Role of volumetric energy density on surface quality and mechanical properties of selective laser melted 310 stainless steel

Abstract

Stainless Steel 310 (SS 310) is a widely used heat-resistant austenitic stainless steel known for its high-temperature applications. This study explores the influence of volumetric energy density (VED), achieved by varying selective laser melting (SLM) process parameters on surface quality and mechanical properties of SS 310. The surface roughness and microhardness varied with VED, showing distinct trends in perpendicular to build direction (PPBD) and parallel to build direction (PBD). The highest yield strength, ultimate tensile strength, and elongation were achieved at VED of 56 J/mm³, surpassing conventionally manufactured SS 310. Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD) analyses revealed that the fine cellular grain structure and grain orientation at a VED of 56 J/mm³ enhance mechanical strength, whereas excessive VED results in grain coarsening and a reduction in grain boundary density. Geometrically necessary dislocation (GND) density contributed to strength but affected ductility when overly accumulated. Fractography revealed ductile failure dominated by fine dimples, irrespective of SLM process parameters. Statistical analysis using ANOVA and response surface methodology (RSM) identified optimal SLM process parameters closely aligned with those of the S5 sample (P = 150 W, v = 750 mm/s).