SiC-MoSi2-Si复合梯度涂层的制备及其抗氧化性能

摘要

为了在高温下保护C/C复合材料,分别采用包埋法在C/C复合材料表面制备了SiC涂层,采用两步包埋法在C/C复合材料表面制备了SiC-MoSi2-Si复合梯度涂层.借助X射线衍射仪、扫描电镜,背散射及能谱等分析手段,研究了涂层的结构.在氧化炉内进行氧化实验,分析发现SiC-MoSi2-Si复合梯度涂层由SiC内层、SiC-Si中间层和MoSi2-Si-SiC外层构成.等温氧化测试结果表明:SiC涂层在1 773 K氧化10h后失重0.8％,而复合涂层试样在1 773 K具有良好的抗氧化性能,在1773 K下氧化10 h后不存在氧化失重,增重0.65％.增重是由于涂层氧化生成SiO2,吸收了氧原子的原因,并且预测随着氧化的进行,由于O2在涂层中的扩散,与基体反应,试样会表现出失重.%A multilayer SiC-MoSi2-Si coating was prepared on the surface of a C/C composite by a two-step pack cementation method,in which the sample was first buried in a powder mixture containing Si,C(graphite),A12O3 and SiC followed by heat treatment at 2 023 K for 2 h in Ar and then treated for a second time in another powder mixture containing MoSi2,Si,SiC and C (graphite).The microstructure of the resulting coating was characterized by XRD,SEM equipped with EDS and backscattered SEM.The isothermal oxidation of the coating was investigated in an electric furnace.Results indicated that the multilayer coating was composed of a SiC inner layer,a SiC-Si gradient middle layer and a MoSi2-Si-SiC outer layer.The mass loss of the coating obtained after only the first step is 0.8％ after oxidation at 177 3 K for 10 h in air while the two-step coating shows no mass loss but a mass gain of 0.65％,indicating that the mass gain due to the formation of SiO2 from Si or SiC is higher than the mass loss from carbon oxidation.