Improved water‑oxygen corrosion resistance of SiC_f/SiC composites modified with SiYBC matrix

In order to address the water‑oxygen corrosion problem of SiC_f/SiC composites, SiC_f/SiC-SiYBC composites were fabricated via chemical vapour infiltration (CVI) combined with reactive melt infiltration (RMI) process. After RMI, SiC_f/SiC-SiYBC composite basically reaches densification, with the density of 2.99 g/cm³ and open porosity of 3.05 vol%. The SiYBC matrix consists of reaction zones and residual alloy and is mainly composed of B₁₂(C,Si,B)₃, YSi₂, SiC, Si and YB₄. The formation mechanism of SiYBC matrix is discussed. The flexural strength and fracture toughness of SiC_f/SiC-SiYBC composite is 508.3 MPa and 26.30 MPa·m^1/2 respectively, which is higher than other matrix-modified ceramic matrix composites reported. After oxidation in water‑oxygen environment at 1400 °C for 100 h, yttrium silicate was formed in situ and the oxide layer protected the composite effectively, with the flexural strength retention rate of 84.5 %. This study provides a novel way to product high-density ceramic matrix composites with excellent water‑oxygen resistance.