Rules of formation of the chemical composition of M23C6 multicomponent carbide in high-temperature steels

The method of phase physicochemical analysis is used to study martensite steels in the Fe−Cr−Ni−Co−Mo−W−V−C system. It is shown that the chemical compositions of two multicomponent phases, i.e., hardened martensite and (Cr, M)23C6 carbide segregated from it in high-temperature tempering are correlated where the concentrations of the elements Mo/W, V/W, and (Cr+V)/(Mo+W) are concerned. The discovered correlation is used for developing a method for calculating the chemical composition of a (Cr, Fe, Co, Ni, Mo, W, V)23C6 carbide with the help of the concentrations of the elements in the α-solid solution and the differences in the atomic radii. It is shown that the alloying elements in the carbide substitute for chromium in correspondence with the principle of dimension. It is inferred that the type of bonding in the chromium sublattice in the carbide is metallic.