基于陶瓷-金属界面形态演化的EB-PVD热障涂层系统寿命预测方法

The evolution of the interfacial morphology between ceramic topcoat and metallic bond coat under thermal fatigue loadings induced by thermally grown oxide (TGO) layer growth and rumpling is identified as one of the most important factors which result in the progressive damage of EB-PVD thermal barrier coating (TBC) systems. However, it was generally simplified as a quasi-static TGO thickening process in previous researches on thermal fatigue life estimation of TBC, and the damage was assumed to be characterized by the TGO thickness and local stress/strain upon the interface with preconfigured constant curves. The effect of growth stress in the oxide and interfacial roughening on the stress redistribution and interfacial toughness degradation in TBC systems was not fully taken into account, which showed significant difference from actual damage. This study focuses on the association between the characteristics of interfacial morphology, the mechanical behavior of individual layer and the damage of TBC systems. Firstly, thermal fatigue experiments are designed and conducted on the specimens with TBC to obtain the evolving interfacial parameters. In order to simulate the TGO growth and rumpling accurately, the optimal transportation meshfree (OTM) method whose material point is dynamically liked with nodes is introduced to solve the existing moving-interface and large-deformation question, and then the critical parameters driving the interfacial morphology to evolve are distinguished. At last a new life prediction methodology considering the influence of interfacial morphology evolution is established and verified to support the endurance assessment and application of EB-PVD TBC systems.

热疲劳载荷下陶瓷顶层与金属粘结层之间界面因热生长氧化物（TGO）生长-皱化而诱发的形态演化，是造成EB-PVD热障涂层（TBC）系统渐进损伤的主要原因之一。以往的TBC热疲劳寿命研究普遍将其简化为准静态的TGO厚度增长过程，假设损伤只取决于TGO厚度与恒定界面曲线下的局部应力应变，极少涉及氧化生长应力和界面粗糙度持续增加对应力重分布及界面韧性下降的影响，这与真实损伤情形存在显著差异。本项目聚焦于陶瓷-金属界面形态特征与TBC各层力学行为及系统损伤之间的关联，通过设计带TBC试样热疲劳试验获取界面演化规律，针对界面形态演化过程中呈现的移动界面、大变形特征，尝试引入采用物质点与节点动态联系的无网格OTM计算框架，精准刻画TGO动态生长及皱化过程，识别主导界面形态演化的驱动力参数，旨在发展一种能够考虑界面形态演化影响的TBC寿命预测方法，为TBC耐久性评估与工程应用提供技术支撑。

国内在研航空发动机涡轮前温度已远超镍基单晶高温合金熔点，在涡轮叶片等热端部件表面使用热障涂层迫在眉睫。热障涂层的使用寿命关系到发动机返修周期，必须在设计阶段予以明确。采用精准、高效的寿命模型对热障涂层寿命消耗情况进行预测，是降低涂层工程应用风险并最大限度发挥其性能优势与潜力的关键环节。然而，由于材料结构与失效机理的极端复杂性，目前的涂层寿命预测研究面临着界面损伤情况难量化、损伤驱动力难识别、工程设计难应用等一系列挑战，严重制约着我国热障涂层应用乃至高性能发动机研制进程。本项目以国内在研型号涡轮叶片用EB-PVD热障涂层体系为对象，从涂层损伤量化、模拟与预测三个方面展开研究。首先，基于涂层剥落机制，通过理论分析结合高精度非接触测试手段，提出了一种新的涂层损伤量化分析方法，建立了涂层剥落抗力与损伤之间的数学模型，获得了涂层界面损伤演化规律，为涂层损伤评价提供了精准、有效手段。然后，为了揭示涂层损伤失效的内在机理，建立了涂层界面形态演化数值模拟方法，实现了氧化生长、相变与应力耦合求解，识别了主导界面损伤的内在驱动力参数，为涂层失效分析及工艺改进提供了重要参考。最后，面向工程设计需求，建立了一种准确、合理、高效的热障涂层损伤力学计算方法，开发了能够与现有构件设计流程相集成的涂层损伤分析与寿命预测软件，并通过了多层次算例与试验验证。