Long term ablation behavior and mechanisms of Y2O3 reinforced Cf/HfB2-SiC composites

Ultrahigh temperature and long-term ablation-resistant properties are critical and challenging for the utilization of materials as the thermal components of hypersonic vehicles. In this work, Y 2 O 3 reinforced C f /HfB 2 -SiC composites are designed and fabricated, which present superior ablation resistance with a mass recession rate of 2.10 mg/s and linear recession rate of 0.67 μm/s (with 3 wt% Y 2 O 3 addition) under long term ablation at a heat flux of 5.5 MW/m 2 (up to ∼ 2700 °C) for 300 s. The long-term ablation mechanisms of the composites are studied and revealed with the help of a detailed microstructure analysis and thermodynamic considerations. It is indicated that Y 2 O 3 reacts with both HfO 2 and SiO 2 , leading to the formation of a stable oxide layer with small HfO 2 -based grains skeleton dispersed in HfO 2 -Y 2 O 3 -SiO 2 glassy phase, subsequently improving the ablation-resistant performance of the composites. This work inspires new strategies for further optimization of ablation resistance of ultra-high temperature ceramic matrix composites.