Stress Corrosion Cracking Behavior of Type 316L and Type 310S Stainless Steels in Fusion Relevant Environments

Abstract

Stress corrosion cracking (SCC) susceptibility of type 316L and type 310S SS in pressurized water (561/613 K) and supercritical water (773 K) at deaerated condition and with dissolved-hydrogen (DH) ranging from 0.014 to 1.4 ppm were examined by means of slow strain rate test (SSRT) method at a strain rate of 5 × 10⁻⁷ s⁻¹. SCC susceptibility of type 316L SS depends on test temperature and DH content. The SCC susceptibility, which was evaluated as a brittle fracture ratio, increased with increasing test temperature from 561 to 613 K, while it became much smaller in supercritical water at 773 K. At 613 K, the fracture ratio of intergranular (IG) SCC increased with increasing DH content in the pressurized water, although almost no IGSCC was observed at 561 K at any DH conditions. However, the IGSCC initiated at near specimen surface and transferred to transgranular (TG) SCC inside the specimen. The SCC susceptibility of type 310S SS is significantly lower than that of type 316L SS in the hydrogenated water at 561 and 613 K, while the trend appears to be reverse at 773 K. It is suggested that higher DH content in water is necessary to trigger IGSCC than TGSCC at 613 K.