The coatings on the steel U10A with maximums of thickness and microhardness derived from ternary saturating blends involving Ti, V, Cr and optimized by means of the Scheffe simplex are studied by the methods of metallographic analysis and soft X-ray spectroscopy. As shown, the concentration of carbon in TiC and (Ti,V,Cr)C coatings is maximal in the internal and central zones, respectively. Interaction of titanium and iron in the central and inner regions of the carbide layer is shown in TiL$_{\alpha}$-bands. Furthermore, small differences in the positions of the longwave contour of CK$_{\alpha}$-bands from the surface and inner area of coverage (Ti,V,Cr)C are associated with a small decrease in the carbon content in this area in comparison with the surface. It should be noted that the carbon content in the interior coverage areas (Ti,V,Cr)C compared to the surface and central zones as well as for TiC coating is minimal. The decrease of carbon amount in (Ti,V,Cr)C coating as compared with TiC coating is reflected in the considerable narrowing of TiL$_{\alpha}$- bands in energy band of $spd$-hybrid bonds. As shown, the near-Fermi overlap of TiL$_{\alpha}$- and CK$_{\alpha}$-bands, the Ti—Fe—C bonds are formed in the central and internal zones of coatings. The changes of microhardness, microbrittleness, and microstrength with the thickness of coatings conform to the level of interatomic interaction in different carbide phase zones.