Process optimization of micro selective laser melting and comparison of different laser diameter for forming different powder

In order to further optimize the optimal process parameters for micro selective laser melting (MSLM) forming SS316L, the process parameters obtained from the orthogonal experiment are investigated in depth using the response surface experiment (Box-Behnken Design: BBD) method in this paper. The regression equation of the density was obtained by ANOVA based on the density of the formed parts as a guide. The correctness of the calculated results is verified, and the expected value is 94.6%. In order to investigate the forming laws of different laser diameter for different powder particle sizes under optimal process parameters, the influence laws were compared and analyzed by characterization parameters such as density, surface roughness, microstructure, microhardness and mechanical properties. The OM of the formed parts revealed that the specimen No. 1 did not have obvious defects. Specimen No. 2 has large size of incomplete melting powder defects. Specimen No. 3 has a large number of small-size sputtering defects. This difference directly affects the mechanical properties of the specimen. Hexagonal cellular, elongated cellular and striped subgrain microstructures are observed in the specimens. The size of the hexagonal cellular and striated subgrain is around 500 nm and the length is around 40 μm.