High-temperature oxidation resistance of sol-gel-derived ZrO2/(Al2O3-Y2O3) coating on titanium alloy

ZrO2/(Al2O3-Y2O3) composite coating was deposited on Ti-6.5Al-3.5Mo-15Zr-0.3Si (at.%) alloy via sol-gel spin coating with the hope to improve its high-temperature oxidation resistance. The as-prepared coating was dense, uniform and crack-free. Isothermal and cyclic oxidation tests of coated and uncoated specimens at 700 A degrees C for 100 h were performed to evaluate its effect on oxidation behavior of the alloy. The results indicated that oxidation resistance and spallation resistance for coated specimen have been remarkably improved, thickness of oxide scale of coated specimen was thinner than that of uncoated one and the scale was composed of deposited Al2O3 outermost layer, a thin TiO2 middle layer and a mixture of Al2O3 and ZrO2 thick innermost layer. The mechanism of the coating having beneficial effects could be attributed to the inhibition of the inward diffusion of O and outward diffusion of Ti and Al, lower thermal stress and good adhesion between the coating and substrate. [GRAPHICS] .