The effect of cold rolling on grain boundary structure and stress corrosion cracking susceptibility of twins in alloy 690 in simulated PWR primary water environment

The effects of cold rolling on the structure and stress corrosion cracking (SCC) susceptibility of twin boundaries in alloy 690 were studied. Most of the twin boundaries were transformed into random high angle boundaries (RHABs) following cold rolling. The transformed twin boundaries (TTBs) showed increased susceptibility to carbide precipitation during subsequent aging at 475 °C. The SCC initiation test in 360 °C hydrogenated water indicated that the prior RHABs exhibited increased SCC susceptibility after cold rolling. Moreover, TTBs become susceptible to SCC due to the promoted outward diffusion of Cr and can enhance the connectivity of susceptible grain boundaries.