Aus der Einleitung: "Das selektive Elektronenstrahlschmelzen (engl. Electron Beam Melting (EBM®)) ist ein pulverbettbasiertes additives Fertigungsverfahren, mit dessen Hilfe metallische Bauteile schichtweise hergestellt werden können. Der schematische Aufbau einer entsprechenden Anlage ist in Abbildung 4 dargestellt. Dabei erfolgt die Strahlerzeugung im Bereich 1 (die Kathode besteht entweder aus Wolfram oder bei den neuesten Systemen aus einkristallinem LaB6). Die Strahlablenkung durch ein elektromagnetisches Linsensystem erfolgt im Bereich 2. Der Bereich 3 ist die eigentliche Baukammer, in der sich unter anderem die Vorratsbehälter für das Pulver, das Rakelsystem sowie die Komponenten des Bauraums (Käfig mit Hitzeschild, Bauplattform mit Startplatte) befinden. ..."

Introduction: Production systems go through changes over time and there are different factors driving the change. Metal Additive manufacturing (AM) could be a factor with industries that already havetaken interest in the manufacturing technique. Qualification and standards of manufacturing guide consistent product quality and could face challenges when implementing AM. However,most publications about metal AM are currently posted from a material point of view. This requires more publications with comprehensive overviews of metal AM and dive deeper into metal AMs industry applications, limitations and challenges. Purpose: The purpose of this thesis is to identify challenges that may arise in the implementation of AM. The intention is also to compare the conventional method of sand casting with AM for metal production targeted at excavators. This is accomplished by specifically highlighting the metallurgical benefits of AM. Research Questions: RQ1: What challenges arise when qualifying AM products for excavators? RQ2: What are the metallurgical benefits of an AM produced product in comparison to a Sand Casted product for excavator bucket teeth? Method: An inductive approach has been taken, with a literature, empirical and case study conducted.The construction of the theoretical framework used information from scientific articles and books. The findings of the empirical study arrived from information gathered through observations and experimentation, with help and interpretation from the case companies. The empirical findings will assist in answering the research questions. The case study consisted of metallurgical testing in form of porosity analysis, microstructure examination, hardness- and chemical composition test. Conclusion: Several challenges were discovered that will impact the qualification of AM products. These can affect the results derived from the case study, providing incorrect data. It can however be seen as beneficial as it provides knowledge of how to reduce or eliminate their impact withfuture analyses.The AM products tested, displayed positive metallurgical properties in comparison with sand casted products. A standout trait was the consistency in the dimension and density of the AM products, displaying how AM can create nearly identical products.

Pure copper (Cu) has the properties of high optical reflectivity and surface tarnishing as well as excellent thermal and electrical conductivity. Accordingly, laser-based additive manufacturing (AM) techniques confront various difficulties to produce thismaterial. In contrast, the electron beam melting (EBM) process is paving to become an excellent method to manufacture AM parts from such materials. This is since theelectron beam is not influenced by the optical reflectivity of the material. Furthermore, EBM works under vacuum that can protect the powder material from oxidization. In addition, the high working temperature and preheating process for each layer canensure a uniform heat input and a much lower cooling rate. Hence, the EBM processcan significantly prevent the parts from delamination failure caused by residual stress. Accordingly, this research work is intended to investigate the EBM processability and geometrical freedom/accuracy of EBM made copper components. The 99.95% pure Cu powder with a particle size range of 45-100μm are used to produce samples. All the samples are built with a certain layer thickness of 50μm with altering parameters, including the processing temperature, line offset, focus offset, beamspeed, and beam current. It is found that the processing temperature of 500°C leadsto low density and severe lateral melting/sintering. Accordingly, the temperature is lowered to 450°C, 400°C, 350°C, and 310°C to control the excessive lateral melting. Since dense parts could only be produced above 400°C, this work focuses on developing 400°C processing temperature with different line offset, focus offset, beamspeed, and beam current. However, it is observed that the processing window of the EBM process is rather narrow, too high or too low energy input could both result in a porous part with severe distortion. After many experimental optimizations runs, the combination of the optimum parameters is reached which can deliver parts with over 99% density and a good geometrical stability. After optimization, the benchmark partsare designed and manufactured according to electrical and thermal applications (using the optimum parameters). Afterwards, the corresponding geometrical freedomand accuracy of the copper components made by EBM is assessed and discussed. / Ren koppar (Cu) har egenskaper som hög optisk reflektivitet och ytans anlöning samt utmärkt termisk och elektrisk ledningsförmåga. Följaktligen möter laserbaserad additiv tillverkning (additive manufacturing, AM) olika svårigheter när det gäller att producera detta material. Däremot är elektronstrålesmältning ("electron beam melting", EBM) på väg att bli en utmärktmetod för att tillverka AM-delar av sådana material. Detta beror på att elektronstrålen inte påverkas av materialets optiska reflektivitet. Dessutom arbetar EBM under vakuum som kan skydda pulvermaterialet från oxidering. Dessutom kan den höga arbetstemperaturen och förvärmningsprocessen för varje lager säkerställa en jämn värmetillförsel och en mycket lägre kylningshastighet. EBM-processen kan därför i hög grad förhindra att delamineringsfel orsakade av restspänningar uppstår. Syftet med detta forskningsarbete är därför att undersöka EBM-processbarheten och den geometriska friheten/precisionen hos EBM tillverkade kopparkomponenter. Det 99,95 % rena Cu-pulvret med ett partikelstorleksområde på 45-100 μm används för att producera prover. Alla prover är byggda med en viss tjocklek på 50 μm med ändrade parametrar, inklusive bearbetningstemperatur, linjeförskjutning, fokusförskjutning, strålhastighet och strålström. Det har visat sig att bearbetningstemperaturen på 500°C leder till låg densitet och allvarlig lateral smältning/sintring. Följaktligen sänks temperaturen till 450°C, 400°C, 350°C och 310°C för att kontrollera den överdrivna laterala smältningen. Eftersom täta delar endast kunde produceras över 400°C, fokuserar detta arbete på att utveckla 400°C bearbetningstemperatur med olika linjeförskjutning, fokusförskjutning, strålhastighet och strålström. Det observeras dock att bearbetningsfönstret för EBMprocessen är ganska smalt, för hög eller för låg energitillförsel kan båda resultera i en porösdel med allvarlig förvrängning. Efter många experimentella optimeringskörningar uppnås kombinationen av de optimala parametrarna som kan leverera delar med över 99% densitet och en god geometrisk stabilitet. Efter optimering designas och tillverkas benchmarkdelarna i enlighet med elektriska och termiska applikationer (med optimala parametrar). Därefter bedöms och diskuteras motsvarande geometriska frihet och noggrannhet hos kopparkomponenterna tillverkade av EBM.

Les procédés de fabrication additive sont aujourd'hui de plus en plus utilisés dans l'industrie. Parmi les différentes technologies existantes, les procédés additifs métalliques, et notamment les procédés en couches, sont les plus prometteurs pour la conception de produits mécaniques. Des travaux ont été menés sur la thématique de la conception de produits réalisés par ces moyens, il traitent principalement du choix du procédé le plus adapté, de l'optimisation de formes ou présentent des cas de reconception. Il n'existe cependant pas de démarche globale de conception de produits qui permettent de prendre en compte les spécificités des procédés additifs en couches, notamment leurs contraintes de fabrication.Lors de ce travail de thèse, les changements que ces procédés introduisent dans le domaine des possibles en conception de produits ont été montrés et illustrés par des pièces réalisées par EBM. De nouvelles opportunités s'offrent au concepteur, comme l'accès à l'ensemble du volume de fabrication, la facilité de réalisation de pièces complexes, la possibilité de réaliser des treillis tridimensionnels et la capacité de produire des mécanismes sans assemblage. Les contraintes de fabrication de ces procédés sont spécifiques. Les phénomènes thermiques lors de la fabrication ont une incidence sur la fabricabilité et la qualité des pièces. La phase de retrait de poudre impose quant à elle des contraintes d'accessibilités. Pour prendre en compte cette évolution, il est nécessaire de concevoir spécifiquement les pièces pour la fabrication additive.Le procédé EBM est au centre du travail réalisé. Il s'agit d'un moyen de fabrication additive en couches, par fusion, à l'aide faisceau d'électrons. Les phénomènes thermiques, qui peuvent causer déformations et mauvaise intégrité de la matière, l'opération de dépoudrage et la problématique de la qualité des pièces fabriquées par EBM ont fait l'objet de caractérisations expérimentales. La durée de fabrication et le coût de revient technique des pièces réalisées par EBM ont également été étudiés, afin d'établir la relation entre durée, coût et géométrie des pièces.Pour de prendre en compte les contraintes explicitées auparavant, et pour bénéficier des importantes libertés que ce procédé offre aux concepteurs, une démarche de conception a été proposée. Cette démarche consiste à générer une ou plusieurs géométries initiales, soit directement par le concepteur, soit par l'utilisation d'outils d'optimisation topologique, à partir de données extraites du cahier des charges. Une fois le balançage de la pièce choisi (en prenant en compte les contraintes de fabrication, le tolérancement de la pièce et la productivité de la fabrication), la pièce est modélisée en incluant un jeu de paramètres pour effectuer une optimisation paramétrique. Cette optimisation permet de dimensionner la pièce, tout en prenant en compte les contraintes de fabrication. A l'issue de cette phase d'optimisation, la géométrie finale est obtenue en prenant en compte les exigences des opérations de parachèvement éventuelles et en définissant les supports, s'ils sont nécessaires. Cette démarche a été illustrée par la reconception de deux pièces mécaniques qui répondent aux exigences de leur cahier des charges fonctionnel, sont fabricables à l'aide du procédé EBM et offrent des gains de masse importants.Enfin, un chapitre particulier est consacré aux perspectives mises en évidence (et ayant parfois fait l'objet de travaux préliminaires) à l'occasion de ce travail de thèse. / Nowadays, the use of Additive Manufacturing processes keeps growing in the industry. Among the numerous kinds of AM processes, metallic additive manufacturing processes, and metallic Additive Layer Manufacturing in particular, are the most interesting from a mechanical designer point of view. Several research studies have been conducted on the topic of Design For Additive Manufacturing, mostly discussing the choice of AM processes or presenting the redesign of parts. There is no specific design methodology for ALM processes that takes their specificities into account.During this PhD thesis, the changes that ALM processes bring to the design space were investigated. The designer has the opportunity to easily manufacture thin parts, complex parts, lattice structures or mechanisms that don't need any assembly. These processes also have specific manufacturing constraints compared to conventional processes. The heat dissipation is the most important factor since it can cause distortions and porosities. Powder removal, surface and geometrical quality also need to be considered during design. A specific design for additive manufacturing methodology is necessary to take these changes into account.This work focuses on the Electron Beam Manufacturing process. Experiments were conducted and analyzed to assess the manufacturability regarding the thermal phenomena (during melting), the powder removal and the quality of the parts produced by EBM. The impact of the part geometry on manufacturing duration and manufacturing cost was also established.In order to use allow designers to use these pieces of information, we suggested a designing methodology. From the requirements of the parts, one or several parts are generated by the designer or by using topological optimization tools. The orientation of the part inside the manufacturing space is set before designing a refined parametric geometry. This parametric geometry is optimized in order to meet the user requirements as well as the EBM requirements. The last step is the modification of the geometry to comply with the finishing operations (machining allowances for example) and the placement of supports, if needed. This methodology was illustrated with the redesign of two example parts and showed important mass savings from the parts (while meeting user and process requirements).The prospects discovered and highlighted during this work, some of which were preliminary investigated, are presented in a specific chapter.

No description available.

This doctoral thesis is devoted to studying the possibilities of using additive manufacturing (AM) and design based on computed tomography (CT), for the production of patient-specific implants within orthopedic surgery, initially in a broad perspective and, in the second part of the thesis focusing on customized clavicle osteosynthesis plates. The main AM method used in the studies is the Electron Beam Melting (EBM) technology. Using AM, the parts are built up directly from 3D computer models, by melting or in other ways joining thin layers of material, layer by layer, to build up the part. Over the last 20 years, this fundamentally new way of manufacturing and the rapid development of software for digital 3D reconstruction of anatomical models from medical imaging, have opened up entirely new opportunities for the design and manufacturing of patient-specific implants. Based on the information in a computed tomography (CT) scan, both digital and physical models of the anatomy can be created and of implants that are customized based on the anatomical models.   The main method used is a number of case studies performed, focusing on different parts of the production chain, from CT-scan to final implant, and with several aims: learning about the details of the different steps in the procedure, finding suitable applications, developing the method and trying it out. The first study was on customized hip stems, focusing on the EBM method and its special preconditions and possibilities. It was followed by a study of bone plates, designed to follow the patient-specific bone contour, in this case a tibia fracture including the whole production chain. Further, four cases of patient-specific plates for clavicle fracture fixation were performed in order to develop and evaluate the method. The plates fit towards the patient’s bone were tested in cooperation with an orthopedic surgeon at Östersund hospital. In parallel with the case studies, a method for finite element (FE) analysis of fixation plates placed on a clavicle bone was developed and used for the comparative strength analysis of different plates and plating methods. The loading on the clavicle bone in the FE model was defined on a muscle and ligament level using multibody musculoskeletal simulation for more realistic loading than in earlier similar studies.    The initial studies (papers I and II) showed that the EBM method has great potential, both for the application of customized hip stems and bone plates; in certain conditions EBM manufacturing can contribute to significant cost reductions compared to conventional manufacturing methods due to material savings and savings in file preparation time. However, further work was needed in both of the application areas before implementation. The studies on the fracture fixation using patient-specific clavicle plates indicated that the method can facilitate the work for the surgeon both in the planning and in the operating room, with the potential of a smoother plate with a better fit and screw positioning tailored to the specific fracture (paper VI). However, a large clinical trial is required to investigate the clinical benefit of using patient-specific plates. The FE simulations showed similar stress distributions and displacements in the patient-specific plates and the commercial plates (papers III to VI).   To summarize: the results of this thesis contribute to the area of digital design and AM in patient-specific implants with broad basis of knowledge regarding the technologies used and areas in which further work is needed for the implementation of the technology on a larger scale. Further, a method has been developed and initially evaluated for implementation in the area of clavicle fracture fixation, including an approach for comparing the strength of different clavicle plates.

In recent years, additive manufacturing (AM) of Alloy 718 has received increasing interest in the field of manufacturing engineering owing to its attractive features compared to those of conventional manufacturing methods. The ability to produce complicated geometries, low cost of retooling, and control of the microstructure are some of the advantages of the AM process over traditional manufacturing methods. Nevertheless, during the building process, the build material undergoes complex thermal conditions owing to the inherent nature of the process. This results in phase transformation from liquid to solid and solid state. Thus, it creates microstructural gradients in the built objects, and as a result,heterogeneous material properties. The manufacturing process, including the following heat treatment that is used to minimise the heterogeneity, will cause the additively manufactured material to behave differently when compared to components produced by conventional manufacturing methods. Therefore, understanding the microstructure formation during the building and subsequent post-heat treatment is important, which is the objective of this work. Alloy 718 is a nickel-iron based super alloy that is widely used in the aerospace industry and in the gas turbine power plants for making components subjected tohigh temperatures. Good weldability, good mechanical properties at high temperatures, and high corrosion resistance make this alloy particularly suitablefor these applications. Nevertheless, the manufacturing of Alloy 718 components through traditional manufacturing methods is time-consuming and expensive. For example, machining of Alloy 718 to obtain the desired shape is difficult and resource-consuming, owing to significant material waste. Therefore, the application of novel non-conventional processing methods, such as AM, seems to be a promising technique for manufacturing near-net-shape complex components.In this work, microstructure modelling was carried out by using multiphase-field modelling to model the microstructure evolution in electron beam melting (EBM) and laser metal powder directed energy deposition (LMPDED) of Alloy 718 and x subsequent heat treatments. The thermal conditions that are generated during the building process were used as input to the models to predict the as-built microstructure. This as-built microstructure was then used as an input for the heat treatment simulations to predict the microstructural evolution during heat treatments. The results showed smaller dendrite arm spacing (one order of magnitude smaller than the casting material) in these additive manufactured microstructures, which creates a shorter diffusion length for the elements compared to the cast material. In EBM Alloy 718, this caused the material to have a faster homogenisation during in-situ heat treatment that resulting from the elevated powder bed temperature (> 1000 °C). In addition, the compositional segregation that occurs during solidification was shown to alter the local thermodynamic and kinetic properties of the alloy. This was observed in the predicted TTT and CCT diagrams using the JMat Pro software based on the predicted local segregated compositions from the multiphase-field models. In the LMPDED Alloy 718 samples, this resulted in the formation of δ phase in the interdendritic region during the solution heat treatment. Moreover, this resulted in different-size precipitation of γ'/γ'' in the inter-dendritic region and in the dendrite core. Themicro structure modelling predictions agreed well with the experimental observations. The proposed methodology used in this thesis work can be an appropriate tool to understand how the thermal conditions in AM affect themicro structure formation during the building process and how these as-built microstructures behave under different heat treatments.

The thesis focuses on exploring the sub-grain structure in stainless steel 316L prepared by additive manufacturing (AM). Two powder-bed based AM methods are involved: selective laser melting (SLM) and electron beam melting (EBM). It is already known that AM 316L has heterogeneous property and hierarchy structure: micro-sized melt pools, micro-sized grains, nano-sized sub-grain structure and nano-sized inclusions. Yet, the relation among these structures and their influence on mechanical properties have not been clearly revealed so far. Melt pool boundaries having lower amount of sub-grain segregated network structures (Cellular structure) are weaker compared to the base material. Compared with cell boundaries, grain boundaries have less influence on strength but are still important for ductility. Cell boundaries strengthen the material without losing ductility as revealed by mechanical tests. Cellular structure can be continuous across the melt pool boundaries, low angle sub-grain boundaries, but not grain boundaries. Based on the above understanding, AM process parameters were adjusted to achieve customized mechanical properties. Comprehensive characterization were carried out to investigate the density, composition, microstructure, phase, magnetic permeability, tensile property, Charpy impact property, and fatigue property of both SLM and EBM SS316L at room temperature and at elevated temperatures (250°C and 400°C). In general, SLM SS316L has better strength while EBM SS316L has better ductility due to the different process conditions. Improved cell connection between melt pools were achieved by rotating 45° scanning direction between each layer compared to rotating 90°. Superior mechanical properties (yield strength 552 MPa and elongation 83%) were achieved in SLM SS316L fabricated with 20 µm layer thickness and tested in the building direction. Y2O3 added oxide dispersed strengthening steel (ODSS) were also prepared by SLM to further improve its performance at elevated temperatures. Slightly improved strength and ductility (yield strength 574 MPa and elongation 90%) were obtained on 0.3%Y2O3-ODSS with evenly dispersed nanoparticles (20 nm). The strength drops slightly  but ductility drops dramatically at elevated temperatures. Fractographic analysis results revealed that the coalescence of nano-voids is hindered at room temperature but not at elevated temperatures. The achieved promising properties in large AM specimens assure its potential application in nuclear fusion. For the first time, ITER first wall panel parts with complex inner pipe structure were successfully fabricated by both SLM and EBM which gives great confidence to application of AM in nuclear industry. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.</p>

The titanium alloy, Ti-6Al-4V, is vastly studied and used in many applications because it has a transformation microstructure, which can be tailored for apt properties that are consistent up to 500°C. Compared to conventional steels, this alloy favours certain applications due to its high specific strength, hardenability, corrosion resistance, biocompatibility and weldability. Its weldability makes the alloy a good candidate for additive manufacturing (AM). Ti-6Al-4V parts are widely built by the AM process of electron beam melting (EBM). However, heat transfer remains crucial in EBM process. The high intensity localized, moving, electron beam heat source and the rapid self-cooling are critical, especially in thin parts/ sections. When thin sections are built by the EBM process, there will be microstructural variation in their build direction, which can lead to the variation of their mechanical properties. It is necessary to understand the microstructure and mechanical properties of thin sections when they are used as functional parts in various applications in aerospace, automotive, medical, etc. industries. The microstructure, tribological behaviour and mechanical properties of Ti-6Al-4V, as-built EBM thin plates were studied by means of various hardness, scratch and tensile testing. The hardness and scratch tests were performed on the thin plates to correlate the microstructural variation. In-situ micro tensile test was performed inside the scanning electron microscope (SEM), to see the sample’s deformation behaviour. Microstructural characterization revealed equiaxed grains in the transverse section and the longitudinal surface exhibited columnar grains elongated along the build direction. The size of the equiaxed grains are found to vary across the thickness of the plate. The indentation and scratch hardness also vary in correlation with the varying grain size across the plate’s thickness. The micro tensile results reveal that the tensile properties of the thin plate are comparable to that of its bulk Ti-6Al-4V counterpart.

Additive manufacturing (AM) is a technology that inverts the procedure of traditional machining. Instead of starting with a billet of material and removing unwanted parts, the AM manufacturing process starts with an empty workspace and proceeds to fill this workspace with material where it is desired, often in a layer-by-layer fashion. Materials available for AM processing include polymers, concrete, metals, ceramics, paper, photopolymers, and resins. This thesis is concerned with electron beam melting (EBM), which is a powder bed fusion technology that uses an electron beam to selectively melt a feedstock of fine powder to form geometries based on a computer-aided design file input. There are significant differences between EBM and conventional machining. Apart from the process differences, the ability to manufacture extremely complex parts almost as easily as a square block of material gives engineers the freedom to disregard complexity as a cost-driving factor. The engineering benefits of AM also include manufacturing geometries which were previously almost impossible, such as curved internal channels and complex lattice structures. Lattices are lightweight structures comprising a network of thin beams built up by multiplication of a three-dimensional template cell, or unit cell. By altering the dimensions and type of the unit cell, one can tailor the properties of the lattice to give it the desired behavior. Lattices can be made stiff or elastic, brittle or ductile, and even anisotropic, with different properties in different directions. This thesis focuses on alleviating one of the problems with EBM and AM, namely the relatively few materials available for processing. The method is to take a closer look at the widely used stainless steel 316LN, and investigate the possibility of processing 316LN powder via the EBM process into both lattices and solid material. The results show that 316LN is suitable for EBM processing, and a processing window is presented. The results also show that some additional work is needed to optimize the process parameters for increased tensile strength if the EBM-processed material is to match the yield strength of additively laser-processed 316L material. / <p>Vid tidpunkten för framläggningen av avhandlingen var följande delarbete opublicerat: delarbete 3 (inskickat).</p><p>At the time of the defence the following paper was unpublished: paper 3 (submitted).</p>