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Abstract-A complex study has been performed of the effect of the technological parameters, which are responsible for the energy states of deposited particles, on the elemental, phase and structure composi tions, hardness, and tribological characteristics of formed vacuum-arc multilayer Mo 2 N/CrN systems with a nanometric thickness. The formation of two phase and structure types has been defined in combined nitride layers: γ Mo 2 N/CrN with the isostructural cubic crystalline lattices and γ Mo 2 N/CrN with non isostructural cubic and hexagonal lattices.

Abstract-Effect of deposition conditions in reactive nitrogen atmosphere on the growth morphology, phase composition, structure, and mechanical characteristics (microhardness) of vacuum-arc multilayer coatings obtained using evaporation of the (Ti6%Si) and Mo cathodes is studied with the aid of raster electron microscopy, energy-dispersive elemental microanalysis, and microindentation. It is demonstrated that nitrogen atoms are redistributed to the region of the strongest nitride-forming element (Ti) in relatively thin layers (about 7 nm) consisting of substances with substantially different heats of formation (−336 kJ/mol for TiN and −34 kJ/mol for MoN). Such a process leads to lamination with the formation of nitride TiN and metal Mo (weaker nitride-forming element). Nitrogen-metal bonds are saturated in the layers of strong nitrideforming elements Ti(Si) when the nitrogen pressure increases from 6 × 10 -4 to 5 × 10 -3 Torr in the condensation procedure. Thus, the compound is filled with nitrogen to the stoichiometric composition and, then, the second system of layers based on molybdenum is saturated with nitrogen with the formation of the γ-Mo 2 N phase. An increase in bias potential U SP from -100 to -200 V stimulates mixing in thin layers with the formation of the (Ti, Si, Mo)N solid solution and leads to a decrease in microhardness from 37 to 32 GPa. DOI: 10.1134/S1063784217050073INTRODUCTION Additional requirements on the surface properties of components and structures emerge due to the development of modern technologies. The desired functional properties can be reached using deposition of relatively thin (with a thickness of up to 10 μm) multielement coatings [1][2][3]. When the vacuum-arc technology is employed, the best (primarily, mechanical) properties are obtained for multielement coatings based on nitrides of transition metals [4][5][6][7][8].Rapid recent progress in structural engineering is related to the study of the composition of multielement coatings, regularities of the formation of structure and stressed state, and the relation of the parameters and physicochemical characteristics [9][10][11]. The corresponding results are used to interpret physical processes of the formation of nanocrystalline solid coatings under strongly nonequilibrium conditions for deposition of vacuum-plasma fluxes [12][13][14]. In this regard, the method for formation of multilayer structures with nanosized periods is employed for efficient control of nanostructure state of coatings [15,16]. Crystallite structures with variable structural nonequilibrium, imperfection, and element distribution in volume and interfacial regions are formed when the composite structures are fabricated [17][18][19][20].

Abstract-The possibilities of structure engineering in multilayer coatings of the MoN-CrN system with relatively low heats of formation of component transition metal nitrides are demonstrated by varying pressure P N of reactive gas (nitrogen) and negative bias voltage -U s applied to a metal substrate. It is established that, by changing P N from 7 × 10 -4 to 3 × 10 -3 Torr, it is possible to obtain coatings in two significantly different structural-phase states. A multilayer nonisostructural composite with hexagonal crystalline lattice in CrN layers and cubic type lattice in MoN layers is formed at low pressure, whereas an isostructural state with cubic lattice in both nitride layers is formed at high pressure. The existence of two types of structural states allows multilayer coatings with controlled hardness to be obtained, which reaches 38 GPa in the isostructural state. DOI: 10.1134/S1063785016050205Using the deposition of multilayer systems, it is possible not only to model the structural state of each separate layer, but also to select the necessary thickness, material, and number of layers per period so as to create artificial structures possessing unique functional properties [1][2][3][4][5].In single-layer coatings based on MoN and CrN, the structure and properties can be varied within broad limits depending on the voltage applied to a substrate and the pressure of nitrogen-containing atmosphere during deposition [6,7]. For this reason, one can expect high sensitivity for these parameters for the structural states and properties of coatings obtained using MoN and CrN as component layers in a multilayer system. The most significant effects can be expected in systems with component layer thicknesses in a nanometer range, which is related to the fact that the highest mechanical properties of nitrides are observed on this scale [8,9].The present work was devoted to studying the influence of negative bias voltage -U s (which determines the energies of deposited particles) and the pressure of nitrogen-containing atmosphere in the reactor chamber (determining the content of nitrogen in the deposit) on the structural-phase state of deposited layers (structure engineering) and their mechanical properties (in particular, hardness).The samples of multilayer coatings of the MoNCrN system were obtained by vacuum-arc-deposition in a modified setup of the Bulat-6 type [10]. The pressure of working (nitrogen-containing) atmosphere during deposition was varied within P N = (7-30) × 10 -4 Torr and the deposition rate was about 3 nm/s. The component metals (Mo and Cr) were supplied from two sources (evaporators) to substrates continuously rotating at 8 rpm, which allowed component layers with thicknesses about 10 nm and coatings with a total number of component layers of up to 960 (480 bilayers) and total thickness of about 9 μm to be obtained. During deposition, a constant negative voltage of -U s = 20, 70, 150, or 300 V was applied to the substrates.The structural-phase state of samples was studied by X-ray diffraction ...

Scanning electron microscopy with energy dispersive element microanalysis, X ray structural analysis, and microindentation were used to study the effect of the deposition conditions in a reactive nitrogen atmosphere on the growth morphology, phase composition, structure, and microhardness of vac uum-arc multilayer coatings produced by the evaporation of cathodes from Mo and (Ti + 6 wt % Si) both after their deposition and after high temperature annealing. It has been established that the use of the composite cathode of Ti and Si allows the formation of the structure state inclined to ordering to form a two phase compound from TiN and Ti 5 Si 3 at high temperature annealing. In this case the coating hard ness increases to a value higher than 45 GPa.