The correlation between the dislocation slip/grain boundary interaction mode and the resistance to SCC initiation of Alloy 690 in simulated PWR primary water

Recurring step straining was applied on Alloy 690 to establish a correlation between the dislocation slip/grain boundary (GB) interaction mode and the resistance to stress corrosion crack (SCC) initiation in high temperature hydrogenated water. The intergranular carbides can suppress the dislocation transmission across GB in thermally treated Alloy 690. GBs that block dislocation slip show higher resistance to SCC initiation than those that transmit slip. Such correlation reveals that the local normal strain near GB is the primary driving force for breaching the surface oxide film over GB which is a critical prerequisite in the SCC initiation of Alloy 690.