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.

The influence of the layer thickness (in the nanometer range) and negative bias potential (-Us) supplied during the deposition on the structure and hardness of the composite vacuum-arc coatings are analyzed for multilayer ZrN/CrN system with a large difference in the atomic weights and radiation-induced defect formation of metal components. It is established that at the layer thickness less than 50 nm, supply of-Us leads to an increase of microstrain in the CrN layers under bombardment by Zr ions with large atomic radius and mass, and the strain relaxation is observed in ZrN layers. The observed effects are explained by an increase in energy of deposited ionized particles when applying-Us that determines the radiation-induced mixing at the interphase boundaries of the layers and leads to the hardness decrease. The highest hardness of 42 GPa in the ZrN/CrN system is achieved upon deposition of thin (20 nm) layers in the absence of-Us.

Abstract-The effect of nanolayer thickness on the structure and properties of nanocomposite multilayer TiN/MoN coatings is revealed. The multilayer (alternating) TiN/MoN coatings are prepared by the Arc PVD method. The selected thickness of the nanolayers is 2, 10, 20, and 40 nm. The formation of two phases-TiN (fcc) and γ Mo 2 N-is found. The ratio of Ti and Mo concentrations varies with varying layer thickness. The maximum hardness value obtained for different thicknesses of the layers does not exceed 28-31 GPa. The stability of TiN/MoN during cutting and tribological tests is significantly higher than that of products with TiN coatings. The nanostructured multilayer coatings with layer thicknesses of 10 and 20 nm exhibit the lowest friction coefficient of 0.09-0.12.

At present, there is an obvious lack of data on the influence of the parameters of the vacuum arc reactive plasma spray deposition process on the phase compo sition, structure, and stress state of widely used nitride coatings. The main attention so far has been devoted to the deposition of transition metal nitrides with high enthalpies of formation, such as TiN, ZrN,. However, under certain conditions, it is also possible to ensure high functional (in particular, mechanical) properties for vacuum arc deposited transition metal nitrides in systems with relatively low enthalpies of formation, such as Cr-N [5] and Mo-N [1]. In the latter case, it should be noted that, based on the thermodynamics of nitride formation in the Mo-N system, a gain in the free energy for the formation of a Mo 2 N phase amounts to 37 kJ/mol and that for δ MoN is 34 kJ/mol [6]. Therefore, it can be expected that, at a relatively low pressure of nitrogen contain ing atmosphere (and, hence, relatively low content of nitrogen in the deposit), the formation of Mo 2 N should be thermodynamically somewhat more favor able than the formation of δ MoN [2, 7].Thus, relatively low enthalpies of formation for compounds of the Mo-N system can lead to a strong dependence of the structural phase and elastically stressed state on the conditions of material formation, in particular, on the energy factor. For highly ionizing methods of vacuum arc plasma deposition of coat ings, this factor is determined to a considerable degree by the negative bias potential (U b ) applied to a sub strate during the deposition process [2,8]. In order to study this influence, we have obtained a series of Mo-N coatings on a Bulat 6 vacuum arc setup [1] at vari ous negative bias potentials, including a floating regime with U b = -(5-8) V and constant bias regimes with U b = -40 and -200 V.Based on the results of previous investigations [1,9,10], optimum conditions for the deposition of Mo-N coatings with high mechanical characteristics (strength, adhesion, friction coefficient) are provided by an arc discharge current of I d = 160 A and a focus ing magnetic field of 75 Oe. The pressure of a reactive nitrogen containing atmosphere was 0.08 or 0.2 Pa. The substrate temperature during deposition did not exceed 350°C, which made it possible to obtain depos its in highly stressed structural states. The evaporated target material was high purity molybdenum of the MChVP grade. The coatings were deposited onto pol ished substrates of 12Kh18N9T chromium-nickel stainless steel, nickel (4 mm thick plates), and copper (5 mm thick plates and 0.2 mm thick foil). After evacuation of the vacuum chamber to a residual pres sure of ~1 × 10 -3 Pa, the surface of substrates was cleaned and activated by bombardment with Mo ions for 3-4 min at a negative bias potential of 1000 V and an arc discharge current of 105 A. Immediately after this preparation, reactive atmosphere was admitted and vacuum arc plasma spray coatings with thick nesses of 0.7-1.1 and 6-7 μm were deposited.Abstract-The effect of su...

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The tribological properties of TiN, MoN, and TiN/MoN coatings have been investigated. It has been shown that, for multilayer (alternate) TiN/MoN coatings, a maximum hardness reaches 29-31 GPa that is significantly less than the hardness of MoN coatings (36.0-40.2 GPa) when changing the deposition conditions. MoN coatings possess lower coefficients of friction compared to TiN coatings, in particular at the initial stages of a scratch test. Two mechanisms of destruction are revealed by the adhesion tests, i.e., a cohe sive failure with a minimum critical loading L C1 and an adhesive test (plastic abrasion) with the appearance of a first crack L C2 . The resistance of multilayer (nanoscale) nanostructured TiN/MoN coatings with a total thickness of up to 8 μm is greater than that of TiN coatings.

The possibilities of structural engineering of multi-period vacuum-arc coatings based on nitrides of transition metals Ti, Cr, Mo, and Zr have been investigated by structural studies (X-ray diffraction and electron microscopy) in combination with measurement of hardness by indentation. The formation of phases with a cubic crystal lattice under nonequilibrium conditions under vacuum arc method of production. The supply of a negative bias potential of-200V in mononitrides leads to the predominant formation of texture of crystallites with the [111] axis. The introduction of thin (about 10 nm) metal layers leads to a decrease in texture perfection [111] and texture formation [100]. This effect is associated with a change in the stress-strain state of nitride layers. It is determined that the composite multiperiod coatings (Me1N/Me2N)/(Me1/Me2) have a greater hardness and greater resistance compared to MeN/Me. For a multiperiod system with damping metal layers-(ZrN/CrN)/(Zr/Cr), superhard coatings with a hardness of 46 GPa were obtained.