Oxidation resistance and thermal shock properties of self-healing SiCN/borosilicate glass-B4C-Al2O3 coatings for C/C aircraft brake materials

SiCN/borosilicate glass-B4C-Al2O3 coating was deposited on carbon fiber-reinforced carbon matrix (C/C) brake materials to protect them from oxidation. Microstructural analysis revealed that the coating was dense and uniform. Fabricated coating showed excellent oxidation resistance and significantly low weight losses after oxidation in dry air for 10 h than SiCN/borosilicate glass-B4C coated samples (ca. 0.12%, 0.51%, and 0.29% at 700, 800, and 900 °C, respectively). B4C is believed to react with the oxygen diffused into the coating to produce B2O3, which could heal cracks of the coating and improve its self-sealing ability and oxidation resistance. The Al2O3 present in the outer glass layer is believed to inhibit volatilization of B2O3, thereby reducing weight losses in air. Fabricated coating also possessed excellent oxidation resistance under fresh and sea water conditions, with cracks and pores generated during oxidization process being effectively healed. Prepared coating materials showed excellent thermal shock resistances after 50 thermal shock cycles, with weight losses being as low as 0.23%.