A Multi-Step Deposition Strategy for β-SiC Coatings on C_f/C Composites: Achieving Breakthrough Oxidation Resistance...

Current SiC coating technologies for anti-oxidation C_f/C composites, such as pack cementation, often rely on high-temperature in situ reaction with severe mechanical property decay. Chemical vapor deposition (CVD) presents a promising alternative for fabricating anti-oxidation SiC coatings with long service life and high mechanical property. However, existing CVD approaches suffer from poor crack sealing and rapid oxidation loss, leading to insufficient anti-oxidation time. Therefore, achieving long-term anti-oxidation SiC coatings using CVD remains a crucial challenge. This work presents a straightforward multi-step deposition strategy for fabricating anti-oxidation C_f/C composites with long service life and high mechanical properties. The anti-oxidation time of β-SiC coated C_f/C composites reached 659 h at 1500 °C for the first time (within <1% mass loss), far superior to the previously reported index by CVD (1500 °C, < 30 h), and acquired over 30% increase in bending strength compared to uncoated C_f/C composites. The inhibition on through-crack sources by multi-deposition strategy can utilize the oxidation barrier of self-derived SiO₂ and keep the stability of coating/substrate interface, thus achieving superior oxidation resistance. This new breakthrough for anti-oxidation C_f/C composites opens doors to a broad range of applications, including thermal fields, engine nozzles, brake discs, chemical combustion chambers, and nuclear first wall materials.