热障涂层先进结构设计研究进展

随着航空航天技术的不断发展，不断提高的涡轮前进口温度及恶劣的使用环境对镍基高温合金的使用性能提出了更高的要求。热障涂层是一种应用于涡轮发动机热端部件的表面技术，通过沉积在镍基高温合金表面，降低合金表面的温度。概述了采用传统单层层状氧化钇部分稳定氧化锆热障涂层的优势，包括较低的制备成本、便捷的制备方式及较低的层间热膨胀失配应力。同时，归纳了单层层状热障涂层在高温环境下存在的问题，包括氧化锆相变与烧结造成的涂层失效，以及热膨胀系数和断裂韧性较差的新型陶瓷材料无法直接制备在黏结层表面。在此基础上重点综述了近年来热障涂层先进结构设计的研究进展，包括双层层状结构、柱状结构、垂直裂纹结构及复合结构热障涂层，其中复合结构包括激光表面改性结构、梯度涂层结构及粉末镶嵌结构热障涂层。针对各种先进结构热障涂层，分别从微观结构、热震寿命、涂层内部应力、耐腐蚀性能、抗氧化性能等方面进行了归纳，并总结了各先进结构热障涂层现阶段发展的不足之处。最后展望了热障涂层先进结构设计的发展方向。

Research Progress of Advanced Structural Design of Thermal Barrier Coatings

Due to their excellent thermal insulation properties, high hardness and good chemical stability, thermal barrier coatings are one of the best solutions for improving the service life of hot end components for turbine engines, reducing fuel consumption, increasing efficiency and improving the thrust-to-weight ratio of engines. In recent years, with the continuous development of thermal barrier coating preparation technology and ceramic layer materials, the structure and various properties of thermal barrier coatings have also been fully developed and the corresponding use effect has been improved. Research on the structural design of thermal barrier coatings at domestic and abroad and the associated performance is presented, and research progress on the advanced structural design of thermal barrier coatings is discussed. Starting from the traditional single-layer laminate structure, the principles of preparing various structural thermal barrier coatings were explained, and the morphological characteristics and performance advantages and disadvantages of various structural thermal barrier coatings were clarified. Based on these four advanced structures, the state of the art in structural design of thermal barrier coatings at home and abroad was investigated. Through the comparison of these technical levels, the research progress in the direction of structural design of thermal barrier coatings at the present stage was affirmed, the shortcomings of structural design of thermal barrier coatings at the present stage were clarified, and the future development direction of structural design of thermal barrier coatings was indicated. Advanced structures for thermal barrier coatings included double-layered structures, columnar structures, vertical cracked structures and composite structures, where composite structures included laser surface modified structures, gradient coating structures and powder mosaic structures. The double-layered structure was the most commonly used advanced structure for thermal barrier coatings due to its simplicity of preparation, low thermal expansion differences within the coating and low thermal expansion mismatch stress. Columnar structures were usually obtained using physical vapor deposition, where the presence of inter-columnar gaps provided additional strain space for the coating and relieved the internal stresses of the coating. Vertical cracks in thermal barrier coatings could also provide additional strain relief and increase coating life, but they were difficult to be prepared and it was difficult to obtain uniformly distributed vertical cracks of controlled depth using atmospheric plasma spraying. Laser surface modification structures were used to remelt the surface of the ceramic layer by laser in order to obtain a flat surface and a dense internal melt layer, which effectively blocked the penetration of molten corrosion into the interior of the coating and provided good protection for the internal coating. Gradient coating structure was a multi-layer composite structure with gradient changes in coating composition, which had no obvious inter-layer interface and regular changes in internal microstructure, which could effectively reduce the difference in thermal expansion coefficients between different materials within the coating, relieve internal stress and increase the thermal shock resistance of the coating under high temperature environment. The powder mosaic structure was a new design of thermal barrier coating structure developed in recent years. By inlaying agglomerated powder inside the ceramic layer, relying on the large number of microscopic pores inside the agglomerated powder, it can improve the thermal insulation performance, sintering resistance and thermal shock resistance of the coating. At present, with the development of thermal barrier coating materials and preparation methods at home and abroad, certain progress has been made in the structural design of thermal barrier coatings, however, there are still certain defects in the actual preparation and application of these advanced structures that need to be remedied. In the future, with the continuous development of coating preparation technology and multi-environmental coupling detection technology, the development of thermal barrier coatings in terms of structural design will be more comprehensive.