Mechanical and Tribological Properties of Multicomponent and Multilayer Vacuum-Arc Coatings Obtained by Sequential and Simultaneous Evaporation of Zirconium and Ti–B–Si–Ni Cathodes

Abstract

The work presents the results of physical, mechanical, and tribological studies of five types of nitride-containing coatings of various architectural structures formed by simultaneous and sequential vacuum-arc evaporation of cathodes made of zirconium alloy E110 and/or cathodes TiBSiNi obtained by self-propagating high-temperature synthesis (SHS). The synthesis of coatings was carried out with the assisting influence of gas-discharge plasma from an autonomous plasma source with a heated cathode. All coatings were deposited on a substrate made of VK8 hard alloy (WC + 8% Co). Using calotesting, it was determined that the thickness of the coatings under study was 3–4 μm. Compared to the ZrN mononitride coating, whose microhardness was 31 GPa, the hardness of other variants of multicomponent and/or multilayer coatings was in the range of 40–42 GPa. X-ray phase analysis, in the case of using TiBSiNi SHS cathodes for evaporation, revealed the presence of high-hard titanium borides in the coating composition, which obviously affected the hardness of the coatings in general. Tribotechnical tests performed according to the pin-on-disk scheme have shown that for multicomponent and multilayer coatings with a composition-gradient binder sublayer and an upper thin, running-in layer, friction coefficients paired with a counterbody (indenter) made of hardened steel 100Cr6 are reduced compared to other types of coatings. In terms of wear resistance, a particularly pronounced advantage was found on the Zr + Zr_xN_y + (Zr + TiBSiNi)N + (TiBSiNi)N coating, in combination with both the counterbody made of 100Cr6 steel and high-hard silicon carbide SiC. In most cases, this is expressed as a multiple reduction in wear parameters compared to other types of coatings. This effect is probably due to the properties of the top layer that provides favorable running-in conditions with a low coefficient of friction and an increase in the adhesion strength of the coating to the substrate, as is confirmed by the results of scratch testing. Taking into account the formed gradient in composition and hardness on such coatings, as well as the layered architecture, the authors believe that they can be characterized as “gradient-layered coatings.”