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...