A Chemo-Thermo-Mechanics Theory: Application to High-Temperature Thermal Barrier Coatings

热障涂层应用于高温合金涡轮叶片，以提供隔热和氧化保护。典型的涂层由氧化物/金属双分子层组成：外层氧化层（面漆）提供隔热，而金属层（粘结层）通过在高温下形成热生长的氧化物提供氧化保护。粘结层氧化是导致涂层失效的主要原因。这项研究的目标是开发一种基于模拟的设计能力，以预测热障涂层的稳定性和耐久性。具体目标是：(i)发展一个连续水平的化学-热-力学理论，用于模拟涂层系统的耦合扩散-氧化-变形和降解。（ii）在数值上实现该理论，并开发基于强大模拟的预测涂层性能的能力。（iii）开展实验研究计划，验证理论的预测能力和基于仿真的设计能力。在过去的40年里，天然气联合循环涡轮机技术已经发展成为主导大规模发电的技术。该技术未来面临的主要技术挑战是：(1)改进燃烧设计以减少排放，同时将燃烧温度提高到1430°C以上（现行标准）；（ii）延长维修间隔之间的运行时间；（三）进一步提高这些复杂系统的可靠性。在这种先进的应用中，单晶涡轮叶片和热障涂层的稳定性和耐久性并不是很好地理解或建模。该研究将为热障涂层在这种恶劣环境下的寿命预测和性能改进提供理论依据。

Thermal barrier coatings are applied to superalloy turbine blades to provide thermal insulation and oxidation protection. A typical coating consists of an oxide/metal bilayer: the outer oxide layer (top-coat) imparts thermal insulation, while the metallic layer (bond-coat) affords oxidation protection through the formation of a thermally-grown-oxide at elevated temperatures. Bond-coat oxidation is the primary cause of coating failure. The goal of this research is to develop a simulation-based design capability to predict the stability and durability of thermal barrier coatings. The specific aims are to: (i) Develop a continuum-level chemo-thermo-mechanics theory for modeling the coupled diffusion-oxidation-deformation and degradation of coating systems. (ii) Numerically implement the theory and develop a robust simulation-based capability for predicting coating performance. (iii) Conduct an experimental research program to validate the predictive capabilities of the theory and simulation-based design capability. Over the past 40 years, natural-gas-combined-cycle turbine-technology has evolved to dominate large scale power generation. The main technological challenges for this technology going into the future are: (i) to improve the combustion design to reduce emissions, while raising firing temperatures beyond 1430°C (the current standard); (ii) to extend operation time between maintenance intervals; and (iii) to further improve the reliability of these complex systems. The stability and durability of single-crystal turbine blades and thermal barrier coatings in such advanced applications is not very well understood or modeled. This research will provide a theoretical basis for life-prediction and performance improvement of thermal barrier coatings in such severe environments.