Stress Corrosion Cracking of CrNi Martensitic Stainless Steel in Concentrated MgCl2Solutions

Abstract

Abstract The stress corrosion cracking (SCC) of CrNi martensitic stainless steels (SSs) was studied chiefly in 42% MgCl2 solution, with a particular emphasis on intercritical heat treatment. Martensitic SSs containing a few percent of Ni have been known to crack readily in concentrated MgCl2 solutions. However, as is demonstrated in this study, when the Cr content exceeds a certain value (∼ 15%), the cracking sensitivity of these steels can be improved considerably by an intercritical heat treatment to the extent that they do not crack in boiling 42% MgCl2 solution. Intercritical tempering results in the formation of a mixed microstructure consisting of tempered martensite and fresh martensite. The attained cracking resistance is not impaired by a second tempering unless the tempering temperature is high enough beyond the ACl temperature to destroy the microstructure achieved by the first intercritical tempering. Thus, there is a range of temperatures in the first and second temperings for these steels to...