Microstructural differences and mechanical performance of stainless steel 316L conventionally processed versus a selective laser melted

Abstract

Metal additive manufacturing (AM) has changed materials design and processing paradigms. However, as it is a layered manufacturing process and due to the complex material-laser interaction, the resulting microstructure differs from conventional counterpart alloys. Since the mechanical properties depend on the microstructure, the functional properties of mechanical components manufactured by laser powder bed fusion (LPBF) thus are significantly influenced by the processing parameters and the scanning strategy. The present research is focused on the microstructure differences between 316L stainless steel processed by LPBF and conventionally processed. Several characterization techniques were employed in this assessment, including optical and electron microscopies, X-ray diffraction, and spectrometry. A finite element analysis (FEA) was conducted to study grain boundaries and orientation and determine the thermal gradient and cooling rate. Moreover, welding-based algebraic models were used to calculate the cooling rate and the cell spacing. The FEA results show good agreement in the prediction of microstructural features, while the algebraic results values are of the same order of magnitude, with a relative error of less than 5% in determining the cell spacing (0.57 mu m). The additively manufactured specimen shows approximately the same ultimate tensile strength (622 MPa); however, a 40% increase in yield strength (532 MPa) and a higher microhardness is observed.