There is scant data in literature on the effect of cold work on the susceptibility to subsequent sensitization of Type 304 stainless steel. Bain, Aborn, and Rutherford (1) in their classic work showed that cold work prior to sensitization of austenitic stainless steels greatly contracted the susceptibility region on the time-temperature diagram. Tedmon, Vermilyea, and Broecker (2) report that 55% cold work followed by 24 hour sensitization at 600°C resulted in large numbers of carbides within the grains and relatively few carbides at grain boundaries. This material showed no grain boundary or general attack in boiling Strauss (acid copper sulfate) solution after 100 hr, thereby demonstrating complete healing of chromium-depleted regions. They also report that material cold worked 80% before sensitization treatment at a lower temperature (400°C) over a long period (1 month) showed severe attack in the Strauss solution. Recently, Briant and Ritter (3) studied the effect of pulling Type 304 specimens in tension to stresses of 345 and 552 MPa on their susceptibility to subsequent sensitization at temperatures ranging from 450 to 700°C. They found that whereas prior cold work hastened the onset of sensitization, the larger cold work resulted in complete healing after 24 hour at 650°C. Earlier, Clarke and Gordon (4) reported that cold work of 20% or less followed by a sensitization treatment markedly decreased the time to failure in both high (100 ppm) and low (0.2 ppm) oxygen water at 288°C when the material was tested at the same percentage of the yield strength. They remark, however, that since cold work of as little as 5% increases the yield strength of this material by a factor of 2, the time to failure of cold worked plus sensitized material and material sensitized without cold work are equivalent when tested at the same stress level. There is therefore a clear need for a thorough study of the effect of prior cold work on subsequent sensitization of Type 304 steel. Such a study is particularly important since most of the reported work on stress corrosion cracking of sensitized austenitic stainless steels deals with materials sensitized in the fully annealed state, whereas in practice austenitic stainless steels are used and welded in the mill-annealed condition, which is equivalent to fully annealed material with some cold work. The sensitization, if it occurs, in the heat affected zone of welds is therefore characteristic of a material that has undergone some cold work prior to sensitization rather than of a material sensitized subsequent to quench anneling. The present study was undertaken to partially bridge the gap in our knowledge of the effect of prior cold work on sensitization. The effect of prior cold work of 5 to 60% on subsequient sensitization at 660°C for two different times of 1 and 16 hrs. was investigated using electrochemical techniques as well as stress corrosion cracking tests at a slow strain rate.
