(中南大学 粉末冶金研究院 粉末冶金国家重点实验室，长沙 410083)
摘 要: 为提高C/C复合材料在高温富氧环境中的抗氧化性能，采用两步刷涂+化学气相沉积法在C/C复合材料表面制备含Si3N4、MoSi2、TaC等添加剂的ZrB2-SiC基多层复合陶瓷涂层。利用XRD和SEM等分析测试手段研究涂层的物相组成和微观结构，并分析讨论涂层在900和1500 ℃的等温抗氧化机理。结果表明：利用两步刷涂+化学气相沉积法制备的ZrB2-SiC基复合陶瓷涂层整体厚度约为200 μm。Si3N4、MoSi2可很好地促进ZrB2-SiC基氧阻挡层的高温烧结，使涂层致密化，并提高涂层在900 ℃的抗氧化性能；与之相比，TaC则不能很好地发挥致密化作用，对涂层在900 ℃时抗氧化性能的提高有限。在900 ℃时，ZrB2-SiC基陶瓷涂层的氧化过程主要受氧在涂层孔隙等缺陷中的扩散所控制，添加剂主要通过改变涂层的致密化程度来影响涂层的抗氧化性能。在1500 ℃氧化过程中，涂层抗氧化性能恶化，但致密的化学气相沉积SiC封填层的引入可显著改善涂层在1500 ℃时的抗氧化性能，涂层表面生成了完整的含有ZrO2和ZrSiO4等高熔点颗粒的SiO2玻璃态氧化膜，为基体提供有效的氧化防护。
关键字: C/C复合材料；ZrB2-SiC基涂层；添加剂；抗氧化机理
（State Key Laboratory of Powder Metallurgy, Powder Metallurgy Research Institute, Central South University, Changsha 410083, China）
Abstract:To improve the anti-oxidation performance of C/C composites under high temperature and oxygen enriched environment, ZrB2-SiC based ceramic coatings with Si3N4, MoSi2 and TaC addition were prepared by two-step slurry painting+chemical vapor deposition (CVD). Phase composition and microstructure of the as-prepared coating were investigated by using X-ray diffractometry and scan electron microscopy, and the isothermal anti-oxidation mechanism at 900 ℃ and 1500 ℃ were also analyzed and discussed. The conclusions are as follows, the thickness of the as-prepared ZrB2-SiC based composite ceramic coating is about 200 μm. The densification and the anti-oxidation properties of the coating can be improved by the addition of Si3N4 and MoSi2, effectively. While the anti-oxidation properties of the coating can not be improved by the addition of TaC effectively at 900 ℃. At 900 ℃, the oxidation process of ZrB2-SiC ceramic coating was mainly controlled by the diffusion of oxygen in pore and other defects in the coating. The anti-oxidation property of coating can be improved by the addition by affecting the density of coating. In the oxidation process of 1500 ℃, the oxidation resistance of the coating decreases. The introduction of the compact structure of CVD SiC sealing layer can improve the oxidation resistance significantly. At 1500 ℃, in oxidation process, SiO2 glassy oxide film with ZrO2 and ZrSiO4 on the coating is generated, this can provide effective oxidation protection for the substrate.
Key words: C/C composite; ZrB2-SiC based coating; additive; anti-oxidation mechanism
