This work investigates the mechanical properties and tribological characteristics of TiN (single layer) and TiN/a-C (double layer, two types of combinations of elastic-plastic properties of media) coatings based on experimental and theoretical approaches. The microstructure of the synthesized coatings and the relief of the front surface were examined using a scanning electron microscope. The analysis of the conformity of the a-C coating was performed using the disturbed total internal reflection method with an IR Fourier spectrometer. The hardness and reduced elastic modulus of the samples were determined through continuous indentation using a Berkovich pyramid. The intensity of wear and the friction coefficient were determined in a sliding friction mode. The findings of a thorough experimental investigation into the coatings were instrumental in formulating a finite element model of indentation into a two-layer elastic-plastic medium, incorporating varied combinations of elastic and plastic characteristics, as well as distinct relative layer thicknesses. The correlation between the parameters of the considered coatings H/E and H³/E² and the wear intensity was established through experimental means. Theoretically, the functional dependencies of hardness and reduced elastic modulus on the relative thickness of the face metastable layer a-C were established. The optimal thickness ratio of the TiN/a-C coating layers has been determined for given elastic-plastic characteristics of the materials. Such a coating will exhibit optimal tribological characteristics.

Using X-ray structural, X-ray phase, and light metallographic microscopy, the mechanisms of the influence of lubricant compositions based on a dispersion medium — C₅–C₉ pentaerythritol ether (TEPE of the surface layers of BrA5 bronze after its friction with St45 steel were studied. Concentrated surfactants (surfactant-like agents) were used as dispersed phases (thickeners): lithium soap of 12-hydroxystearic acid (12-LioSt), calcium soap of 12-hydroxystearic acid (12-CaoSt), and complex calcium soap, which includes a composition of salts of 12-hydroxystearic and acetic acids (k-Ca). It has been shown that after friction of bronze, there is a variable change in the yield strength of the surface layer of the samples in all lubricant compositions (the Rebinder and Roscoe effects). The appearance of internal residual stresses in this layer as a result of tribo-deformation includes a mechanism of upward diffusion, which causes a concentration redistribution of components in the material, up to a complete cleaning of the subsurface layer from the atoms of the alloying element (selective transfer mode). It has been shown that the adaptive changes in the mechanical characteristics of the material (positive or negative) and its wear resistance depend on the colloidal-chemical indicators of the surface and oxidative activity of the lubricant composition (hydrophilic-lipophilic balance). Thus, adding 12-LioSt to the basic TEPE C₅–C₉ environment reduces the wear rate of bronze by 1.3 times, adding k-Ca reduces it by 6.5 times, and adding 12-CaoSt increases it by 10 %.

The need to use Solid Lubricating Coating (SLC) arose already with the launch of the first space satellites, in which cold welding of articulated joints took place. SLC have the following main advantages [1, 2, 4]: low evaporation in a vacuum, low friction coefficient, and performance in zero gravity. They can be used in outer space conditions over a wider temperature range than frost-resistant plastic lubricants. The selection of the most suitable SLC [3-6] requires a thorough study of their tribotechnical characteristics depending on the design of friction units, frictional interaction parameters, and environmental characteristics. SLC are capable of operating in a wide range of temperatures in air, vacuum, and gas environments; they have a radiation resistance of 10⁶—10¹⁰ rad depending on the binder; they are capable of withstanding high contact loads and are insensitive to zero gravity. The most widespread SLC are in the form of suspensions of solid lubricant with a binder, applied by a spray gun with subsequent curing by heat treatment. A wide range of coatings has been developed: VNIINP-213, VNIINP-512, VNIINP-513, APF-5, EONIT-3 and Dimolits.

We conducted tribological testing of the above coatings using various friction pair configurations, in air and vacuum, at various temperatures, and across a wide range of loads and sliding speeds.

These data are important for selecting coatings for friction components being developed for spacecraft.

It is shown that during drilling, cleaning of drilling solution using centrifugal decanters minimizes the presence of abrasive particles in the system and reduces mechanical wear of structural elements and pumping units. The results of a comparative analysis of the resource of the initial nozzle design and three proposed modifications, differing in surface geometry and orientation relative to the direction of rotation of the drum, are presented. A comprehensive assessment of the effect of design changes on the particle escape velocity and, as a result, on the wear rate was carried out using an analytical model for calculating the amount of wear during particle impact.

A discrete-element model of the processes accompanying the operation of a centrifugal decanter (movement of drilling solution along the centrifuge screw) has been developed. The time before the formation of critical wear (destruction) of the nozzle surfaces is calculated. The influence of geometric and design param-eters of centrifugal decanter nozzles on the efficiency of the drilling solution cleaning process has been studied. It is shown that reducing the height and diameter of the nozzles to 34 mm and 37 mm, respectively, increased the surface wear time by 1.5 times.

An analytical evaluation of the resource of cylindrical nozzle surfaces for various design options has been performed. A significant increase in service life is achieved by changing the inclination of the cylindrical surfaces of the nozzles against the direction of rotation of the drum. The wear time of the nozzle surface increases 12.5 times.

The study presents the results of an investigation into the tribological properties of hardening discrete coatings in vacuum, as well as composite coatings based on them with the addition of a solid lubricant layer. The subject of the research is discrete coatings based on thin TiBN films, formed by magnetron sputtering of material through photoresist masks of various geometric configurations, using explosive photolithography technology. Composite coatings were produced by magnetron deposition of a solid lubricant MoS₂ layer onto the discrete TiBN coating. The study evaluates the influence of the discrete structure geometric parameters (characteristic size of discrete elements, coating continuity, and thickness) on wear resistance and the coefficient of friction. It also examines the failure mechanisms of the investigated coatings under high contact loads in vacuum conditions.

Steel plates made from 12Сr18Ni10Ti (AISI 321 equivalent) sheet were used as substrates. The wear-resistant TiBN coatings were deposited by magnetron sputtering of a TiB target in an argon and nitrogen environment. The solid lubricant coatings were deposited by magnetron sputtering of a stoichiometric MoS₂ target in an argon environment. Tribometric tests of the coated samples were carried out using a high-vacuum tribometer equipment in a “sphere-on-flat” configuration, employing a strain gauge measurement system. Scanning electron microscopy was used to analyze the morphological features of wear tracks. Discrete TiBN coatings with characteristic element sizes ranging from 460 mm to 805 μm and continuity values from 0.25 to 0.7 were used in the study; the coating thickness varied from 0.88 mm to 2.11 μm.

The results demonstrate a significant influence of the discrete structure parameters on the tribological performance. Samples with discrete elements of 700 μm in diameter, 1 μm in thickness, and 0.6 continuity showed the best wear resistance and the most stable coefficient of friction. Incorporating a solid lubricant MoS₂ layer into the discrete coating significantly reduced the coefficient of friction to the range of 0.03—0.07 and improved frictional stability during prolonged operation in vacuum.

These findings confirm the promising potential of using discrete hardening coatings combined with solid lubricant layers for tribological units operating in extreme conditions. The proposed approach can be applied to extend the service life of components in vacuum and space equipment.

Mining of solid minerals is associated with increased metal consumption of the tool used, which is associated with wear resistance, therefore, in order to reduce the metal consumption of the industry, it is necessary to increase the wear resistance of the tool. The matrix structure for excavator bucket teeth is martensite, but as a rule, not only the hardness determines the metal's ability to resist wear, but also a certain proportion of plasticity and viscosity. An analysis of operational experience provides some information regarding the durability of teeth with various mechanical properties, but there are still no scientifically sound requirements for the choice of material for excavator bucket teeth.

The aim of the work is to determine the optimal chemical composition and final heat treatment to provide the necessary set of mechanical properties of the metal teeth of the excavator buckets, depending on the operating conditions.

Experimental samples were produced in induction furnaces with a capacity of up to 120 kg. The heat treatment of the samples consisted of quenching in oil and high or low tempering for each sample. The wear resistance test was carried out on an installation representing a sample fixed in the spindle of the machine, which makes a transverse movement and simultaneously rotates around its axis.

Steel with 0.4 % C (1720 MPa temporary resistance) has the highest strength indicators compared to

0.3 % C (1680 MPa) at the same level of plastic characteristics. An analysis of the wear resistance test results showed the most severe wear conditions for SiC abrasives with a dimension of 200 microns (66—71 m/g; 82—89 m/g). The high hardness of the steel after quenching and low tempering guarantees better wear resistance of 130—133 m/g, compared with quenching and high tempering of 95—110 m/g. The main mechanisms of wear during wear are micro-cutting and plastic extrusion.

Taking into account the established requirements for steels for excavator bucket teeth, the corresponding 30KHGNMFL (No. 1) steels are recommended for various rock conditions, where high wear resistance and cold resistance are required, and 40KH2GN2MFL (No. 3) steel for a more temperate climate. Low tempering after quenching is recommended for a more temperate climate, quenching and high tempering are necessary to ensure cold resistance.

The article demonstrates the relationship between a decrease in energy efficiency and the load-carrying capacity of worm gears with an increase in the amplitude of torque oscillations as the mating load increases. An analysis of the causes of the increase in the amplitude of torque oscillations with increasing gear load is conducted. It is shown that the disruption of the self-oscillation mode occurring in a worm gear should occur due to an increase in the friction coefficient, which depends on the lubrication conditions, in particular, on the thickness of the lubricant film. The paper demonstrates that in the case of lubrication of the gear with standard mineral oil with a nanomodified additive, the loss of stability of self-oscillations occurs at significantly higher loads (290 N×m) than in the case of lubrication with standard mineral oil without the additive (230 N×m), which indicates greater resistance of this option to disturbing effects, and can be explained by the greater thickness of the lubricant film. In this paper, graphs of the worm gear efficiency versus braking torque were obtained for various lubricant options. It was shown that the increase in efficiency when using standard mineral oil with a nanomodified additive (a nanodispersed suspension of serpentine in a solution of fatty acid salts) compared to standard mineral oil is associated with improved antifriction properties of the coupling and a decrease in the amplitude of torque oscillations. The paper demonstrates that the stability of the worm gear under loading effects can be experimentally assessed by measuring the amplitude of torque oscillations on the high-speed shaft of the gear. To expand the range of permissible loads, it is necessary to improve the antifriction properties of the lubricant by using a nanomodified additive, which leads to a decrease in the amplitude of self-oscillations of the worm shaft, a decrease in the friction path, and a reduction in power losses.

The paper studies the microstructure, phase composition, mechanical properties and tribological characteristics of copper matrix composites of the Cu–Fe–FeCr–MoS₂–C system reinforced with TiC–Ti composite inclusions sized 100—140 and 140—200 μm. The composites under study were obtained by sintering under pressure, and the content of reinforcing TiC–Ti inclusions was 3 vol. %, 5 vol. %, 7 vol. %, 9 vol. % and 11 vol. %. It is shown that the hardness of the composites under study increases with the addition of metalceramic inclusions TiC–Ti increases to 15 HBW 10/250/30, which is more than 40 % higher than the hardness of the matrix composite. It is revealed that composites reinforced with TiC–Ti inclusions have greater wear resistance compared to the matrix composite without the introduction of reinforcing inclusions. It was found that the composite containing 7 vol. % TiC–Ti inclusions 100—140 μm in size has the highest wear resistance, and an increase in the inclusion content to 9 vol. % and 11 vol. % leads to an increase in the wear intensity of the composite. With the introduction of more than 7 vol. % TiC–Ti composite inclusions 140—200 μm in size, a decrease in wear resistance also occurs. The maximum friction coefficient is demon-strated by the composite reinforced with 11 vol. % TiC–Ti inclusions 100–140 μm in size, which is 0.36 ± 0.03, and with an increase in the inclusion size to 140—200 μm, the highest friction coefficient is observed with the introduction of 7 vol. % TiC–Ti.

Comparative physical and mechanical and tribotechnical studies of the effect of various C₆₀ fullerene contents in polymethylmethacrylate (PMMA) polymer films on sliding friction have been carried out during Finger-Disc testing. It is shown that an increase in the concentration of the fullerene modifier to 1 % leads to a decrease in surface roughness at the nanoscale and the coefficient of friction of PMMA paired with aluminum alloy D16. As the concentration of C₆₀ fullerenes in polymer films increases to 3 %, they coagulate and form inhomogeneously distributed nano-concentrators with a diameter of about 150 nm. At the same time, the tribological properties of polymer films deteriorate. The coefficient of friction of PMMA paired with aluminum alloy D16 increases compared to the initial state. With an increase in the content of fullerene C₆₀ in polymer films, their density and microhardness increase, and the burgundy color appears and unambiguously increases. When PMMA was rubbed in its initial state (without the addition of C ₆₀) in combination with aluminum alloy D16, adhesive processes were detected, and as a result, aluminum was transferred to the polymer film with an increase in the coefficient of friction. The studied films turned out to be heterogeneous in composition and properties, subjected to warping, with insufficient dispersion of the material at the nanoscale.

The effect of gamma irradiation on some physico-mechanical and tribological properties of VK-8 cemented carbide was investigated. Samples were CNMG 120408-46 indexable cutting inserts (manufacturer “Sandvik MKTS”, Russia) intended for turning. They were subjected to gamma irradiation at various doses from 20 to 200 kGy and in different gaseous environments (air and nitrogen). Irradiation was carried out on an industrial GUD-300M facility using ⁶⁰Co sources. Tests showed that after irradiation, a decrease in the electrical resistivity of the samples was observed, confirming the hypothesis of microstructure ordering in the irradiated material. Hardness measurements before and after irradiation did not reveal significant changes. However, a significant increase in the wear resistance of the material during cutting of various steels was established, from 1.5 to 6 times, depending on the absorbed irradiation dose, the steel being machined, and the cutting parameters. It is suggested that there exists an “optimal” level of gamma irradiation, below and above which the effect of radiation modification decreases. Determining this level requires separate tests for each material studied. Nevertheless, general trends of increased wear resistance have been established in this article.