MAX相作为活性扩散阻挡层延缓抗高温氧化涂层退化机理

项目提出MAX相（Cr2AlC,Ti2AlC,Ti2AlN）薄膜作为高温合金上抗氧化涂层的元素互扩散活性阻挡层的新思路。研究合金基体/NiCrAlY涂层、合金基体/MAX相薄膜/NiCrAlY涂层体系在900oC-1100oC下不同时间的真空退火以及空气中恒温和循环氧化行为，包括测试氧化动力学，细致分析断面上新相形成与元素分布，表征涂层体系的界面结合，深入了解高温下元素互扩散、MAX薄膜相与结构随温度和时间的演变及其对涂层抗氧化性能与退化的影响、涂层体系热匹配性等，进而明了氧化过程中MAX相薄膜阻挡元素互扩散效应及其与Al活度、M化合物(Cr-C,TiC,TiN)种类的关系，并建立MAX相薄膜作为活性扩散阻挡层的作用模型。研究对深入了解MAX相与金属材料界面反应、相组成与结构演变规律具有理论意义；同时对发展新的扩散阻挡层材料体系，从而改善现有高温防护涂层抗氧化性能和服役寿命具有实用价值。

This project focuses on the performances of MAX Phase films (such as Cr2AlC, Ti2AlC, Ti2AlN) as active diffusion barrier in superalloy substrate/NiCrAlY coating system. Vacuum annealling, isothermal oxidation and cyclic oxidation of superalloy/NiCrAlYcoating and superalloy/MAX film/NiCrAlY coating systems will be investigated at 900oC-1100oC for different time, including the determination of oxidation kinetics, careful characterizations of the formation of new phases and the distributions of relative elements on the cross sections of test specimens, and the evaluation of interface adhesion in the coating system. The interdiffusion of elements at superalloy/MAX film and MAX film/NiCrAlY coating interfaces, the variations of constituent phase and microstructure of MAX film with temperature and time, effects of MAX film on oxidation resistance and degeneration of NiCrAlY cotaing , and thermal suitability of the coating system will be explored. Thereby, the diffusion barrier effect of MAX film and its correlations with Al activity and kinds of binary M carbide or nitride will be understood thoroughly. Finally, the models involving in the variations of constituent phase and microstructure of MAX film with temperature and time, and its barrier layer effect will be established. This project is significant for better understanding interface reactions of MAX phase and metal, and the evolution of constituent phase and microstructure of MAX phase materials. It is also significant for developing new diffusion barrier materials, and then improving oxidation resistance and service life of conventional NiCrAlY coating.