Work

Influence of fabrication on microstructure and heat affected zone width in weldments of nuclear reactor pressure vessel steel

Year: 2026

Type: article

Abstract: Electron beam (EB) welding and powder metallurgy with hot isostatic pressing (PM-HIP) are advanced fabrication techniques that offer potential advantages for nuclear reactor pressure vessel (RPV) manufacturing. This study investigates the effects of EB welding, fabrication methods, and post-welding heat treatments on microstructural properties of RPV steels. Phase distribution, crystallite size, microstrain, and dislocation density are determined via synchrotron X-ray diffraction (SXRD). Retained austenite is found in austenitized samples, while the austenitizing heat treatment eliminates retained austenite, producing a uniform microstructure. The Rosenthal solution underestimates the HAZ width in PM-HIP materials, likely due to increased porosity, higher dislocation density, and finer grain size in PM-HIP weldments. A proposed modified Rosenthal solution, reducing density by accounting for porosity, matches the SXRD-measured HAZ width with a 0.65% error. Structure–property correlations demonstrate that, in homogeneous microstructures, dislocation density strongly correlates with nanohardness. However, in heterogeneous microstructures such as PWHT weldments, nanohardness is also influenced by hetero-phase interfaces introduced by retained austenite, which enhance resistance to plastic deformation. Ultimately, the modified Rosenthal solution and structure–property relationships identified in this work can inform the design of materials, welding procedures, and heat treatments to enhance the long-term reliability and safety of RPVs.

Source: Materials & Design

DOI: 10.1016/j.matdes.2026.115521