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通过热力学计算分析了分别使用NH4Cl和CrCl3.6H2O两种不同激活剂时,各个共渗元素的卤化物蒸汽压分压的变化,得到了实现Nb-Si基原位复合材料上Si-Cr-Y三元包埋共渗的最佳条件。采用包埋共渗法在Nb-Si基原位复合材料表面制备了Si-Cr-Y共渗涂层,研究了涂层的组织形貌、成分及其相组成。结果表明:使用NH4Cl做激活剂,通过调整包埋渗料的成分,可以在适当的温度下实现Si-Cr-Y的三元共渗。当渗料成分为12Cr-6Si-0.75Y2O3-5NH4Cl-76.25Al2O3(质量分数)时,在1350℃可以实现Si-Cr-Y三元共渗。制备的涂层具有多层结构,分为外层、内层和明显的互扩散层。互扩散层的存在,表明涂层的形成是一个连续生长过程,伴随着Cr、Si、Y元素向基体内的扩散。涂层的主要成分由Cr2(Nb,Ti)、(Nb,Ti)5Si3和HfSi2组成,Y元素的添加起到了细化涂层的作用。
The thermodynamic calculation was used to analyze the change of partial pressure of halide vapor pressure of each infiltrating element when NH4Cl and CrCl3.6H2O were used respectively. The results showed that the pressure drop of Si-Cr-Y Ternary embedding the best conditions. Si-Cr-Y co-permeation coating was prepared on the surface of Nb-Si-based in-situ composites by the embedding and infiltration method. The morphology, composition and phase composition of the coating were studied. The results show that the use of NH4Cl as activator, by adjusting the composition of the embedded permeable material, can be achieved at the appropriate temperature ternary Si-Cr-Y infiltration. When the material is 12Cr-6Si-0.75Y2O3-5NH4Cl-76.25Al2O3 (mass fraction), Si-Cr-Y ternary permeation can be achieved at 1350 ℃. The prepared coating has a multilayer structure, which is divided into an outer layer, an inner layer and a distinct interdiffusion layer. The existence of interdiffusion layer indicates that the formation of the coating is a continuous growth process accompanied by the diffusion of Cr, Si and Y elements into the matrix. The main component of the coating is composed of Cr2 (Nb, Ti), (Nb, Ti) 5Si3 and HfSi2, and the addition of Y element plays a role of refining the coating.