Powder recycling effects on porosity development and mechanical properties of Hastelloy X alloy during laser powder bed fusion process

This study compares and analyzes the morphology, size, oxygen content, and microstructure of virgin and recycled powders after six iterations to assess the mechanical properties of the Hastelloy X alloys fabricated via laser powder bed fusion (LPBF). Compared to the virgin powder, the average particle size and oxygen content for the recycled powder are increased by 22% and 48%, respectively, which promotes the laser absorptivity of the powder bed from 0.45 to 0.64, resulting in the rapid transitioning of the keyhole to a precarious state. The porosity of the LPBF Hastelloy X alloy manufactured using the recycled powder was 1.47%, which was significantly higher than that of the parts prepared using the virgin powder. However, only a slight difference in the grain size was observed in the LPBF Hastelloy X alloys manufactured from the virgin and recycled powders. A 20.8% reduction in the plasticity of the LPBF Hastelloy X manufactured from the recycled powder was observed after six iterations. The evolution of the printed defects evolution during the recycling process was revealed. Importantly, a printed defect diameter larger than 40 µm can significantly affect crack initiation and propagation in LPBF products.