双层氧化物生长下热障涂层的界面失效与应力演化

在长时高温服役环境下，热障涂层（TBCs）会在内部的陶瓷层（TC）和粘结层（BC）之间生成由Al2O3层和混合性氧化物层（MO）组成的双层热生长氧化物（TGO）。其中，后期生成的MO 由于其疏松多孔、脆性大等特点，极易造成涂层内微裂纹的形成和扩展，导致涂层的过早剥落。因此，依据双层TGO 生长的扩散—氧化模型，在考虑材料非线性变形行为的基础上，运用生死单元法模拟TBCs 内双层TGO 异向生长下涂层界面的失效与应力演化过程。结果表明：MO 的生长会大幅度提升涂层界面的拉伸应力水平，易导致MO/TC 界面在高温阶段波峰区域和冷却阶段斜坡中心区域发生破坏及失效；MO/TC 界面的失效会引起BC 层波峰处更高的拉伸应力，促进冷却阶段Al2O3/BC 界面从波峰向波谷处的破坏；MO/TC 界面失效后，hAl2 O3 /hMO 的增加会加速Al2O3/BC 界面的破坏。

Interfacial Failure and Stress Evolution of Thermal Barrier Coatings underthe Growth of Double-layer Thermally Grown Oxide

In a high temperature service environment for a long time, coatings (TBCs) generate a double layer of thermally grown oxide (TGO) consisting of an Al₂O₃ layer and a mixed oxide layer (MO) between the internal top coat layer (TC) and the bond coat layer (BC). Among them, the late generated MO is highly susceptible to the formation and expansion of microcracks within the coating due to its looseness and porosity and brittleness, which leads to premature spalling of the coating. Therefore, in this paper, based on the diffusion-oxidation model of double-layer TGO growth, the failure and stress evolution process of the coating interface of the coating interface under the anisotropic growth of double-layer TGO within TBCs is investigated by using the birth-death cell method, considering the nonlinear deformation behavior of the material. The results show that: the growth of MO will significantly increase the level of tensile stress at the coating interface, which will easily lead to damage and failure of the MO/TC interface in the peak area at the high temperature stage and in the center of the slope at the cooling stage; failure of the MO/TC interface causes higher tensile stresses at the peak of the BC layer and promotes the destruction of the Al₂O₃/BC interface from the peak to the valley during the cooling stage; after the failure of the MO/TC interface, the increase of accelerates the damage of the Al₂O₃/BC interface.