Surface finish and properties enhancement of selective laser melted 316L stainless steel by surface mechanical attrition treatment

Selective laser melting (SLM) has been used to produce stainless steel components with nearly full density, targeting real engineering applications. However, materials processed by SLM suffer from an inherent problem of poor surface finish, which is not suitable for many practical applications. It is thus necessary to improve the surface finish and surface integrity of SLM components through post processing. The aim of this work is to improve the surface finish of SLM 316L stainless steel by surface mechanical attrition treatment (SMAT), which involves bombarding the SLM sample surface with steel balls at a vibration frequency of 40 Hz for 10 min to 80 min. The surface finish, morphology, hardness and unlubricated sliding friction and wear behaviour were investigated. The results show that SMAT is very effective in smoothing the SLM 316L surface, reducing the surface roughness by up to 96% and achieving a surface finish comparable to that produced by surface grinding. SMAT also has the added benefits of increasing surface hardness, reducing friction and improving dry sliding wear resistance of SLM 316 L stainless steel.