IGSCC crack growth in simulated BWR environment – Effect of nitrogen content in non-sensitised and warm rolled austenitic stainless steel

Effect of nitrogen level in strain hardened stainless steel (SS) on crack growth rate (CGR) in simulated boiling water reactor conditions has been the focus of this study. Type 304 LN stainless steel has been used in a warm rolled condition containing two different levels of nitrogen. Clear intergranular (IG) fracture was observed in both the stainless steels. The CGR increased 3 times in the stainless steel with higher level of nitrogen at all levels of dissolved oxygen and this was related to the increase in yield strength due to rolling and dynamic strain aging (DSA).

Research highlights
► Rolled non-sensitised material simulating constrained weldment used for testing.
► Nitrogen (N) in SS 304L adversely affects the IGSCC crack growth rate (CGR).
► Three fold increase in CGR occurred due to increase in N from 0.08 to 0.16 wt.%.
► Increase in CGR attributed to higher yield strength and dynamic strain aging.
► Clear intergranular fracture observed in these experiments.