Correlation of microstructure and stress corrosion cracking initiation behaviour of the fusion boundary region in a SA508 Cl. 3-Alloy 52M dissimilar weld joint in primary pressurized water reactor environment

Correlation of microstructure and stress corrosion cracking (SCC) initiation behaviour of the fusion boundary (FB) region in a SA508 Cl. 3-Alloy 52M weld joint in primary pressurized water reactor environment was investigated. Cr-depletion at the grain boundary and strength mismatch in the FB region are the two causes for SCC initiation in the FB region. The partially mixed zone between the dilution zone (DZ) of Alloy 52M and SA508 Cl. 3 has a retardation effect on SCC initiation. This is attributed to the decrease of strength mismatch and the alleviation of strain concentration adjacent to the grain boundary in DZ.