Microstructure and creep strength of different γ/γ′-strengthened Co-base superalloy variants

The influence of W, Ta, Ti, Nb, V, Si, Mo, Ir and Cr on the high temperature properties of γ/γ′-strengthened Co–Al–W superalloys was investigated. All alloys exhibited a γ/γ′ microstructure with remarkably differing γ′ volume fractions. W, Ta, Ti, Nb and V increased the γ′ volume fraction and γ′ solvus temperature. An increased W content and alloying of additional elements, except Ir, decreased the liquidus temperature. First creep experiments revealed a creep strength comparable with polycrystalline Ni-base superalloys and the importance of grain boundary strengthening.