Enhancing fatigue performance of laser powder bed fused metals through controlling contour parameters and structures

Abstract

Side surface quality is a critical concern in the fatigue performance of laser powder bed fused (PBF-LB) components. Increasing contour passes with customized parameters along sample edge can tune side surface/subsurface quality and thereby enhance fatigue resistance. This study critically evaluates the surface and subsurface characteristics resulting from varying contour parameters and their impact on the fatigue performance of PBF-LB 304L steel through multiple detailed characterizations. The fatigue damage mechanisms for varying contour parameters are investigated through fatigue fractography, temperature field analysis, and microstructural evolution. Results indicate that optimal contour parameters differed from infill parameters due to the energy absorption from powder fusion and solidification remelting. The contour defects, including spherical vapor cavities and irregular lack-of-fusion (LoF) defects resulting from inappropriate parameters, significantly degrade fatigue lifetime due to their high-stress concentration factors. Appropriate contour parameters (approximately 300 J/mm³ in energy density) can minimize defect content while simultaneously enhancing microstructural heterogeneity in the contour region. The identified physical mechanisms of defect formation and fatigue damage will assist in designing and optimizing contour process for enhancing fatigue performance.