The effect of weld chemistry on the oxidation of Alloy 82 dissimilar metal welds

Alloy 82 dissimilar weld joints between carbon steel and Alloy 600 were exposed to a simulated primary water environment consisting of hydrogenated steam at 480°C and 1bar. Dilution due to mixing from the parent materials to the weld was significant, particularly in the root where there was Fe enrichment (35at.%) and Cr depletion (10at.%). The heterogeneous composition of the weld from root to crown resulted in differences with respect to surface versus internal oxidation. A Fe-rich surface oxide formed on the weld root which may help to prevent embrittlement and SCC by internal intergranular oxidation.