Microstructure and Oxidation Resistance Of Tio2 Modified Multilayer Coating Prepared by Hapc/Mao

A TiO2-Nb2O5-SiO2-Al2O3/NbSi2/NbAl3 multilayer coating was prepared on Nb alloys through halide activated pack cementation (HAPC) and micro-arc oxidation (MAO). The multilayer coatings were composed of a TiO2-Nb2O5-SiO2-Al2O3 outer layer, a NbSi2 middle layer and an Al-rich inner layer. The isothermal oxidation resistance of TiO2-Nb2O5-SiO2-Al2O3/NbSi2/NbAl3 multilayer coated Nb alloy was investigated at 1200 °C. Besides, the microstructure evolution and element diffusion of the composite coating were studied. The results showed that after oxidation at 1200 °C for 50 h, weight gain of TiO2-Nb2O5-SiO2-Al2O3/NbSi2/NbAl3 coating sample was 8.54 mg/cm2, which was significantly lower than the coating sample without TiO2. An improvement in the high-temperature oxidation resistance of coating with TiO2 should be ascribed to the formation of continuous and compact oxide scale on the surface