高温防护涂层是航空发动机涡轮叶片在高温严苛环境下高效运行的保障。但涂层与氧化膜的热膨胀系数在界面处存在跃变，热循环中产生的热应力容易导致氧化膜的开裂和剥落，造成涂层的过早失效。本项目提出将热障涂层粘结层设计为纳米柱状晶梯度涂层的思路，使涂层的热膨胀系数沿厚度方向梯度变化，以解决热应力在氧化膜界面集中的问题。本项目通过掺杂陶瓷相以调节涂层的热膨胀系数，实现热膨胀系数由基体到氧化膜均匀过度。为保证涂层的抗氧化性，将梯度涂层优化为纳米柱状晶组织结构，该结构可大幅降低涂层形成氧化膜所需的临界Al含量，并为Al元素的扩散提供大量快速通道。本项目中以AlN作为掺杂相，通过热疲劳实验和微观组织分析，阐明AlN掺杂相对氧化膜生长的影响；揭示在热疲劳作用下，氧化膜和界面的演变行为；建立梯度涂层在热疲劳作用下的失效机制。该项目的完成有望为研发兼具耐高温、长寿命的新型高温防护涂层提供实验依据和理论支持。

High temperature protective coating is the guarantee that advanced aeroengine blades operate at extreme environment in an effective way. However, when blades undergo sharp changes of temperature, thermal stress would generate within the thermal growth oxides (TGO) due to the mismatch in coefficient of thermal expansion (CTE) between TGO and coatings. As a result, cracks or spallation may appear on TGO after repeated heating up and cooling down, leading to premature failure of coatings. This project proposes the design idea of nano-columnar structured gradient coating, which has the characteristics of gradient change of CTE along the thickness direction. The coating design is expected to solve the problem of stress concentration at the TGO interface. This project adjusts the CTE of coatings by doping ceramic phase to achieve a uniform change in the CTE from the substrate to TGO. To ensure the oxidation resistance of the gradient coating, the gradient coating is optimized to a nano-columnar crystal structure, which can greatly reduce the critical Al content required for coatings to form TGO and provide a large number of channels for the diffusion of Al elements. In this project, AlN is used as the doping phase, and the effects of AlN doping on the growth of TGO are studied through thermal fatigue experiments and microstructure analysis. This project is expected to reveal the changes of TGO and interfaces under thermal fatigue, and establish the failure mechanism of the gradient coating. The completion of this project is expected to provide experimental basis and theoretical support for the development of novel long service-life coatings in aeroengine industry.