Silicon carbide-based ceramic matrix composites protected by environmental barrier coatings (EBCs) present a promising materials solution for next-generation gas turbines. Developming more robust and efficient EBCs is therefore of significant technological importance. During the service in high-temperature oxidative environments, there is a thermally grown oxide (TGO) layer, spontaneously formed in the EBC system. TGO is recognized as a critical factor for the degradation and failure of EBCs, yet the detailed mechanisms of TGO growth and its effect on EBC failure remain unclear. In this study we develop a comprehensive chemo-mechano-phase-field model to simulate growth of the TGO in EBCs, factoring in creep and deformation, and especially the cracking behaviors. The volume expansion due to TGO growth and the resulting large inelastic deformation are addressed by using our recently developed, so-called incremental realization of inelastic deformation (IRID) algorithm, in combination with an adapted Hu-Chen spectral solver for elasticity. Simulations of TGO growth are performed considering different growth modes of TGOs determined mainly by the ratio of oxidant permeability in the topcoat to that in the TGO itself. Large-scale three-dimensional (3D) simulations are performed to model the formation of interconnecting vertical/channel cracks (often called ‘mud cracks’). The simulated crack morphology are in excellent agreement with the experimental observations from the literature. The simulations also provide insights into the cracking of EBCs and its dependence on the structure and constituent properties of the coating system. These results demonstrate the developed damage model can be a useful tool for design of more durable EBCs.

中文翻译：

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环境阻隔涂层中热生长氧化物的相场建模和损伤演变


由环境阻隔涂层 （EBC） 保护的碳化硅基陶瓷基复合材料为下一代燃气轮机提供了一种前景广阔的材料解决方案。因此，开发更强大、更高效的 EBC 具有重要的技术意义。在高温氧化环境中使用期间，EBC 系统中会自发形成热生长的氧化物 （TGO） 层。TGO 被认为是 EBC 降解和衰竭的关键因素，但 TGO 生长的详细机制及其对 EBC 衰竭的影响仍不清楚。在这项研究中，我们开发了一个全面的化学-机械-相场模型来模拟 EBC 中 TGO 的生长，同时考虑蠕变和变形，尤其是开裂行为。通过使用我们最近开发的非弹性变形增量实现 （IRID） 算法，结合适应性的 胡-Chen 弹性光谱求解器，解决了由于 TGO 增长引起的体积膨胀和由此产生的大非弹性变形。考虑到 TGO 的不同生长模式，主要由面漆中的氧化剂渗透性与 TGO 本身的渗透性之比决定，对 TGO 生长进行模拟。执行大规模三维 （3D） 模拟以模拟互连垂直/通道裂缝（通常称为“泥浆裂缝”）的形成。模拟的裂纹形态与文献中的实验观察结果非常吻合。仿真还提供了对 EBC 开裂及其对涂层系统结构和组成特性的依赖性的见解。这些结果表明，开发的损伤模型可以成为设计更耐用的 EBC 的有用工具。