Enhanced water-oxygen corrosion resistance of SiC_f/SiC composites modified by novel rare-earth disilicate (4RE_0.25)₂Si₂O₇

Severe performance degradation of SiC_f/SiC composites in high-temperature water-oxygen environments of aircraft engines critically limits their engineering applications. This study addresses the challenge by synthesizing a four-component rare-earth disilicate solid solution (4RE_0.25)₂Si₂O₇ (RE = Yb, Y, Lu, Tm) via solid-state reaction and fabricating SiC_f/SiC-(4RE_0.25)₂Si₂O₇ composites with multilayered matrix structure using combined chemical vapor infiltration (CVI), slurry impregnation (SI), and polymer infiltration and pyrolysis (PIP) processes. The results demonstrate that (4RE_0.25)₂Si₂O₇ exhibits a β-phase monoclinic structure with homogeneous rare-earth distribution at the microscale, exhibiting exceptional thermal stability and a thermal expansion coefficient matching that of the SiC matrix. During static water-oxygen corrosion at 1400 °C, the (4RE_0.25)₂Si₂O₇ phase develops a continuous barrier layer through grain growth and interconnection, effectively suppressing the diffusion of corrosive species. After 50 h of corrosion, the composites retain 88.82 % of their initial flexural strength, representing a 20 % improvement compared to the unmodified composites.