Effects of Ti addition on microstructure and the associated corrosion behavior of a 22Cr-5Ni duplex stainless steel

The effects of Ti addition on microstructure and the associated electrochemical properties of 22Cr-5Ni duplex stainless steel were evaluated using X-ray diffraction, X-ray electron probe microanalysis, electron backscattered diffraction, scanning Kelvin probe force microscopy, scanning electron microscopy-energy-dispersive X-ray spectroscopy, electrochemical techniques, and X-ray photoelectron spectroscopy. The results indicated that the addition of a minor amount of Ti refined the grains, improved the pitting potential, and lowered passive current densities remarkably. However, excessive content could cause an imbalance of phase proportion of ferrite and austenite phases and precipitation of the coarse TiN particles. The films on the base and Ti-containing alloy have a similar chemical composition, but the addition of Ti enriched the chromium in the passive film. In particular, the ratio of Cr2O3 and Mo6+ increased, which helped to form a comparatively homogeneous and stable passive film on the duplex stainless steel.

Automated summary

The addition of Ti can refine grains, improve pitting potential, and lower passive current densities, but an excessive amount can cause phase imbalance and precipitation of coarse particles. The increase in the ratio of Cr2O3 and Mo6+ in the passive film helps to form a stable film.