Interfacial failure behavior is a major concern during the service of thermal barrier coatings (TBCs). Quantitative study on interfacial failure behavior of TBCs at high temperatures remains a great challenge. In this study, an high-temperature cross-sectional indentation (HCSI) method based on X-ray imaging was developed. The out-of-plane displacement of TBCs was measured by digital radiography (DR) technology. The morphology of the interfacial crack was characterized by an computer tomography technology. It was found that the interfacial fracture region tended to be semi-elliptical shaped. The strain energy during HCSI was quantified and analyzed by finite element analysis (FEA). The composite stress intensity factor (SIF) and the mixed modal angles at high temperatures were obtained by analyzing the stress field at the crack tip. Interfacial toughness of TBCs at RT, 400 °C, and 800 °C were obtained. The interfacial toughness changes little ranging from RT to 400 °C, while it sharply decreases ranging from 400 °C to 800 °C. A prediction model for the evolution of interfacial toughness with temperature was obtained. The competition mechanism of interfacial cracks at different temperatures was discovered. The relationship between the change in interfacial toughness and the failure mode evolution was discussed.

中文翻译：

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热障涂层 (TBC) 在高温下的界面失效行为：基于 X 射线成像的原位压痕研究

界面失效行为是热障涂层 (TBC) 使用过程中的一个主要问题。 TBC 高温界面失效行为的定量研究仍然是一个巨大的挑战。在这项研究中，开发了一种基于X射线成像的高温横截面压痕（HCSI）方法。通过数字射线照相（DR）技术测量了TBC的面外位移。通过计算机断层扫描技术对界面裂纹的形貌进行了表征。结果发现，界面断裂区域趋于半椭圆形。通过有限元分析 (FEA) 对 HCSI 期间的应变能进行量化和分析。通过分析裂纹尖端的应力场，得到了高温下的复合应力强度因子（SIF）和混合模态角。获得了 TBC 在 RT、400 °C 和 800 °C 下的界面韧性。从RT到400℃，界面韧性变化不大，而在400℃到800℃范围内，界面韧性急剧下降。获得了界面韧性随温度变化的预测模型。发现了不同温度下界面裂纹的竞争机制。讨论了界面韧性变化与失效模式演化之间的关系。