Elemental partitioning, lattice misfit and creep behaviour of Cr containing gamma ' 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 gamma matrix decrease partitioning of W to gamma'. Furthermore, Cr significantly enhances the gamma' volume fraction, decreases the gamma/gamma' 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 gamma'-A(3)B phase (L1(2) type), while Co and Ni reside in the 'A' sublattice.