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.