MECHANISM OF FORMATION OF NI-SC INTERMETALLIC COMPOUND LAYERS ON A NICKEL SURFACE IN MOLTEN HALIDES

The use of intermetallic compounds (IMC) based on rare-earth metals en ables the problem of precision alloying to be solved. During investiga tion of the electrochemical synthesis of nickel-scandium IMC, the mech anism of formation was determined. Scandium cations with highest oxida tion state and subions of alkaline metals were shown to take part in t ransfer of the electronegative component of the alloy onto the nickel substrate. Both the amount of scandium incorporated into nickel and th e phase composition of the layers formed depend on temperature, proces s duration, current density, mass ratio of scandium metal and molten s alts, and the initial concentration of scandium ions. Thermodynamic pr operties of the IMC were calculated using chronopotentiometric data. S ix plateaux with constant potentials were recorded on the discharge cu rve, which is in agreement with the number of two-phase regions in the nickel-scandium phase diagram. From the results of the calculation it was concluded that in all compounds the bonds are predominantly coval ent.