层级高效热障涂层热-力耦合失效机理研究

The conventional Y2O3?stabilized ZrO2 (YSZ) thermal barrier coating (TBC) is susceptible to sintering, phase transformation, and oxygen influx at the operating temperature. In comparison, the design of multi-ceramic-layer TBC can substantially improve the thermal and chemical stabilities, the efficiency, and lifetime of gas turbine engines. However, the complexity and diversity of its hierarchical structures and severe operating conditions make the failure mechanisms of multi- ceramic-layer TBC significantly different from those of traditional single-ceramic -layer TBC. In this proposal, we aim to understand in detail the thermomechanical failure of the double?ceramic?layer TBC composed of the traditional thermal insulation material and the top?coated ceramic layer, and to provide an evaluation frame of damage evolution in such configurations. We will study the interfacial fracture behavior by systematically varying the crack geometries, the crack propagation paths, and the material parameters of different components. We will investigate the processes of crack nucleation, growth, and coalescence of isolated interfacial defects, the resulting delamination, and eventual buckling under thermomechanical load using the experimental and numerical schemes. We target to quantify the functional dependence of the overall system performance on the material parameters and thickness ratio of ceramic coating layers, interactions with environmental species and conditions, as well as the number of thermal cycles. Understanding the underlying failure mechanisms and damage evolution will provide the theoretical basis to enhance the durability and reliability of the advanced multi-ceramic-layer TBC.

层级热障涂层是解决常规热障层高温易相变、烧结和透氧之短板的重要手段。陶瓷面层独特的热物理及力学性能导致层级热障涂层的失效机理更为复杂，与传统热障涂层大不相同。本项目以特殊热障材料覆盖于传统涂层之上的新型双陶瓷层热障涂层为对象，发展一种多裂纹任意路径扩展数值算法，考察热?力耦合环境下新的层级热障涂层中裂纹萌生、扩展和聚合规律，构建材料性能控制参量与各层级陶瓷组元热力学参数及几何尺寸间的函数表达，揭示层级热障涂层热-力耦合失效机理，建立其失效评估方法，为层级热障涂层强度评价提供理论基础。

层级热障涂层是解决常规热障层高温易相变、烧结和透氧之短板的重要手段。陶瓷面层独特的热物理及力学性能导致层级热障涂层的失效机理更为复杂，与传统热障涂层大不相同。本项目以新型双陶瓷层热障涂层为对象，对双陶瓷层热障涂层高温力学性能进行了实时测试，考察了不同厚度比双陶瓷层热障涂层的力学性能及实时损伤演化规律，数值研究了各组元几何、物理参数对热障涂层失效模式的影响，揭示了层级热障涂层的应力演化机制与失效机理，提出了基于临界裂纹密度的界面失效评价方法，为层级热障涂层强度评价提供了理论基础。