Fundamental in-situ Investigations on the Changes of Particle Properties during Powder Bed Fusion of Cu-based materials using a Laser Beam, Depending on the Atmosphere and the Exposure Parameters

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The overarching goal is to develop a basic understanding of the influence of changes in particle properties in the Powder Bed Fusion (PBF) process of pure Cu-powder and the associated influence on the laser energy coupling, the microstructure formation process, and the associated mechanical, and physical properties. This project focuses on the absorption of oxygen by Cu-powder surfaces, investigations on the change in powder properties and their influence on reusability and the necessary process-technical adjustments concerning powder conditioning (recycling) and the exposure parameters or the process gas atmosphere. Therefore, high-resolution in-situ X-ray diffraction experiments will be carried out to investigate the interactions occurring in the PBF-process between the bulk powder with specific and well-known properties, the process gas atmosphere, and the laser beam. The knowledge gained will be used to derive measures (targeted aging of powder surfaces by pre-oxidation, recycling) which allow reproducible PBF processing of Cu-bulk powder. Targeted surface conditioning through the formation of oxides, and the deposition of thin Ni-layers is intended to increase laser absorption, which on the one hand, contributes to increasing the process speed and, on the other hand, enables the PBF-processing of materials with high reflectivity (Cu) for the lasers typically used today (wavelength ≈1060 nm). It will also be investigated whether the melt viscosity (smooth surfaces and minor post-processing by machining) can be influenced by the introduction of oxygen (by particle oxidation, via the process gas by using mixed gases) into the PBF-process. The aforementioned scientific questions with high technological relevance are answered in a project consortium, in which the competences concerning powder processing and the evaluation of powder properties (HAM), the characterization of the microstructure and the associated material properties (FUW), and the in-situ re-melting tests and aging tests for mapping the oxidation and reduction kinetics of bulk powder (FPTUDo) are available.