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Abstract: A 7-layer (Al2O3–Y2O3)/Pt laminated coating was successfully prepared on a Ni-based superalloy by magnetron sputtering methods. It is observed that the as-prepared coating has dense and refined brittle/ductile laminated nanostructure. Cyclic oxidation tests were adopted to investigate the oxidation and spallation resistance of this novel laminated coating. The results revealed that the 7-layer (Al2O3–Y2O3)/Pt laminated coating can significantly improve the high-temperature oxidation resistance and spallation resistance of the Ni-based superalloy. In such laminated coating, the multi-sealed (Al2O3–Y2O3) and Pt layers can effectively suppress the inward diffusion of oxygen to an extremely low level, providing super oxidation resistance at 1200°C for 1000h. In addition, the excellent high-temperature mechanical properties of the (Al2O3–Y2O3)/Pt laminated coating are mainly induced by the increased thermal expansion coefficient and the brittle/ductile laminated composite structure by means of energy release mechanisms. [Copyright &y& Elsevier]

Abstract: 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 (<2.0wt.%) 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 200h 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. [Copyright &y& Elsevier]