On dislocation networks and superdislocations in Re-containing nickel-based SX superalloy under different creep conditions

In this paper, the creep behaviors and deformation mechanisms of a 3 wt% Re-containing single crystal superalloy, are investigated under two tough conditions of 1120 °C/137 MPa and 850 °C/690 MPa. The detailed TEM observation on interfacial dislocation networks and superdislocations are analyzed to interpret the creep resistance. Results show that at 1120 °C/137 MPa, dislocation networks degrade into unstable structures and give rise to the universal shearing of superdislocations. At 850 °C/690 MPa, three mechanisms including superdislocation pairs, stacking faults, and bypassing loops jointly contribute to the plastic deformation. In addition, the comparison of superdislocations and creep performance of superalloys with different Re contents are concluded. In general, the deficiency of interfacial dislocation networks and γ′ phases in resisting dislocation climbing and shearing causes the poor creep performance, which could be improved by stabilizing interfacial dislocation networks with additional W contents. This paper guides the composition optimization of low-cost third-generation superalloys in the future. • The degradation of interfacial networks into unstable configurations accelerates the γ′-shearing of superdislocations. • Superdislocations, stacking faults, and Orowan bypassing loops coexist at the intermediate temperature of 870 °C/690 MPa. • Stabilizing interfacial dislocation networks is available to enhance the creep resistance of low-Re SX superalloys.