Creep properties of a low-cost 3rd generation nickel-based single crystal superalloy with orientation deviated from [001] direction

Abstract

In this paper, the creep properties and deformation mechanisms of a low-cost 3rd generation nickel-based single crystal superalloy deviating 1.5°, 7.8°, and 14.7° from [001] direction were studied at 800 °C/760 MPa and 1100 °C/137 MPa. The microstructure after full heat treatment and creep rupture of specimens were observed by scanning electron microscopy (SEM). The dislocation configurations of specimens after creep rupture were observed by transmission electron microscopy (TEM). The results indicate that specimens with different orientation deviations exhibit strong anisotropy at 800 °C/760 MPa, and the creep lives of specimens decrease with the increase of θ angle. In specimens A (1.5°) and B (7.8°), the creep deformation is controlled by multiple <112>{111} slip systems, which would produce working hardening. Multi-directional stacking faults are apt to form stacking fault (SF) locks, which inhibit the slipping and cross-slip of dislocations and then increase creep life of the specimen. In specimen C (14.7°), the creep deformation is controlled by single <112>{111} slip system, unidirectional stacking faults cut into γ′ particles, causing rapid failure of the alloy. The creep anisotropy of specimens with different orientation deviations is insignificant at 1100 °C/137 MPa. The same N-type rafted structures and the dislocation networks with similar spacing form in three specimens, which have the same ability to hinder dislocations cutting into γ′ particles.