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和二硅化钼的复相(SiCn-MoSi2)抗氧化涂层.分别采用XRD和SEM等测试手段对涂层的晶相组成和显微结构进行了表征. 主要研究了沉积电压对涂层显微结构及高温抗氧化性能的影响, 分析了涂层试样在1500℃下的静态氧化行为及热循环失效机理. 结果表明: 外涂层主要由MoSi2和β-SiC晶相组成. 当沉积电压为100~180V时, 外涂层的致密程度、厚度及抗氧化性能随着沉积电压的升高而提高. 沉积电压过高(220V)时, 复合涂层中出现裂纹等缺陷, 涂层的氧化保护能力相应减弱. 抗氧化性能测试表明复合涂层可在1500℃的静态空气中有效保护C/C复合材料346h, 失重率仅1.41wt%. 涂层的高温失效是由于涂层试样在热循环过程中产生了贯穿性裂纹导致的.
In order to protect carbon/carbon (C/C) composites from oxidation at high temperature, a nano SiCn-MoSi2 coating was prepared on SiC pre-coated C/C composites by novel hydrothermal electrophoretic deposition. The phase compositions of the as-prepared coatings were analyzed by XRD, the morphologies of the multi-layer coatings were observed by SEM and the high temperature anti-oxidation properties of the multi-coatings were investigated by isothermal oxidation test. The influence of hydrothermal electrophoretic deposition voltage on the phase composition, microstructure and high temperature oxidation resistance of the multilayer coating were particularly investigated. The invalidation behavior of the coated sample during the thermal cycle process was analyzed. Results show that the outer layer coatings are mainly composed of β-SiC and MoSi2 phases. The thickness, density and anti-oxidation properties of the SiCn-MoSi2 coating are improved with the increase of deposition voltage from 100V to 180V. However, cracks are observed at a high deposition voltage (220V) and the decrease in oxidation resistance is detected. The multi-layer coatings deposited at 180V exhibit excellent oxidation resistance ability, which can effectively protect C/C composites from oxidation in air at 1500℃ for 346h with a weight loss of 1.41%. The failure of the coating after 80 thermal cycles between 1500℃ and room temperature is due to the generation of cross-cracks in the coating during the test.
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