一种第三代单晶高温合金中高温横向持久性能

Transverse stress rupture properties of athird generation single crystal superalloyat medium and elevated temperatures

研究一种镍基第三代单晶(single crystal,SC)高温合金在760℃/800 MPa,980℃/250 MPa与1100℃/137 MPa条件下的横向持久性能。结果表明:在760℃/800 MPa,980℃/250 MPa与1100℃/137 MPa条件下,该合金横向持久寿命与伸长率均低于纵向;横向与纵向持久断裂后的位错组态特征一致,760℃/800 MPa条件下断裂后γ′相中存在相交的层错,而1100℃/137 MPa条件下断裂后γ/γ′相界面形成位错缠结与高密度位错网;横向与纵向在760℃/800 MPa条件下为类解理断裂与韧窝断裂的混合断裂,而在980℃/250 MPa与1100℃/137 MPa条件下为韧窝断裂;第一代单晶高温合金DD3、第二代单晶高温合金DD6与本研究的第三代单晶高温合金中高温横向持久断裂机制基本一致;外应力方向垂直于定向凝固过程形成的一次枝晶间界面,是横向持久性能低于纵向的主要原因。

At the conditions of 760℃/800 MPa,980℃/250 MPa and 1100℃/137 MPa,the transv-erse stress rupture properties of a nickel-based third generation single crystal superalloy were investigated.The results show that the stress rupture life and elongation of the transverse specimens are lower than those of the longitudinal specimens at 760℃/800 MPa,980℃/250 MPa and 1100℃/137 MPa.The dislocation configurations of the stress ruptured transverse and longitudinal specimens are the same.There are intersecting stacking faults in theγ′phases after stress ruptured at 760℃/800 MPa,and the dislocations are tangled and high densities of dislocation networks have formed at theγ/γ′interface after stress ruptured at 1100℃/137 MPa.The transverse and longitudinal specimens show quasi-cleavage and dimple mixture mode at 760℃/800 MPa,while they both show dimple mode at 980℃/250 MPa and 1100℃/137 MPa.The fracture mechanisms of transverse specimens of the first generation single crystal superalloy DD3,the second generation single crystal superalloy DD6 and the third generation single crystal superalloy in our study at medium and elevated temperatures are basically the same.The main reason for the transverse specimens have a lower stress rupture properties than the longitudinal specimens is that the external applied stress is perpendicular to the primary interdendritic interface formed during the directional solidification process.