Effect of alloying elements on stacking fault energies of γ and γ' phases in Ni-based superalloy calculated by first principles

The first-principle calculations were employed to investigate the effect of alloying elements on stacking fault energies of gamma-Ni and gamma'-Ni3Al phases in Ni-based single crystal superalloys. The results showed that Co, Cr, Mo, Ta, Ti, W, Re and Ru elements decreased the stacking fault energy of gamma-Ni phase with increasing the concentration, but increased the stacking fault energy of gamma'-Ni3Al phase except Co and Cr elements. And, Co had a more significant effect than Cr in decreasing the unstable stacking fault energies of two phases. Furthermore, the interaction effect of Co and Cr elements was calculated that it significantly reduced the stable stacking fault energy of gamma' phase but had no obvious effect on the that of gamma phase. Finally, two alloys with different Co contents were crept at 750 degrees C/750 MPa condition, and the creep life in 12Co alloy was about 118 h, which was basically half of that in 9Co alloy (242 h). The microstructure observation indicated that the width of stacking fault in gamma' phase in 12Co alloy was increased by 51.8 nm, and the stable stacking faults energy of gamma' phase was reduced by 9.1 mJ/m(2) compared to those in 9Co alloy.