Powder Bed Fusion (PBF) processes are widely adopted additive manufacturing techniques, known for its capability to produce complex geometries with high precision. However, the economic and environmental sustainability of PBF is strongly connected to its powder. In order to achieve a sustainable production, the principle “reduce, reuse and recycle” can be applied. In general, additive manufacturing processes are meant to follow the principle of a reduced material consumption due to the near-net shaped production with a minimized need for subtractive machining after processing. However, recycling and reuse of powder in additive manufacturing need to come into focus to further strengthen this approach. Up to now, most studies focus on the reuse of high-quality powders. These powders are in most cases stemming from cost-intensive gas atomization processes with highly pure feedstock materials in order to meet the demands such as narrow particle size distributions, spherical morphologies, good flowability, and low oxygen content. However, from an economic and environmental point of view the utilization of powders with lower quality would be desirable. The low quality can be defined, e.g. by non-spherical shaped powder due to alternative production processes leading to or by chemical impurities stemming from the feedstock [1].

In the present studies, non-optimal feedstock materials, such as recycled materials, were employed in additive manufacturing processes, i.e., laser-based and electron-based powder bed fusion of metals. In the electron-based additive manufacturing process, mechanically recycled Ti6Al4V powder grades were utilized leading to a higher defect population. Under mechanical loading, differences between the specimens built with gas-atomized and recycled powder were found [2]. In the laser-based process, a powder mixture as shown in Figure 1 was used. The process of hydriding-dehydriding was used in order to produce Ti6Al4V powder directly from scrap. The results indicate that while recycled powders can maintain acceptable performance within certain recycling limits, which means that critical thresholds exist beyond the quality deteriorates. These findings contribute to establishing guidelines for powder manufacturing strategies, aiming to balance sustainability with high-performance manufacturing.

References
[1] J. Richter et al. International Journal of Fatigue, 2023, 168, 107468.
[2] J. Richter et al. International Journal of Fatigue, 2023, 176, 107903.

Dr.-Ing. Julia Richter