Corrosion behaviour of additively manufactured 316L stainless steel

Additive manufacturing (AM) has been the focus of innovation in manufacturing industries during the last decade owing to its advantages over traditional manufacturing, particularly its capability to build complex 3D geometries in a single step that can save a lot of time and money. Selective laser melting (SLM), as a powder-bed AM technique, builds an object at rapid solidification rates in a layer-upon-layer manner using a high-energy laser beam. This process occurs under an extremely high temperature and rapid cooling conditions, leading to a microstructure that is different from that of the conventionally-produced counterpart. Although lots of research has been devoted to understanding the physical concept of SLM processing and mechanical properties, corrosion performance of parts produced by SLM has not been sufficiently explored. In this paper, an attempt was made to explain how SLM processing influences corrosion performance of type 316L stainless steel with an emphasis on localized corrosion, intergranular corrosion, and erosion-corrosion properties. It has been found that, in the case of a high-density SLM-produced specimen, the localised and intergranular corrosion resistances showed significant improvements compared to their commercial counterpart. While the SLM-produced 316L stainless steel exhibited a weaker erosion-corrosion resistance relative to the commercial one. Mechanisms behind this unique corrosion behaviour were briefly discussed based on electrochemical tests and microscopy analysis.