The machinability of stainless steel 316 L fabricated by selective laser melting: Typical cutting responses, white layer and evolution of chip morphology

Additive manufacturing is gradually applied in the manufacturing of functional near-net-shape components made of hard-to-machine metallic materials such as austenite stainless steel 316 L. However, due to the poor surface roughness and low dimension accuracy, the as-built components fabricated by selective laser melting (SLM) cannot be utilized directly, and post-processing processes including conventional machining have to be applied to meet the stringent quality requirements in industry. This paper comprehensively investigates the machinability of SLMed stainless steel 316 L in hard turning processes through comparison with the machining of wrought 316 L parts. Typical cutting responses including cutting force, surface roughness, chip formation and micromorphology of the machined surfaces were analyzed; underlying mechanisms of the formation of the white layer and the causes leading to different hardness in the white layer were discovered; interactions of work hardening and thermal softening of the workpiece materials were discussed; the evolution of serrated chips were explored by taking into account the influence of microstructures and the Johnson-Cook parameters. The new findings have also revealed how cutting depth, a critical machining parameter, affects the plastic deformation in machining SLMed 316 L.