Stress corrosion crack propagation affected by microstructures for nuclear steam turbine rotor steels in the simulated environment

Abstract

The propagation behavior of stress corrosion cracking (SCC) for two CrNiMoV steels in the simulated environment of low-pressure nuclear steam turbine rotor was systematically investigated by microstructural characterizations, electrochemical measurements, slow strain rate tensile tests, and crack growth rate (CGR) measurements. The results showed that both the corrosion susceptibility and stress corrosion susceptibility increased with the increase of localized residual strain, yield strength, and the decrease of grain size. With the higher stress corrosion susceptibility, the SCC CGR of Steel A was higher than Steel B in the corrosive solution at 80 °C, however, at 180 °C the SCC CGR of Steel A was lower than Steel B under the lower applied K. The change of SCC CGR was strongly affected by crack branches, crack deflections and plastic deformation during the SCC propagation, which may have some correlations with the microstructural distribution.