To further understand the effect of Ta additive on the creep damage for polycrystalline Ni-base superalloys, creep rupture tests on powder metallurgy (PM) superalloys with various Ta were carried out under different conditions in this study. The results indicated that the multiple crack propagation and damage mechanisms could occur at the identical creep condition. These different fracture mode areas had distinct boundaries on the fracture surface, its size could be altered by Ta addition. However, the effects of Ta were radically changed by the creep conditions. The creep rupture mechanism transformed significantly with temperatures and applied stresses, and even subversive laws appeared in the creep life for high-Ta alloys. The substructure observation after creep rupture demonstrated that the annealing coherent twin boundaries gradually lose coherence with the matrix, which could become sites for cavities nucleation or crack propagation that followed. Furthermore, the creep-induced microtwins were critical for the creep damage and rupture. The electron back-scattered diffraction (EBSD), high-resolution transmission electron microscope (TEM) imaging, and quantitative elemental analysis assisted in comprehending these alterable creep rupture mechanisms.

为进一步了解 Ta 添加剂对多晶 Ni 基高温合金蠕变损伤的影响，本研究在不同条件下对含有不同 Ta 的粉末冶金 (PM) 高温合金进行了蠕变断裂试验。结果表明，在相同的蠕变条件下，可能会出现多种裂纹扩展和损伤机制。这些不同的断裂模式区域在断裂表面上具有明显的边界，其大小可以通过添加Ta来改变。然而，蠕变条件彻底改变了 Ta 的影响。蠕变断裂机理随温度和外加应力发生显着变化，高Ta合金的蠕变寿命甚至出现了颠覆性规律。蠕变断裂后的亚结构观察表明，退火共格孪晶界逐渐失去与基体的共格性，这可能成为随后的空洞形核或裂纹扩展的场所。此外，蠕变诱导的微孪晶对于蠕变损伤和破裂至关重要。电子背散射衍射 (EBSD)、高分辨率透射电子显微镜 (TEM) 成像和定量元素分析有助于理解这些可变的蠕变断裂机制。