Combination of cold work and heat treatment on stress corrosion cracking susceptibility of l-grade stainless steel

In order to clarify the stress corrosion cracking (SCC) mechanism of L-grade stainless steels, intergranular corrosion tests, SCC susceptibility test in high-temperature pure water and grain boundary analysis of Type 316L SS were performed. Effects of fabrication process, cold work and heat treatment, have been considered in this study. After solution heat treatment (SHT), reduction in thickness due to cold work of 0-10% and heat treatment at 500 to 700C for maximum 1000 hours were given to the test material. Time-Temperature-Sensitization (TTS) curve for the intergranular corrosion shifted to short time with increasing the cold work ratio. As a result of grain boundary analysis, it was found that the Laves phase precipitated prior to the M23C6 phase. Narrow chromium depleted zone was found along the Laves phase. SCC test was carried out after grinding the surface of the specimen. In the specimens with narrow Cr depleted zone, intergranular cracking following to the transgranular cracking was observed. Surface cold working and narrow chromium depleted zone along the Laves phase were considered to be the cause for TGSCC and IGSCC, respectively.