采用水热电泳沉积法在SiC-C/C复合材料表面制备纳米碳化硅(SiC_n)涂层. 采用XRD和SEM对涂层的晶相组成、表面和断面的微观结构进行了表征. 主要研究了水热沉积温度对涂层的结构及高温抗氧化性能的影响, 并分析了涂层试样在1600℃的高温氧化气氛下失效行为. 结果表明:纳米碳化硅涂层主要由β-SiC组成. 涂层的致密程度和厚度随着水热沉积温度的升高而提高. 随着水热温度的提高, 涂层试样的抗氧化性能也有明显的提高. 在120℃水热沉积温度下制备的涂层试样可在空气气氛1500℃下有效保护C/C复合材料202h,而氧化失重仅为2.16×10~(-3)g/cm~2. 在1600℃下氧化64h后失重为3.7×10~(-3)g/cm~2. 其高温失效是由于长时间的氧化挥发后表面SiO_2膜不能完全封填表面缺陷, 内涂层中产生了贯穿性的孔隙所致.
Nano-SiC coatings (SiC_n) 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 SiCn 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~(-3)g/cm~2. While the weight loss of coated C/C composites after 64h oxidation at 1600℃ in air is 3.7×10~(-3)g/cm~2. The failure of the coatings is due to the long time volatilization of SiO_2 thin film at high temperature, which makes the coating defects fail to be self-cured by SiO_2 glass layer and form the penetrative microholes in the SiC bonding layer.
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