Comparative study of the SCC behavior of E690 steel and simulated HAZ microstructures in a SO₂-polluted marine atmosphere

Simulated microstructures of the typical CGHAZ, FGHAZ, and ICHAZ of an E690 welded joint were prepared with heat treatment at peak temperatures of 1300, 850, and 750°C, respectively. Slow strain rate tensile (SSRT) tests were implemented to investigate the stress corrosion cracking (SCC) behavior of E690 steel and the simulated HAZ microstructures in a SO₂-polluted marine atmosphere. Results revealed that E690 steel and its simulated HAZ microstructures all had a high SCC susceptibility in the simulated SO₂-polluted marine atmosphere with a combined mechanism of AD and HE. The SCC susceptibility gradually increased in the following order: BM, CGHAZ, FGHAZ, and ICHAZ. The cracking mode of BM and CGHAZ was transgranular, whereas that of FGHAZ and ICHAZ was intergranular. The lower SCC susceptibility of BM and CGHAZ was probably due to the impeding effect of lath bainitic grain boundaries on SCC propagation, whereas the higher SCC susceptibility of FGHAZ and ICHAZ was attributed to the facilitating effect of M-A islands on crack initiation and propagation.