Study on anti-ablation properties of HfB₂-TaSi₂ coatings prepared by atmospheric plasma spraying

To improve the oxidation resistance of HfB₂-based coatings in high-temperature environments, HfB₂-TaSi₂ coatings with different TaSi₂ additions have been developed by using atmospheric plasma spraying technique(APS). The oxidation resistance of the coating was studied with oxyacetylene at 1750 °C. The results confirmed that the glass-phase SiO₂ layer formed by the coating ablation after adding TaSi₂ plays a role in sealing the pores. Meanwhile, Ta₂O₅ formed upon the oxidation of TaSi₂ increased the viscosity of the SiO₂ glass phase, which leads to a certain self-healing ability of the oxide layer. In addition, Ta₂O₅ reacts with HfO₂ to produce Hf₆Ta₂O₁₇ with excellent phase stability, which forms a dense equiaxed crystal band and has a strong oxygen inhibition ability. The HfB₂ coating containing 20 vol% TaSi₂ has the best oxidation resistance with a mass ablation rate of 4.85×10⁻⁴ g/s. These results indicate that TaSi₂ modified HfB₂ coating has good ablative resistance, and provides effective ablative protection for carbon fiber reinforced carbon substrate.