电泳沉积制备新型热障涂层粘结层及失效机理研究

Thermal barrier coatings (TBCs) are widely used in gas-turbines for aerospace and power generation industry to increases the engine efficiency and prolong the lifetime of engine components. As the most important constituent in TBCs systems, the bond coat directly affects the failure mode and the lifetime of the systems. Conventionally, the bond coat is produced by thermal spray, electron beam physical vapour deposition or aluminising process. In some cases, bond coat is produced with electroplating of Pt on superalloy substrates and then thermal diffusion between the Pt layer and substrate to produce bond coat. However, those fabrication methods are difficult to control the composition and the microstructure of the bond coat. In addition, the substrate will introduce additional effect on the bond coat. Therefore, it is difficult to distinguish and identify the factors which affect the spallation of TGO and failure of TBCs. ..The initial objective of this research is to develop a novel bond coat fabrication technique, electro-phoretic deposition (EPD) coupled with sintering in vacuum, to produce bond coats with controlled microstructure and composition. EPD has been developed by the applicant's team to produce top coat for TBC applications. In this research the bond coat will be produced with and without substrate, so the effect of substrate on the bond coat can be examined. To control the damaging effect of element diffusion, eg. sulphur, on the TGO/bond coat strength, a composite coating containing oxide particles will be produced using EPD where the oxide is used with intention to attract sulphur, ie. reduce the migration of sulphur to the TGO/bond coat interface, leading to strengthening of the TGO/bond coat interface. In addition, the composite bond coat will be also produced to increase the mechanical property of bond coat which is also a key factor controlling the spallation of TGO...The second objective is to understand how microstructure and composition of bond coat affect the mechanical properties, residual stresses and the interface bonding strength of the TGO/bond coat system. The proposed research will be developed based on the applicant's extensive research experience on characterisation of TBCs for more than 10 years. The strength of this proposal lies in combination of novel fabrication and extensive characterisation study of TBCs, which should lead to enhanced performance and lifetime of TBCs.

热障涂层是现代高性能航空发动机、工业燃气轮机的关键材料，它能大幅提高发动机工作效率并延长组件使用寿命。粘结层作为热障涂层体系的核心，直接控制热障涂层的失效方式及寿命。传统粘结层的制备一般通过热喷涂、气相沉积和渗铝扩散，不但难于控制成分和微观结构，而且在处理过程中容易引入基体的影响，因此无法将影响热障涂层失效的各种因素分离出来。本项目旨在开发一种新型粘结层制备技术。利用电泳沉积结合真空烧结，制备结构、成分及力学性能可控的粘结层。通过比较包含基体和不含基体的粘结层，揭示基体的影响。同时利用氧化物弥散强化，来抑制杂质硫偏析，增加界面结合强度，并改善界面形貌，减少裂纹产生。此外，通过系统研究粘结层成分结构对氧化层-粘结层系统的力学性能、残余应力、及界面结合强度的影响，设计出性能优异的粘结层。本研究基于申请人过去在此领域长期工作经验，将新型制备技术与系统表征相结合，加深对热障涂层失效机理的理解。

粘结层作为热障涂层体系的核心，是控制热障涂层失效的关键因素。传统的粘结层的制备方法如热喷涂、气相沉积、渗铝扩散，不仅难于控制成分和微观结构，而且制备过程中容易受到基体的影响。课题组通过结合电泳沉积和真空结两种方法的优势，制备了结构成分以及性能可控的粘结层，系统研究了不同基体、粘结层中活性元素及其氧化物对粘结层的高温性能的影响，揭示了影响粘结层失效的因素，加深了对热障涂层时效机理的理解。依托本项目经费资助，已在Scripta Mater.、J. Am. Chem. Soc.、Corros. Sci.等国际知名期刊发表文章9篇，待发表文章3篇。