Evolution of a low-alloy steel/nickel superalloy dissimilar metal weld during post-weld heat treatment

The design of the dissimilar metal weld investigated here is aimed at applications in steam generator a sodium-cooled nuclear reactor, with multi-decade lifespan demanding operational conditions. It consists narrow-gap joint between 2.25Cr-1Mo low-alloy steel and an austenitic alloy using nickel-based 82 as filler material. This study focuses on understanding microstructural micromechanical evolution near fusion boundary region nickel during post-weld heat treatment, notably electron probe micro-analysis nano-indentation. difference matrix phase chemical composition two alloys leads to large potential for carbon, which mobile treatment temperature. A number fine-scale characterization techniques were used assess gradient composition, hardness, microstructures across boundary, both as-welded after treatment. complete analysis permits highlight understand main changes occurring opens way their long term service