Selective Laser Melting of Stainless Steel 316L for Mechanical Property-Gradation

Abstract

With an end goal of creating single-alloy functionally-graded additively manufactured (FGAM) parts, this paper investigates the manufacture and properties of stainless steel 316L samples via a pulsed selective laser melting (SLM) process. The focus is on elucidating the underlying causes of property variations (within a functionally-acceptable range) through material characterization and testing. Five samples (made via different volumetric energy density-based process parameter sets) were down-selected from preliminary experimental results and analyzed for their microstructure, mechanical and physical properties (hardness, density/porosity, Young’s modulus). It was observed that property variations resulted from combinations of porosity types/amounts, martensitic phase fractions, and grain sizes. Based on these, various functionally-graded specimens of different sizes were built as per ASTM standards, each having intended property changes along its gauge volumes. The presented findings establish that a methodical control of microstructure and mechanical properties could be obtained in a repeatable and reproducible manner by changing the process parameters. This work lays the foundation for understanding and tuning the global mechanical performance of FGAM bulk structures as well as the role of interfacial zones.