添加B对包渗法制备MoSi2涂层显微组织及静态抗氧化性能的影响

采用包渗法在Mo基体表面制备了B强化的MoSi2涂层,研究了涂层的显微结构、元素分布、相组成以及静态高温抗氧化性能。结果表明:涂层与基体之间通过扩散形成牢固的冶金结合,涂层整体厚度为80～120μm,共由三层组成。涂层中B元素沿晶界扩散富集引起的晶格畸变,使得Si在MoSi2中的扩散系数减小,导致B强化MoSi2涂层中间层厚度相对纯MoSi2涂层中间层厚度减小,但涂层整体厚度增大。经1200℃静态氧化2h后,B强化的Mo-Si2涂层失重为0.6mg/cm2,大大小于纯MoSi2涂层失重量(1.3mg/cm2),表面生成一层致密的SiO2为主体的氧化膜,阻止了涂层的进一步氧化。

EFFECT OF B ADDITION ON THE MICROSTRUCTURE AND STATIC OXIDATION RESISTANCE OF MOSI2 COATING PREPARED BY PACK CEMENTATION

The high-temperature oxidation-resistant MoSi2 coating with B addition on Mo substrate was prepared by pack cementation.The structure,composition and phase distribution and static oxidation resistance of the coating were investigated by SEM,EDS and XRD.The results indicate that the interface between the coating and the substrate is of metallurgical bond.Three-layer structures are formed by diffusion from outside to inside.The coating is full dense and the thickness is 80~120 μm.The thickness of middle layer is reduced because of the decreased diffusion coefficient of silicon in MoSi2 with the addition of boron,but the thickness of whole coating is increased.The weight loss of Mo-Si-B sample is only 0.6 mg·cm-2 after static oxidation at 1200℃ for 2 h,which is far less than that of Mo-Si sample of 1.3 mg·cm-2.The dense SiO2 glassy layer formed on the surface of the coating by the self-oxidation of MoSi2,prevents oxygen from further diffusion.