GRAIN-BOUNDARY SEGREGATION AND IGSCC IN COLD-WORKED TYPE-304-SS

Applied-potential constant extension rate tensile (CERT) tests were conducted on unirradiated, mill-annealed type 304 (UNS S30400) stainless steel in an attempt to reproduce irradiation-assisted intergranular stress corrosion cracking (IGSCC) in the laboratory. To simulate highly irradiated material, the test material was cold worked and given a low-temperature anneal. Significant (10%) IGSCC was obtained in samples that had been cold rolled 30%, aged at 500°C for 700 hours, and CERT tested under an anodic potential of O VSHE. The results of Auger electron spectroscopy showed that the amount of intergranular phosphorus segregation could be correlated with the degree of IGSCC and elongation measured in the tests. The depth of intergranular attack in the HNO3/Cr+6 corrosion test could also be correlated with the amount of phosphorus segregation.