Microstructure Evolution and Corrosion Behavior of Deformed Austenitic Stainless Steel Manufactured by Selective Laser Melting

The effect of room temperature deformation on the microstructure and corrosion behavior of selective laser-melted (SLM) 316L steel in 0.9 wt.% NaCl medium was explored by electrochemical tests, microstructural analysis, and passive film characterization. The irregular evolution of corrosion behavior was first found in the deformed SLM 316L steel. The corrosion resistance of SLM 316L steel improved with increasing room temperature deformation level reached the maximum at 20% deformation, and then weakened with further increasing deformation below 40%. Microstructural analysis indicated that the deformation twins passed through the molten pool boundaries when the deformation was 20%, but not when the deformation was 40%. The dislocation density, Σ3, and low-angle grain boundaries increased slightly with increasing deformation below 20%, but they increased distinctly with deformation level greater than 20%. Besides, room temperature deformation modified the oxide content of the surface passive film, especially for the chromium oxide, which affected the corrosion resistance of passive film. Above results indicate that low room temperature deformation level of SLM 316L stainless steel is feasible to improve its corrosion resistance and optimize the passive film.