Water droplet erosion response of 316L steel manufactured conventionally and additively using selective laser melting

• SLM 316L steel shows higher erosion resistance than its conventional counterpart. • Additive manufacturing prolongs the incubation period of water droplet erosion. • Erosion resistance of SLM steel is anisotropic, linked to the build direction. • Stress relief heat treatment results in optimal erosion resistance for SLM 316L. The technological manufacturing history of a material is one of the essential factors that affect its microstructure and related mechanical properties. This fact becomes even more significant when replacing the conventional material with another variant, such as one prepared using additive manufacturing (AM), like selective laser melting (SLM). As the specific hierarchical microstructure inherent to the SLM process may potentially alter the resistance of a material against liquid droplet erosion, the comparative experimental tests using an ultrasonic water jet generator were performed on several variants of AISI 316L stainless steel, namely conventional wrought material with typical polyhedral grains and material produced using SLM with characteristic microstructure including melt pools, columnar grains, and solidification/dislocation cells. Besides the as-built SLM microstructure, two other modifications resulted from heat treatment at different annealing temperatures. Flat surfaces, parallel and perpendicular to the building direction of all microstructure variants, were subjected to water droplet erosion from an ultrasonically excited pulsating water jet (PWJ). The possible effect of microstructure anisotropy of SLM 316L steel on erosion damage was assessed. Different time exposures were employed to cover all erosion stages from the incubation period to material removal, and the response of all material variants to PWJ was related to their characteristic microstructures with an emphasis on erosion mechanisms. SLM microstructure exhibited prolongation of the incubation period and higher resistance in erosion wear in comparison with its conventional counterpart. The orientation of the build direction affected the response of the SLM material to water jet impingement.