Thermodynamic justification of chemical reactions in the system B₄C — boratic flux — Fe under the conditions of RF-heating is presented. It is shown that the process of high-speed (30–120 s) steel boriding is probable at RF-heating of carbonaceous low alloyed steels 65Mn, 50CrMn in mix material containing B₄С and boratic flux П-0.66 (according to the Russian classification), composite wear-resistant coating containing Fe_nB borides, suballocated in Fe–B eutectics matrix being formed on the surface of steel part. Two reactions of Fe_nB borides formation and 3 reactions of coating forming have been chosen on the basis of thermodynamic calculations of 13 theoretically possible chemical reactions using Le Chatelier and J. Gibbs criteria which have been calculated at a first approximation in the interval of temperatures of 298–1498 K. It has been established that wear-resistant coating on the surface of a steel part is formed at high-speed RF-borating due a number of reactions between the components of fusion mixture and integrated topochemical reaction of interaction of boron active forms with iron.