The single effect of microstructure, residual strain and geometric structure on the stress corrosion cracking behavior of scratched alloy 690TT

Scratched area on alloy 690TT were treated by relief annealing (RA) and solution annealing plus thermal treatment (SATT), respectively, and then detailed characterization and immersion tests in simulated pressurized water reactor environment were carried out. RA reduces residual strain but not changes microstructure stratification, which causes stress corrosion cracking (SCC). SATT eliminates both strain and microstructure stratification, preventing SCC. Meanwhile, the independent effects of geometric structure, strain and microstructure on SCC behavior were investigated. Specifically, geometric structure is necessary but not sufficient for crack initiation. While the residual strain mainly enhances propagation, and the microstructure promotes both initiation and propagation.