Microstructure and Correlation of Fracture Strength on Additively Processed Nuclear Grade Stainless Steel under Monotonic Load

Wire arc additive manufacturing (WAAM) emerges as a promising technique for fabricating nuclear‐grade stainless steel (SS) components with complex geometries and strong mechanical performance. Herein, SS347 is successfully deposited using WAAM to fabricate a defect‐free wall structure and fracture strength is evaluated using single‐edge notch bend (SENB) test. Fracture strength of WAAM‐fabricated SS347 is found to be 209.26 MPa√m, which is ≈8.3% higher than that of wrought (WR) SS347 counterpart (191.74 MPa√m), primarily due to microstructural anisotropy and residual stress effects inherent to the additive process. Detailed microstructural analysis reveals the presence of elongated columnar grains, NbC precipitates, and localized knife‐line attack zones, all of which significantly influence crack initiation and propagation paths. Crack behavior is further analyzed using generalized finite element method (GFEM), which successfully simulates crack growth stages with a deviation of less than 2.5% from experimental results. The study underscores the viability of WAAM for fabricating SS347 components suitable for nuclear pressure vessel application and validates GFEM as a reliable tool for predicting fracture performance in additively manufactured metallic structures.