Oxidation behaviour of SiC coated C/C-ZrC-ZrB2-SiC composites in wind tunnel at 1600°C

SiC coating was prepared on the surface of C/C-ZrC-ZrB2-SiC composites by chemical vapour deposition (CVD). The microstructures and phase compositions were characterised by scanning electron microscopy and X-ray diffraction respectively. The CVD SiC coating exhibited a dense structure with a thickness of 30-40 mu m. Oxidation behaviour of the coated sample was studied in a wind tunnel at 1600 degrees C. Thermogravimetric analysis of C/C-ZrC-ZrB2-SiC was measured. The results show that the coated sample fractured after being exposed in the wind tunnel for 21 h. The failure of the SiC coating is attributed to excessive local stress caused by the change of thermal expansion coefficient, resulting in the generation of cracks and holes. Once the failure of SiC coating appears, the fracture would not happen quickly due to the addition of ceramics (ZrC, ZrB2, SiC), which could promote the oxidation resistance performance and increase the stability of C/C composites in complicated service condition.