The properties of superalloys are usually deteriorated by the coarsening of nano-sized γphase,which is the primary strengthening component at high temperature.Stabilizing the γphase represents one of the key challenges in developing next-generation superalloys.Here,we fabricate a cobalt-base superalloy with nanoscale coherent γphase(Ni,Co)3(Al,Ti,Nb),which is isolated by stacking-fault ribbons in the alloy matrix as a result of Suzuki segregation of alloying atoms,and demonstrate that this new nanostructure can slow down the coarsening of γphase at high temperature.As a result,the Co-Ni-base superalloy displays a considerably high tensile-yield point exceeding 1650 MPa at room temperature and 1250 MPa at 1073 K,which are markedly higher than those of the commonly used nickel-and cobalt-base superalloys,thereby paving a new way for developing superalloys with exceptional mechanical performances and thermal stability.