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Influence of energy input on spatter generation of 316L stainless steel fabrication by SLM in vacuum

316L stainless steel plate was fabricated by spatter free selective laser melting (SLM). 316L stainless steel has excellent properties such as corrosion resistance and hardness. But it is difficult to form into complicated structures because of hard to work material. SLM can fabricate complicated shapes because it builds a 3D material layer-by-layer from a powder. Some issues, however, have yet to be resolved, including dimensional accuracy, surface finishes, processing time, and mechanical properties such as surface roughness and hardness. There is some problems that spatter is generated by metal powder scattering on when the laser is irradiated to the powder. Due to the spatter, the input energy to the powder bed becomes insufficient because the laser is absorbed the spatter particle. Therefore it is required the technology to suppress the amount of spatter for SLM process. In this study, in order to clarify the mechanism of the spatter free process, the 316L stainless steel was fabricated by SLM and observed the behavior of powder during the laser irradiation by high speed video camera. As the results, it was revealed that the amount of spatter was depended on the input energy of laser. At the laser fluence of 20 kJ/cm2 , the amount of spatter was minimized, and surface roughness on the fabricated sample was improved to 3.5 μm from 30μm.