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The structure, the stress-strain state, and the mechanical properties (hardness and wear resistance) of titanium nitride coatings deposited on a substrate by a vacuum-arc method at constant (from -5 V to -230 V) and high-frequency pulse (-1000 V) negative potentials are studied. The laws of formation of the coatings are determined. The formed coatings are analyzed using a model of two-level action of the implanted ions on them.

Abstract-The effect of the pressure of the nitrogen atmosphere during the formation of vacuum arc nitride coatings based on high entropy alloys of the Ti-Zr-Hf-V-Nb-Ta system on their structure, hardness, and tribotechnical characteristics is considered. It is shown that strong nitride forming components lead to the dependence of the structural state and properties on the pressure of the nitrogen atmosphere during coating deposition. Deposition at a nitrogen pressure of 0.4 Pa results in the formation of a texture with the [111] axis when the applied bias potential is -70 V and when the bias potential is equal to -150 V the textural structure is biaxial ([111] and [110]) textures and high value of hardness of 51 GPa Along with that the highest value of wear resistance (under oxidizing mechanical wear) is inherent to coatings formed under the pressure of nitro gen of 0.09 Pa. The strongest microdeformation of coating crystallites corresponds to this pressure.

Using vacuum-arc evaporation method we fabricated periodic multilayered TiN/MoN structures with different bilayer periods λ ranging from 25 to 100 nm. Rutherford backscattering (RBS), X-ray diffraction (XRD), scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) and microhardness measurements were used for investigations of composition, structure and mechanical properties of the multilayered coatings. We found that molybdenum nitride and titanium nitride layers grown on steel show local partial epitaxy and columnar growth across interfaces. A molybdenum-titanium carbide interlayer was evidenced between the substrate and the multilayer. Molybdenum nitride and titanium nitride layers contain small (5-30 nm) grains and are well crystallized with (100) preferred orientation. They were identified as stoichiometric fcc TiN and cubic γ-Mo 2 N. Non-cubic molybdenum nitride phases were also detected. The hardness of the obtained structures achieved great values and maximal hardness was 29-31 GPa for multilayered structure with 50 nm period. Hardness of the obtained coatings is 25% higher in comparison with initial single-layer nitride coatings, wherein plasticity index (H/E) of multilayered structure is 0.075. © 2014 Elsevier Ltd. All rights reserved. IntroductionRefractory metals are widely used in modern materials science as basic elements for coatings with high functional properties, such as nitride coatings. Improving the properties of such coatings using multicomponent or multilayered systems is a very actual task nowadays.Ion-plasma deposition or coating's deposition using vacuum arc cathode evaporation seems to be a very promising way of fabrication of protective coatings [1][2][3][4][5][6][7][8][9][10][11][12]. In the presented paper we investigated TiN/MoN multilayered coatings with different bilayer periods form 25 to 100 nm.We should point, that multilayered, multicomponent and nanostructured coatings are widely used in modern materials science for increasing of protective properties of different industrial products, and for improving their hardness, wear and corrosion resistance, oxidation resistance under the influence of high temperatures and so on [4][5][6][7][8][9][10][11][12][13][14][15]. Experimental procedureTiN/MoN samples were deposited on A 570 Grade 36 and AISI M2 high speed cutting steel substrates (steel disks, diameter is not higher than 30 mm, 5 mm thickness, in a delivery state -these samples were used for tribotechnical tests) under different deposition regimes. A second series of substrates with 2 mm thickness and 20 mm diameter were used for RBS, SEM, EDS, TEM, and nano-and microhardness tests. Substrate surface was treated using glow discharge in order to clean and activate it before deposition. For multilayer TiN/MoN coating deposition we used a vacuum-arc device Bulat-6 with two evaporators (Ti and Mo) [14], which allows deposition of nanostructured coatings in pulsed mode with variable pulse amplitude and pulse frequency. Fig. 1 shows a schematic of the de...

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