O.V. Bondar

The effect of nanolayer thickness on the structure and properties of multilayer TiN/MoN coatings

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-Mo2N—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.

Influence of implantation of Au− ions on the microstructure and mechanical properties of the nanostructured multielement (TiZrHf VNbTa)N coating

It has been found that the phase with the fcc lattice of the NaCl structural type is formed due to the vacuum-arc deposition of the nanostructured multicomponent (TiZrHfVNbTa)N coating. Implantation of negative Au− ions with a dose of 1 × 1017 cm−2 leads to the formation of a disordered polycrystalline structure without a preferred orientation of the fcc phase and nanocrystallites from 5–7 to 1–3 nm is size, which are dispersed in a layer up to 35 nm in depth. Nanohardness increases to 33 GPa, and the Vickers hardness reaches 51 GPa. Gold nanoclusters are formed in the near-surface region, while the fcc lattice and the formation of local Au regions are observed in the coating itself. Fragments with the hcp lattice are formed at depths above 180 nm because of the low nitrogen concentration.

Comparison of tribological characteristics of nanostructured TiN, MoN, and TiN/MoN Arc-PVD coatings

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 cohesive failure with a minimum critical loading LC1 and an adhesive test (plastic abrasion) with the appearance of a first crack LC2. 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.

Composition, structure and tribotechnical properties of TiN, MoN single-layer and TiN/MoN multilayer coatings

Results of comprehensive investigations of nanostructed TiN and MoN single-layer coatings as well as multilayer coatings consisting of TiN/MoN alternating layers have been considered. The coatings have been deposited by a promising modern method of cathode-arc evaporation (vacuum-arc method). The elemental and phase compositions of coatings, their tribological and physico-mechanical properties: friction coefficient, wear, adhesion, hardness, and elastic modulus have been studied and the mechanisms of the coatings fracture have been discussed.

The effect of the deposition parameters of nitrides of high-entropy alloys (TiZrHfVNb)N on their structure, composition, mechanical and tribological properties

Nitrides of high-entropy alloys TiZrHfVNb produced using a vacuum-arc cathode evaporation have been studied using scanning electron and atomic force microscopies, energy dispersive, Rutherford ions backscattering, and X-ray diffraction analyses, microhardness measurements, and tribological tests. It has been found that the deposition parameters affect the structure, surface morphology, distribution of elements, mechanical and tribological properties of the coatings under study.

Structure and physicomechanical properties of NbN-based protective nanocomposite coatings: A review

This review summarizes the present-day achievements in the study of the structure and properties of protective nanocomposite coatings based on NbN, NbAlN, and NbSiN prepared by a variety of modern deposition techniques. It is shown that a change in deposition parameters has a significant effect on the phase composition of the coatings. Depending on the magnitude of negative potential on the substrate, the pressure of nitrogen or a nitrogen–argon mixture in the chamber, and the substrate temperature, it is possible to obtain coatings containing different phases, such as NbN and SiNx (Si3N4), AlN, and NbAl2N. It is found that, in the case of formation of the ε-NbN phase, the coatings become very hard; their hardness achieves values on the order of 53 GPa. At the same time, they remain thermally stable at temperatures of up to 600°C, chemically inert, and resistant to wear. The effect of the nanograin size, the volume fraction of boundaries and interfaces, and the point defect concentration on the physicomechanical properties of these coatings is described. Niobium nitride-based coatings can be used in superconducting systems and single-photon detectors; they are capable of operating under the action of strong magnetic fields of up to 20 T; they can be used in integrated logic circuits and applied as protective coatings of machine parts, edges of cutting tools, etc.

The microstructure of a multielement nanostructured (TiZrHfVNbTa)N coating and its resistance to irradiation with Au– ions

The formation of a phase with a FCC lattice of the NaCl structure type is observed following the deposition of a multielement nanostructured (TiZrHfVNbTa)N coating. An increase in pressure results in a change in the preferred orientation of crystallite growth from the [100] axis perpendicular to the growth plane to [111]. The implantation of negative Au– ions with a dose of 1 × 1017 cm–2 and a concentration of 2.1 at % leads to the formation of a disordered polycrystalline structure with no preferred orientation of the FCC phase, reduces the size of nanocrystallites from 8 to 1–3 nm in a layer with a depth of up to 30–35 nm, and increases the nanohardness to 33.0 GPa. The large difference in atomic radii of refractory metals and the reduction in the size of nanograins in the coating contribute to an increase in hardness (51 GPa).

Structural analysis of multilayer metal nitride films CrN/MoN using electron backscatter diffraction (EBSD)

The electron backscatter diffraction (EBSD) analysis method was used for studying structure and properties of multilayer nitride CrN/MoN coatings fabricated by cathode arc physical vapour deposition (Arc-PVD). Samples were deposited on steel substrate with different single layer thickness from tens nanometers to 1 micron and with total thickness of coatings up to 8-13 μm. Colour grains mapping, grain size distribution profiles, pole figures and texture analyses were the main research instruments. Studying of obtained coatings was performed on specially prepared polished cross-section samples. The dependence between single layer thickness and grain size of materials, which is also changing through depth profile of the coating, was observed. In addition, it was possible to study phase composition, prevailing crystals orientation, dominant texture and grains growth. Studying of grains size, as well as other indicated parameters, is a very important task because it gives an information about grains interfaces volume, which causes changes in mechanical properties of material. Obtained results were cross-checked by X-ray diffraction analysis (XRD) where it was possible.

Physical and Mechanical Properties of (Ti-Zr-Nb)N Coatings, Fabricated by Vacuum-Arc Deposition

By vacuum-arc evaporation of a multielement Ti + Zr + Nb cathode in a nitrogen atmosphere, (Ti–Zr–Nb)N coatings are deposited on steel substrates. The coatings are characterized by a columnar structure with nanosized (10–63 nm) crystallites of the main FCC nitride phase (Ti–Zr–Nb)N. At maximal nitrogen pressure PN = 4 × 10–3 Torr, an axial structure of growth of (Ti–Zr–Nb)N crystals with [111] axis is formed, and a maximal coating microhardness value about 45 GPa and adhesion strength of 67 GPa are reached. The friction factor for the system of “coating–Al2O3” is 1.1. Such coatings seem to having prospects as protective ones for couples of friction and cutting tools.

Influence of the bilayer thickness of nanostructured multilayer MoN/CrN coating on its microstructure, hardness, and elemental composition

Multilayer nanostructured coatings consisting of alternating MoN and CrN layers were obtained by vacuum cathode evaporation under various conditions of deposition. The transition from micron sizes of bilayers to the nanometer scale in the coatings under investigation leads to an increase in hardness from 15 to 35.5 GPa (with a layer thickness of about 35 nm). At the same time, when the number of bilayers in the coating decreases, the average Vickers hardness increases from 1267 HV0.05 to 3307 HV0.05. An increase in the value of the potential supplied to the substrate from–20 to–150 V leads to the formation of growth textures in coating layers with the [100] axis, and to an increase in the intensity of reflections with increasing bilayer thickness. Elemental analysis carried out with the help of Rutherford backscattering, secondary ion mass spectrometry and energy dispersion spectra showed a good separation of the MoN and CrN layers near the surface of the coatings.