Experimental investigation of creep behavior along the build height of stainless-steel 316L fabricated via selective laser melting

The aim of this study was to contribute to the existing knowledge on the creep behavior of 316L stainless steel (SS) produced through selective laser melting (SLM). Creep tests were conducted on samples extracted from the wall in the build direction at 650 °C under various load conditions using a small punch (SP) creep test machine. The results revealed that the creep response was anisotropic and strongly dependent on the building height of the cubic block. Specifically, the average creep life was approximately three and five times higher in the bottom region than that in the top and middle regions, respectively. This indicates that the middle region was more susceptible to creep damage, resulting in inferior creep resistance, whereas the bottom region exhibited higher creep resistance. Interrupted tests were performed to elucidate variations in the internal creep damage level. The creep-damage mechanism was assessed based on the geometrically-necessary dislocations (GNDs) density and characteristics of the melt pool boundary (MPB). Additionally, creep tests demonstrated that SS316L stainless steel manufactured by SLM processing has an inferior creep life compared with conventional SS316L material, a phenomenon that can be attributed to the nano-sized cell structure and average grain size boundaries.