Preparation and Ablation Properties of Y₂SiO₅ Coating for SiC-Coated C/C Composites by Supersonic Plasma Spraying

Y₂SiO₅ coating was prepared on the surface of SiC-coated C/C composites by supersonic plasma spraying at different powers of 35, 40, 45, and 50 kW. The microstructures and phase compositions were characterized by scanning electron microscopy and x-ray diffraction, respectively. Roughness of the coating was measured by a confocal laser scanning microscope. Bonding force between Y₂SiO₅ outer coating and SiC inner coating was measured by a scratch tester. The results show that Y₂SiO₅ coating prepared at the spraying power of 45 kW possesses the biggest deposition rate, minimum surface roughness (Ra = 11.12 μm), and maximum bonding force (up to 28 N). The linear and mass ablation rates of Y₂SiO₅ coating prepared at 45 kW are 2.6 μm/s and 0.031 mg cm⁻² s⁻¹ in the heat flux of 2.38 MW/m² under oxyacetylene torch. During ablation, a glassy layer of SiO₂ + Y₂O₃ was formed, acting as a barrier to high-speed gas flow of oxyacetylene flame.