A Multi‐Step Deposition Strategy for β‐SiC Coatings on C _f /C Composites: Achieving Breakthrough Oxidation Resistance and Mechanical Properties

Abstract 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 SiO 2 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.