Corrosion and Wear Properties of Cr Coating and ZrO2/Cr Bilayer Coating on Zr-4 Alloy

Abstract

In this study, duplex surface treatments were used to prepare a ZrO2/Cr bilayer coating on zirconium alloy cladding for enhancing the wear and corrosion behaviors. The surface and cross-section morphology of coated Zr-4 alloy was characterized; the results show that the Cr- and ZrO2/Cr-coated samples had similar morphology, and more obvious surface undulates could be observed on the ZrO2/Cr coating than the pure Cr coating owing to the rough surface of the plasma electrolytic oxidation coating. Wear and electrochemical behavior in 1200 mg/L H3BO3 and 2.2 mg/L LiOH solutions of original and coated Zr-4 alloy were investigated. The electrochemical corrosion test indicated the coated Zr-4 alloy exhibited better corrosion resistance behavior than the original Zr-4 alloy. The potentiodynamic polarization curves and corrosion morphology suggest the pitting corrosion occurred on the surface of the original and coated Zr-4 alloy. The ZrO2/Cr-coated Zr-4 alloy had better corrosion resistance due to the dual protection of the PEO layer and Cr coating. The wear behavior of the original and coated Zr-4 alloy was also investigated under a constant load of 5 N. The results reveal that the coated Zr-4 alloy had better wear resistance, and the PEO layer was found to significantly enhance the wear resistance of the Zr-4 alloy.