Effect of Energy Input on the Residual Stress of Additively Manufactured Stainless Steel

Laser powder bed fusion (LPBF) additive manufacturing offers significant design flexibility for nuclear reactor components, made possible by the localized laser melting (70–300 µm) of a powder bed. Although, the localized melting is inherent to exceptionally high cooling rates (10⁵–10⁷ K/s), conducive to evolving high residual stresses; these stresses can cause warpage, delamination, solidification cracking, or premature failure under mechanical loading. Establishing fundamental correlations between the laser input energy density and residual stress is crucial for optimizing LPBF processing. In this study, stainless steel 316 plates (235×85×12 mm³) were fabricated using LPBF, with eight discrete sections printed at systematically increasing energy densities. Neutron diffraction was employed to characterize residual stress, with approximately 260 voxels (slit size: 2×2 mm²) sampled along the build direction to capture plane strain. Additional sample examination consisted of dimensional and surface roughness with light profilometry, characterizing microstructural variations using electron microscopy, and tensile mechanical testing. This presentation will highlight the influence of energy density on the cooling rate and resulting microstructure and how residual stress contributes to yield strength. The findings provide fundamental insights to better optimize LPBF energy density for nuclear component fabrication by reducing uncertainties in residual stress formation and mechanical performance.