Abstract: Nanocrystalline microstructure in the surface layer of 1Cr18Ni9Ti stainless steel induced by high-energy shot peening is characterized by means of X-ray diffractometry and transmission electron microscopy. The effects of surface nanocrystallization induced by shot peening on polarization behavior and corrosion resistance of the steel are also investigated by polarization curves and pit corrosion tests. And the surface morphologies of the corrosion samples have been characterized by scanning electron microscopy. The results show that shot peening can cause the surface nanocrystallization, that is, the nanocrystalline microstructure with average grain size of ~18 nm forms in the surface layer of the sample, and furthermore, induce a-martensite of about 15% in volume fraction. With increasing the depth from the shot-peened surface, the grain size increases, but the volume fraction of a martensite decreases. The surface nanocrystallization can improve the potentiodynamic polarization behavior of 1Cr18Ni9Ti stainless steel in 3.5% NaCl solution. Comparing to as-received coarse crystalline counterpart, the passive film on the surface of shot-peened sample is easier to form and more stable. Shot peening-induced surface nanocrystallization can markedly enhanced the corrosion resistance of 1Cr18Ni9Ti stainless steel in the chlorion-contained solution.

Key words: 1Cr18Ni9Ti stainless steel, Corrosion resistance, Shot peening, Surface nanocrystallization