Enhanced high temperature ablation resistance of dense ZrB₂–Al₂TiO₅ composite coating by very low-pressure plasma spraying

ZrB₂-based composite coatings with addition of Al₂TiO₅ were prepared via very low-pressure plasma spraying using mechanically mixed powder of ZrB₂ and Al₂O₃-40 wt%TiO₂ (AT40). The ablation behavior of the composite coating was investigated using a high temperature plasma jet at a temperature of ∼2500^oC. Results demonstrate the addition of AT40 improved the ablation resistance of the ZrB₂ coatings at high temperatures. The coating with 17 vol%AT40 addition exhibited the lowest ablation rate, approximately 1.33 μm/s, which is only one-third of that of the pure ZrB₂ coating. The added AT40 filled the pores between ZrO₂ crystals during ablation, reducing oxygen penetration and lowering the ablation rate. However, excessive addition of AT40 hindered gaseous B₂O₃ release and thus led to large pore formation, impairing the protective effect. The ZrB₂-AT40 coating is a promising candidate for high-temperature applications.