热障涂层过渡层力学行为的光测力学方法、技术及应用

Multilayered thermal barrier coatings (TBCs) are key materials for thermal protection of metallic components in gas-turbine engines. The mechanical properties and behaviour of interlayers (bond layer and thermally grown oxide) have a significant influence on the durability of TBCs. However, due to the reduced dimensionality, complex structure and demanding operating environment, the experimental characterization methods are deficient, and the damage failure mechanism remains unclear. Accordingly, with interlayers as the object of research, this project aims to develop methods and techniques of high-temperature optical mechanics, to characterize and analyse their key mechanical constants, thermo-mechanical coupling behaviour and macro/micro stress. Specifically, to develop fabrication techniques of multiscaled high-temperature speckles across interface and thermo-mechanical coupling optical system; by means of multilayered geometry design and elastic theory derivation, to build a high-temperature elastic modulus testing model based on the strain difference between coated and uncoated parts; combined with optical full-field deformation measurement, microstructure and surface shape characterization, to clarify the damage mechanism of interlayers in complex environment, such as mechanical properties degradation and rumpling evolution, and then to reveal the failure modes of interface; to develop measurement methods of macro/micro stress, and to systematically analyse stress distribution of curved interlayers. Ultimately, laying a foundation for the elucidation of failure mechanism of TBCs.

多层结构热障涂层是燃气轮机热端部件的关键热防护材料。其中，过渡层（粘接层和热生长氧化层）的力学性能与行为对热障涂层的耐久性有重要影响。然而由于其尺寸微小，结构复杂，且服役环境苛刻，相关的实验表征方法较为匮乏，损伤失效的机理不够明确。鉴于此，本项目拟以过渡层为研究对象，发展高温光测力学方法与技术，针对其关键力学参数、热力耦合行为与宏微观应力进行表征与分析。即发展多尺度跨界面的高温散斑制备技术，研制热力耦合光学测试系统；通过多层结构几何构型设计与弹性理论推导，建立基于喷涂/未喷涂区域之间应变差异的高温弹性模量测试模型；结合光学全场变形测试、微结构及表面形貌表征，阐明复杂环境下过渡层的力学性能劣化与皱曲演化等服役损伤机制，并揭示界面失效模式；发展宏微观应力测试方法，系统分析曲面过渡层的应力分布规律。最终为热障涂层失效机理的阐明奠定基础。

热障涂层是现代高性能航空发动机和燃气轮机的重要热防护材料和关键技术之一。其中过渡层-基体材料和结构的力学性能对热障涂层可靠性有重要影响。本项目开展了热障涂层过渡层力学行为的光测力学方法、技术及应用研究。发展了1200℃高温多尺度散斑变形载体制备技术和基于双棱镜的集成化单镜头三维数字图像相关（3D DIC）等光学测量方法，并研制了1200℃热力耦合加载-高温变形同步测试系统，实现了极端环境下宏微观变形场的高精度测试。进一步建立了基于应变差异的单层/多层涂层弹性模量测试模型、残余应力反演模型和多尺度DIC-预拉伸测试技术，获得了涂层弹性模量、应力演化规律和界面粘接性能。此外，基于裂尖变形场，提出了裂纹张开率（COR）新参数和基于COR的裂纹闭合效应表征新方法，阐明了考虑闭合效应的高温疲劳裂纹扩展等服役损伤行为。结果表明，所发展的光测力学方法、技术和系统可较好满足服役环境下的测试需求，所获得的膜基结构力学参量和高温疲劳裂纹扩展模型等可为热障涂层相关研究工作提供有益参考，具有重要科学意义。