Long-term oxidation behavior of carbon/carbon composites with a SiC/B4C–B2O3–SiO2–Al2O3 coating at low and medium temperatures

• A SiC/B4C–B2O3–SiO2–Al2O3 dual-layer coating was designed and fabricated.
• It can protect C/C for 250 h at 800 °C, 90 h at 900 °C and 90 h at 1000 °C.
• Al2O3 contents greatly affect the coating’s self-sealing ability and stability.
• An appropriate amount of Al2O3 could stabilize the glass phase for long time.

To achieve the long-term oxidation protection of carbon/carbon composites at low and medium temperatures, a SiC/B4C–B2O3–SiO2–Al2O3 coating was applied on the composites. The coating exhibits a dual-layer structure with a dense SiC inner layer and B4C–B2O3–SiO2–Al2O3 multi-phase outer layer. The effects of Al2O3 contents and oxidation temperatures on the oxidation behavior of the coated C/C were investigated. The results shows that the coating with 7.7 wt.% Al2O3 performs excellent self-healing ability and can protect the C/C composites with weight losses of less than 1% for 250 h at 800 °C and for 90 h at 900 °C and 1000 °C.