Stress corrosion cracking of a welded supermartensitic stainless steel: effect of PWHT

摘要

The role of grain boundary sensitization on the intergranular Stress Corrosion Cracking resistance of heat affected zones in welded supermartensitic stainless steels have been studied. Slow strain rate tensile tests are performed on specimen sampled across multiplepass welds. The effects of the carbon content and chromium to carbon ratio on the resistance to Stress Corrosion Cracking are highlighted. The examination of carbon replica in transmission electron microscopy show that these differences are related to the grain boundary coverage by chromium carbides. A sensitisation phenomenon in heat affected zones is proposed as being the primary cause for the sensitivity to stress corrosion cracking. Post-weld heat treatments are a practical solution to this problem and simulated heat treatments demonstrate a time-temperature dependence that is compatible with the kinetics of chromium diffusion in bcc ferrite. The transposition of these results to four-points bend testing is discussed.