Influence of Forging and Annealing on the Microstructure and Corrosion Behavior of Austenitic Stainless Steel

Abstract

The deformed microstructure and corrosion behavior of 316LN austenitic stainless steel after warm forging and annealing have been explored by using electron backscatter diffraction (EBSD) and electrochemical corrosion test methods in marine environment. An attempt has been made to understand the effect of warm forging and annealing on the microstructure and electrochemical behavior of 316LN stainless steel. The results indicate that the corrosion rate decreases after annealing of forged samples because annealing improves the repassivation capacity of forged samples. In the Tafel plot, the value of Ecorr shifts toward the passive direction after annealing of forged samples which indicates that a more protective passive film of Cr2O3 is formed on the surface of annealed sample after forging. The EBSD micrographs show that refinement of grain occurs after warm forging, and due to refinement, grain boundaries are not clearly visible after forging. EBSD microstructure shows that grain coarsening occurs after annealing of forged sample and the optimum strength and corrosion resistance were observed in annealed sample after forging. The value of impact strength decreases and hardness increases after increasing the percentage of deformation, and optimum impact strength and hardness were observed in annealed sample after warm forging.