Preparation and characterization of supersonic plasma sprayed Al–Al2O3–Cr2O3 composite coatings on magnesium alloy substrate

Abstract

Magnesium alloys have poor wear and corrosion resistance, which limits their wider industrial applications. In order to improve wear and corrosion resistance, Al–Al2O3–Cr2O3 composite coatings with different Al, Al2O3 and Cr2O3 compositions were prepared on magnesium alloy substrate using supersonic plasma spraying technology. The surface morphology, porosity, and microstructure of Al–Al2O3–Cr2O3 coatings were analyzed. The wear and corrosion resistance of Al–Al2O3–Cr2O3 coatings were evaluated. The results showed the surface morphology of the composite coating was flat, and the cross-sectional structure had a layered structure with close interlayer bonding, and also the structure was uniform and fine. The A70A15C15 coating exhibited the lowest porosity (0.56 %), whereas the porosity of A30A35C35 coating was the highest (only 1.61 %). The wear resistance of the composite coating increased with increasing Al2O3–Cr2O3 compositions, and the A30A35C35 coating showed the best wear resistance, with a 90.58 % reduction in volume wear rate when compared with that of the magnesium alloy substrate. Based on electrochemical impedance spectroscopy testing, the A50A25C25 coating had the slowest corrosion rate and best electrochemical corrosion resistance. Therefore, the preparation of the Al–Al2O3–Cr2O3 coating by supersonic plasma spraying on magnesium alloy substrate is a promising technique for improving its wear and corrosion resistance.