An approach to producing AM-HIP 316 L nuclear reactor core internal components with powder bed fusion laser beam (PBF-LB) and hot isostatic pressing

Components made by additive manufacturing (AM) often exhibit anisotropy in their microstructure and mechanical properties due to the layer-by-layer fabrication approach. Post-processing treatments, such as heat treatment or hot isostatic pressing (HIP), may play a crucial role in minimizing these anisotropies and enhancing the overall performance of components. In this study, AM 316 L austenitic stainless steel baffle bolts were designed and fabricated by Powder Bed Fusion Laser Beam (PBF-LB), followed by HIP. A range of AM processing parameters was employed to optimize the density and quality of the printed components. The subsequent HIP treatment was primarily aimed at enhancing overall densification and improving the material's toughness. The as-printed 316 L exhibited anisotropy in both grain size and mechanical properties. Hot isostatic pressing led to increased density, stress relaxation, reduced defects, and a widening of the gap between YS and UTS, indicating improved strain-hardening capacity. This enhanced separation is beneficial from an application standpoint, as it provides greater safety margins and better deformation tolerance under service loads. Analytical models are presented to predict melt-pool size and yield strength, and their predictions are compared with microstructural and tensile measurements. The developed material through AM and AM+HIP will be studied further at light water reactor condition and Irradiation assisted stress corrosion cracking will be performed to check the material and process compatibility.