The surface segregation of ZrC carbide from the ZrC0.82–NbC0.83 solid solutions has been investigated using the X-ray diffraction, electron microscopy, X-ray microanalysis, and laser mass analysis. A method for including the energy of the interfaces in the free energy of mixing, which ensures the determination of the compositions of the solid solution in which the surface segregation can be observed, has been proposed for the carbide solid solution.