Mechanistic understanding of the temperature dependence of crack growth rate in alloy 600 and 316 stainless steel through high-resolution characterization

Abstract

Stress corrosion cracking of Alloy 600 (A600) and 316 stainless steel (316SS) exposed to simulated pressurized water reactor primary water at temperatures of 320–360 °C has been investigated and compared. Intergranular oxidation developed ahead of all crack tips prepared from these two alloys. High-resolution characterization reveals that there are two main rate-controlling mechanisms contributing to crack propagation: a diffusion-based and a mechanical deformation-based. The different temperature dependence of crack growth rate (CGR) in A600 and 316SS can be explained after confirming that the two rate-controlling mechanisms exhibit different “weights” in the two alloys. The diffusion-based mechanism plays a dominant role in accelerating the CGR of A600, while the mechanical deformation-based mechanism is responsible for the observed CGR decrease of 316SS at higher temperatures.