Multi-layered gradient (Zr,Nb)N coatings deposited by the vacuum-arc method

Abstract

Multi-layered gradient (Zr,Nb)N coatings were deposited with vacuum-arc evaporation of pure Zr and Nb metal cathodes. The gradient of the Nb concentration through the thickness was obtained by varying the arc discharge current with a Nb cathode within 80–150 A under the constant pressure of a working Ar/N2 gas mixture and a constant current of arc discharge with a Zr cathode. These coatings were studied by scanning and transmission electron microscopes, X-ray diffraction analysis, micro- and nanoindentation, and tribological measurements. The synthesized coatings show a high hardness, relatively low Young's modulus, relatively high H/E ratio, a high degree of elastic recovery, low surface roughness, a low friction coefficient, and a low wear rate. These coatings also feature a multiphase and multi-layered nanocrystalline structure with alternation of only layers with higher and lower Nb concentration.