The Effect of Cold Rolling and Aging Treatment on the Stress Corrosion Cracking of SUS 316L and SUS 316 Stainless Steels in High Temperature Water

Recently, stress corrosion cracking (SCC) was observed in lots of Japanese BWR components made of L grade stainless steels (SS) with very low carbon content. SCC of L grade SS is quite different from the conventional IGSCC of SUS 304 SS since no sensitization is observed in the cracked region. Hence, the purpose of this study is to determine the material condition which is the most susceptible to such type of SCC. The SCC test was conducted by the creviced bent beam (CBB) method in high temperature water containing 8 ppm dissolved oxygen. The test specimen was cold rolled and/or heat treated at a temperature range from 873 K to 1073 K. The maximum SCC susceptibility was obtained in the as-received condition with cold rolling ratio of 10% for both SUS 316L and SUS 316 SS. The fracture surface consisted of mainly intergranular SCC with a small fraction of transgranular SCC similar to those observed in the actual components of BWR.