化学气相反应法制备不同碳基体表面SiC涂层组织结构分析

采用化学气相反应法, 以同种工艺分别在石墨和C/C复合材料表面制备了SiC涂层, 借助X射线衍射仪(XRD)、扫描电镜(SEM)及能谱分析等手段分析了涂层的微观结构, 研究了不同碳基体对SiC涂层结构和表面形貌的影响, 并初步对比考察了涂层的高温抗氧化性能. 结果表明: 制备的SiC涂层整体致密, 与基体结合良好, 但存在明显的结构差异. 石墨表面制得的SiC涂层呈梯度分布, 涂层主要由致密外层及过渡内层组成, 而C/C复合材料表面制得的SiC涂层仅由致密外层组成; 在1823 K的空气氧化氛围中, 与C/C复合材料SiC涂层试样相比, 石墨SiC涂层试样表现出更好的高温抗氧化性能, 经30 h氧化及7次循环热震实验后, 涂层试样的氧化失重率仅为0.182%.

Analysis on the Structure Variation of SiC Coatings on Different Carbon Materials Prepared with Chemical Vapor Reaction

To protect carbon materials from oxidation, SiC coatings were prepared on carbon/carbon (C/C) composites and graphite by the chemical vapor reaction (CVR) in the same condition. Microstructure of the as-prepared coating was studied by using XRD, SEM and EDS analyses. The influence of different carbon substrates on the structure and surface morphology of the SiC coating was discussed, and then the oxidation resistance of the two obtained samples was tested and compared. The results show that: though the two as-prepared coatings are compact and have a good bonding ability with substrate, they reveal an obvious structure difference. The obtained SiC coating on graphite shows a gradient distribution, which consists of the dense out-layer and inner transitional layer; while the coating on C/C composites only reveals a dense out-layer structure. The oxidation test indicates that the SiC coated graphite exhibits better anti-oxidation property than the SiC coated C/C composites, and after oxidation in air at 1823 K for 30 h and the thermal cycling between 1823 K and room temperature for 7 times, the weight loss of the coated graphite is only 0.182%.