Effect of work hardening on stress corrosion cracking propagation in SUS316L stainless steel

Abstract

Stress corrosion cracking (SCC) growth tests were conducted on type 316L stainless steels (SS) with different cold rolling reductions of 10% to 40% under a simulated boiling water reactor coolant condition. In these tests, constant loads were applied to each compact tension (1 T-CT) specimen to maintain the initial stress intensity factors (K) to 20 MPa√m or 30 MPa√m. The crack growth rate increased with increasing the micro-Vickers hardness (Hv) and was larger than the tentative criterion of SCC growth rate for work hardened L-grade SS proposed by Kumagai, et al. at Hv>250. However, the crack morphology of specimens with high cold rolling reductions (Hv> 250) was quite different form that observed in the actual components. Only a 10% cold rolled specimen with Hv230 showed intergranular cracking, the same cracking morphology as that in the heat affected zone of the damaged shrouds. This result would suggest that the heavily cold rolled specimens with Hv>250 should not be used to obtain the crack growth data for prediction of SCC propagation behavior in the actual components because of the different crack morphology.