Superhard CrN/MoN coatings with multilayer architecture

Main regularities of the formation of microstructure and properties of multilayer nanostructured CrN/MoN films with periodically changing architecture of layers were considered. Coatings were fabricated by vacuum-arc evaporation of the cathodes (Arc-PVD) in nitrogen atmosphere (p(N) was 0.4, 0.09 and 0.03 Pa). CrN and gamma-Mo2N nitride phases with fcc lattices and a small volume of metastable MoNx cubic phase were formed in the films at pN = 0.4 Pa. The decrease of p(N) to 0.09 Pa causes the formation of beta-Cr2N hexagonal phase. Preferential crystallographic orientation changes from [311] to [111] and [200] when bias voltage U-b is -20, -150 and -300 V respectively. The nanocrystallites size in coatings with bilayer thickness lambda = 44 nm decreases to 5.8 nm. The microdeformation grows from 0.4 to 2.3% when U-b changes to -20 V. Coatings show high hardness of 38-42 GPa and H/E = 0.107. In a couple with results of tribological tests, coatings demonstrate strong wear resistance, which makes them appropriate and promising for industrial applications as protective ones. The effect of deposition conditions (p(N), U-b, lambda) on composition, structure, hardness, toughness and wear resistance was studied to achieve superior mechanical and physical properties of coatings with long lifetime in harsh environment. (C) 2018 Elsevier Ltd. All rights reserved.