EFFECT OF GRAIN-BOUNDARY CR CONCENTRATION PROFILES ON STRESS-CORROSION CRACKING SUSCEPTIBILITY IN 304-STAINLESS-STEEL

Very narrow chromium (Cr) depletions with widths below 10nm were produ ced by a heat treatment which controlled a growth of Cr carbides at a grain boundary (GB) in type 304 stainless steel. A Correlation between the Cr depletion profile and intergranular stress corrosion cracking (IGSCC) susceptibility in a high temperature water was investigated. I GSCC susceptibility was affected especially by the Cr concentration as compared with the Cr depletion width at GB. The susceptibility increa sed at the Cr concentration below about 15mass%. No IGSCC susceptibili ty was observed when there was no Cr depletion at GB. The above mentio ned results in heat treated materials almost corresponded with that in neutron irradiated materials.