一种新型镍基单晶高温合金蠕变断裂行为及机制

Creep Fracture Behavior and Mechanism of a New Nickel-Based Single-Crystal Superalloy

摘要:

对一种新型镍基单晶高温合金在1100 ℃/140 MPa的条件下进行了蠕变性能测试、组织形貌观察及成分分析，研究了该合金在蠕变断裂过程中，蠕变速率的变化特点及蠕变前后组织的演变特征，揭示了新型镍基单晶高温合金的蠕变断裂机制。结果表明：该合金的蠕变寿命为104.5 h，应变量可达到33.58%，蠕变速率随应变整体呈现出先递减后递增，最后趋于稳定直至断裂的现象。在蠕变初始阶段，蠕变速率随时间延长呈现先降低再回升而后再降低的现象。此外，蠕变断口组织由韧窝与撕裂棱构成，无明显滑移面，断口内部存在氧化物和再结晶组织，断口内空洞呈现长条状，且垂直于应力轴，表现为微裂纹聚集型断裂机制。

Abstract:

A new type of nickel-based single-crystal superalloy was subjected to creep performance test, microstructure observation, and composition analysis under the condition of 1100 °C/140 MPa. The variation characteristics of the creep rate during the creep fracture process and the microstructure evolution before and after creep were investigated, thereby revealing the creep fracture mechanism of the new nickel-based single-crystal superalloy. The results indicate that the creep life of the alloy is 104.5 h, and the strain can reach 33.58%. The creep rate decreases first, then increases, and finally tends to be stable until fracture. At the initial stage of creep, the creep rate decreases first, then rises and finally decreases again with time. Furthermore, the creep fracture microstructure is composed of dimples and tearing edges without obvious slip planes. Oxides and recrystallized structures exist inside the fracture surface, and the voids inside the fracture are elongated and perpendicular to the stress axis, showing a fracture mechanism of microcrack accumulation.