Thermomechanical Fracture of Compositionally Graded Thermal Barrier Coatings with Time-Dependent Behavior

热障涂层(TBCs)为柴油发动机、燃气轮机和飞机发动机等高温应用提供了提高性能的潜力。成分渐变的热障涂层提供了一种极佳的替代方案，可通过涂层厚度提供性能的逐渐过渡，从而增强抗热机械损伤的能力。本项目的目标是通过分析和实验研究具有相似热阻但不同结构的组成梯度材料系统。在高温下，陶瓷/粘结涂层合金混合物组成的下层中的热激活时间依赖(粘塑性)效应预计将变得显著。因此，建议：(1)开发新的模型，以预测氧化锆涂层合金混合物的粘塑性行为；(2)使用这些模型来研究具有相似热阻的成分梯度热障涂层体系中的时间相关行为、裂纹萌生和扩展；(3)在高热流密度下进行控制实验，以验证分析预测。预计结果将产生设计指南，允许TBC设计者优化分级TBC系统的架构，以实现特定温度加载条件下更高的耐久性。此外，这些研究将增强两相和成分梯度材料系统中粘塑性变形和断裂领域的基本科学知识。这一新知识将被纳入本科生和研究生课程，并有助于对妇女和少数民族本科生的教育，使他们有可能开始研究生学习。

ABSTRACTThermal barrier coatings (TBCs) offer the potential of increased performance for high temperature applications such as diesel engines, gas turbines and aircraft engines. Compositionally graded TBCs offer an excellent alternative to enhance the resistance to thermomechanical damage by providing a gradual transition in properties through the coating thickness. The objective of this project is to study analytically and experimentally, compositionally graded material systems of similar thermal resistances, but different architectures. At high temperatures, thermally activated time-dependent (viscoplastic) effects in the lower layers comprised of ceramic/bond coat alloy mixtures are expected to become significant. Therefore it is proposed to: (1) develop new models that allow the prediction of viscoplastic behavior of zirconia-bond coat alloy mixtures; (2) to use these models to study the time-dependent behavior, crack initiation and propagation in compositionally graded TBC systems of similar thermal resistances; (3) to perform controlled experiments with high heat fluxes that provide verification of the analytical predictions. The results are expected to yield design guidelines that would allow TBC designers to optimize the architecture of graded TBC systems to achieve improved durability for specific temperature loading conditions. In addition, these investigations will enhance basic scientific knowledge in the areas of viscoplastic deformation and fracture in two-phase and compositionally graded material systems. This new knowledge will be incorporated in undergraduate and graduate courses and help in the education of women and minority undergraduate students with the possibility they may embark on graduate studies.