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This book chapter elaborates on different additive manufacturing (AM) processes of copper and copper alloys. The scope is to give the reader a basic understanding of the state-of-the-art of copper additive manufacturing by different AM technologies, such as laser powder bed fusion (LPBF), laser metal deposition (LMD), binder jetting (BJ), and metal-fused filament fabrication (M-FFF). Furthermore, we want the reader to be able to use this knowledge to find and assess potential use cases. Recently, with the commercial availability of green laser sources, the difficulties for laser processing of pure copper were overcome, which gave AM technologies, such as LPBF and LMD new momentum and increased interest. AM technologies involving a subsequent sintering step. They are relatively new and gained interest due to fast build-up rates (BJ) or ease of operation (M-FFF). We will cover important material-related properties of copper and its implications for manufacturing and application (e.g. absorption, sinterability, conductivity, and its dependency on impurities). Further, we address applications for AM copper, present the state-of-the-art for above mentioned AM technologies and share our own recent research in this field.

Hybrid manufacturing, which, e.g., combines additive manufacturing with conventional machining processes, can be a way of overcoming limitations currently encountered in additive manufacturing. Cryogenic milling might be a viable option for hard-to-cut materials, as it leaves a contamination-free surface and can increase surface quality and tool life compared to conventional cooling concepts. In this study, the influence of cryogenic milling with carbon dioxide on titanium Ti-6Al-4V specimens manufactured with laser metal deposition (LMD) was investigated regarding tool wear and surface integrity in comparison to dry machining and machining with cooling lubricants. Moreover, additional layers of material were deposited on top of conventionally and cryogenically machined surfaces by means of LMD. The interface zone was then examined for defects. The milling process was closely monitored by means of thermal and high-speed imaging. Optical and tactile surface analysis provided evidence that lower roughness values and improved surface qualities could be obtained with cryogenic machining in comparison to dry machining. Moreover, significantly less tool wear was observed when a cryogenic cooling medium was applied. Although the utilization of conventional cooling lubricants resulted in satisfying surface qualities, substantial residual contamination on the milled surface was detected by means of fluorescence analysis. These contaminants are suspected to cause defects when the next layer of material is deposited. This is supported by the fact that pores were found in the weld bead applied on top of the milled specimens by means of LMD. Conversely, cryogenic machining resulted in very clean surfaces due to the residue-free evaporation of the coolant. Hence, a good metallurgical bonding between the weld bead and the milled substrate could be achieved. The results indicate the great potential of cryogenic milling in hybrid manufacturing, especially in terms of intermediate machining, as it provides residue-free surfaces for subsequent material deposition without an additional cleaning step and can significantly prolongate tool life.

In the last few years, there has been increasing interest in the processing of aluminum alloys using additive manufacturing (AM) processes. Thanks to their properties, aluminium alloys are extensively used in aerospace, rail, and automotive industries. Laser metal deposition (LMD), among the AM processes, can manufacture complex features as well as reinforcement structures on pre-existing complex parts. The work performed within the SAMOA project aims to expand the knowledge of the material properties of aluminum alloys when the LMD process is performed under atmospheric conditions. Both common alloys (AlSi10Mg, AlSi1Mg) and AM-specific alloys (AM205 and AlSi1Mg + 1 wt. %Zr) were analyzed and compared. Results show significantly lower amounts of internal defects and higher mechanical properties in AM-specific alloys. This database of mechanical properties will be used to design, simulate, and fabricate reinforcement structures on car frames to enhance their crash resistance and increase vehicle security. Moreover, to reduce material waste, the SAMOA project focuses also on the effects of powder recycling by analyzing both chemical and physical changes in the powder. The higher concentration of oxygen and hydrogen was separately analyzed by artificially increasing their concentration by heat treating AlSi10Mg powder. Results showed similar processability with a reduction in UTS of −31.4% and an increased elongation at fracture of +112.5%. Recycled powder, on the other hand, could not be easily collected, sieved, and reused since the identified physical and chemical changes of the powder lower its processability.

The present paper addresses the phenomena of hot cracking of nickel-based superalloys in the perspective of hybrid Laser Metal Deposition (combined application of induction and laser). This includes an extract of relevant theoretical considerations and the deduction of the tailored approach which interlinks material–scientific aspects with state-of-the-art manufacturing engineering. The experimental part reflects the entire process chain covering the manufacturing strategy, important process parameters, the profound analysis of the used materials, the gradual process development, and the corresponding hybrid manufacture of parts. Furthermore, hot isostatic pressing and thermal treatment are addressed as well as tensile testing at elevated temperatures. Further investigations include X-ray CT measurements, electron backscattered diffraction (EBSD), and scanning electron microscopy (SEM) as well as light optical microscope evaluation. The fundamental results prove the reliable processibility of the high-performance alloys Mar-M-247 and Alloy 247 LC and describe in detail the process inherent microstructure. This includes the grain size and orientation as well as the investigation of size, shape, and distribution of the γ′ precipitates and carbides. Based on these findings, the manufacturing of more complex demonstrator parts with representative dimensions is addressed as well. This includes the selection of a typical application, the transfer of the strategy, as well as the proof of concept.

In order to achieve high powder and energy efficiencies of Direct Metal Deposition processes knowledge about the basic effects of the interaction of the particle on the liquid surface is mandatory. ...

This study focused on the potential of topology optimization (TO) for metallic tertiary structures of spacecrafts produced by the additive manufacturing (AM) technique laser powder bed fusion. First, a screening of existing conventionally manufactured products was carried out to evaluate the benefits of a redesign concerning product performance and the associated economic impact. As a result of the study, the most suitable demonstrator was selected. This reference structure was redesigned by TO taking into consideration the AM process constraints. Another major aim of this work was to evaluate the possibilities and challenges of AM (accuracies, surface quality, process parameters, postmachining, and mechanical properties) in addition to the redesign process. A comprehensive approach was implemented including detailed analysis of the powder, mechanical properties, in-process parameters, and nondestructive inspection (NDI). All measured values were used for a back loop to the design process, thereby providing a final robust redesign. Finally, the fine-tuned demonstrator was built up in an iterative process. The parts were tested under representative conditions for the application to verify the performance. The demonstrator qualification test campaign contained thermal cycling, vibration testing, static load testing, and NDI. Thus, an improvement in technology readiness level up to ""near flight qualified"" was reached.

Advanced Manufacturing (AM) has the potential to improve existing technologies and applications in terms of performance, light-weighting and costs. In the context of the SME4ALM initiative, launched by DLR and ESA, the company Kampf Telescope Optics GmbH (KTO) in cooperation with the Fraunhofer Institute for Material and Beam Technology (IWS) have assessed the feasibility of AM to build a high-performance optical mirror for space applications. For the assessment of the AM potentials, a mirror design concept for cryogenic instruments for observations in the IR and NIR range was baselined. In a second step, Nickel-Phosphorus (NiP) was selected as optical coating. The combination of coating and mirror material is a primary design driver for optical performance. Both materials must have a very similar CTE as well as be compliant to modern optical manufacturing (diamond turning, polishing). As a promising candidate for NiP coating the AlSi40 was selected for the mirror structure. The potential advantages of AM for optical mirrors in terms of mechanical performance, cost, and manufacturing time were exploited. The achievement of those objectives was / will be demonstrated by: 1. verifying AM material properties and manufacturability of AM mirrors by material sample tests and subcomponent tests 2. designing AM mirror demonstrator by structural, thermal, and optical performance analysis 3. applying and elaborating AM specific design methods (topology optimization, sandwich structures with internal microstructures, monolithic design, etc.) 4. manufacturing, assembling, and testing AM mirror demonstrator to verify manufacturability and optical performance 5. comparing optical and mechanical performance of the AM mirror demonstrator to a conventional mirror by numerical analysis to exploit potential advantages of AM

Recently, additive manufacturing (AM) by laser metal deposition (LMD) has become a key technology for fabricating highly complex parts without any support structures. Compared to the well-known powder bed fusion process, LMD enhances manufacturing possibilities to overcome AM-specific challenges such as process inherent porosity, minor build rates, and limited part size. Moreover, the advantages aforementioned combined with conventional machining enable novel manufacturing approaches in various fields of applications. Within this contribution, the additive manufacturing of filigree flexure pivots using 316L-Si by means of LMD with powder is presented. Frictionless flexure pivot bearings are used in space mechanisms that require high reliability, accuracy, and technical cleanliness. As a contribution to part qualification, the manufacturing process, powder material, and fabricated specimens were investigated in a comprehensive manner. Due to its major impact on the process, the chemical powder composition was characterized in detail by energy dispersive X-ray spectroscopy (EDX) and inductively coupled plasma optical emission spectrometry (ICP-OES). Moreover, a profound characterization of the powder morphology and flowability was carried out using scanning electron microscopy (SEM) and novel rheological investigation techniques. Furthermore, quantitative image analysis, mechanical testing, laser scanning microscopy, and 3D shape measurement of manufactured specimens were conducted. As a result, the gained knowledge was applied for the AM-specific redesign of the flexure pivot. Finally, a qualified flexure pivot has been manufactured in a hybrid manner to subsequently ensure its long-term durability in a lifetime test bench.

Additive manufacturing processes have the potential to produce near-net shaped complex final parts in various industries such as aerospace, medicine, or automotive. Powder bed based and nozzle based processes like laser metal deposition (LMD), laser powder bed fusion (LPBF), and electron beam melting (EBM) are commercially available, but selecting the most suitable process for a specific application remains difficult and mainly depends on the individual know-how within a certain company. Factors such as the material used, part dimension, geometrical features, as well as tolerance requirements contribute to the overall manufacturing costs that need to be economically reasonable compared to conventional processes. Within this contribution, the quantitative analysis of basic geometrical features such as cylinders, thin walls, holes, and cooling channels of a special designed benchmark demonstrator manufactured by LMD; LPBF and EBM are presented to compare the geometrical accuracy within and between these processes to verify existing guidelines, connect the part quality to the process parameters, and demonstrate process-specific limitations. The fabricated specimens are investigated in a comprehensive manner with 3D laser scanning and CT scanning with regard to dimensional and geometrical accuracy of outer and inner features. The obtained results will be discussed and achievable as-built tolerances for assessed demonstrator parts will be classified according to general tolerance classes described [DIN ISO 2768-1, Allgemeintoleranzen—Teil 1: Toleranzen fur Langen- und Winkelmase ohne einzelne Toleranzeintragung (1991). Accessed 26 February 2018; DIN ISO 2768-2, Allgemeintoleranzen—Teil 2: Toleranzen fur Form und Lage ohne einzelne Toleranzeintragung (1991). Accessed 26 February 2018].

In metal additive manufacturing, microstructural inhomogeneities, like anisotropic mechanical strength and geometric limitations in directed energy deposition, electron beam melting, or selective laser sintering, have led to the exploration of alternative techniques in recent years. Among these techniques, fused filament fabrication is an attractive alternative due to its successes in producing dense parts, approaching traditional manufacturing specifications. Despite this success, many challenges remain to produce reliable parts with reproducible properties using FFF, particularly in the thermal treatment for part densification. Here are presented results of using a polyolefin-based binder system loaded with 55-59 vol. % Ti-6Al-4V powder to create a printable filament. Printed Ti-6Al-4V parts using these filaments were sintered at temperatures ranging from 900 to 1340 °C and evaluated by x-ray diffraction, scanning electron microscopy and optical microscopy. The sintered samples demonstrated a linear decrease in v-phase from 15 to 11 vol. % with increasing temperature, while residual stress and Young's modulus increased. Additionally, the density of printed and sintered Ti-6Al-4V parts could be increased up to 91 % of the theoretical density of Ti-6Al-4V by increasing the sintering temperature up to 1340 °C. Samples that were sintered at 1340 °C showed a higher Young's modulus compared to SLM samples, likely due to the increased a-phase in samples sintered at 1340 °C.

Additive Manufacturing (AM) processes as Laser Metal Deposition (LMD) addresses various benefits such as the build-up of complex shaped parts, the possibility of functional integration, reduced lead times or the use of difficult machinable materials compared to conventional manufacturing possibilities. Beside mentioned advantages, the use of more than one material in a component strongly increases the field of applications. Similar to structures in nature, multi-material arrangements can be realized by (I) sharp intersections from one material to the other (e. g. in the case of a thin corrosion protection), (II) graded structures enabling smoother material transitions (e. g. dissimilar materials joined together without defects), (III) composite structures with enclosed particles in a matrix material as well as by (IV) in-situ alloying of different material compositions. Due to varying material properties (e.g. thermo-physical, mechanical, optical), the combination of materials often requires a detailed investigation of occurring process phenomena and well-chosen modifications of the process regimes. Within this paper, (a) the right material feeding as well as powder interaction between various materials in Laser Metal Deposition, (b) the suitable selection of laser wavelengths for different materials, (c) process window adjustments by means of additional sensor equipment, (d) limitations of material combinations as well as (e) results and material characterization of multi-material parts are discussed. Phenomena are discussed by means of exemplary industrial applications, e.g. from the jet engine or medical business.

Mittels Laser-Pulver-Auftragschweißen lassen sich komplexe Leichtbaustrukturen ressourcenschonend und mit geringem Fertigungsaufwand erzeugen. Potenziell lassen sich mit dem Verfahren auch konventionell gefertigte Großbauteile ersetzen. Die Projektpartner Fraunhofer IWS, Photon, Arnold und Bombardier streben eine Gewichtsreduktionen von 10 bis 15 % für Komponenten in der Schienenfahrzeugtechnik an. Aus Designsicht gibt es bei der additiven Fertigung im Gegensatz zu konventionellen Fertigungsverfahren kaum geometrische Grenzen, da endformnah und formfrei generiert werden kann. Die am Computer erstellten CAD-Dateien können stark von klassischen Formvorgaben abweichen und somit optimal an topologieoptimierte und bionische Leichtbaukonzepte angepasst werden. Fertigungstechnisch überwindet ein kontinuierlich ablaufender additiver Fertigungsprozess die für die konventionelle Fertigung geltenden Einschränkungen. Als wesentliche Vorteile ergeben sich eine stark verkürzte Prozesskette und eine Steigerung der Bauteilkomplexität. Es wird versucht, das dargestellte Konzept der Erzeugung topologieoptimierter Großbauteile mittels Laser-Pulver-Auftragschweißen bis Ende des Forschungsvorhabens im Februar 2020 auf Seitenwandsegmente von Fahrzeugprototypen zu übertragen und unter anwendungsrelevanten Bedingungen technisch und wirtschaftlich entsprechend zu testen.

In the future, ceramic materials will find even more applications in aerospace, energy, and drive technology. Reasons for this are the comparatively low density and good long-term stability at high temperatures for applications for components exposed to high temperatures, e.g., of engines. By using increasing combustion temperatures through the use of ceramics increases the efficiency of modern drive systems [Ohnabe, Masaki, Onozuka, Miyahara, and Sasa, Compos. Part A Appl. Sci. Manuf. 30, 489–496 (1999)]. Despite the high interest of the aviation industry to increase the use of ceramic materials, the time- and energy-consuming classical production of these materials and the concomitant limiting factors in terms of shape and size are still a drawback [Krenkel, Ceramic Matrix Composites Fiber Reinforced Ceramics and their Applications (WIY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2008)]. This paper follows a new approach to producing ceramic matrix composites (CMCs). The laser material deposition (LMD) and selective laser melting techniques were used to investigate the coupling of different laser wavelengths into ceramic materials. By combining different energy sources and utilizing wavelength-dependent energy coupling, the additive manufacturing application of ceramic materials to metallic substrates was tested. With the knowledge gained from wavelength-dependent energy coupling, the potential for the production of CMCs should be demonstrated by means of LMD.In the future, ceramic materials will find even more applications in aerospace, energy, and drive technology. Reasons for this are the comparatively low density and good long-term stability at high temperatures for applications for components exposed to high temperatures, e.g., of engines. By using increasing combustion temperatures through the use of ceramics increases the efficiency of modern drive systems [Ohnabe, Masaki, Onozuka, Miyahara, and Sasa, Compos. Part A Appl. Sci. Manuf. 30, 489–496 (1999)]. Despite the high interest of the aviation industry to increase the use of ceramic materials, the time- and energy-consuming classical production of these materials and the concomitant limiting factors in terms of shape and size are still a drawback [Krenkel, Ceramic Matrix Composites Fiber Reinforced Ceramics and their Applications (WIY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2008)]. This paper follows a new approach to producing ceramic matrix composites (CMCs). The laser material deposition (LMD) and se...

Additive manufacturing design rules are different from those of conventional fabrication techniques. These allow geometries that would not be possible to achieve otherwise. One example of applicati ...

A major part of additive manufacturing focuses on the fabrication of metallic parts in different fields of applications. Examples include components for jet engines and turbines and also implants i ...

Additive manufacturing processes are frequently discussed in a competitive manner instead of being considered synergetically. This is particularly unfavorable since advanced machining processes in combination with additive manufacturing can be brought to the point that the results could not be achieved with the individual constituent processes in isolation [K. Gupta, R. F. Laubscher, and N. K. Jain, Hybrid Machining Processes—Perspectives on Machining and Finishing (Springer, New York, 2016), p. 68]. On that basis, boundary conditions from selective laser melting (SLM) and laser metal deposition (LMD) are considered in mutual contemplation [A. Seidel et al., in Proceedings of 36th International Congress on Applications of Laser & Electro-Optics, Atlanta, GA, 22–26 October 2017 (Fraunhofer IWS, Dresden, 2017), pp. 6–8]. The present approach interlinks the enormous geometrical freedom of powder-bed processing with the scalability of the LMD process. To demonstrate the potential of this approach, two different strategies are pursued. Firstly, a hollow structure demonstrator is manufactured layer wise via LMD with powder and subsequently joined with geometrically complex elements produced via SLM. Afterward, possibilities for a microstructural tailoring within the joining zone via the modification of process parameters are theoretically and practically discussed. Therefore, hybrid sample materials have been manufactured and interface areas are subjected to microstructural analysis and hardness tests. The feasibility of the introduced approach has been demonstrated by both fields of observation. The process combination illustrates a comprehensive way of transferring the high geometric freedom of powder-bed processing to the LMD process. The adjustment of process parameters between both techniques seems to be one promising way for an alignment on a microstructural and mechanical scale.Additive manufacturing processes are frequently discussed in a competitive manner instead of being considered synergetically. This is particularly unfavorable since advanced machining processes in combination with additive manufacturing can be brought to the point that the results could not be achieved with the individual constituent processes in isolation [K. Gupta, R. F. Laubscher, and N. K. Jain, Hybrid Machining Processes—Perspectives on Machining and Finishing (Springer, New York, 2016), p. 68]. On that basis, boundary conditions from selective laser melting (SLM) and laser metal deposition (LMD) are considered in mutual contemplation [A. Seidel et al., in Proceedings of 36th International Congress on Applications of Laser & Electro-Optics, Atlanta, GA, 22–26 October 2017 (Fraunhofer IWS, Dresden, 2017), pp. 6–8]. The present approach interlinks the enormous geometrical freedom of powder-bed processing with the scalability of the LMD process. To demonstrate the potential of this approach, two differe...

Conventional tactile and optical testing methods are not capable to detect complex inner geometries or complex surface shapes. Detecting porosities in parts is also not possible with those nondestructive methods. Among other material parameters, geometrical accuracy is essential to determine part's quality. Additive manufacturing processes also have to be optimized regarding geometry deviations caused by distortion or unfavorable orientation in the build chamber. For additive manufactured parts that incorporate previously mentioned features, high-performance computer tomography is the more suitable nondestructive testing method. Components of different materials such as plastics, ceramics, composites, or metals can be completely characterized. This nondestructive testing method was used for porosity analysis regarding the shape and local distribution of pores in an additive manufactured part to find correlations concerning the most suitable process conditions. The measured part data were also compared to original CAD files to determine zones of deviation and apply specific process strategies to avoid distortion. This paper discusses the results of integrating high-performance computer tomography (power: 500 W, max. part size: O 300 mm, 300 × 430 mm2) in a productionlike environment of additively manufactured parts for a wide range of technologies (i.e., electron beam melting and selective laser melting).Conventional tactile and optical testing methods are not capable to detect complex inner geometries or complex surface shapes. Detecting porosities in parts is also not possible with those nondestructive methods. Among other material parameters, geometrical accuracy is essential to determine part's quality. Additive manufacturing processes also have to be optimized regarding geometry deviations caused by distortion or unfavorable orientation in the build chamber. For additive manufactured parts that incorporate previously mentioned features, high-performance computer tomography is the more suitable nondestructive testing method. Components of different materials such as plastics, ceramics, composites, or metals can be completely characterized. This nondestructive testing method was used for porosity analysis regarding the shape and local distribution of pores in an additive manufactured part to find correlations concerning the most suitable process conditions. The measured part data were also compared to ...

In order to lead to a competitive advantage, there is the need to carefully consider the pros and cons of state-of-the-art manufacturing techniques. This is frequently carried out in a competitive ...

Laser-based additive manufacturing (AM) technologies such as laser metal deposition have been introduced in various fields of applications. Laser metal deposition is not only used for the fabrication of complete new parts but also for the purpose of repair and redesign. Therefore, weld beads with dimensions above 1 mm were mostly used in the past. In some cases, bead widths can even exceed 10 mm or more. However, the build-up of filigree parts by means of submillimeter structures has gained interest during the last several years. Fabrication of structures with small dimensions requires different process modifications along the process chain. This includes not only general process strategies but also adjusted system components. The changed process yields material deposition of varying geometries possibly used in aerospace, space, medical technology, and microtooling. Additionally, it can also be used in the repair of worn or damaged microparts. In this paper, the aforementioned process modifications are shown and demonstrated. In addition, high-speed process observations are discussed and, finally, the fabricated parts are analyzed. The latter includes nondestructive and also destructive methods. Based on the combination of changed process elements, a stable laser-based AM procedure is presented, which is already in production.

Meanwhile the laser build-up welding technology is a well industrially established technique for highly precise coating tasks and additive manufacturing. By means of new precise powder nozzle systems, modified process equipment as well as suited manufacturing strategies, the generation of customized components can be realized up to a detail resolution within the double-digit micrometer range. This opens a variety of new applications, e. g. in aviation, tooling industry or medical technology.

Functionalization of surfaces as well as the precise generation of metallic components are increasingly required in specific applications, especially in aviation, medical technology and micro tooling industry. The utilization of such parts is not only combined with beneficial properties including, for example, almost no porosity or cracking even on complex shaped parts, but also high flexibility and high robustness in processing. Some applications even require rapid adaptations of the generated geometry, e. g. to satisfy personal requirements of patients in the area of medical parts.By means of strongly reduced melt pool dimensions the generation of miniaturized structures and components can be realized up to a detail resolution within the double-digit micrometer range. This can be reached by the use of suitable laser sources (e. g. fiber and disc lasers). It also requires the implementation of precise powder nozzle systems, modified process equipment and new coating strategies supported by CAD/CAM interfaces. High precision laser cladding yields small heat affected zones and improved near-net shape contours. The interaction of complementary equipment permits a good reproducibility, but typically a rather low deposition rate.The comparison with high productive laser cladding which is characterized by deposition rates up to 15 kg/h shows the huge variability of this process. Hence, there is almost an order of magnitude of three between the smallest and the largest laser cladded weld bead track.Functionalization of surfaces as well as the precise generation of metallic components are increasingly required in specific applications, especially in aviation, medical technology and micro tooling industry. The utilization of such parts is not only combined with beneficial properties including, for example, almost no porosity or cracking even on complex shaped parts, but also high flexibility and high robustness in processing. Some applications even require rapid adaptations of the generated geometry, e. g. to satisfy personal requirements of patients in the area of medical parts.By means of strongly reduced melt pool dimensions the generation of miniaturized structures and components can be realized up to a detail resolution within the double-digit micrometer range. This can be reached by the use of suitable laser sources (e. g. fiber and disc lasers). It also requires the implementation of precise powder nozzle systems, modified process equipment and new coating strategies supported by CAD/CAM interf...