Influence of Deformation and Annealing on Microstructure and Corrosion Behavior of Austenitic Stainless Steel

Abstract

Microstructure and corrosion behavior of warm deformed 316LN stainless steel was investigated in primary water reactor (PWR) environment by electrochemical corrosion test methods and SEM. An attempt has been made to understand the effect of warm deformation and heat treatment on the microstructure and electrochemical behavior of 316LN stainless steel. The corrosion rate is drastically increases after deformation as compare to un-deformed samples because protective oxide film is destroyed after deformation. The results indicate that the corrosion rate decrease after stress relief and solution annealing of deformed samples because heat treatment improved the repassivation capacity of deformed samples. The Ecorr shifted toward the passive direction after stress relief and solution annealing of deformed samples which indicate that a more protective passive film (Cr2O3) form on the surface of the deformed samples. It can be seen that the stress relief and solution annealing heat treated samples have less pit as compare to un-deformed samples which indicate that deformed samples have more pitting resistance as compare to un-deformed samples. Surface of the samples after corrosion test in PWR solution is investigated by SEM and it is observed that number of pits and depth of pits reduced after solution annealing and stress relief treatment of deformed sample as compare to un-deformed samples