The work investigated roller knives made of tool steel X12MF with a nickel–copper coating applied by diffusion alloying and subsequent intensive plastic deformation (IPD) with contact stresses from 3.0 to

4.5 GPa. The following methods were used: optical and transmission electron microscopy; X-ray diffraction and microrentgenospectral analysis. Tribological and corrosion tests, measurements of microhardness and roughness were carried out. It is shown that after applying Ni–Cu coating and IPD at a voltage of 3.5 GPa, there was not only a decrease by 2 times in the coefficient of friction, 2.1 times wear, 2.5 times the roughness of the roller surface, compared with uncoated steel, but also an increase in the setting load to 1400 N. At the same time, a dislocation substructure was formed in the coating with a minimum size of 23 nm coherent scattering regions and a maximum value of 1.25 % microdeformation of the crystal lattice, which indicated the presence of large elastic distortions of the crystal lattice. The transverse size of dislocation subgrains (small areas inside the crystalline grains, separated by small-angle boundaries, which consist of dislocation grids formed during deformation and creating an internal substructure) (35—47 nm) decreased by 5 times compared to the initial state (200—256 nm). In the high-resolution mode, the presence of predominantly small-angle boundaries in the coating structure was detected, which had a greater penetrating ability to redistribute alloying elements. It can be assumed that chromium from steel X12MF, being in solid solution, was redistributed along the small-angle dislocation boundaries of the elongated polygonized nanostructure. In the coating, an increase in the concentration of Cr, compared with the initial state, led to an increase in its relative resistance to wear and corrosion.

Despite high thermal-oxidative stability and chemical inertness, standard perfluoropolyether lubricants are susceptible to catalytic decomposition at high temperatures in the presence of metals, leading to corrosion and limiting their use. A solution to this problem may be the use of perfluoroalkyl-substituted triazines, which exhibit significantly higher corrosion-oxidative stability. The aim of this study was to evaluate the feasibility of using synthesized perfluoroalkyl-substituted polytriazines (PFPT) with molecular weights ranging from 932 to 2920 as lubricants and compare their tribological properties with those of the commercial perfluoro-polyether (PFPE).

A number of PFPT samples (bis-triazines and oligotriazine) were studied by DSC, TGA methods and boiling points were determined. Tribological tests were carried out using the plane-to-plane design (ShKh15 steel/12Kh1 steel) at room temperature. The average friction coefficient (f_av) was determined for each PFPT sample, with f_av consistently increasing with increasing PFPT molecular weight. It was shown that the friction coefficient of PFPT (0,12—0,18) is comparable to that of PFPE (0,13) and significantly lower than that of dry friction (0,27).

The results confirm the potential of PFPT as chemically inert and thermally stable lubricants. Their tribotechnical characteristics are comparable to those of commercial PFPE, indicating the possibility of combined use or replacement.

Results of evaluating the tribotechnical characteristics of polymer composite materials based on lowdensity polyethylene PE273, modified with various fillers: polyethylene wax (5 %), graphite with carbon black (15 %), and ultra-high molecular weight polyethylene (5 % UHMWPE), are presented.

The aim of the work was to evaluate the friction coefficient during contact with snow and the wear resistance of the materials under conditions of dry friction at extreme load-speed parameters.

The studies were conducted using a specialized tribometer, simulating ski operating conditions, and a 2070 SMT-1 friction machine. It was found that the introduction of 5 % UHMWPE into the base polymer reduces the friction coefficient by a factor of 2—3 (to 0.02—0.08) in the temperature range from –10 °C to 0 °C. Furthermore, this composition-maintained operability at friction over steel at velocity 0,5 m/s at contact pressures up to 1.0 MPa, while other studied composites failed at 0.75 MPa.

The results of the work are of practical importance for the development of sliding surfaces for sports and transportation means operating under extreme conditions of temperature and load.

The purpose of the study is to determine by finite element method the stress-strain state and behavior of the contact interactions characteristics under various loading conditions of the liner-shaft system, which is used for materials research when operating under conditions of frictional and mechanical fatigue. The cases of loading the system with different ratios of contact forces applied to the liner and bending forces applied to the shaft are considered. The verification of the obtained results is carried out using beam theory and contact theory. According to the results of the study, it is shown that depending on the direction and magnitude of the bending load, it is possible to form contact area of three different shapes: rectangular, elliptical and divided into two parts. Furthermore, optimal load ratios minimizing the von Mises stresses were identified: in the liner with co-directed F_b and F_N at a ratio of F_N/F_b = 20—50 (e.g., at F_N = 500 N, F_b = 25 N); in the shaft with oppositely directed F_b and F_N at a ratio of F_N/ F_b = 20 (e.g., at F_N = 500 N, F_b = 25 N). Thus, the presented approach to modeling volumetric damage in a friction pair, one element of which is loaded by a non-contact force, provides an opportunity to solve optimization and damage management problems for complex technical systems by controlling boundary conditions without costly design or material changes.

The elemental composition and chemical bonds in a diamond-like carbon film on the surface of a tungsten-cobalt alloy base were studied using X-ray photoelectron spectroscopy. The ratios sp²/sp³ bond fractions were determined using various parameters of the CKLL Auger spectra excited in X-ray photoelectron spectrometers; the average values were 0.32/0.68. It was revealed that the tribological interaction of a counterbody in the form of an aluminum oxide ball with the base material begins with a friction coefficient of approximately 0.4, and with the diamond-like film surface with a friction coefficient of approximately 1.0. With further sliding, starting from approximately 25,000 sliding cycles, the friction coefficient with the tungsten-cobalt base increases to ~ 0.65, and the friction coefficient with the diamond-like film drops to values of ~ 0.50. In the range of 20,000—25,000 sliding cycles, the friction coefficient of the counterbody on the diamond-like film drops to ~ 0.32, then returns to 0.62. The values characterizing the wear of the counterbody when interacting with a hard alloy base are higher than when interacting with the surface of the diamond-like film. The obtained results confirm that films of this type are technologically feasible for use in friction units that require a combination of high deformation resistance under heavy loads and high corrosion resistance at high temperatures and in adverse environmental conditions.

A new approach to measuring wear in sliding friction units based on the use of cluster analysis of acoustic emission signals accompanying the operation of the triboassembly is proposed and experimentally investigated. A special feature of the proposed approach is that the contribution of each mechanism of damage to the friction unit, identified in a multidimensional field of acoustic emission features with a time reference for their manifestation, is taken into account in the total wear, which makes it possible to track the dynamics of wear of the friction unit directly during observation (measurement). The study was conducted by comparing the use of two promising threshold-free clustering algorithms for acoustic data relative to the standard amplitude threshold method for detecting and identifying acoustic emission events, which allowed us to gain an idea of the advantages of the proposed approach relative to the current level of development of this type of technology. The results showed that the use of multiparametric cluster analysis to detect the type of damage (wear) mechanism allows for a minimum 45 % increase in the probability of detecting friction surfaces setting compared to the amplitude threshold method, while maintaining the probability of detecting a bully at the same level. It has been found that the proposed approach makes it possible to estimate wear without stopping the friction unit with an average discrepancy in the wear assessment between alternative methods of measuring wear and the proposed one at an average level of 16 % throughout the measurements. The results obtained allow us to consider the proposed approach as a promising on-line method for acoustic emission diagnostics and monitoring of the technical condition of sliding friction catches.

The article is devoted to the study of the prospects of using aluminum alloy parts with an oxide-ceramic coating applied to the friction surface by the method of microarc oxidation in friction units operating due to lubrication by the liquid medium in which they operate or which is pumped by this mechanism. Such mechanisms and friction units include elements of pumping and compressor equipment used in the oilfield industry (shut-off valves, parts of centrifugal, vane, slide, gear and other pumps, some threaded connections). In this situation, the coupled friction surfaces are constantly lubricated by the working medium (water, oil, water-oil emulsions).

Tribotechnical tests were carried out on a laboratory installation, the friction unit of which consisted of a rotating roller made of aluminum alloy of the AMg6 brand and a tape made of aluminum foil of the AD1 brand with a thickness of 100 microns sliding along it. An oxide-ceramic coating was applied to both parts by microarc oxidation. A solution containing sodium liquid glass in the amount of 13 g/l and potassium hydroxide in the amount of 2.5 g/l was used as the electrolyte. The oxidation process was carried out in a symmetrical anode-cathode mode using industrial alternating current with a frequency of 50 Hz at a constant current density of 6 A/dm² to a final voltage of 400 V.

Laboratory tests have shown that aluminum alloy parts with an oxide-ceramic coating can be successfully used in friction units characterized by low contact pressures and sliding speeds. At the same time, the very high corrosion resistance of oxide-ceramic coatings protects friction units from the effects of aggressive me-dia (reservoir water with increased mineralization, water-oil emulsions containing hydrogen sulfide, carbon dioxide), as well as from abrasive particles always present in the extracted and accompanying fluids. The use of aluminum alloys in friction units with a surface hardened by microarc oxidation will reduce the weight of pumping and compressor equipment, for example, submersible multistage pumping units, which reduces the cost of lifting operations, and will also improve the operational reliability and durability of oilfield pumping and compressor equipment.

This article presents a method for determining the friction coefficients of an antifriction coating based on silver with the addition of molybdenum disulfide or graphite in a vacuum. The method of determining the coefficients of friction is implemented on a vacuum tribometer. The dependences of the friction coefficients in the contacting pair are obtained — steel SHX-15 and an antifriction coating based on silver with the addition of molybdenum disulfide, and in another case graphite, depending on the ambient pressure. The value of the average coefficient of friction in a pair of a ball made of SHX-15 steel and a ring with an antifriction coating containing 94 % silver and 6 % molybdenum disulfide at an atmospheric pressure of 1000 mbar is 0.114 with a standard deviation of 0.012, and at a pressure of 0.03 mbar 0.168 with a standard deviation of 0.01.

For an antifriction material based on silver with the addition of 6 % graphite, the coefficient of friction varies from 0.144 to 0.26 when the pressure changes from 1000up to 0.03 mbar. Analytical dependences of the coefficient of friction for both antifriction materials on the height of lift in the atmosphere have been obtained, which will make it possible to develop a methodology for calculating spherical articulated bearings for high-altitude aircraft.

This article examines the gear transmission of a two-stage gearbox as a tribological system whose performance is determined by friction conditions and the contact fatigue endurance of the tooth surfaces. The geometric parameters of the transmission were calculated and contact and bending stresses were analyzed using the APM WinMachine software package. It has been shown that when using steel 45 with heat treatment — hardening with high tempering, the acting contact stresses reach the maximum permissible values, which leads to intensive wear and a short transmission life. To improve durability, it is proposed to replace the gear pinion and wheel material with 20CrNi structural alloy steel with a chemical-thermal carburization treatment, which reduces the relative level of contact stresses and increases contact endurance. An analysis of the influence of loading cycle parameters on the contact and bending stresses determining the nature of tooth wear is conducted. It is shown that for cemented gears, the calculated fatigue stresses do not depend on the cycle parameters, which indicates increased stability of the tribological characteristics of the transmission.