Mechanical alloying of the elemental powder mixture of nickel–multiwalled carbon nanotubes (Ni–CNT) and nickel–spectroscopic grade graphite (Ni–SGG) is performed in a high energy planetary ball mill under the same technological modes. Nanocrystalline NiC$_x$ carbide ($x$ = 0.3–0.4) synthesized is examined by X-ray diffraction methods (phase and structural analysis, determination of the real structure parameters, $etc.$). The carbides synthesized are ferromagnets, the coercive force of which ($H_c$ = 6–12 kA/m) depends on the amount of interstitial carbon atoms in octahedral voids of Ni crystal lattice. It is shown that an allotropic form of carbon (SGG or CNT) used at mechanical alloying effects the charge components interaction as well as the crystal structure and properties of final synthesis products.