热障涂层扁平梭形孔隙内颗粒减缓熔融CMAS渗入的流动机理

Flow Mechanism of Particles Mitigating Molten CMAS Infiltration within Flat Fusiform Pores of Thermal Barrier Coatings

摘要

高温熔融钙镁铝硅酸盐 (CMAS) 侵蚀是导致航空发动机热障涂层 (TBCs) 失效的关键因素，涂层微观结构调控是物理阻断 CMAS 渗入的核心手段。本研究针对具有优异抗 CMAS 渗入的热障涂层中多孔嵌入颗粒团簇 (PEPC) 结构，建立了二维蠕动流与粒子追踪耦合模型，深入揭示了扁平梭形孔隙内颗粒几何特征对 CMAS 渗入动力学的影响机理。研究表明：在双颗粒尺度下，大颗粒与微间距的耦合显著增强孔喉节流效应，而垂直于流向的颗粒排布可消除流场屏蔽作用，最大化颗粒阻滞效能。在多颗粒尺度下，平均颗粒间距是决定抗渗性能的主导因素，研究揭示了其对抗渗性能的非线性阈值的控制规律，在 72% 孔隙率 PEPC 结构中临界值约为 0.7 μm。本研究阐明了颗粒间距、孔隙率与曲折度之间的强耦合阻滞机制，发现增加小颗粒占比可同时实现减小平均间距与提升流道曲折度的双重阻滞效果。

Abstract

The infiltration and subsequent degradation induced by molten calcium-magnesium-alumina-silicate (CMAS) at high service temperatures remain a critical challenge triggering premature failure of thermal barrier coatings (TBCs) in advanced aero-engines. Consequently, tailoring coating microstructures to physically block CMAS intrusion has emerged as a core strategy to boost coating durability. Focusing on the Porous Embedded Particle Clusters (PEPC) structure, which possesses outstanding CMAS resistance potential, this study systematically investigates the infiltration dynamics of molten CMAS. A coupled numerical model integrating two-dimensional creeping flow and particle tracing is established to reveal how geometric features of particles inside flat spindle-shaped pores influence CMAS infiltration and the corresponding underlying mechanisms. Simulation results show that at the dual-particle scale, the synergistic matching of large particles and micro-gaps greatly strengthens the throttling effect of pore throats. Meanwhile, arranging particles perpendicular to the flow direction effectively suppresses the hydrodynamic shielding effect and maximizes barrier efficiency. At the multi-particle scale, average particle spacing is proven to be the primary factor dominating anti-CMAS infiltration capacity. A nonlinear threshold control mechanism is uncovered, identifying a critical spacing of roughly 0.7 μm for PEPC structures with 72% porosity; below this threshold, infiltration resistance rises sharply. Furthermore, this work reveals a strong synergistic barrier mechanism coupling particle spacing, porosity and pore tortuosity. It is demonstrated that raising the fraction of fine particles produces a dual barrier effect by simultaneously narrowing average particle spacing and increasing flow channel tortuosity. Ultimately, these results reveal the physical nature of infiltration suppression in PEPC architectures, laying a solid theoretical basis for microstructure optimization of next-generation high-performance TBCs.

关键词

热障涂层 / 熔融 CMAS / 微观孔隙结构 / 蠕动流模拟 / 渗入机理

Key words

thermal barrier coating / molten CMAS / micro-pore structure / creeping flow simulation / infiltration mechanism

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