Effect of Hf and Ta on the tensile properties of PM Ni-based superalloys

Abstract

In this work, the effects of Hf and Ta on the tensile properties of PM Ni-based superalloys at different temperatures were investigated. From room temperature to 750 °C, Ta significantly enhanced the tensile strength by reducing stacking fault energy, increasing the γ′ volume fraction, and promoting γ′ splitting. However, Ta was detrimental to tensile ductility because it obviously inhibited intragranular deformation. Hf had no obvious effect on tensile strength, but significantly improved high-temperature tensile ductility by promoting intragranular deformation, increasing the equivalent width of the γ channel, reducing the density of the annealing twin boundaries, and increasing the equi-cohesive temperature. We also found that Hf and Ta showed interaction strengthening, which became more significant with increasing temperature. At high temperatures, it fully reflected the advantage of the synergistic effect of Hf and Ta, which not only significantly improved the strength of the alloys but also maintain fair ductility.