The influence of recycling metal powder in the gas atomization process on the produced powder’s chemical composition

In powder based additive manufacturing (AM), precise control of the chemical composition is necessary to achieve optimal properties in manufactured components. At SSAB, low alloyed steel powder for additive manufacturing is produced using gas atomization. However, the particle size distribution from the atomization process contains a size fraction coarser than typically used for AM processes. To increase sustainability and economic feasibility, it is important to reuse this fraction as input material in subsequent melts. To determine the influence of the amount of powder added, and the number of remelts, the chemical composition of the produced powder was traced using elemental analysis (LECO) and Optical Emission Spectroscopy (OES). Over 40 batches were analysed, with powder additions ranging from 0 to 30%. The study found a systematic loss of silicon and an increase in nitrogen, whereas oxygen and carbon were relatively stable. It was shown that by proper adjustment of process parameters, the variation in alloying elements can be minimized, even with large additions of powder. The flowability of the atomized powders was assessed with minimal differences between melts.