Oxidation resistance of SiC/SiC composites containing SiBC matrix fabricated by liquid silicon infiltration

The mechanical behavior and oxidation resistance of SiC/SiC-SiBC composites were studied in this work. According to the debonding criterion of He and Hutchinson, the debonding could occur at the BN interphase, which insures that the fibers can well play the strengthening and toughening performance. The oxidation resistance of SiC/SiC-SiBC composites consisting of SiC fibers with thermal expansion coefficients (CTE) of 5.1 × 10⁻⁶ K⁻¹ and 4.0 × 10⁻⁶ K⁻¹ was compared. The composites consisting of SiC fibers with higher CTE show slight weight changes at 800, 1000, and 1200 °C, and the corresponding strength retention ratios are 109.6%, 103.2% and 102.9%, exhibiting excellent oxidation resistance. The CTE of composites consisting of SiC fibers with higher CTE matches well with the CTE of SiC coating, so rarely no cracks can be formed in the coating, which inhibits the inward diffusion of oxidizing medium and leads to high strength retention ratios after oxidation tests.