水热温度对SiC-C/C复合材料表面水热电泳沉积MoSi2抗氧化涂层的影响

采用水热电泳沉积法和固相渗透法在C/C复合材料表面制备了MoSi2/SiC复合抗氧化涂层。分别采用X射线衍射、扫描电子显微镜和等温静态氧化实验对复合涂层的晶相组成、显微结构和抗氧化性能进行了表征。主要研究了水热电泳沉积温度对MoSi2外涂层显微结构及高温抗氧化性能的影响,重点分析了涂层试样在1500℃和1630℃下的静态氧化行为及失效机理。结果表明:外涂层主要由MoSi2和少量MoO3晶相组成。外涂层的致密程度、厚度及抗氧化性能随着水热温度的升高而提高。MoSi2/SiC复合涂层具有较好的抗氧化和抗热震能力,在1 500℃下有效保护基体320 h同时经历17次1 500℃与室温之间的热循环后,氧化失重率仅为1.07%;在1630℃下氧化88 h后失重率为2.17%。复合涂层在1 630℃下的氧化失效主要是由于经过长时间氧化后SiO2玻璃膜层不能及时有效填补涂层中的缺陷,涂层试样在热循环过程中产生了贯穿性的孔洞导致的。

Influence of Hydrothermal Temperature on Preparation of MoSi2 Oxidation Protective Coating for SiC-C/C Composites by Hydrothermal Electrophoretic Deposition

A MoSi2 /SiC multilayer anti-oxidation coating for C/C composites was prepared by pack cementation with a later hydrothermal electrophoretic deposition.The phase compositions,morphologies and anti-oxidation properties of the prepared coatings were analyzed by XRD,SEM and isothermal oxidation test.The influence of hydrothermal temperature on the phase composition,microstructure and oxidation resistance of the coating was investigated.And the oxidation behavior of the as prepared coated samples at 1 500 ℃ and 1 630 ℃ was particularly analyzed.Results show that the outer coatings are mainly composed of MoSi2 phase with a little MoO3 crystalline phase.The thickness,density and anti-oxidation properties of the MoSi2 coating improve with the increase of the hydrothermal temperature.The MoSi2 /SiC coatings exhibit excellent oxidation resistance and thermal shock resistance,which can effectively protect C/C composites from oxidation in air at 1 500 ℃ for 320 h and 17 thermal cycles between 1 500 ℃ and room temperature with a weight loss of 1.07%.The weight loss is 2.17% after oxidation in air for 88 h at 1 630 ℃.The failure of the coating at 1 630 ℃ is due to the generation of cross-holes in the coating during the thermal shock,which can not be self-cured by the SiO2 glass layer after long time of oxidation.