Effect of Cr and N on Stress Corrosion Cracking Behavior of Fe-18Mn Steel

Abstract

High-Mn steels developed for offshore industries require good resistance to stress corrosion cracking (SCC) in seawater. Elements like Cr and N are often added to improve the resistance to SCC. In this study, the SCC behavior of Fe18Mn3Cr0.1N and Fe19Mn19Cr0.6N steels in artificial seawater was examined. Slow strain rate tests were conducted at a nominal strain rate of 10-6/sec in air and artificial seawater under anodic and cathodic applied potentials. The tensile ductility drop in artificial seawater was compared to air and evaluated as the resistance to SCC. It was found that both specimens showed intergranular cracking in artificial seawater under both anodic and cathodic applied potentials. The intergranular SCC was more severe under anodic applied potential than cathodic applied potential. However the sensitivity to SCC in artificial seawater was substantially reduced in Fe19Mn19Cr0.6N specimen with higher Cr and N content, as compared to the Fe18Mn3Cr0.1N specimen under both applied potentials. Potentiodynamic tests in artificial seawater showed an increase in pitting corrosion potential, rather than corrosion potential, with increasing Cr and N content in high-Mn steel. The SCC behavior of high-Mn steels with different Cr and N contents was discussed based on micrographic and fractographic observations. Key words: stress corrosion cracking, high-Mn steel, artificial seawater