Effect of Strain Rate on Stress Corrosion Cracking Sensitivity of Domestic Nickel-Based Alloy in Supercritical Water Environment

The stress corrosion cracking (SCC) sensitivity of domestic nickel-based alloy C-HRA-1 in supercritical water environment of 650 ℃ and 25 MPa at different strain rates was studied by slow strain rate test (SSRT). The fracture morphology and surface crack morphology of samples were observed by scanning electron microscope (SEM), and the element composition and distribution near the crack tip were analyzed by energy dispersive spectrometer (EDS). The results show that C-HRA-1 exhibited SCC sensitivity at different strain rates, and the SCC sensitivity increased with the decrease of strain rate. In the process of stress corrosion, the formation and propagation of cracks were affected by the coupling of oxidation and mechanics. The grain boundary oxidation occurred at the crack tip, which reduced the crack tip bonding force and led to crack propagation.