The wear resistance of diamond-like a-C:H coatings deposited onto substrates of R6M5 steel through intermediate Ti-C layers with a titanium concentration of 10 to 90% is studied. The a-C:H coatings with a thickness of 1500 nm are fabricated via the destruction of acetylene in the plasma of a non-self-maintained discharge generated by an electron beam in a mixture of acetylene and argon. Intermediate Ti–C layers with a thickness of ~100 nm are fabricated by the arc sputtering of a titanium alloy (VT-1-0) cathode in the acetylene-argon plasma of a non-self-maintained discharge. The partial pressure of argon is kept constant (0.03 Pa), and that of acetylene varied from 0.01 to 1 Pa. An increase in the acetylene pressure is accompanied by a decrease in the titanium concentration in Ti–C. Testing the coatings in a jet of silicon-carbide particles with an average size of 100 microns, incident normally to the surface at a speed of 10 m/s, shows that the composition and structure of the intermediate layers have a significant effect on the stability of a-C:H coatings. An increase in the carbon content in the Ti–C structure leads to a decrease in the size of crystal inclusions in the amorphous matrix, increasing the probability of the formation of interphase boundaries that inhibit the movement and generation of dislocations (the source of crack origin), the advance of which destroys the hard coating. Amorphous carbon in Ti–C provides good interlayer adhesion. During the deposition of a-C:H on Ti–C, there is a cohesive bonding between the same phases (carbon) and adhesive bonding between different phases (carbon and titanium carbide).

The composition, structure and corrosion behaviour of CrxAly(SOC coatings fabricated by the arc discharge techniques using Cr-Al-Si and graphite cathodes were studied. X-ray photoelectron spectroscopy, X-ray energy-dispersive spectroscopy, nuclear reactions, and Rutherford backscattering methods were applied to determine composition of the coating, X-ray diffraction and transmission electron microscopy - to investigate the structure of the coating. Corrosion tests were performed in an electrochemical cell in a 3.5%NaCl solution. Depletion of the cathode surface of chromium, screening of Cr+ by C+ in plasma, and selective etching of the coating upper layers are accompanied by a decrease of Cr/(Al +Si) ratio in the coatings compared to the cathode. The carbon content (C-C) in CrxAl(Si)(y)C, determined by XPS, EDS and NR, differs by several times. The C-C, measured by NR correlates with the results of Raman spectroscopy and confirms the existence of a continuous carbon matrix in CrxAly(Si)C. Cr is chemical bonded with carbon, silicon - with carbon and aluminum. The Al-Si system provides the structure feature of CrxAl(Si)(y)C: a network of aluminum intersects the amorphous matrix. The mechanical mismatch and weak bond between the Al structures and the amorphous matrix may be the reason for the formation of defects in the form of cracks and microchannels along the boundaries.

The wear-resistant coatings formed by the vacuum ion-plasma codeposition of titanium and carbon have been studied in this work. Single-layer and multilayer coatings with the systematically repeated [(Ti1 – xCx/a-C] pair are deposited onto P8M5 and 18KhN10T steel substrates. The highest erosion resistance is inherent in the multilayer [Ti0.2C0.8/a-C]40 coating with a layer thickness of 25 nm. The erosion wear rate of this coating is 1.6–1.8 times lower than the wear rate of the single-layer а-С and Ti0.2C0.8 coatings. The wear of [Ti0.2C0.8/a-C]40 occurs layer by layer without crumbling of individual square sections of the coating, thus increasing its service life. The interphase boundaries in the Ti0.2C0.8 composite layer, as well as the Ti1 ‒ xCx → а-С interface boundaries, serve as a barrier for the propagation of microcracks, decreasing the probability of macrocracking, which destroys the continuity of a coating.

There were investigated tribological properties of CrAlSiC coatings deposited by two techniques. In both techniques a plasma source of a cathode-arc discharge with Cr-Al-Si composite target served the source of Cr, Al, and Si atoms during coating deposition. A plasma source of a pulsed cathode-arc discharge with graphite cathode and a gas discharge device to generate a non-self-sustained discharge in argon-acetylene mixture have been used for generating carbon plasma in first and second techniques, correspondingly. First coating has a low coefficient of friction. Under frictional action, coating wears out uniformity without chipping. Second coating is less resistant to frictional action.

CrAlSiC films deposited under various conditions of carbon-plasma generation (PVD or PACVD) are investigated. A plasma source of cathodic-arc discharge with a Cr–Al–Si cathode and a source of pulsed cathodic-arc discharge with a graphite cathode are used for the deposition of a CrAlSiC(I) film. A plasma source of cathodic-arc discharge with a Cr–Al–Si cathode and a gas-discharge device for generating a non-self-sustaining discharge in an argon-acetylene mixture are applied for the deposition of a CrAlSiC(II) film. The sources work together in both processes. The film structure is investigated using electron microscopy and Raman spectroscopy. The hardness and elasticity modulus are determined by nanoindentation; the friction coefficient is tested with the reciprocating motion of a steel ball without lubrication. It is found that the condition of generating carbon plasma (graphite sputtering or destruction of acetylene) has a significant effect on the structure and properties of CrAlSiC. CrAlSiC(I) consists of an amorphous phase with inclusions of silicon-carbide nanograins 10–30 nm in size. On the surface there are protrusions with a size of 2–4 µm. These features provide a high hardness and low friction coefficient. No crystalline formations are found in the amorphous matrix of CrAlSiC(II). On the surface there are bubble-like formations up to 15 microns in size. This coating is inferior to CrAlSiC(I) in terms of hardness and resistance to friction. Under friction the film is destroyed by chipping fragments. CrAlSiC(I) can be recommended for practical application.

The paper examines carbon 0.5-1µ thick coatings obtained through various physical vapour deposition and chemical vapour deposition methods on stainless steel and tool steel substrates. Their composition, morphology and physical properties have also been studied. The correlations of erosive wear resistance and H3/E2ratio (where H is hardness and E is elastic modulus) have been identified for carbon coatings in regards to the production method. Ta-C carbon coatings demonstrate high resistance to dynamic loads with erosive wear in a sand-blast machine.

The main features of high-voltage electropulse consolidation (H-VEC) of powder materials and the unique possibilities of the method caused by them are considered. The electrothermal processes in the H-VEC at the contacts between the powder particles and in the macroscale of the whole consolidated sample are analyzed. The results of calculations of the dynamics of closure (collapse) of interparticle pores in the consolidated material are presented.

The field of applicability of bending of thin disks test on an annular support and the “Brazilian test” for short cylinders is discussed. These methods are used to determine the tensile strengths of the materials formed by electric pulse powder consolidation. These techniques of testing small samples make it possible to study the influence of technological factors on the strengths of the consolidated materials.

CrAlC and CrAlSiC films have been obtained and investigated. Simultaneous sputtering of graphite and Cr05Al05 or Cr035Al055Si0 08 targets was used for films deposition. The structure of the films is amorphous-nanocrystalline. The doping of CrAlC films with silicon is accompanied by an increase in their crystallinity due to the formation of silicon carbide particles. Structural changes make CrAlSiC films harder with a higher resistance to plastic deformation.

Single CrAlC, CrAlSiC and multilayer [CrAlC/a-C]n, [CrAlSiC/a-C]n coatings have been fabricated and investigated. Joint use of arc plasma source with Cr-Al(Si) cathode and pulsed arc plasma source with graphite cathode was applied to single coatings deposition. Diamond-like a-C layers alternate with CrAl(Si)C in multilayer coatings. The doping of CrAlC with silicon is accompanied by an increase in their crystallinity due to the formation of silicon carbide particles. Structural changes make CrAlSiC films harder with a low friction coefficient and a high resistance to plastic deformation. The multilayer coatings are crack resistant.

The structures, wear resistances, and corrosion behaviours of Cr-Al-C and multilayer [Cr-Al-C/a-C](n) coatings, fabricated by physical vapour deposition (PVD), plasma-assisted chemical vapour deposition (PACVD), or their combination, were studied. A Cr-Al target served as a source of chromium and aluminium, while a graphite target or acetylene served as sources of carbon. Depending on the type of carbon source, Cr-Al-C or Cr-Al-C(H) coatings were obtained. Multilayer [Cr-Al-C/a-C](20) and [Cr-Al-C(H)/a-C:H](20) coatings were fabricated by alternating pair layers of [Cr-Al-C (PVD)/a-C (PVD)] and [Cr-Al-C(H) (PVD-PACVD)/a-C:H (PACVD)], respectively. a-C and a-C:H are hydrogen-free and hydrogenated diamond-like carbons. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy were employed to investigate the coating structures. Along with the amorphous matrix, chromium carbide, and CrxAl1-xC nanograins, clusters of nanocrystalline graphite as spherical inclusions and plates, probably of several graphene layers, were observed in Cr-Al-C. This structure provided high hardness and corrosion resistance. Along with the amorphous matrix, Cr2AlC and chromium carbide nanoclusters and clusters of nanoscale CVD diamond with wide boundaries of sp(2) bonded carbon were observed in Cr-Al-C(H), whose hardness did not exceed 8.9 GPa. The multilayer structures significantly increased the wear resistances. The specific coefficient of wear rate (SCWR) of [Cr-Al-C/a-C](20) was five times lower than that of Cr-Al-C. Hybrid PVD-PACVD technology provided favourable conditions for the formation of wear-resistant coatings. The SCWR of [Cr-Al-C(H)/a-C:H](20) was 47 times lower than that of [Cr-Al-C/a-C](20). The high wear resistance of the multilayer coatings was associated with the structure, low friction coefficient, high crack resistance, and strengthened interface boundaries.

A method is proposed for determining the elastic modulus of a material from the results of bending tests performed on a prismatic sample using simultaneously the method of digital correlation of images for precise measurement of the displacements of points in the sample. This procedure was tested in three-point bending of steel and graphite samples. The effect of the ratio of the distance between the supports to the height of the cross-section of the sample on the reliability of the determined elastic modulus of the material is evaluated. The values obtained for the modulus of elasticity of steel and graphite agree with the characteristic values for the investigated materials when the ratio of the distance between the supports to the height of the cross-section of the sample is greater than 7.

Numerical simulations of the neck formation during tension of cylindrical specimens have been carried out in an approach of simplified elastoplastic properties of the material and large strains. The results have been compared to those of a similar simulation done in another computation code. Regularities of the strain localization and neck development, dependence of the neck location on elastoplastic properties of material, in particular, on strain hardening modulus are illustrated. Tensile tests of cylindrical samples of different types and sizes have been carried out. It has been shown that in the samples of the same type and sizes made of the same material, the neck is formed dominantly on the same place. Strain diagrams of materials obtained in tests are transformed into true stress - strain diagrams. These diagrams have been used as models of the elastoplastic behavior of materials in simulations of the neck formation on models imitating the experimental samples. A qualitative agreement of the test and numerical simulation results have been obtained. In simulations of the neck formation, in some cases the formation of a pair of symmetrically located necks have been found. This prediction was verified in tensile stress experiments with real time registration of deformation by the method of digital image correlation. It has been found that following the stage of uniform straining, two symmetrically located regions of concentration of transverse strains are formed. Eventually one of these regions breaks up, while the second one gives rise to a neck, which in turn results in the failure of the sample.

The article provides an experimental basis for application of the disk sample loaded by the Brazilian test method (disk compression in the diameter plane) for the brittle strength assessment of the metallic materials during testing of the small-sized samples. The research presents a strong correlation between strength of the cast iron, assessed by the testing of disk samples and the tensile strength. The method was used to study the mechanical properties of heavy tungsten pseudo-allows obtained by exposure to high-voltage electric pulse.

The article presents results of design analysis of stress and strain in the disk sample loaded by the Brazilian test (disk compression in the center plane). The research established correlations of the diameter and thickness of the sample acceptable to obtain reliable values of material strength in response to stress. Presented a strong relation of average tensile stresses in the central area of the disc to the stress parameter used to determine the strength of brittle rock materials