Powder Degradation Analysis In Reused Pure Tungsten For Electron Beam Melting (ebm)

Additive manufacturing (AM) enables unparalleled design freedom and geometric complexity, driving its adoption in aerospace and medical fields. A major advantage of metal powder AM technologies, such as Electron Beam Melting (EBM), is its ability to reuse unused metal powder, reducing material waste and costs. However, reusing powder repeatedly alters its properties, affecting the final product. Despite its significance, research on powder degradation remains limited, primarily focusing on alloys like Ti-6Al-4V. This thesis investigates the degradation of pure tungsten powder reused over multiple Electron Beam Melting (EBM) cycles. A literature review revealed general powder-reuse mechanisms across additive manufacturing (AM) technologies but also a notable lack of studies focused on tungsten and limited reporting of key experimental details needed for reproducibility. Comparisons between virgin powder and reused powder showed consistent trends: a reduction of fine particles, a slightly narrower particle size distribution, relatively stable sphericity, slightly reduced flowability, lower bulk density, and a minor increase in oxygen content. In the produced samples, microstructures consisted of elongated, directional grains parallel to the build direction and equiaxed grains on transverse planes, with no clear reuse-related trends. Relative density decreased with increasing reuse, likely linked to narrower PSD, reduced packing efficiency, and rising oxygen content. Overall, tungsten demonstrated good robustness under reuse, maintaining acceptable powder and part characteristics through 16 cycles. The findings also highlight persistent gaps in the literature, particularly the lack of standardized reporting, which challenges reproducibility in powder-reuse studies