Effect of powder size and processing parameters on surface, density and mechanical properties of 316L elaborated by Laser Powder Bed Fusion

Despite the attractive capabilities of additive manufacturing (AM) technology, the industrialization of these processes remains very low. This is attributed to the complexes physical phenomena involved in the AM process and the layered structure of the produced parts. Intense research work is still needed for the prediction and optimization of AM parts mechanical properties. In this study, the influence of particle size distribution (PSD) of stainless steel 316L (SS 316L) powders on AM parts properties was investigated. Four PSD were used to produce test parts and compare the resulting porosity, surface roughness and macro-hardness. The SS 316L specimens were fabricated by Laser Powder Bed Fusion process (LPBF) on a SLM 125HL machine using variations in laser power and scan velocity. Computed scan tomography (CT) was used to characterize the defects. Lack of fusion and keyhole defects were detected. Defects were detected even in nearly dense parts. The powder size distribution was found to affect the porosity. Results from CT tests were used to identify the minimum achievable porosities for each powder, through the appropriate selection of process parameters. The macro-hardness and surface roughness were found to vary with the powder properties.