铌基NbSi_2涂层的制备及其高温氧化性能

Preparation and Oxidation Property of NbSi_2 Coating on Nb Substrate

在金属铌表面制备NbSi_2涂层,采用SEM和XRD分析涂层的微观结构和物相组成,研究了涂层样品在1 200℃和1 450℃大气环境下的氧化行为.结果表明:NbSi_2涂层致密均匀,以NbSi_2为主相,含少量Nb_5Si_3相;1 200℃氧化时,由于生成的小颗粒Nb_2O_5不影响SiO_2的流动性,其弥散分布于SiO_2中而形成连续致密的氧化层,有效阻隔了氧的入侵,抗氧化时间可达120 h,其单位增加质量为7.42 mg·cm^(-2);1 450℃氧化时,由于生成粗大颗粒的Nb_2O_5阻碍了SiO_2的流动,氧化层疏松多孔,抗氧化性能较差.

NbSiz coating was prepared on the surface of Nb substrate. The high temperature oxidation behavior of NbSi2 coating samples at 1 200 ℃ and 1 450 ℃ in air was studied, microstructures and phase compositions of the coating were further analyzed by scanning election microscopy（SEM） and X-ray diffraction （XRD）. The results demonstrated that NbSi2 coating was dense and uniform, composed of NbSi2phase and a small amount of NbsSi3 phase. During the oxidation of 1 200 ℃ in air, small particles of Nb205 was formed which caused no block to the liquidity of SiO2 but distributed uniformly in SiO2, to form a dense oxide film on the surface of NbSi2 coating. So NbSi2 coating could protect Nb substrate from oxidation at 1 200 ℃ in air for 120 h and that of mass gain was only 7.42 mg. cm-2. The coating exhibited good oxidation resistance at 1 200 ℃ due to Nb2 05 particles While the poorly oxidation resistance of NbSi2 coating at 1450℃ was attributed to big particles of Nb2Osproduced at 1450℃, which blocked off the flow of SiO2 to form loose and porous oxide film.