热障涂层在飞机APU中的应用、失效形式与维护方法

Application,Failure Modes and Maintenance Methods of Thermal Barrier Coatings in Aircraft APU

飞机辅助动力装置(Auxiliary Power Unit,APU)是当前主流民用飞机上必不可少的部件,而热障涂层在APU中的应用能够减少发动机油耗、提升效率、延长热端部件的使用寿命。首先概述了飞机辅助动力装置的结构和工作原理,以及热障涂层的材料及结构体系。其次归纳了飞机APU常见热端部件中热障涂层的制备技术及应用特点,主要对大气等离子(Air Plasma Spraying,APS)和电子束物理气相沉积(Electron–Beam Physical Vapor Deposition,EB–PVD)等2种热障涂层进行了论述。在此基础上,重点综述了热障涂层在民用飞机APU中的典型失效形式,包括高温氧化失效、烧结失效、CMAS腐蚀、颗粒物冲击等,同时结合热障涂层热生长氧化物(Thermally Grown Oxide,TGO)生长、应变能释放、蠕变与疲劳、颗粒物沉积、外来物损伤等行为,对以上失效形式的失效机理进行了重点论述;分别从微观结构观察、断裂力学参数计算、有限元建模等方面详细阐述了飞机APU热障涂层的失效分析手段与方法。最后结合航空公司的实际运营情况对提升APU使用寿命和系统可靠性给出了基于热障涂层的维护建议和预防措施。

The aircraft auxiliary power unit(APU)is an indispensable component on the main types of modern civil aircraft,while the application of thermal barrier coatings(TBCs)in APU can reduce engine fuel consumption,improve engine efficiency,and extend the service life of hot section components.This article firstly makes an overview of the structure and working principle of the aircraft APU,as well as the material and structure system of the TBCs.Secondly,the article summarizes the preparation technology and application characteristics of TBCs on hot section components of aircraft APU,mainly focusing on two types of TBCs:Air Plasma Spraying(APS)and Electron-Beam Physical Vapor Deposition(EB-PVD).On this basis,the article concludes the typical failure modes of TBCs applied in civil aircraft APU:including high-temperature oxidation failure,ablation failure,CMAS corrosion,particle impact,etc.At the same time,the failure mechanism of the above failure modes are discussed combining with TGO growth,strain energy release,creep and fatigue,particle deposition,foreign object damage and other behaviors.In addition,the failure analyzing means and methods of aircraft APU TBCs are elaborated in detail from the aspects of microstructure observation,fracture mechanics calculation,and finite element modeling.Finally,maintenance suggestions and precautions based on TBCs are given to improve the service life and system reliability of APU according to the actual situation of air companies.