Incubation Time of Stress Corrosion Cracking for Type 316L and Type 316 Stainless Steels by CBB Method in High Temperature Water

Abstract

Incubation times of stress corrosion cracking (SCC) for mill annealed and cold rolled type 316L stainless steel (SS) and type 316 SS were examined by the creviced bent beam method in oxygenated high temperature water at 561 K. SCC was observed in type 316L SS after exposure of 1000 h to the test environment, although type 316 SS showed SCC susceptibility after exposure of 500 h. The fracture surface of both type 316L SS and type 316 SS consisted mainly of intergranular SCC with a small fraction of transgranular SCC similar to those observed in the actual components. The maximum SCC crack length [a] on the specimen surface increased in proportion to the logarithm of the exposure time [t] for each SS as ;a=700×ln(t)–4334 : type 316L SS,a=1078×ln(t)–6347 : type 316 SS.The incubation times of 490 h and 360 h were obtained for type 316L SS and type 316 SS, respectively, from the relationship between the crack length and the test time. The SCC incubation times were larger than that of sensitized type 304 SS by >3 times showing higher resistance to SCC of mill annealed, low carbon stainless steels.