The lack of oxidation resistance of niobium alloy greatly limits its application as high temperature structural material. Although the anti-oxidation performance of niobium alloy can be significantly improved by the surface anti-oxidation coating system, the single anti-oxidation coating system is still slightly insufficient for the application requirements of long life, thermal shock resistance and dynamic high temperature resistance. Among the many anti-oxidation coating systems, the composite silicide coating system is considered as the most potential anti-oxidation coating system for niobium alloy surface due to its compact structure, excellent thermal stability and "self-healing" ability. However, the application of composite silicide coating system still has many limitations:

(1) The composite silicide coating and niobium alloy are prone to mutual diffusion at high temperature. The solid solution capacity of niobium alloy is large, which is more obvious at high temperature. The diffusion study of nb-mosi2 system at 1200 ℃ and 1500℃ showed that [89], nb-rich (Nb, Mo) 5Si3 phase appeared at the end of the interface near MoSi2, while Mo rich (Mo, Nb) 5Si3 compound appeared at the end of the interface near the Nb. This will cause the interface between the MoSi2 coating and the niobium alloy substrate to grow due to the mutual diffusion of elements, resulting in the appearance of interfacial phagocytic coating, resulting in the structural instability of the MoSi2 coating at high temperature, and then lead to the coating protection failure. Therefore, appropriately increasing the interfacial barrier layer [88], reducing the diffusion activation energy of elements at the interface, and realizing the homogenization of tissues and components at the interface are crucial to preventing the "thermal decay" of the silicide coating.

(2) The thermal protection performance of the composite silicide coating system is in urgent need of improvement.