Computational thermodynamics and genetic algorithms to design affordable γ′-strengthened nickel–iron based superalloys

Computational thermodynamics based on the CALPHAD approach (Thermo-Calc software) are used to design creep-resistant and affordable superalloys for large-scale applications such as power plants. Cost is reduced by the introduction of iron and by avoiding the use of expensive alloying elements such as Nb, Ta, Mo, Co etc. Strengthening is ensured by the addition of W, and of Al and Ti to provoke the precipitation of γ′. However, the addition of iron reduces the maximum possible volume fraction of γ′. The latter is maximized automatically using a genetic algorithm during simulation, while keeping the alloys free of undesirable phases at high temperatures. New superalloys with 20 wt% Cr are designed, with Fe content up to 37 wt%. They should be forgeable, weldable, oxidation resistant and significantly cheaper than existing alloys with equivalent properties. (paper)