Effects of Nitrogen and Cold Work on the Sensitization of Austenitic Stainless Steels. Final Report

摘要

This paper reports work done under Electric Power Research Institute Contract RP1574-1. The research addresses two concerns: the effects of nitrogen and molybdenum additions and the effects of cold work on the sensitization of unstabilized austenitic stainless steels. The results show that nitrogen and molybdenum are beneficial elements. Cold work prior to sensitization is very deterimental if it induces martensite. The presence of martensite is harmful because the diffusion coefficients of chromium and carbon are much greater in the body-centered tetragonal martensite than in the face-centered-cubic austenite. Consequently, sensitization can occur very rapidly within martensite. This occurrence is particularly noticeable at temperatures below the nose of the time-temperature-sensitization curve for a completely austenitic alloy. We also found that grinding of surfaces produces martensite. This deformation-induced martensite could sensitize at 288 exp 0 C within 2 to 10 years. (ERA citation 07:053708)