Yttrium silicate coatings for SiC coated C/C composites prepared by atmospheric plasma spraying

Different yttrium silicate coatings for SiC-coated C/C composites were designed and prepared by an atmospheric plasma spray method to prevent the C/C composites from oxidation. XRD profiles showed that the coating was composed of Y₂SiO₅, Y₂Si₂O₇, and Y₄Si₃O₁₂. SEM showed that the gradient SiC/Y₄Si₃O₁₂/ Y₂Si₂O₇/Y₂SiO₅ coating had a more compact surface than the other coatings did. Isothermal oxidation tests at 1500°C in air showed that the weight loss curves of the as-prepared C/C composites showed a linear tendency with time and the weight loss rate of all coated samples increased significantly after 73 h. The coating could protect the C/C composites from oxidation at 1500°C for 73 h in air with a weight loss rate of 1.01 × 10^-4 g · cm^-2 · h^-1. The SiC/Y₄Si₃O₁₂/ Y₂Si₂O₇/Y₂SiO₅ was the better coating at high temperature than other coatings.