Thermophysical properties and sintering resistance of novel Al2O3/YTaO4 thermal barrier coatings

In this paper, YTaO4 (0AYT) thermal barrier coating and 10 wt% Al2O3-YTaO4 (10AYT) thermal barrier coating were prepared by using the atmospheric plasma spraying. The thermophysical and high temperature anti- sintering properties of the coatings at different heating temperatures were thoroughly investigated. Due to the phonon-point defect scattering mechanism by doping a small amount of Al3+ during the high-temperature spraying process, the thermal conductivity of the as-sprayed 10AYT coatings is lower than that of the as- sprayed 0AYT coatings. And the thermal conductivity of the as-sprayed coatings (0.53 W center dot m-1 center dot K-1, 1000 degrees C) was about 73 % lower than that of the YTaO4 dense bulk (1.97 W center dot m- 1 center dot K- 1, 1000 degrees C) and about 45 % lower than that of the YSZ thermal barrier coating. The thermal expansion coefficient (TEC) of the as-sprayed 10AYT coating is lower than that of as-sprayed 0AYT coating because that the TEC for gamma-Al2O3 is lower than that of T '-YTaO4. At the same time, both the thermal conductivity and the TEC of the coatings increased with increasing heating temperature. The bond strength of the coatings was 50.6 +/- 0.3 MPa at a ceramic layer thickness of 200 mu m. The porosity, Young's modulus, and hardness values of the coatings tended to stabilize after sintering at 1300 degrees C and 1600 degrees C for 300 h. No other phases were formed during the sintering process. This indicated that both two coatings had excellent sintering resistance and high temperature phase stability.