Microstructural and electrochemical behaviour of severely surface-deformed 316L steel manufactured by conventional and selective laser melting routes

Abstract

This study thoroughly examines the influence of conventional and selective laser melting (SLM) routes and surface mechanical attrition treatment (SMAT) on the microstructural and electrochemical properties of 316L steel. Compared to wrought specimens, the SLM specimens exhibit significantly smaller grains (∼41 vs. ∼83 µm) and higher dislocation density (∼7.2 × 1013 vs. ∼3.7 × 1012 m−2). Both specimens show nearly doubled surface hardness after SMAT, with the SLM surface displaying a ∼30 nm grain size and minimal α’ phase. The microstructure significantly influences passivation and corrosion behaviour. The SLM specimens exhibit superior electrochemical characteristics to wrought counterparts in SMATed (0.00299 mmpy) and non-SMATed (0.00771 mmpy) conditions. SMAT effectively eliminates surface porosity, enhancing the passivation and corrosion resistance of SLM steel.