Film cooling hole structures significantly influence vibration fatigue performance of Ni-based single crystal turbine blades. This study investigates the vibration fatigue behavior and failure mechanism of film cooling hole structure of Ni-based single crystal superalloy at high temperature by using the plate specimens with film cooling holes. The vibration fatigue cracks are all initiated at the edge of the film cooling hole on specimen surface, and the macroscopic crack path is a straight line path. At the microscopic scale, the crack path at 850 °C is a Zigzag path, but the crack path at 980 °C still shows a straight line path. The crack initiation of the specimen shows the oxidation crack nucleation in the stress concentration area under the coupling effect of high temperature and alternating stress. The macroscopic crack propagation direction at high temperature depends on the stress gradient direction of the resolved shear stress. At the microscopic scale, the crack propagation at 850 °C is the dislocation slip-climb mechanism, and the crack propagation at 980 °C more inclined to produce only the dislocation climb mechanism. The vibration fatigue cracks have the temperature dependence. The high temperature environment promotes the activation of slip system and the enhancement of dislocation mobility, the microscopic raft structure promotes the crack propagation along the γ phase with a large number of dislocations, the oxidation crack promotes the oxygen to enter the alloy matrix, which accelerates the Mode-I crack propagation.

中文翻译：

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Ni基单晶膜冷却孔结构在高温下的振动疲劳行为及失效机理


薄膜冷却孔结构显著影响镍基单晶涡轮叶片的振动疲劳性能。本研究以带膜冷却孔的板样为研究对象，研究了镍基单晶高温合金膜冷却孔结构在高温下的振动疲劳行为及失效机理。振动疲劳裂纹均始于试件表面的薄膜冷却孔边缘，宏观裂纹路径为直线路径。在微观尺度上，850 °C 时的裂纹路径是锯齿形路径，但 980 °C 时的裂纹路径仍然显示直线路径。试件的裂纹萌生表现在高温和交变应力耦合作用下应力集中区的氧化裂纹成核。高温下的宏观裂纹扩展方向取决于解析的剪切应力的应力梯度方向。在微观尺度上，850 °C 时的裂纹扩展是位错滑移爬升机制，而 980 °C 时的裂纹扩展更倾向于只产生位错爬升机制。振动疲劳裂纹具有温度依赖性。高温环境促进了滑移系统的激活和位错迁移率的增强，微观筏状结构促进了裂纹沿位错数量较多的γ相扩展，氧化裂纹促进了氧进入合金基体，从而加速了 I 型裂纹的扩展。