Creep properties and deformation mechanisms of two Nb-containing low-cost third-generation single crystal superalloys

Two low-cost third-generation single crystal superalloys with varying Nb contents were valuated for creep properties at 1100 °C/137 MPa. The deformation mechanism of two Nb-containing superalloys was extensively analyzed by microstructure and dislocation configuration analysis. The creep tests revealed that the 1Nb alloy demonstrated significantly higher creep lives compared with the 0.5Nb alloy. During the primary creep stage, the 1Nb alloy exhibited narrower matrix channel width than the 0.5Nb alloy, which increased resistance to dislocation bowing. As creep progressed, the 1Nb alloy developed thicker γ′ rafts and smaller dislocation networks spacing compared with the 0.5Nb alloy, resulting in reduced dislocation climbing rate. Consequently, the 1Nb alloy exhibited an extended steady state creep stage. During the accelerated creep stage, the 1Nb alloy formed denser dislocation networks, effectively preventing superdislocations from cutting into γ′ phase. This comprehensive investigation of deformation mechanisms by microstructure evolution and dislocation configurations provides essential guidance for developing third-generation low-cost single crystal superalloys. • Compared with 0.5Nb alloy, 1Nb alloy shows better creep property. • The improvement of creep property is closely related to morphology of interfacial dislocation networks. • Like-quadrilateral dislocation networks can effectively prevent dislocations from cutting into γ′ phase.