Isothermal oxidation property of the Al2TiO5/Tio2/Zro2 composite coating on TC4 alloy prepared by micro-arc oxidation

Abstract

The isothermal oxidation behaviours of Al2TiO5/TiO2/ZrO2 composite coating on titanium alloy (TC4) deposited by micro-arc oxidation technique were studied at different temperature points of 1073, 1173 and 1273 K in dry air. The surface morphology and phase composition of all coated samples were investigated before and after oxidation by SEM and XRD, respectively. The weight gaining curves of the coated samples were plotted and the high temperature oxidation rates were evaluated, showing that the oxidation kinetics followed the parabolic rate law. And with increasing oxidation temperature, their oxidation rates also increased. The original phases of Al2TiO5/TiO2/ZrO2 coating on TC4 alloy consisted mostly of Al2TiO5 and R-TiO2 intermixed with small amounts of ZrO2 and the phased changed into mainly of R-TiO2, Al2O3 and little Al2TiO5 when after 1273 K oxidation for 1 h, whose average parabolic rate constant was 6.43 × 10−13 g2 cm−4 s−1, greatly lower than that of blank samples, 6.01 × 10−12 g2 cm−4 s−1, indicative of a good oxidation resistance for the Al2TiO5/TiO2/ZrO2 composite coating on TC4 surface.