The Effect of Prior Cold Work on the Degree of Sensitization in Type 304 Stainless Steel

The effect of prior cold work of 0 to 60% on subsequent sensitization of Type 304 stainless steel at 660 C was studied from anodic polarization scans in 1N HClO4 + 0.2N NaCl and 0.5M H2SO4 + 0.01 M KSCN solutions and from SCC behavior in room temperature 1N H2SO4 at 150mVSHE at a strain rate of 10−6 sec−1. Small amounts (5 to 20%) of prior cold work sharply enhanced the susceptibility to subsequent sensitization. With increasing amounts of prior cold work, heating at 660° for 1 or 16 hours resulted in progressively more widespread precipitation of carbides within and across the grains. This presumably shortened diffusion paths for chromium and, along with the expectedly faster chromium diffusion rate in cold worked metal, resulted in partial to total absence of sensitization in specimens that were highly cold worked (>40%) prior to the sensitization treatment.