新型高隔热柱/层跨尺度双模结构热障涂层及其长寿命服役机理

Thermal barrier coatings (TBC) are protective layers applied to the surface of hot metallic components in gas turbine engines, which are frequently utilized in aircraft propulsion and power generation. TBC can provide a reduction in temperature of the underlying substrate that leads to improved component durability. Meanwhile, the fuel efficiency can be increased by allowing an increase of the inlet temperature in turbine. Therefore, advanced TBC has found its critically important role in development of next generation gas turbine engines towards high performance. .As two key performances, thermal barrier effect and resistance to spallation exposed to high temperature guide the material selection, structural tailoring and process optimization of the TBC. Regarding the thermal barrier effect, lamellar TBC is the best choice, owing to its microscopic pores vertical to heat flux. However, sintering leads to significant degradation of strain tolerance during thermal exposure. As a result, the lamellar TBC often has a poor performance on lifetime. Regarding the resistance to spallation, the columnar TBC has proven its benefit in extending lifetime. The reason is that macroscopic pores parallel to the heat flux enable the columnar TBC a high strain tolerance. However, the current columnar TBC often has dense microscopic regions, resulting in the weakened performance of thermal insulation. In brief, it is a huge challenge for lamellar or columnar TBC to realize the high thermal insulation and the long lifetime simultaneously until now..This study proposed a novel trans-scale TBC structure design, combining microscopic lamellar structure with macroscopic columnar structure. Therefore, this bimodal structure of TBC would realize the collaborative design on high thermal insulation and long lifetime. To begin with, a model with bimodal structure will be developed to analyze the formation of macroscopic vertical pores in lamellar coatings and to predict the thermal/mechanical properties of bimodal coatings. The aim is to guide the following preparation of the bimodal TBC in experiment. Subsequently, a new method based on strong shock of water will be used to prepare the bimodal TBC. Effects of internal and external parameters on the formation of macroscopic vertical pores will be investigated, in order to realize the preparation control of the bimodal TBC. Finally, gradient thermal cyclic test will be used to investigate the multiscale, multidirectional evolution of bimodal structure under combined factors, along with the exploration of mechanism in long lifetime. In brief, the novel bimodal TBC would meet the requirements of high thermal insulation and long lifetime of next generation TBC, which would provide fundamental contribution to the development of advanced gas turbine engines.

新一代高隔热、长寿命热障涂层(TBC)，是我国自主发展先进航空发动机和燃气轮机的核心技术。然而，目前高隔热层状结构难以维持较长的服役寿命，而长寿命柱状结构则牺牲了部分隔热功能。因此，现有的单模TBC难以兼具高隔热和长寿命。本研究提出具有宏观柱状、微观层状的新型双模结构TBC设计，巧妙地将高隔热层状结构与长寿命柱状结构进行宏/微观跨尺度结合，实现TBC高隔热长寿命的协同设计。首先，建模分析层状涂层的宏观纵向成孔机制，阐明新型涂层宏/微观双尺度的设计要求；随后，基于强流冲击急冷新方法，发展新型柱/层结构的制备调控工艺；最后，采用梯度热循环测试，探究多因素耦合下新型涂层的高温多尺度、双极化构效演变规律，揭示其长寿命服役机理。本项目提出的新型跨尺度柱/层双模结构TBC，兼具高隔热、长寿命的优越综合性能，对发展先进燃气轮机和航空发动机具有重要理论价值和技术支撑意义。

高隔热、长寿命热障涂层(TBC)，是我国自主发展先进航空发动机和燃气轮机的核心技术。本研究针对常规热障涂层制备方法难以兼顾实现高隔热和长寿命的难题，基于等离子喷涂热障涂层在高温服役中的构效演变规律和性能退化机理，提出了在高隔热层状结构内实现纵向开裂成孔的方法，以协同优化涂层的隔热功能和服役寿命。研究内容包括：（1）试验研究了层状热障涂层高温服役中的性能退化机制，明确了涂层高隔热性能对内部孔隙形貌和尺度的依赖性，为高性能涂层结构设计奠定理论基础；（2）基于数值模拟分析，研究了纵向孔隙结构参数对涂层开裂行为的影响，优化了高隔热层状热障涂层内纵向成孔结构设计方法；（3）发明了层状结构纵向成孔方法，基于水冷收缩的原理，通过在涂层面内引入大的瞬态拉伸应变，突破了常规层状结构难以纵向开裂的难题，在保持高隔热的同时，延长服役寿命。项目研究成果对发展先进燃气轮机和航空发动机具有重要理论价值和技术支撑意义。