Effect of annealing treatment on the microstructure evolution and corrosion behavior of 316L stainless steel manufactured by laser powder bed fusion

The microstructure and corrosion behavior of 316L stainless steel (316L SS) fabricated by laser powder bed fusion (LPBF) and subsequently annealed at 800 o C, 1000 o C, and 1200 o C for 4 h were investigated. Surface characterization and electrochemical measurements were employed. The results showed that the annealing treatment did not alter the phase composition of LPBF 316L SS. However, the grain size increased progressively with annealing temperature increasing. The low angle grain boundaries (LAGBs) gradually decreased and the cellular substructures inside the grains disappeared after annealing treatment. The LPBF 316L SS would recrystallize and numerous recrystallized twin grains appear at 1200 °C annealing treatment. The electrochemical tests revealed that annealing treatment detrimentally affected the corrosion resistance of the LPBF 316L SS. The passive film formed on the annealed samples became less stable with higher charge carrier density. Meanwhile, the thickness and the O 2- /OH - ratios of the passive film decreased after annealing treatment. These indicated that the annealing treatment reduced the protection of the passive film.