Vorrichtung zur generativen Fertigung eines dreidimensionalen Körpers in einem Pulverbett mit mehreren Rakeln

The invention relates to a device for the generative production of a three-dimensional body in a powder bed having a production region, which has a lowerable surface on which the powder bed is arranged, and having a plurality of doctor blades for uniform distribution of a supplied powdery material over the surface of the powder bed. The device furthermore has an apparatus for carrying out translational movements of the doctor blades over the surface of the powder bed, and an apparatus by means of which at least one energy beam is directed onto the surface of the powder bed, the focal spot thereof being movable in two dimensions

Pure Copper: Advanced Additive Manufacturing

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

A comprehensive study on fused filament fabrication of Ti-6Al-4V structures

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 β-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 α-phase in samples sintered at 1340 °C

Additive Manufacturing of β-NiAl by Means of Laser Metal Deposition of Pre-Alloyed and Elemental Powders

The additive manufacturing (AM) technique, laser metal deposition (LMD), combines the advantages of near net shape manufacturing, tailored thermal process conditions and in situ alloy modification. This makes LMD a promising approach for the processing of advanced materials, such as intermetallics. Additionally, LMD allows the composition of a powder blend to be modified in situ. Hence, alloying and material build-up can be achieved simultaneously. Within this contribution, AM processing of the promising high-temperature material β-NiAl, by means of LMD, with elemental powder blends, as well as with pre-alloyed powders, was presented. The investigations showed that by applying a preheating temperature of 1100 °C, β-NiAl could be processed without cracking. Additionally, by using pre-alloyed, as well as elemental powders, a single phase β-NiAl microstructure can be achieved in multi-layer build-ups. Major differences between the approaches were found within substrate near regions. For in situ alloying of Ni and Al, these regions are characterized by an inhomogeneous elemental distribution in a layerwise manner. However, due to the remelting of preceding layers during deposition, a homogenization can be observed, leading to a single-phase structure. This shows the potential of high temperature preheating and in situ alloying to push the development of new high temperature materials for AM

Advanced manufacturing approach via the combination of selective laser melting and laser metal deposition

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

Microstructure of NiAl-Ta-Cr in situ alloyed by induction-assisted laser-based directed energy deposition

The development of new high temperature materials for coatings as well as structural components is an important topic to contribute to a higher efficiency and sustainability of e.g. gas turbine engines. One promising new class of high temperature materials are NiAl-based alloys. Within this study, the microstructure and microhardness of NiAl-Ta-Cr alloys with varying Cr and Ta content were investigated. Graded specimens were fabricated by laser-based directed energy deposition utilizing an in situ alloying approach by mixing elemental Ta and Cr as well as pre-alloyed NiAl powder. Thermodynamic calculations were performed to design the alloy compositions beforehand. Inductive preheating of the substrate was used to counter the challenge of cracking due to the high brittleness. The results show that the cracking decreases with increasing preheating temperature. However, even at 700 °C, the cracking cannot be fully eliminated. Scanning electron microscopy, X-ray diffraction and electron backscatter diffraction revealed the formation of the phases B2-NiAl, A2-Cr and C14-NiAlTa within NiAl-Ta and NiAl-Cr alloys. For NiAl-Ta-Cr compositions, deviations regarding the phase formation between calculation and experiment were observed. Maximum hardness values were achieved within the NiAl-Ta and NiAl-Ta-Cr systems for the eutectic compositions at 14 at.-% Ta with maximum values above 900 HV0.1

Additive manufacturing with high-performance materials and light-weight structures by laser metal deposition and laser infiltration: Blog Beitrag

In laser metal deposition, parts are generated by use of a large variety of different alloys in industrial fields such as aviation, energy, tooling or medical technology. Due to permanently increasing requirements (e. g. enhanced system efficiencies or environmental standards) in almost all fields of applications the use of very high-performance materials, which unfortunately tend to have a high crack-sensitivity, is more and more required. In addition the placement of metallic materials on composite structures (e. g. CFRP) is a challenging but interesting material combination due to the light weight of the resulting structure. In this paper, processing of these material combinations is discussed and examples of (potential) applications are shown

Comparison of dimensional accuracy and tolerances of powder bed based and nozzle based additive manufacturing processes: Paper presented at ICALEO 2019, International Congress on Applications of Lasers and Electro-Optics, October 7-10, 2019, Orlando, Florida

Additive Manufacturing (AM) 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 in a certain company. Factors such as the material used, part dimension, geometrical features as well as tolerance requirements contribute to the overall manufacturing costs which 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 is 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 in [1, 2]

Process characteristics in high-precision laser metal deposition using wire and powder

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

Grain size manipulation by wire laser direct energy deposition of 316L with ultrasonic assistance

The epitaxial growth of coarse and columnar grain structures along the build direction of additive manufactured metals is a usual phenomenon. As a result, as-built components often exhibit pronounced anisotropic mechanical properties, reduced ductility, and, hence, a high cracking susceptibility. To enhance the mechanical properties and processability of additive manufactured parts, the formation of equiaxed and fine grained structures is thought to be most beneficial. In this study, the potential of grain refinement by ultrasonic excitation of the melt pool during laser wire additive manufacturing has been investigated. An ultrasound system was developed and integrated in a laser wire deposition machine. AISI 316L steel was used as a substrate and feedstock material. A conversion of coarse, columnar grains (d(m) = 284.5 mu m) into fine, equiaxed grains (d(m) = 130.4 mu m) and a weakening of typical -fiber texture with increasing amplitude were verified by means of light microscopy, scanning electron microscopy, and electron backscatter diffraction analysis. It was demonstrated that the degree of grain refinement could be controlled by the regulation of ultrasound amplitude. No significant changes in the dendritic structure have been observed. The combination of sonotrode/melt pool direct coupling and the laser wire deposition process represents a pioneering approach and promising strategy to investigate the influence of ultrasound on grain refinement and microstructural tailoring.Godkänd;2023;Nivå 0;2023-09-05 (hanlid);Konferensartikel i tidskrift</p