Microstructural evolution of SiC coating on C/C composites exposed to 1500 °C in ambient air

Oxidation-resistant coatings are essentially required to improve oxidation resistance performance of carbon/carbon (C/C) composites for applications under oxygen-containing atmosphere at elevated temperatures. In this work, thick and loose SiC coating was prepared by pack cementation (PC) to offer protection for C/C composites. Coating thickness, phases, anti-oxidation properties, and failure behavior at 1500 degrees C were characterized in ambient air for the as-prepared SiC coated specimens. As-prepared loose SiC coating with 150 pm thickness shows good oxidation resistance due to outstanding self-heal ability of SiO2. Weight loss of SiC coated specimens exposed to 1500 degrees C in ambient air is about 2.1% after oxidation for 58 h. Microstructural observation of SiC coated specimens after long-term oxidation indicates that bubbles caused by immigration and expansion of CO2 gas introduce defects. These defects cannot be rapidly healed by SiO2, which is main reason for SiC coating failure.