Abstract: Nano-SiC coatings (SiCn) were deposited on SiC-C/C composites surface by a hydrothermal electrophoretic deposition. Phase compositions, surface and cross-section morphologies of the as-prepared multilayer coatings were characterized by XRD and SEM. The influences of hydrothermal deposition temperatures on the microstructures and high temperature oxidation resistance of the SiC_n coatings were particularly investigated. And the invalidation behaviors of the as-prepared multilayer coatings coated samples at 1600℃ were analyzed. Results show that the as-prepared nano-SiC outer layers are composed of β-SiC. The thickness and density of the nano-SiC coatings improve with the increase of hydrothermal temperature. With the increase of hydrothermal temperature, the anti-oxidation properties of the coating samples increase. The prepared coating samples deposited at 120℃ can effectively protect C/C composites from oxidation at 1500℃ in air for 202h with weight loss only about 2.16×10^-3g/cm². While the weight loss of coated C/C composites after 64h oxidation at 1600℃ in air is 3.7×10^-3g/cm². The failure of the coatings is due to the long time volatilization of SiO2 thin film at high temperature, which makes the coating defects fail to be self-cured by SiO₂ glass layer and form the penetrative microholes in the SiC bonding layer.

Key words: C/C composites, nano-SiC, hydrothermal electrophoretic deposition