The Structure and Properties of IV–VI Group Transition Metal Carbonitride Films and Coatings (Review)

Films/coatings of IV–VI group transition metal carbonitrides (TMCNs) were the subject of examination due to prominent properties characteristic of corresponding binary transition metal carbides and nitrides. The papers reviewed below concern the experimental and theoretical study of the structure, chemical bonding, mechanical (hardness, elastic modulus, wear resistance, tribology) and optical properties, thermal stability, and resistance to oxidation of transition metal carbonitrides in dependence on the deposition methods and conditions, composition, and thermal treatment. It has been shown that TMCN films can exist in two forms: as a solid solution with C and N atoms occupying the interstitial sites, and as a nanocomposite consisting of nanocrystalline TMCN phase embedded into an amorphous a-C or a-CN matrix. The first-principle calculations showed that the valence electron concentration (VEC), defined as the number of valence electrons per formula unit, is a significant indicator of the structural, thermodynamic and mechanical properties of TM carbonitrides. The overall results indicate a narrow region between VEC = 9 and 10, with TMCNs being ductile but demonstrating high hardness, mechanical, and thermal stability. As such, they are expected to exhibit the highest toughness. Experimental study confirmed the theoretical predictions and showed that the TMCN films/coatings exhibit rather high mechanical properties and low coefficients of friction, retain their structure upon annealing, and show high oxidation resistance. So, the films/coatings of IV–VI transition metal carbonitrides are promising materials for various technology applications.