The Influence of Hydrogen on Corrosion Fatigue Crack Growth Behavior in Type 304/304L Stainless Steel in Elevated Temperature Deaerated Pressurized Water

Corrosion fatigue crack growth rates (FCGRs) in Type 304/304L stainless steel containing different levels of sulfur are observed to vary significantly during testing at high stress ratios in elevated temperature (288 – 338°C) deaerated pressurized water (DPW). Under comparable loading conditions, environmentally enhanced FCGRs, 10x – 100x higher than those measured in elevated temperature (288°C) air, are observed in low sulfur (<0.001 wt.%) stainless steel while a less pronounced environmental enhancement in FCGRs in elevated S (0.006 wt.% – 0.032 wt.%) stainless steel is observed. The focus of this work is to evaluate the deformed microstructure in the vicinity of crack tips to discern the physical mechanisms responsible for the disparities in observed FCGRs. Potential hydrogen-based mechanisms for these disparities will be discussed.