Uniaxial Creep Properties of 316L Stainless Steel Manufactured by Laser Powder Bed Fusion

Abstract

Abstract 316L stainless steel has long been used in high temperature applications. As a well-established laser powder bed fusion (LPBF) alloy, there are opportunities to utilise additive manufacturing in such applications. However, to date there is limited creep data on LPBF material. Uniaxial round bar creep tests have been performed at 700 °C and characterised using power-law relations to evaluate the creep strain and rupture properties of LPBF 316 L. Samples were manufactured in two orientations denoted (i) vertical i.e. loading direction parallel to the build direction and (ii) horizontal, i.e. loading direction perpendicular to the build direction. The creep response was found to be anisotropic with specimen build orientation, with samples loaded perpendicular to the build direction (Horizontal) exhibiting faster minimum creep rates than samples built parallel to the build direction (Vertical). This was mainly attributed to the columnar grain structure revealed by electron back scattering diffraction (EBSD), which was aligned with the build direction of the LPBF samples. The vertical samples generally exhibited significantly longer rupture lives than horizontal samples, unless influenced by deleterious porosity. The results were compared to existing test data performed at 650 °C and similar trends were seen at both temperatures, though higher creep rates and shorter rupture times resulted from the higher temperature, as expected.