This article deals with the new surface hardening method for producing diamond-like multicomponent carbide coatings on tool hard alloys by high-temperature thermochemical heat treatment. The structure and properties of the obtained coatings are examined. For three-component systems for diffusion saturation of hard alloys, optimization of the powder mixtures was performed with respect to the wear resistance and microhardness of the multicomponent carbide coatings. The “composition-properties” diagrams were plotted using the obtained mathematical expressions. The optimal carbide coatings permit enhancing substantially the microhardness and service life of different hard alloy tools.