Abstract The fracture mechanism and microstructure evolution around film-cooling holes in a nickel-based single crystal superalloy specimen under tensile creep at high temperatures were investigated using thin-walled plate specimens with close-packed film-cooling holes. The results demonstrated that the film-cooling hole structure has a weakening effect on the specimen for the creep life and creep ductility. In the specimen with the film-cooling holes, a large number of small cracks formed from initial cracks along the direction of the maximum resolved shear stress during the high-temperature creep process, and the cracks propagated along the direction perpendicular to the loading stress direction. Further, the microstructure evolution of the γ′ phase around the edge of the film-cooling holes was closely related to the local stress. While N-type rafting occurred in the high-stress zone, no significant change of microstructure was observed in the low-stress zone. Further, a modified damage model of the crystal plasticity theory was used to simulate the deformation of the specimen with cooling holes under multi-axial stress state, and the results of finite element analysis (FEA) agreed with both the test results and fracture morphology.

中文翻译：

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镍基单晶高温合金试样薄膜冷却孔周围蠕变破裂机制及微观结构演变

摘要 采用密排薄膜冷却孔的薄壁板试样，研究了镍基单晶高温合金试样在高温拉伸蠕变下薄膜冷却孔周围的断裂机理和微观组织演变。结果表明，薄膜冷却孔结构对试件的蠕变寿命和蠕变延展性有弱化作用。在带有薄膜冷却孔的试件中，在高温蠕变过程中，初始裂纹沿最大分辨剪应力方向形成大量小裂纹，裂纹沿垂直于加载应力方向的方向扩展. 此外，薄膜冷却孔边缘周围γ'相的微观结构演变与局部应力密切相关。N型漂流发生在高应力区，而在低应力区没有观察到显着的微观结构变化。进一步利用晶体塑性理论的修正损伤模型模拟带冷却孔试样在多轴应力状态下的变形，有限元分析(FEA)结果与试验结果和断口形貌一致。