Microstructure and properties of Al2O3/TiO2 nanostructured ceramic composite coatings prepared by plasma spraying

► We prepared Al2O3/TiO2 nanostructured ceramic coatings by plasma spraying. ► The coatings were composed of bimodal structure. ► The properties of the coatings depend on the spraying power and TiO2 content. Al2O3/TiO2 nanostructured ceramic composite coatings were prepared on 6063 aluminum alloy substrates by plasma spraying in this paper. The microstructure and properties such as micro-hardness, wear resistance and corrosion resistance were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness tester, frictional wear testing machine and salt spray test. The results showed that both α-Al2O3 and γ-Al2O3 phases exist in the as-sprayed nanostructured ceramic composite coatings, and the content of γ-Al2O3 phase increases with increasing the spraying power, while rutile TiO2 phase exists in the coatings. The as-sprayed coatings were composed of bimodal structure, i.e., completely melted lamellar and partially melted particulate structure. Effects of both plasma spraying power and TiO2 content on hardness and wear resistance as well as corrosion resistance of the as-sprayed coatings were obvious.