Microstructure and properties evolution of plasma sprayed Al2O3-ZrO2-TiO2 coatings during high temperature and thermal shock resistance.

Al2O3-ZrO2 and Al2O3-ZrO2-TiO2 composite coatings were prepared by plasma spraying. The effects of TiO2 on the microstructure evolution and thermal shock resistance of the Al2O3-ZrO2 coating at high temperature were investigated. The results show that there was no phase transformation present in the two coatings after heat treatment at 800°C, and they were composed of t-ZrO2, α-Al2O3 and γ-Al2O3 phases. The Al2O3-ZrO2 coating after heat treatment at 1200°C consisted of t-ZrO2 and α-Al2O3, and the Al2O3-ZrO2-TiO2 coating consisted of t-ZrO2, α-Al2O3 and rutile-TiO2. The high temperature heat treatment reduced the porosity of the two coatings, and the hardness of the two coatings increased first and then decreased. The thermal shock resistance of the two coatings could be improved effectively by spraying the bonding layer and selecting TC4 titanium alloy as the substrate. And the Al2O3-ZrO2-TiO2 coating had a longer thermal cycle life than the Al2O3-ZrO2 coating. [ABSTRACT FROM AUTHOR]