热障涂层-基体体系界面高温疲劳和断裂性能的实验研究

热障涂层(TBCs)作为发动机叶片的热防护涂层,能够显著提高叶片在高温环境下的使用寿命.本文围绕TBCs-镍基高温合金基体体系的界面性能,展开了比较系统的实验研究.通过实验方法得到了等温热处理前后陶瓷层的弹性模量、硬度及陶瓷层-粘结层界面的微结构的变化.结果显示,随着等温热处理时间的增加,弹性模量及硬度先增加后降低；氧化层随等温热处理时间和温度的增加逐渐增厚.利用本文提出的多相位角界面断裂韧性试验方法,建立了以应力强度因子为表征参数的TBCs界面失效准则.在假定界面间为粘性接触的条件下,预测了界面承载能力随陶瓷层弹性模量和氧化层厚度的变化趋势.通过热循环实验研究了TBCs-基体体系的热疲劳性能及失效机理.随着热循环高温保温时间的增加,热疲劳寿命先升高后降低,失效模式由界面失效转化为界面失效与陶瓷层失效并存；体系的失效由陶瓷层及氧化层的应变能密度、陶瓷层、氧化层及界面的断裂韧性,以及它们和界面微结构缺陷的相互作用共同决定.

Experimental Investigation on High-Temperature Fatigue and Fracture Properties at the Interface Between Thermal Barrier Coatings (Tbcs) and Nickel Based Superalloy Substrate

Employed as thermal protection coating for engine blades, thermal barrier coatings (TBCs) can significantly increase service life of these components in a high-temperature environment. A systematic investigation on the properties of interface between TBCs and nickel based superalloy substrate was carried out. The elasticity modulus of ceramic layer, the hardness of ceramic coat and the microstructure change near the ceramic layer - adhesive layer interface before and after isothermal heat treatment were experimentally obtained and compared. Results show that during isothermal heat treatment, the ceramic coat sintering has occurred but there is not phase transformation; besides, both Young's modulus and the hardness increase first then decrease along with the heat treatment time increasing; the thickness of oxide layer grows along with the heat treatment time and temperature increasing. Moreover, by using multi-phase angle interfacial fracture toughness test method proposed in this paper, a failure criterion for TBCs interface was established in terms of stress intensity factors as characterization parameters. Assuming the interfaces is viscous contact, the evolution of interface carrying capacity along with the increasing of ceramic coat Young's modulus and oxide layer thickness was predicted. Thermal fatigue properties and failure mechanism of interface between TBCs and nickel based superalloy substrate were investigated by thermal cycling test. Results reveal that along with the increase of thermal cycle temperature holding time, the fatigue life increases first then decreases, and the failure mode translates from single interface failure into both interface failure and ceramic failure.