Transverse stress rupture properties of a third generation single crystal superalloy at medium and elevated temperatures

Abstract

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 the γ' phases after stress ruptured at 760℃/800 MPa, and the dislocations are tangled and high densities of dislocation networks have formed at the γ/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.

Keywords

• a third generation single crystal superalloy
• transverse stress rupture property
• fracture mechanism
• dislocation configuration