Research On Microstructure And Properties Of YSZ Thermal Barrier Coatings With Different Doping Ni/Al Ratios By Epd Technical

In this paper YSZ thermal barrier coatings with different doping ratios of Ni, Al elements were deposited on Ni-based superalloy Inconel 600 by EPD technique. The topic was to study the effect of different doping ratio of Ni, Al elements on phase evolution, oxidation resistance, bond strength of composite coatings. Moreover, the sample were sintered under CH₄ atmosphere to study the effect of atmosphere on phase evolution, oxidation resistance, bond strength of composite coatings.Result show that the phase constitutions varied with the different doping mole ratio of Ni:Al. After sintered in vacuum at 1100℃ for 2 h, t-ZrO₂ and AlNi are present in the products of YSZ（Ni: Al=1:3） coated samples, t-ZrO₂ and AlNi3 phase are present in YSZ（Ni: Al=1:2） coated samples, t-ZrO₂ and Ni in YSZ（Ni: Al=1:1）coated sample. t-ZrO₂, Al2O3 and NiAl2O4 were found in YSZ（Ni: Al=1:3） and YSZ（Ni: Al=1:2） coated samples and after oxidation in air at 1000℃ for 50 h.However, t-ZrO₂ and NiO phase were found in YSZ（Ni: Al=1:1） coated samples.Moreover, after oxidation in air for 50 h Ni and Cr elements enriched at the interface of coating and substrate which enhanced the bond strength of coating. Al element enriched at the surface of coatings after oxidation for 50 h which improved the density and enhanced the oxidation resistance of composite coating.After sintering in CH₄ atmosphere at 1100℃ for 2 h both of the samples contained ZrC phase. YSZ（Ni, Al=1:3） contained ZrC and t-ZrO₂ phase; YSZ（Ni:Al=1:2） contained ZrC, Ni and t-Zr O₂ phase; YSZ（Ni:Al=1:1） coated sample contained Ni and t-ZrO₂ phase. During sintering Al is likely to have some solid solubility in（200） plane of ZrC phase in YSZ（Ni, Al=1:3） and YSZ（Ni: Al=1:2）coated samples. And these Al elements oxidized to Al2O3 phase which filled the poresand micro-cracks in coating which can prevent O diffusion into the coating and enhanced the oxidation resistance of coatings. In the other way, Al2O3 phase can surround the YSZ crystals and by creation of compressive stress prevent its phase transformation. Moreover, Ni and Cr elements enriched at the interface of coating and substrate after oxidation which enhanced the bond strength of coating.