l’heure actuelle les principales applications des procédés additifs. Dans ce contexte de nombreux challenges restent à résoudre pour atteindre la maitrise de ces procédés. L’un des principaux verrous à l’utilisation de la fabrication additive métallique reste la dimension des pièces pouvant être obtenues. La catégorie de technologie Direct Energy Deposition (DED), en particulier le dépôt de poudres par fusion laser, offre une solution à ce verrou en construisant la matière sans limites de dimension ni de forme. Afin d’augmenter la compréhension de ce procédé des travaux à la fois expérimentaux et numérique ont été conduit. Ces travaux s’attachent à la maitrise d’aciers à très hautes performances pour la production de planchers blindés ainsi qu’à la prédiction de la géométrie de cordon par la simulation numérique dans des temps de calcul très court.L’obtention de trois aciers inoxydable martensitique présentant de très hautes performances mécaniques (Re> 1000MPa, Rm> 1200 MPa et A%>12%) a été réalisée grâce à la maitrise des conditions thermiques au cours de la fabrication. Une attention particulière est portée sur la stabilité de la microstructure lors de la construction d’un volume par Laser Metal Deposition – poudre. L’évolution de comportement mécanique de ces matériaux en fonction de traitements thermiques et de la direction de sollicitation est également discuté.Une nouvelle stratégie numérique permettant l’obtention de la forme de la surface libre du bain fondu au moment de la solidification a été développée. Cette stratégie numérique permet de modéliser la géométrie des cordons à partir des paramètres procédés sans réaliser de calcul thermo-fluide. Le modèle numérique est également capable de reproduire l’affaissement de l’épaisseur de couche au cours de la construction d’un mur dans des temps de calcul très courts Additive manufacturing allows a greater freedom of geometry thanks to the layer-by-layer construction of the parts from a CAD model. Reparation, prototyping and functionalisation are the main applications of the additive processes. Therefore, many challenges are still to overcome in order to master those processes. One of the main challenges is the dimensions of the parts built by metallic additive manufacturing.The Direct Energy Deposition technologies, specifically powder fed Laser Metal Deposition, are a solution to build parts without neither dimension nor geometric limitations. Experimental and numerical work has been conducted in the objective of improving the understanding of this process. This work focus on mastering high mechanical performances as well as predict bead geometry thanks to the numerical simulation.Three martensitic stainless steel showing high mechanical performances (YS> 1000MPa, UTS> 1200 MPa et E%>12%) are obtained. A specific attention has been paid to the microstructure and its stability during the build-up the volumes. The effect of the heat treatments on the mechanical properties was investigated to improve the performances.A new numerical strategy simulating the freeform of the melt pool surface has been developped. The strategy allow the modelisation of the bead’s geometry from process parameters without any thermo-fluid calculation. The model is able to reproduce the bead’s thickness evolution during a wall build-up in short computation time

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Segerstark, Andreas. "Additive Manufacturing using Alloy 718 Powder : Influence of Laser Metal Deposition Process Parameters on Microstructural Characteristics." Licentiate thesis, Högskolan Väst, Avd för tillverkningsprocesser, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-8796.

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Additive manufacturing (AM) is a general name used for production methodswhich have the capabilities of producing components directly from 3D computeraided design (CAD) data by adding material layer-by-layer until a final component is achieved. Included here are powder bed technologies, laminated object manufacturing and deposition technologies. The latter technology is used in this study.Laser metal deposition using powder as an additive (LMD-p) is an AM processwhich uses a multi-axis computer numerical control (CNC) machine or robot toguide the laser beam and powder nozzle over the deposition surface. Thecomponent is built by depositing adjacent beads layer by layer until thecomponent is completed. LMD-p has lately gained attention as a manufacturing method which can add features to semi-finished components or as a repair method. LMD-p introduce a low heat input compared to arc welding methods and is therefore well suited in applications where a low heat input is of an essence. For instance, in repair of sensitive parts where too much heating compromises the integrity of the part.The main part of this study has been focused on correlating the main processparameters to effects found in the material which in this project is the superalloy Alloy 718. It has been found that the most influential process parameters are the laser power, scanning speed, powder feeding rate and powder standoff distance and that these parameters has a significant effect on the dimensionalcharacteristics of the material such as height and width of a single deposit as wellas the straightness of the top surface and the penetration depth.To further understand the effects found in the material, temperaturemeasurements has been conducted using a temperature measurement methoddeveloped and evaluated in this project. This method utilizes a thin stainless steel sheet to shield the thermocouple from the laser light. This has proved to reduce the influence of the emitted laser light on the thermocouples.

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Khademzadeh, Saeed. "Assessment and Development of Laser-Based Additive Manufacturing Technologies For Metal Microfabrication." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3424951.

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Nowadays many devices are produced in very small sizes or containing small features for particular application such as biomedical and microfluidic devices. Based on this demand, manufacturing processes should be developed for implementation of micro features in different ranges of sizes. A broad range of microfabrication technologies have been developed which have different applications and capabilities such as laser ablation, plating, photolithography, lithography and electroplating. However, such techniques are restricted when utilized to new microproducts which need the employment of a diversity of materials and have complicated three-dimensional geometries. Additive manufacturing (AM) needs each layer to be fabricated according to an exact geometry defined by a 3D model. This concept seems suitable for production of complicated parts with micro features. Development of robust metal additive manufacturing for microfabrication opens a new window toward miniaturization of metallic parts such as design and production of porous implants containing micro features and micro pores (50-500 µm). This work covers the development of micro additive manufacturing through two laser based AM processes with two different concepts: Micro direct metal deposition (µDMD) and selective laser melting (SLM). Nowadays, NiTi shape memory alloys are among the most interesting materials in the field of bioengineering and medical applications. Assessment of both techniques for production of NiTi porous scaffolds for biomedical application was carried out in this thesis. Long-term fixation of biomedical implants is achievable by using porous materials. These kinds of materials can develop a stable bone-implant interface. A critical aspect in production of porous implants is the design of macro and micro pores. At the first step of this thesis, the process parameters of both technologies were optimized to obtain full density samples. Secondly, porous scaffold structures with geometry controlled porosity were designed and manufactured using both technologies. Investigations using X-ray diffraction and scanning electron microscopy equipped with energy dispersive spectroscopy showed that B2-NiTi phase with small quantity of unwanted intermetallics can be obtained by micro direct metal deposition of mechanically alloyed Ni50.8Ti49.2 powder. Micro direct metal deposition was optimized through a set of process parameters and designed experiments to improve the geometrical accuracy and repeatability of micro fabrication. Micro X-ray computed tomography were used to analyze the surface topography, micro porosity, and deviations of products with respect to nominal geometrical models. Below 10% deviation to nominal geometrical models was achieved in hollow NiTi samples through a set of micro direct metal deposition process parameters and designed experiments. A comprehensive study was conducted on Ni50.8 Ti49.2 (at%) alloy to discover the influence of SLM process parameters on different aspects of physical and mechanical properties of NiTi parts. The provided knowledge allowed choosing different optimized parameters for production of complicated geometry with micro features maintaining the phase composition through the sample. For the first time and in this thesis, without going through any solid solution and heat treatments, single phase austenite was obtained in SLM NiTi parts with the selection of three different regimes of process parameters. This knowledge led to manufacture of NiTi bony structure applying different process parameters for the border and internal parts. The experimental results showed that SLM process with specific process parameters is a feasible micro additive manufacturing method to implement the complicated internal architecture of bone. It is an important issue in production of customized prostheses.

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Elhamali, S. O. "Material deposition and laser annealing of metal oxide thin films for electronics fabricated at low temperature." Thesis, Nottingham Trent University, 2016. http://irep.ntu.ac.uk/id/eprint/29062/.

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With an aim to investigate methods to realise low thermal-budget fabrication of aluminium doped zinc oxide (AZO) and indium gallium zinc oxide (IGZO) thin films, a dual step fabrication process was studied in this research. Initially, an experimental programme was undertaken to deposit AZO and IGZO films by radio frequency (RF) magnetron sputtering with no external substrate heating and at a wide range of deposition parameters including oxygen to argon ratio, RF power, and sputtering pressure. Thereafter, the samples were subjected to post-depositing annealing in air at ambient temperature utilising the advantages of excimer laser annealing (ELA) with a pulsed krypton fluoride (KrF) excimer laser at different laser fluences and number of pulses. The electrical, structural, compositional, and optical properties of the fabricated samples were systematically investigated as a function of the fabrication (deposition and annealing) conditions. A range of thin film characterisation techniques was used including 4-point probe (4PP), Van der Pauw (VDP), Hall Effect, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Atomic-force microscopy (AFM), Energy-dispersive X-ray spectroscopy (EDX), and optical transmittance and reflectance spectroscopy. Sputter-deposition of AZO and IGZO at room temperature revealed that the electrical properties of the deposited films are profoundly controlled by the deposition conditions applied. Low sputtering pressure of 2 mTorr is desired to obtain the best quality materials. However, high RF power of 180 W (4 W/cm2) is required to produce AZO with enhanced crystallinity, high electron density, and thus low resistivity. While, moderate RF power of 50 W (1.1 W/cm2) is applied to produce amorphous IGZO films with moderate-to-high resistivity suitable for thin film transistors (TFTs). The oxygen to argon ratio is found to have the most significant impact on defining the electrical properties for both AZO and IGZO. The resistivity of IGZO films was dependant on their metallic composition which in turn is controlled by the deposition conditions. TFTs were fabricated on silicon substrates with 40 nm thick IGZO as the active layer deposited at room temperature and different growth conditions. TFT performance was largely affected by the active layer deposition conditions. TFTs with the optimised IGZO, deposited at 50 W and 2 mTorr of 2% oxygen to argon ratio, exhibited a field effect mobility of 0.67 cm2/Vs, an on/off current ratio of 5x105, a turn on voltage of -0.15 V, and a subthreshold swing S of 0.28 V/decade. Upon ELA, AZO showed a resistivity reduction which is shown to result from increasing both the free electron density and mobility. When the optimised as-deposited AZO, 180 nm thick deposited at 180 W and 2 mTorr of 0.2% oxygen to argon ratio, annealed with 5 pulses at 125 mJ/cm2, a 50% resistivity reduction to 5x10-4 Ω.cm was obtained. It was demonstrated that average grain size increase, oxygen related defects decrease, and aluminium activation in doped ZnO are the origin of the AZO resistivity reduction upon ELA. Rapid thermal annealing (RTA) was also examined on AZO; RTA in nitrogen at 300°C for 20s increased the AZO gain size and doping efficiency leading to similar resistivity reduction to that achieved by the optimised ELA. Both ELA and RTA enhanced the AZO visible transmission to > 85 %, while the near infrared transmission was degraded due to higher electron density after annealing. The electro-optical properties of the optimised AZO samples obtained by ELA and RTA, which are very close to those of standard tin doped indium oxide (ITO), demonstrate the viability of AZO as an attractive transparent conducting material for various electronic applications. The potential use of AZO for photovoltaics (PVs) as well as the AZO stability against damp heat exposure were also examined. PVs with optimised ELA and RTA treated AZO samples showed comparable power conversion efficiency (PCE) to that of PVs with high-quality commercial ITO. The damp heat stability of AZO samples was strongly dependant on the fabrication conditions. In regard to IGZO, ELA increased the free electron density and mobility leading to better conductivity, while the amorphous structure is maintained. ELA with single pulse at a low energy density of 30 mJ/cm2 resulted in an improved performance for IGZO TFTs on silicon substrates achieving a field effect mobility of 3.33 cm2/Vs, an on/off current ratio of 3x107, a turn on voltage of +0.35 V, and a subthreshold swing S of 0.27 V/decade. Moreover, ELA was successfully applied to IGZO TFTs on polymer flexible PEN leading to TFTs with enhanced performance. Hence, a combination of RF magnetron sputtering at room temperature and ELA, which are both efficiently applicable to thin films mass production, has been demonstrated to provide a low thermal budget fabrication route for functional materials including AZO, as the most promising substitute to ITO in a wide range of applications, and IGZO as the most attractive material for TFT applications. This combination is an alternative thin film fabrication route to using elevated substrate temperature or post-deposition thermal annealing typically applied in the dominant literature reports, to obtain thin films with suitable characteristics.

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Stoffell, B. "Metal transport and deposition in hydrothermal fluids : insights from laser ablation microanalysis of individual fluid inclusion." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504926.

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Kelly, Shawn Michael. "Characterization and Thermal Modeling of Laser Formed Ti-6Al-4V." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/33104.

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The current work focuses on three aspects of laser formed Ti-6Al-4V: an evaluation of the as-deposited and heat treated macro and microstructures and preliminary results obtained from a model developed to calculate the temperature profile resultant of the laser forming process. A â solution treat and ageâ heat treatment with a variable cooling rate was performed on the Laser Formed Ti-6Al-4V single line builds. Increasing the cooling rate decreases the acicular alpha grain size in the basketweave WidmanstÃ¤tten alpha plus untransformed beta microstructure. Distinct features of the as-deposited macrostructure include: large columnar prior-beta grains that have grown epitaxially through multiple deposited layers; a well defined heat affected zone in the substrate; and the presence of â layer bands,â a macroscopic banding present at the top of every layer except for the last three layers to be deposited. The nominal microstructure between the layer bands consists of acicular basketweave WidmanstÃ¤tten alpha outlined in untransformed beta. The alpha grain width is smaller just above a layer band and larger just below a layer band. The microstructure of the layer band consists of larger colonies of acicular alpha outlined in untransformed beta. The gradient in the alpha grain size and presence of the layer band is due to thermal cycling as opposed to segregation effects which were ruled out using quantitative compositional analyses. Through analysis of the microstructural results the gradient in the nominal microstructure and formation of the layer band in layer n was caused by the deposition of layer n+2, and n+3, respectively. A thermal model has been developed to assist in the prediction and interpretation of the as-processed microstructure. The model is used to explain that the microstructural evolution of the layer bands and gradient microstructure in layer n is due to the deposition of layer n+2. The difference in the two analyses of microstructural evolution based on microstructural observations and thermal model results are due to differences in the parameter sets used to build and model the deposit. Master of Science

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Lindell, David. "Process Mapping for Laser Metal Deposition of Wire using Thermal Simulations : A prediction of material transfer stability." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-85474.

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Additive manufacturing (AM) is a quickly rising method of manufacturing due to its ability to increase design freedom. This allows the manufacturing of components not possible by traditional subtractive manufacturing. AM can greatly reduce lead time and material waste, therefore decreasing the cost and environmental impact. The adoption of AM in the aerospace industry requires strict control and predictability of the material deposition to ensure safe flights. The method of AM for this thesis is Laser Metal Deposition with wire (LMD-w). Using wire as a feedstock introduces a potential problem, the material transfer from the wire to the substrate. This requires all process parameters to be in balance to produce a stable deposition. The first sign of unbalanced process parameters are the material transfer stabilities; stubbing and dripping. Stubbing occurs when the energy to melt the wire is too low and the wire melts slower than required. Dripping occurs when too much energy is applied and the wire melts earlier than required. These two reduce the predictability and stability that is required for robust manufacturing. Therefore, the use of thermal simulations to predict the material transfer stability for LMD-w using Waspaloy as the deposition material has been studied. It has been shown that it is possible to predict the material transfer stability using thermal simulations and criterions based on preexisting experimental data. The criterion for stubbing checks if the completed simulation result produces a wire that ends below the melt pool. For dripping two criterions shows good results, the dilution ratio is a good predictor if the tool elevation remains constant. If there is a change in tool elevation the dimensionless slenderness number is a better predictor. Using these predictive criterions it is possible to qualitatively map the process window and better understand the influence of tool elevation and the cross-section of the deposited material. Additiv tillverkning (AT) är en kraftigt växande tillverkningsmetod på grund av sin flexibilitet kring design och möjligheten att skapa komponenter som inte är tillverkningsbara med traditionell avverkande bearbetning. AT kan kraftigt minska tid- och materialåtgång och på så sett minskas kostnader och miljöpåverkan. Införandet av AT i flyg- och rymdindustrin kräver strikt kontroll och förutsägbarhet av processen för att försäkra sig om säkra flygningar. Lasermetalldeponering av tråd är den AT metod som hanteras i denna uppsats. Användandet av tråd som tillsatsmaterial skapar ett potentiellt problem, materialöverföringen från tråden till substratet. Detta kräver att alla processparametrar är i balans för att få en jämn materialöverföring. Är processen inte balanserad syns detta genom materialöverföringsstabiliteterna stubbning och droppning. Stubbning uppkommer då energin som tillförs på tråden är för låg och droppning uppkommer då energin som tillförs är för hög jämfört med vad som krävs för en stabil process. Dessa två fenomen minskar möjligheterna för en kontrollerbar och stabil tillverkning. På grund av detta har användandet utav termiska simuleringar för att prediktera materialöverföringsstabiliteten för lasermetalldeponering av tråd med Waspaloy som deponeringsmaterial undersökts. Det har visat sig vara möjligt att prediktera materialöverföringsstabiliteten med användning av termiska simuleringar och kriterier baserat på tidigare experimentell data. Kriteriet för stubbning kontrolleras om en slutförd simulering resulterar i en tråd som når under smältan. För droppning finns två fungerande kriterier, förhållandet mellan svetshöjd och penetrationsdjup om verktygshöjden är konstant, sker förändringar i verktygshöjden är det dimensionslös ”slenderness” talet ett bättre kriterium. Genom att använda dessa kriterier är det möjligt att kvalitativt kartlägga processfönstret och skapa en bättre förståelse för förhållandet mellan verktygshöjden och den deponerade tvärsnittsarean.

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Diop, Ngom Balla. "Structural and physical properties of ReN i03 (Re=Sm, N d) nanostructured films prepared by Pulsed Laser Deposition." University of the Western Cape, 2010. http://hdl.handle.net/11394/8229.

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Philosophiae Doctor - PhD Very few systems allow the study of the relationship between structural changes and physical properties in such a clear way as rare earth nickelate ReNi03 perovskites (Re (rare earth) = Pr, Nd, Sm and Gd). Synthesized for the first time by Demazeau et al [1] in 1971 and completely forgotten for almost twenty years, these compounds have regained interest since the discovery of high-temperature superconductivity and giant magnetoresistive effects in other perovskite-related systems. Due to its Metal-Insulator Transition (MIT) and thermochromic properties, the rare earth nickelate perovskite ReNi03 has received a great deal of attention for the past ten years in their thin films form [12]. Such unusual electronic and optical features are all the more interesting since the metal-insulator transition temperature (TMn) can be tuned by changing the Re cation: LaNi03 is metallic. No minimum of the metallic conductivity of Sm0 . ssNd 0.45Ni03, as observed by Gire et al [12] (entropic effect), was reported by Ambrosini and Hamet [11]. It has been suggested by Obradors et al. [13] that changing the rare earth cation in the ReNi03 system, acts as internal chemical pressure (increasing internal pressure by substituting the rare earth cation with another one of larger ionic radius) which can lead, as for the isostatic pressure experiment, to a tunability of the metal-insulator transition temperature [14, 15]. Obradors et al [13] reported on a decrease of T MIT upon increasing isostatic pressure but with remaining metallic properties of PrNi03 and NdNi03 (same magnitude and thermal dependence of the electrical resistivity)

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Mazzucato, Federico. "Additive manufacturing through micro direct laser metal deposition technology: influence of the material and process parameters on the product quality." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3426196.

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Direct Laser Metal Deposition is a laser based Additive Manufacturing technology that is finding a growing employment and industrial application in sectors such as aerospace, automotive, biomedical, and electronics. Its great success is mainly related to its great capability to manufacture a wide range of material (both metals and ceramics) and its potentiality to confer a high degree of geometrical complexity to the realized artefacts. Part of its wide industrial diffusion is related to its great flexibility and versatility, which allow different process operations at time such as coating, repairing, and additively manufacturing new components as well. Research works, patents and developments of new Direct Laser Metal Deposition systems applied at the macro-scale represent a relevant part of the current State of the Art in metal Additive Manufacturing technologies. Nevertheless, to the best of Author’s knowledge, no research activities were carried out on the feasibility of Direct Laser Metal Deposition process applied at the micro-scale. This Ph.D. research work deals with the application of the Direct Laser Metal Deposition process at the micro-scale. The feasibility and the technical issues in downscaling the technology from macro to micro are discussed and analysed. The main parameters affecting the process are identified and their influence on the dimensional accuracy, structural integrity, surface roughness, and internal porosity of realized micro artefacts is investigated. The experimental results show the feasibility in applying the Direct Laser Metal Deposition process at the micro-scale thanks to the assumption of a new building approach for the artefact realization. The deposition of 3D full dense artefacts with very low surface roughness and a limited “stepwise” effect is demonstrated. Moreover, it is underlined the need of a new deposition nozzle concepts to increase the powder deposition efficiency and to ensure a high powder particle mass concentration in correspondence to the molten pool. This Ph.D. thesis is the first research work investigating the feasibility and application of the Direct Laser Metal Deposition technology at the micro-scale, representing a significant step forward in the development of the Manudirect ® MSL50 machine and providing a great contribution in terms of research activities in the field of Additive Manufacturing. Direct Laser Metal Deposition è una tecnologia additiva appartenente alla famiglia delle Direct Laser Deposition Technologies, dove il componente viene realizzato in modo additivo, strato dopo strato e senza l’utilizzo di utensili da taglio, attraverso l’impiego di una sorgente laser che localmente interagisce con polvere metallica depositata in modo diretto. L’interesse attorno a questa tecnologia è cresciuto in modo sostanziale negli ultimi anni, trovando sempre maggiore impiego in settori industriali quali l’aerospaziale, l’automobilistico, il biomedicale e l’elettronico. Grazie alle sue caratteristiche tecnologiche non convenzionali e alle sue uniche potenzialità, il processo di Direct Laser Metal Deposition combina l’elevata complessità geometrica conferita al prodotto alla possibilità di processare un’ampia gamma di materiali metallici, spaziando dalle leghe di Titanio a quelle di Nickel, dalle leghe di Rame ai Cermet. Un ulteriore aspetto e vantaggio tecnologico correlato con questa tecnologia riguarda la sua forte flessibilità e versatilità nel prestarsi ad essere impiegata in diversi processi tecnologici quali: coating, repairing e, non per ultimo, Additive Manufacturing. Ad oggi, l’attività scientifica in ambito Additive Manufacturing di metalli si focalizza principalmente sull’analisi dell’applicazione del processo di Direct Laser Metal Deposition su scala macro-metrica, in quanto, assieme alla tecnologia di Selective Laser Melting, risulta essere la tecnologia che riscuote maggior interesse in ambito scientifico-industriale. Tuttavia, ad oggi, poca attenzione è stata rivolta nell’analizzare l’applicabilità di tale processo su scala micro-metrica. La possibilità di produrre parti dall’elevata complessità geometrica e dal costo relativamente contenuto, attraverso la deposizione di materiali innovativi e difficilmente lavorabili per le tecnologie tradizionali (quali fresatura e tornitura per esempio), aprirebbe nuovi fronti applicativi e tecnologici a forte vantaggio di settori quali il biomedicale o l’elettronico dove la produzione di micro-componenti ad oggi trova forti limitazioni in termini di costi di produzione e fattibilità del componente. Questo lavoro di ricerca, quindi, si prefigge l’obiettivo di analizzare l’applicabilità della tecnologia di Direct Laser Metal Deposition su scala micro-metrica. La fattibilità e le problematiche tecnico-processuali legate allo “down-scaling” di tale processo da una scala macro ad una micro vengono trattate ed analizzate, investigando come i parametri di processo influenzino l’accuratezza dimensionale, la finitura superficiale e l’integrità strutturale della parte realizzata per Additive Manufacturing. Inoltre, tale attività ha lo scopo di dimostrare la fattibilità nel realizzare micro-strutture massive full-dense con un ottima rugosità superficiale, identificando le maggiori problematiche a livello processuale e proponendo nuovi futuri sviluppi miranti al miglioramento di tale tecnologia in ambito micro. Il lavoro di ricerca qui presentato rappresenta una forte spinta motivazionale ed innovativa all’ esplorazione della tecnologia di Direct Laser Metal Deposition applicata nel micro Additive Manufacturing di metalli, in particolare nel motivare futuri ricercatori nello sviluppare e migliorare le performance sistemi già esistenti come quello impiegato in questo progetto (sistema per micro-lavorazioni additive Manudirect ® MSL50).

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Curnis, Agathe. "Évolution métallurgique et corrosion à haute température de matériaux à gradient de composition élaborés par procédé Laser Metal Deposition - powder." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCK018.

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Les matériaux à gradient de composition présentent de nombreux avantages et notamment celui d’adapter localement le matériau en fonction de la sollicitation perçue par la pièce tout en limitant les risques d’incompatibilités entre les matériaux. Ce travail de thèse s’est concentré sur la réalisation d’un système de matériaux à gradient de composition par procédé Laser Metal Deposition-powder à partir d’un substrat en acier faiblement allié jusqu’à un alliage 625. Ce système multi-matériaux devant présenter une bonne tenue à la corrosion à haute température, son comportement à 800 et 650°C sous air de laboratoire, en absence ou en présence d’espèces chlorées, a été étudié.La caractérisation du système à gradient, dans un état brut de fabrication a révélé différentes microstructures et phases en présence dans les différentes régions du gradient. Lors de vieillissements à 800°C, des évolutions métallurgiques ont été mises en avant, notamment au niveau de l’alliage 625, avec la précipitation de la phase δ.La résistance à l’oxydation du système a été étudiée sous air de laboratoire à 800°C jusqu’à 2 500 h. Une cinétique parabolique liée à la formation de couches protectrices de chromine a été mise en avant. La présence d’un dépôt de NaCl accélère de manière catastrophique la dégradation de l’alliage 625. Dans ce cas, les couches de produits de corrosion sont très épaisses, très fissurées ou écaillées, composées majoritairement de NiO, Cr2O3 et d’oxydes de type spinelle Ni-Cr-Fe. La région de métal située à l’interface avec la couche d’oxyde est fortement endommagée, notamment par la formation d’un réseau de pores interconnectés permettant la diffusion rapide des espèces chlorées dans le cadre du mécanisme d’oxydation active se produisant dans ces conditions. En comparaison, à 650°C, la dégradation du matériau en présence du dépôt solide de NaCl est nettement ralentie, les couches de produits de corrosion sont moins épaisses et le substrat métallique très peu endommagé. Les différences de comportements entre les deux températures peuvent être comprises à travers des différences microstructurales et de volatilité de chlorures métalliques Compositionally graded materials offer numerous advantages, including the ability to locally adjust the material composition to adapt it to service conditions while minimizing the risks of incompatibilities between materials. This thesis work focused on the development of a compositionally graded material system using the Laser Metal Deposition-powder process, starting from a low-alloy steel substrate to alloy 625. As this multi-material system is expected to exhibit good high-temperature corrosion resistance, its behavior in an air atmosphere at 800°C and 650°C, with and without a NaCl solid deposit, was studied.Characterization of the as-built compositionally gradient system revealed various microstructures and phases depending on the regions of the gradient. Metallurgical evolutions were highlighted during aging at 800°C, particularly in alloy 625 with the precipitation of the δ phase.The oxidation resistance of the system was studied in an air atmosphere at 800°C for up to 2 500 h. Parabolic kinetics related to the formation of a protective Cr2O3 layer were highlighted. The presence of a NaCl deposit catastrophically accelerated the degradation of alloy 625. In this case, the corrosion scale was thick, highly cracked or spalled and mainly composed of NiO, Cr2O3, and (Ni,Cr,Fe)3O4. The metal region at the interface with the oxide layer was severely damaged, especially by the formation of an interconnected voids network allowing the rapid diffusion of chlorinated species in the active oxidation mechanism occurring under these conditions. In comparison, at 650°C, material degradation with a NaCl deposit was significantly slowed, with a thinner corrosion scale, and a less damaged substrate. Differences in behavior between the two temperatures can be understood through differences in microstructural characteristics and the volatility of metal chlorides."

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Gopagoni, Sundeep. "Microstructure Evolution in Laser Deposited Nickel-Titanium-Carbon in situ Metal Matrix Composite." Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc33154/.

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Ni/TiC metal matrix composites have been processed using the laser engineered net shaping (LENS) process. As nickel does not form an equilibrium carbide phase, addition of a strong carbide former in the form of titanium reinforces the nickel matrix resulting in a promising hybrid material for both surface engineering as well as high temperature structural applications. Changing the relative amounts of titanium and carbon in the nickel matrix, relatively low volume fraction of refined homogeneously distributed carbide precipitates, formation of in-situ carbide precipitates and the microstructural changes are investigated. The composites have been characterized in detail using x-ray diffraction, scanning electron microscopy (including energy dispersive spectroscopy (XEDS) mapping and electron backscatter diffraction (EBSD)), Auger electron spectroscopy, and transmission (including high resolution) electron microscopy. Both primary and eutectic titanium carbides, observed in this composite, exhibited the fcc-TiC structure (NaCl-type). Details of the orientation relationship between Ni and TiC have been studied using SEM-EBSD and high resolution TEM. The results of micro-hardness and tribology tests indicate that these composites have a relatively high hardness and a steady-state friction coefficient of ~0.5, both of which are improvements in comparison to LENS deposited pure Ni.

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Golalikhani, Maryam. "Structure and electronic properties of atomically-layered ultrathin nickelate films." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/353844.

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Physics Ph.D. This work presents a study on stoichiometry and structure in perovskite-type oxide thin films and investigates the role of growth–induced defects on the properties of materials. It also explores the possibility to grow thin films with properties close or similar to the ideal bulk parent compound. A novel approach to the growth of thin films, atomic layer-by-layer (ALL) laser molecular beam epitaxy (MBE) using separate oxide targets is introduced to better control the assembly of each atomic layer and to improve interface perfection and stoichiometry. It also is a way to layer materials to achieve a new structure that does not exist in nature. This thesis is divided into three sections. In the first part, we use pulsed laser deposition (PLD) to grow LaAlO3 (LAO) thin films on SrTiO3 (STO) and LAO substrates in a broad range of laser energy density and oxygen pressure. Using x-ray diffraction (θ-2θ scan and reciprocal space mapping), transmission electron microscopy (TEM) and x-ray fluorescence (XRF) we studied stoichiometry and structure of LAO films as a function of growth parameters. We show deviation from bulk–like structure and composition when films are grown at oxygen pressures lower than 10-2 Torr. We conclude that the discussion of LAO/STO interfacial properties should include the effects of growth–induced defects in the LAO films when the deposition is conducted at low oxygen pressures, as is typically reported in the literature. In the second part, we describe a new approach to atomically layer the growth of perovskite oxides: (ALL) laser MBE, using separate oxide targets to grow materials as perfectly as possible starting from the first atomic layer. We use All laser MBE to grow Ruddlesden–Popper (RP) phase Lan+1NinO3n+1 with n = 1, 2, 3 and 4 and we show that this technique enables us to construct new layered materials (n=4). In the last and main section of this thesis, we use All laser MBE from separate oxide targets to build the LaNiO3 (LNO) films as near perfectly as possible by depositing one atomic layer at a time. We study the thickness dependent metal-insulator transition (MIT) in ultrathin LNO films on an LAO substrate. In LNO, the MIT occurs in thin films and superlattices that are only a few unit cells in thickness, the understanding of which remains elusive despite tremendous effort devoted to the subject. Quantum confinement and structure distortion have been evoked as the mechanism of the MIT; however, first-principle calculations show that LaNiO3 remains metallic even at one unit cell thickness. Here, we show that thicknesses of a few unit cells, growth–induced disorders such as cation stoichiometry, oxygen vacancies, and substrate-film interface quality will impact the film properties significantly. We find that a film as thin as 2 unit cells, with LaO termination, is metallic above 150 K. An oxygen K-edge feature in the x-ray absorption spectra is clearly inked to the transition to the insulating phase as well as oxygen vacancies. We conclude that dimensionality and strain are not sufficient to induce the MIT without the contribution of oxygen vacancies in LNO ultrathin films. Dimensionality, strain, crystallinity, cation stoichiometry, and oxygen vacancies are all indispensable ingredients in a true control of the electronic properties of nanoscale strongly–correlated materials. Temple University--Theses

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Xu, Chencheng Verfasser], Georg [Akademischer Betreuer] [Roth, and Regina [Akademischer Betreuer] Dittmann. "In situ studies of the growth and oxidation of complex metal oxides by pulsed laser deposition / Chencheng Xu ; Georg Roth, Regina Dittmann." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1156786304/34.

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Xu, Chencheng [Verfasser], Georg [Akademischer Betreuer] Roth, and Regina [Akademischer Betreuer] Dittmann. "In situ studies of the growth and oxidation of complex metal oxides by pulsed laser deposition / Chencheng Xu ; Georg Roth, Regina Dittmann." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://nbn-resolving.de/urn:nbn:de:hbz:82-rwth-2016-069305.

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Weerasinghe, Hasitha C. "Electrical characterization of metal-to-insulator transition in iron silicide thin films on sillicone substrates." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001677.

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Kölbach, Moritz [Verfasser], Roel van de [Akademischer Betreuer] Krol, Alfred [Gutachter] Ludwig, and Roel van de [Gutachter] Krol. "Pulsed laser deposition of efficient ternary metal oxide photoelectrodes / Moritz Kölbach ; Gutachter: Alfred Ludwig, Roel van de Krol ; Betreuer: Roel van de Krol." Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1185571825/34.

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Perini, Matteo. "Additive manufacturing for repairing: from damage identification and modeling to DLD processing." Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/268434.

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The arrival on the market of a new kind of CNC machines which can both add and remove material to an object paved the way to a new approach to the problem of repairing damaged components. The additive operation is performed by a Direct Laser Deposition (DLD) tool, while the subtractive one is a machining task. Up to now, repair operations have been carried out manually and for this reason they are errors prone, costly and time consuming. Refurbishment can extend the life of a component, saving raw materials and resources. For these reasons, using a precise and repeatable CNC machine to repair valuable objects is therefore very attractive for the sake of reliability and repeatability, but also from an economical and environmental point of view. One of the biggest obstacles to the automation of the repairing process is represented by the fact that the CAM software requires a solid CAD model of the damage to create the toolpaths needed to perform additive operations. Using a 3D scanner the geometry of the damaged component can be reconstructed without major difficulties, but figuring out the damage location is rather difficult. The present work proposes the use of octrees to automatically detect the damaged spot, starting from the 3D scan of the damaged object. A software named DUOADD has been developed to convert this information into a CAD model suitable to be used by the CAM software. DUOADD performs an automatic comparison between the 3D scanned model and the original CAD model to detect the damaged area. The detected volume is then exported as a STEP file suitable to be used directly by the CAM. The new workflow designed to perform a complete repair operation is described placing the focus on the coding part. DUOADD allows to approach the repairing problem from a new point of view which allows savings of time and financial resources. The successful application of the entire process to repair a damaged die for injection molding is reported as a case study. In the last part of this work the strategies used to apply new material on the worn area are described and discussed. This work also highlights the importance of using optimal parameters for the deposition of the new material. The procedures to find those optimal parameters are reported, underlying the pros and cons. Although the DLD process is very energy efficient, some issues as thermal stresses and deformations are also reported and investigated, in an attempt to minimize their effects.

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Dissertations / Theses on the topic 'Laser Metal Deposition (LMD)'

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