An investigation of the corrosion behavior of 316L stainless steel fabricated by SLM and SPS techniques

The microstructure and corrosion characteristics of 316L stainless steel specimens fabricated by spark plasma sintering (SPS) and selective laser melting (SLM) techniques were investigated. SPS specimens have a relatively low density compared with SLM specimens. Microstructural analysis showed that SPS specimens consisted of fully and partially sintered regions and contained initial pores, which are located at the powder boundaries (PBs). SPS specimens have relatively low density and high kernel average misorientation (KAM) values near the interface of the pores and the matrix. In the case of SLM specimens, the scanning strategy did not affect the spatial distribution of the KAM, while it affected the extent of surface defects. Electrochemical analysis revealed that the corrosion behavior of SPS specimens was similar to localized corrosion, and weak levels of passive protection were observed in the anodic response curves due to the initial surface pores. SLM specimens with well-connected scan tracks showed passivation behavior similar to that of as-rolled specimens. Moreover, due to a homogeneous microstructure distribution and lower porosity, in NaCl solutions the SLM specimens showed corrosion performance that was significantly enhanced compared with that of SPS specimens. Cross-sectional analysis of corroded SPS specimens revealed that the configuration and connectivity of pores (or small cavity) affected the morphology of open spaces under the corroded surface.