Isabelle Günther, Benjamin Zillmann, Thomas Niendorf
Power electronics feature small functional structures, which are preferably made of pure copper and are built on sensitive ceramic-based substrates, so called Direct Bonded Copper (DBC) substrates. A novel additive manufacturing (AM) approach employs the laser powder bed fusion (PBF-LB/M) process to manufacture the functional structures directly onto the DBC, eventually enabling the reduction of manufacturing cost and effort. Processing of pure copper in the PBF-LB/M process is challenging due to its reflectivity and its thermal conductivity. Additionally, using a DBC in the PBF-LB/M process leads to complex multi-material interactions. Focusing on the application, the processability of pure copper with a green and an infrared laser in the same machine setup was investigated. The influence of laser wavelength and process parameters on the resulting part properties was analyzed, differences between both wavelengths were pinpointed, and suitable parameter sets were identified.
Keywords: additive manufacturing; laser powder bed fusion; ceramic-based substrate; pure copper; laser wavelength
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David Sommer, Maximilian Peters, Cemal Esen, Ralf Hellmann
As lattice structures in various designs are used in additive manufacturing for lightweight components, the mechanical characterisation and fracture behaviour is of upmost importance for their industrial application. In this study, the fatigue behaviour of Inconel 718 lattice structures is evaluated, comparing sole PBF-LB/M to a hybrid additive manufacturing process combining PBF-LB/M with in-situ high-speed milling. At first, the static and dynamic mechanical load behaviour of different packing densities is analysed, determining the compressive strength and the endurance limit. Secondly, hybrid additive manufactured components are compared to PBF-LB/M built parts with respect to these mechanical properties, revealing improved compressive properties and modified regimes of fatigue. In addition, differences in fracture behaviour are qualified by fractographic and surface analysis. Overall, it can be summarized that the mechanical load characteristics, especially the fatigue behaviour, are improved for hybrid additively manufactured components with a superior surface quality of Ra < 1 µm.
Keywords: Hybrid Additive Manufacturing; Lattice Structures; Fatigue Behaviour; Inconel 718
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Microstructural Fracture Behaviour of PBF-LB/M Inconel 718 Components within different HIP Processes
David Sommer, Ben Truetsch, Cemal Esen, Ralf Hellmann
We report on a study of different hot isostatic pressing (HIP) cycles, improving the mechanical properties of additively manufactured Inconel 718 components. For this, PBF-LB/M built components are post-processed by different HIP sequences, as gas pressure and processing time are varied, leading to differences in microstructure and material characteristics. Static and dynamic mechanical testing are performed, evaluating the changes in mechanical properties with particular focus on the ultimate tensile strength and endurance limit. Furthermore, metallographic analysis is employed to investigate the achieved density and microhardness. Microstructural analysis, showing the grain boundaries, is used to identify generated phases and precipitations of the material matrix. Moreover, the fracture behaviour is classified by grain deformation during mechanical testing. As the HIP leads to microstructural changes of Inconel 718 components, mechanical properties can be improved significantly, enhancing the ultimate tensile strength and simultaneously the endurance limit.
Keywords: Hot isostatic pressing; Fatigue Behaviour; Ultimate Tensile Strenght; Microstructure; Inconel 718
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T. Eismann, T. Griemsmann, M. Ernst, J. Duesing, M. Springer, P. Dyroey, R. Kalms, M. Müller, P. Wessels, J. Neumann, N. Schwarz, B. Grefen, S. Linke, E. Stoll, S. Kaierle
The Moon serves as a stepping stone for humanity’s space colonization. Due to high transportation costs, utilizing lunar resources is considered essential for further development in space applications. Lunar regolith and its simulants exhibit a wide range of particle size distributions (PSDs). Simulants prepared under terrestrial conditions retain moisture, requiring pre-drying. Within this work, the influence of these characteristics on the melting process similar to a powder bed fusion process has been investigated.
Simulant powders with different PSDs (particle sizes ≤ 1000 µm) and drying states (undried, 300 °C and 800 °C for 4 h) were processed in a vacuum chamber and the fabricated specimens profoundly analyzed. The results show an increase in specimen mass with larger particles and higher drying temperatures. No correlation of the PSD and drying temperature on the porosity was observed. Processing of undried simulants caused the formation of discontinuous melt tracks and a significant chamber pressure increase.
Keywords: In situ resource utilization, Laser beam melting, Regolith melting, Regolith
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Jens Niedermeyer, Timo Witte, Fabian Schlenker, Jan Philipp Wahl, Myriam Maalaoui, Marcus Oel, Ina Meyer, Berend Denkena, Roland Lachmayer
Additive manufacturing offers great potential in the aircraft sector due to its high degree of design freedom and new material developments such as Scalmalloy®, a light aluminum alloy with high mechanical properties. Related works show a lack of knowledge about the additive manufacturing of Scalmalloy®, so this paper aims to identify optimal process parameters. A design of experiment is performed, and the hardness, tensile strength, and surface roughness are measured. After that, design parameters are investigated. With the optimized process parameters, a density of 99.87 % is achieved. The hardness is 168.5 HV0.3, and the tensile strength is 541.7 MPa after thermal treatment. Surface roughnesses between 19 and 49 Ra are measured depending on the build direction. Minimum manufacturable dimensions are defined for walls, cylinders, and inclination angles. The identified process parameters and the characterization of mechanical properties deliver fundamental knowledge to enable the utilization of Scalmalloy® for aircraft applications.
Keywords: Powder bed fusion of metals using a laser beam (PBF-LB/M); Additive manufacturing; Scalmalloy®; Process parameter development; Aircraft applications