Elemental partitioning, lattice misfit and creep behaviour of Cr containing <i>γ</i>′ strengthened Co base superalloys

Abstract

Novel Cr containing Co-Al-W base superalloys were studied by atom probe tomography and neutron diffraction. Cr is found to predominantly partition to the γ matrix and decrease partitioning of W to γ′. Furthermore, Cr significantly enhances the γ′ volume fraction, decreases the γ/ γ′ lattice misfit and deteriorates the creep resistance. Addition of Ni to the Cr containing alloys affects partitioning of W and Al, further decreases the lattice misfit and results in the formation of irregularly shaped precipitates. Al, W and Cr tend to occupy the ‘B'sublattice in the γ′-A 3 B phase (L1 2 type), while Co and Ni reside in the ‘A’ sublattice.