C／SiC复合材料表面化学气相沉积涂覆SiC涂层及其抗氧化性能

PREPARATION OF SiC COATINGS ON SURFACE OF C/SiC COMPOSITES BY THE CHEMICAL VAPOR DEPOSITION AND THEIR OXIDATION RESISTANCE BEHAVIOR

采用化学气相沉积法,在1100℃,在碳纤维增强碳化硅复合材料表面制备SiC涂层,研究了涂层连续沉积和分4次沉积(每次沉积时间为6h)所制备的SiC涂层的微观结构和涂层样品的氧化性能。结果表明:两种SiC涂层的厚度均约为40μm,且4次沉积制备的SiC涂层为一个连续的整体。涂层连续沉积时,表面只出现裸露裂纹;分4次沉积制备时,表面出现大量边缘有SiC生长锥的附着裂纹,附着裂纹在高温氧化时易发生自愈合。与连续涂层样品相比,4次涂层能显著提高C/SiC样品的抗氧化性能。4次涂层样品经1400℃,50h氧化后,质量损失为0.88%,质量损失速率稳定在6.30×10–5g/(cm2·h),且4次涂层样品具有优异的抗热震性能。

SiC coatings on the surface of carbon fiber reinforced silicon carbide composites were prepared by the chemical vapor deposition （CVD） at 1 100 ℃. The microstructure and oxidation resistance of two coatings made by continuous deposition and by four-times CVD （each deposition time is 6h） were compared. The results show that the thicknesses of the two kinds of coatings are both about 40 μm and the coating made by four-times deposition retains its integrity in the cross section. The surface of the coating made by continuous deposition has naked cracks. There are adhesive cracks with SiC growth cones on the coating made by four-times deposition. The adhesion cracks could be self-sealed easily at high temperatures in oxidizing atmospheres. The oxidation resistance of the four-times coating is better than that of the continuous coating. After oxidation at 1 400 ℃ for 50h, the mass loss and mass loss rate of the C/SiC sample with a four-times coating of SiC are 0.88% and 6.30 × 10^-5g/（cm^2·h）, respectively, and the coating shows excellent thermal shock resistance.