Effect of Solution Annealing on Alpha Prime Martensitic Microstructure of Cold Rolled AISI316L Stainless Steel

Abstract

The effects of solution annealing on alpha prime (α) martensitic microstructure of cold rolled AISI316L austenitic stainless steel have been studied using XRD and corrosion analysis technique. Based on the good compatibility to high temperature water environment, AISI316L austenitic stainless steel is widely used for internal structural materials of light water reactors. However, recently, Stress Corrosion Cracking (SCC) was detected in the stainless steels for the applications in some commercial PWR plants. In this paper, the root cause of the SCC and its countermeasure are discussed on the basis of martensitic transformation in relationship with solution annealing and alpha martensitic microstructure. The martensitic contents of cold rolled AISI316L stainless steel decreased as solution annealing time increased with higher temperature. The mode of martensitic content change was deeply related to the solution annealing time and temperature. Therefore, it is considered that solution annealing and alpha prime martensitic microstructure play an important role in SCC resistance of cold rolled AISI316L. This leads us to conclude that the SCC resistance of AISI316L can be enhanced by the optimal solution annealing.