Tribocorrosion resistance of 316 L steel produced by SLM: Conceptual interpretation based on microstructure and microhardness

The article compares the wear resistance of 316L stainless steel produced by additive manufacturing (AM) and by conventional processing. Tests were conducted for three wear-process variants characterized by different material removal intensities: purely mechanical wear under cathodic polarization conditions, “moderate” tribocorrosion in 3.5% NaCl at open circuit potential (OCP), and “severe” tribocorrosion at a potential within the passive region. It was found that AM 316L steel exhibited approximately 50% lower tribocorrosive wear. The superior tribocorrosion resistance was associated with a strain-hardening effect induced by frictional interactions. For AM 316L steel, a hardness increase of 20–60% within the wear track was observed, whereas for conventionally manufactured 316L steel the hardness increase ranged from 4% to 20%. Attention was drawn to the fact that the AM 316L steel include the presence of porosity and a higher fraction of low-angle grain boundaries. The article proposes a conceptual interpretation intended to explain the influence of material removal kinetics on the strain-hardening effect in the near-surface layer and on tribocorrosive wear, taking into account the differences between the two variants of 316L steel. The conception was supported by FIB micrographs of microstructural changes in the investigated steels beneath the wear track. Variations in the depth of the plastically deformed zone (and thus the probable hardened region) may indicate the existence of the correlation described in the conceptual interpretation, between the intensity of material removal from the specimen surface and the hardening of the near-surface layer, and consequently the wear behavior, particularly under tribocorrosion conditions.