Insight into the acceleration in oxidation kinetics ahead of stress corrosion crack of alloy 690 in simulated PWR primary water

The acceleration in oxidation kinetics beyond a stress corrosion crack of alloy 690 in simulated PWR primary water was clarified by comparing the oxide depths at two identical carbide/matrix interfaces along a single grain boundary. Compact chromia layer formed along these two interfaces at vastly different rates. Stress concentration ahead of the crack tip only slightly increased the oxidation rate as the crack is still very shallow. Deformation localization near the crack plays a dominant role in accelerating oxidation kinetics as the associated high vacancy concentration can promote the diffusivity of oxygen by over an order of magnitude.