Characterization of microstructure, local deformation and microchemistry in Alloy 690 heat-affected zone and stress corrosion cracking in high temperature water

With increasing the distance from the weld fusion line in an Alloy 690 heat-affected zone, micro-hardness decreases, kernel average misorientation decreases and the fraction of Σ3 boundaries increases. Chromium depletion at grain boundaries in the Alloy 690 heat-affected zone is less significant than that in an Alloy 600 heat-affected zone. Alloy 690 heat-affected zone exhibits much higher IGSCC resistance than Alloy 600 heat-affected zone in simulated pressurized water reactor primary water. Heavily cold worked Alloy 690 exhibits localized intergranular stress corrosion cracking. The effects of metallurgical and mechanical properties on stress corrosion cracking in Alloy 690 are discussed. - Highlights: • High Vickers hardness and KAM near the Alloy 690 weld fusion line. • Low fraction of Σ3 boundaries near the fusion line. • High grain boundary chromium content in Alloy 690 HAZ. • Higher SCC resistance in Alloy 690 HAZ than in Alloy 600 HAZ. • Locally intergranular PWSCC in 40% cross-rolled Alloy 690.