Degradation Mechanisms in LPBF Parts Fabricated with Recycled Powder Under Suboptimal Storage

Abstract Laser powder bed fusion (LPBF) processing produces metal parts with unique geometry and properties; however, it also creates a lot of unused or waste powder after printing. This waste powder can make the process unsustainable unless methods of handling and recycling the powder are used. Quantifying the effects of powder recycling on the parts' microstructure and mechanical properties is highly important, particularly if the reused powder is subject to non-optimal powder handling, as would be the case in distributed manufacturing. This study evaluates the quantifiable impact of non-optimally stored powder properties on the degradation mechanism of microstructure and mechanical properties. It is observed that powder particle size and oxidation increase, leading to increased flowability and laser absorption of the powder bed, which increases melt pool depth by 11% and porosity by 0.4%. The parts have comparable surface roughness among the reused and virgin cases; however, lower microhardness due to increased columnar dendrites, while tensile properties decline due to increased porosity.