Preparation and high-temperature properties of Au nano-particles doped α-Al2O3 composite coating on TiAl-based alloy

Au nano-particles doped α-Al2O3 composite coatings were successfully prepared on TiAl-based alloy by electrodeposition, using the Al2O3 sols with minor addition of HAuCl4 solution. The even distribution of Au nano-particles (<2.0 wt.%) in the α-Al2O3 matrix has been observed. Isothermal oxidation tests of the samples coated with the as-prepared novel coatings at 900 °C in static air for 200 h shown that the oxygen inward diffusion can be effectively suppressed to a low level. The results of high-temperature cyclic oxidation test at 900 °C in air revealed that the oxidation and spallation resistance of TiAl-based alloy were improved significantly under thermal cycling. In the as-prepared coatings, cracks were shielded by means of crack bridging and the fracture resistance of the formed scales can be improved by toughening effects of the composite structure. Surface scratching tests after the cyclic oxidation exhibited that the adhesion of the formed composite scale on TiAl-based alloy was remarkably improved by the Au nano-particles doped α-Al2O3 composite coating.

► The Au nano-particles doped Al2O3 coatings were prepared by electrodepositon. ► The prepared coatings exhibit excellent oxidation and spallation resistance. ► Coating with more Au (wt.%) provides better oxidation and spallation resistance. ► The Au doped Al2O3 composite structure enhances the strength of the oxide scale. ► The oxidation rate of substrate alloy and the cost of Au are both extremely low.