Modification of ceramic coatings developed for friction units is an important area of research aimed at improving their tribological characteristics. This paper presents ceramic coatings formed on aluminum alloys B95 and D16 by the microarc oxidation (MAO) method in a single-stage technological process with inclusions of Al–Cu–Fe quasicrystals. The technology of rubbing quasicrystals into the coating surface during final polishing was also used. Friction and wear tests were carried out according to the ASTM G99 standard paired with a tungsten carbide ball. Analysis of the surface and cross sections by the SEM microscopy method showed that the modification affects the coating structure. Quasicrystals are concentrated in the pores and participate in the friction process. Addition of small amount of modifier to the electrolyte, as well as the rubbing technology, make it possible to reduce the friction coefficient and wear rate compared to purely ceramic coatings obtained on the B95 alloy. A larger amount of modifier gives a negative result. Adding a modifier to the electrolyte when forming coatings on D16 alloy leads to an increase in the friction coefficient and a decrease in wear resistance.

The aim of the work is to study the distribution of oxygen in the contact layer of steel 45 during pin-on-ring dry friction against C235 steel under high-density electric current (> 100 A/cm²).

The formation of a transfer layer on the contact surface of the counterbody and the formation of a melt on the contact surface of the transfer layer were shown by the electron microscopy method. The melt has weak signs of adhesive interaction, which is an indicator of high melt viscosity. X-ray spectral microanalysis of the contact surface of the transfer layer showed an oxygen content of 30 at. %, which serves as an indicator of FeO formation. The oxygen concentration corresponded to a concentration of about 60 vol. % FeO. The oxygen concentration in the cross-section of the transfer layer at a distance of 3 μm from the contact surface was about 10 at. % that corresponds to about 20 vol. % FeO. The X-ray phase analysis method established the predominance of FeO and α-Fe in the contact surface of the transfer layer of C45 steel, i. e. about 90 vol. % FeO. These data indirectly prove the existence of a FeO concentration gradient directed into the depth of the transfer layer and allow us to state that the melt consists of neutral atoms or ions of iron and oxygen.

An increase in the current density in the contact leads to an increase in the electrical conductivity of the contact and to a decrease in the friction coefficient. This allows us to assume an increase in the amount of melt in the contact space with an increase in the current density. An increase in the current density leads also to an increase in the sliding stage (“slip”) during sliding in the stick–slip mode and to a decrease in the friction coefficient. The obtained data can serve as a guideline in the design of current-collecting friction units for powerful electric motors and generators.

The article is devoted to the study of the possibility of reducing the cost of complex calcium sul-fonate grease (CCSG) through the use of by-products of the production of ultra-alkaline calcium sul-fonate (UCS).
The purpose of the work is to evaluate the prospects for the use of calcium compound concen-trate (CCC), a by-product of the production of ultra–alkaline calcium sulfonate, to reduce the cost of CCC production while ensuring a given level of their operational characteristics.
The article proposes a variant for the manufacture of CCSG based on sulfonated compounds of various origins and describes a method for monitoring the synthesis using infrared (IR) spectrometry.
The synthesis of CCSG samples based on ultra-alkaline calcium sulfonate and a concentrate of calcium compounds is described, with control of the lubricant manufacturing process using IR spec-troscopy and assessment of its rheological properties and tribological characteristics (penetration, drop point, colloidal stability, welding load, critical load). It has been established that samples of lub-ricants based on UCS and CCS demonstrate high performance characteristics comparable to their for-eign counterparts.
It is shown that the use of by-products of the UCS production is acceptable and advisable, while it opens up the possibility of reducing the cost and improving the environmental conditions of CCSG production.

A novel friction tester has been developed that simultaneously implements three types of mechanical effects on metal samples: oblique impact, rolling friction, and sliding friction. The main unit of the installation is a driver mounted on a shaft with indenters located in its sockets — steel rollers with a diameter of 32 mm and a weight of 0.2 kg. The mechanism is actuated by a servo drive, which allows smooth adjustment of the angular rotation speed in the range from 0 to 1500 min^–1. The indenters are made of quenched and low-tempered ball bearing steel. During the testing process, the rollers, freely located in the driver sockets, have the ability to rotate relative to their axes and roll along the surfaces of the samples. Under the action of the centrifugal force generated by the rotation of the driver, the rollers come into contact with the studied samples and wear them out. During one revolution of the driver, each of the samples is subjected to roller impacts twice. The impacts are carried out simultaneously, which reduces vibrations of the parts of the device. Tribological tests of Hadfield steel in the austenitic state, 95Cr6Mo3V3SiTi steel quenched and tempered at 545 °C, as well as boron- and chromium-alloyed alloy formed by the method of non-vacuum electron beam cladding were carried out using the developed device. The samples made of 95Cr6Mo3V3SiTi steel possessed the highest level of wear resistance. The features of the mechanisms of destruction of the surface layers of metal alloys are revealed.

The purpose of the work is to increase the efficiency of high-speed blade cutting of heat-resistant alloys based on improving the tribotechnical characteristics of wear-resistant coatings by developing and introducing multicomponent cathodes — targets from sintered high-entropy alloys when applied by the magnetron method.
At the preliminary stage, the composition of the powder material was selected; technologies for obtaining high-entropy target cathodes (with a diameter of 20 mm and 70 mm) obtained by high-temperature spark plasma sintering have been developed; control of their parameters is provided: density, grain-size analysis, electrical conductivity, hardness and crack resistance. The morphology of the sintered samples was examined by scanning electron microscopy and non-dispersive analysis. Technological equipment for magnetron coating system in various gas media is manufactured. Tribotechnical tests were carried out on tribometers and during blade cutting of various grades of steels and alloys, based on the results of which the most effective compositions of multilayer composite nanostructured high-entropy wear-resistant coatings were determined, in particular Al20Ti20Zr15V15Cr15Nb15 and Al20Hf10Ni15Ti25W10Zr20, providing improved cutting performance of chromium-nickel alloys EI654 and EI698 VD.
Comparative tests of commercially used wear-resistant coatings and coatings made of high-entropy target cathodes were carried out: Al20Hf10Ni15Ti25W10Zr20; Al20Ti20Zr15V15Cr15Nb15; Al20Hf15V15Cr15Ti15Ta10W10; Ti15Zr15Cr15Ni10W10V10Nb15Al10; Ti20Hf15Mo15W10V10Nb15Al15; Ti40Zr10Cr10Ni10W10Mo10Nb10 et al. According to the results of studies in the longitudinal turning of chromium-nickel alloys EI-654 and EI-698 VA, an increase in the efficiency of using high-entropy coatings on a cutting tool by an average of 20—25 % was confirmed.

This work presents a study on the development and evaluation of the tribological characteristics of metal matrix composites (MMCs) based on aluminum bronze CuAl7, reinforced with tungsten (W) and tungsten carbide (WC) particles, produced using electron beam additive manufacturing (EBAM).
The aim of the study is to obtain wear-resistant materials based on aluminum bronze with a surfaceengineered composite layer of CuAl7–W–WC and to investigate their tribological performance under dry sliding conditions at room and elevated temperatures in air.
The authors employed a combined wire–powder feed method, which enabled the fabrication of composite coatings with a uniform distribution of the reinforcing phase. Samples were produced from pure bronze (CuAl7), as well as composites containing 10 vol. % (CuAl7–W5–WC5) and 20 vol. % (CuAl7–W10–WC10) of reinforcing particles. It was established that the addition of W and WC significantly reduces the wear rate compared to pure bronze, while the friction coefficients of the composites remain comparable to those of the base material.
The wear mechanisms of the obtained MMCs were identified as predominantly oxidative, with the formation of a multilayered tribofilm containing copper and iron oxides, acting as a solid lubricant. The presence of reinforcing particles limits direct contact with the counterbody and suppresses plastic deformation of the matrix, thereby enhancing wear resistance. This study demonstrates the potential of EBAM technology for precise surface modification and provides new insights into the wear mechanisms of MMCs under hightemperature sliding conditions. The developed materials can be used in the manufacturing of components with enhanced wear resistance, such as those used in mechanical engineering and aerospace applications.

The structure and tribological properties of sintered Al–40Sn alloy reinforced with Al3Ti particles of different volume concentrations were studied. The composite samples were sintered at 710 °C for 1 hour and then compacted in a closed die at a temperature of 250 °C and a pressure of about 300 MPa. Wear resistance tests were carried out using a tribotester Tribotechnic (France) in the absence of lubrication according to the pin-on-disk scheme at a constant sliding speed of 0.6 m/s, increasing the load every 1000 m of friction path. A steel disk made of hardened grade 40X steel with a hardness of 48—50 HRC was used as a counterbody. It was found that the concentration of hard particles of ~ 32 % by volume ensures maximum wear resistance of the sintered Al–Al3Ti–Sn samples. A further increase in the content of aluminides up to ~ 40% by volume leads to the formation of a significant number of brittle contacts between the hard particles, which negatively affects the wear resistance of the studied materials. It was concluded that in order to increase the wear resistance of composites of this system, it is necessary to achieve uniform distribution of hard phase particles around the perimeter of matrix grains. It was found that the wear intensity of Al–Al3Ti–Sn composites increases with increasing pressure on the friction surface, while the value of the friction coefficient decreases and is practically independent of the composition of the studied materials. The wear mechanism of the composite samples of hybrid phase composition under dry friction against a steel disk is considered. The wear process of the composites of this system is carried out by two main mechanisms: deformation-oxidative wear through plastic deformation of a thin surface layer and its embrittlement by small oxide particles, as well as fatigue wear through involvement in deformation by shear of grains of the upper layer of the sample with their subsequent delamination along tin interlayers that have exhausted their plasticity resource.

The article discusses the results of studies of the wear resistance of structural steels used for the production of shafts of volumetric rotary pumps. A special feature of this type of pump is the extremely small gaps between its working bodies, which are about 10—25 microns and depend on the amount of shaft wear at the junctions with the sliding bearings. Nitriding in glow discharge is the most effective method of ensuring high wear resistance of parts. It is shown that one of the negative phenomena during the wear of the nitrided layer is the formation of abrasive particles as a result of discoloration, which contribute to the caricature of the sleeve surface and, as a result, intensify the wear process. The purpose of the work is to study the wear resistance of steel nitrided in a glow discharge using pretreatment methods of surface plastic deformation, implantation with medium-energy ions, magnetic pulse treatment, as well as combined activation methods. The following activation modes of the surface layer were used before ion nitriding: shot blasting with steel microbeads with a diameter of 50—100 microns at a speed of 30—70 m/s; implantable ions — nitrogen; dose — 1.3·1017 ion/cm2; rate of radiation dose — 1·1015 ion/s; ion implantation energy: 25 keV. Magnetic pulse processing (MPР) with a pulse power from 2 kJ to 8 kJ, its duration from 5 microseconds to 40 microseconds and the number of pulses from 2 MPT to 5 MPT. It is shown that the most effective method of preliminary, before the process of activation of the material of the surface layer of steel is medium-energy ion implantation, which allows to increase the wear resistance of the nitrided layer of 40Cr steel by 5.7 times, and 40 CrNi steel by 4.5 times, compared with conventional ion nitriding.

The paper discusses the development and application of domestic hardening oil during the heat treatment of elastic terminals for rail fasteners. The paper presents the results of laboratory comparative tests of the developed oil and its imported counterpart. The study of the effect of the cooling properties of hardening oils on the hardness and structure was conducted during the heat treatment of samples made of 38Si7 steel, which is used for the production of elastic terminals. The cooling properties of hardening oils were evaluated using the UZS-2 device for determining the cooling characteristics of technological and hardening media. It has been shown that the developed prototype of the quenching oil provides a maximum cooling rate of 94.2 °C/s, a maximum cooling rate temperature of 615.8 °C, a cooling time of 7.03 s to 600 °C, a cooling time of 10.3 s to 400 °C, a cooling time of 39.3 s to 200 °C, and a cooling rate of 7.84 °C/s at 300 °C. At the same time, the hardness of the 38Si7 steel blanks after hardening is 53.2—54.6 HRC. As a result of the industrial tests, it was found that the developed hardening oil meets the requirements of the technological process of heat treatment of elastic terminals for rail fasteners made of 38SI7 steel and allows to reduce the cost of purchasing an imported analogue.

This work investigates the tribological characteristics of the surface of carbon steel alloyed with bismuth oxide with the addition of an oxidizer or a reducing agent, specifically lithium nitrate or highly dispersed graphite powder, respectively. Tribological tests were performed in contact with an aluminum alloy AZh1 under boundary lubrication conditions.
It was established that carbon interacts with bismuth oxide during the alloying process under high-temperature laser treatment, leading to the formation of metallic bismuth, which negatively affects the performance of the tribological pair under high contact load. Furthermore, a higher carbon content in the powder mixture results in a greater amount of reduced bismuth oxide in the steel surface and a lower load-carrying capacity of the pair at a constant speed of 9.0 m/s. Conversely, the decomposition of lithium nitrate with the release of oxygen during high-intensity laser processing leads to an increased proportion of oxidized bismuth in the alloyed surface. The addition of the oxidizer significantly improves the tribological characteristics of the pair under boundary lubrication friction conditions. A possible mechanism for the occurrence of ultralow friction and wear coefficients during sliding friction under boundary lubrication for the “bismuth-oxidealloyed steel vs. aluminum alloy” friction pair is proposed.

Ultrasonic impact treatment is a surface strengthening technique that utilizes ultrasonic vibrations to enhance the topography, stress, hardness, and other surface characteristics of materials, thereby improving their resistance to wear, corrosion, and similar performance attributes. This paper focuses on the application of ultrasonic impact treatment on 1045 steel, which underwent this process subsequent to quenching. Experimental analysis of the surface hardness and roughness of untreated, quenched, and ultrasonic impact-treated 1045 steel specimens demonstrates that the quenching process results in a 37.4 % increase in surface hardness and a 32.9 % reduction in surface roughness. In comparison, the ultrasonic impact treatment leads to a more substantial improvement, with a 47.2 % increase in surface hardness and a 56.4 % decrease in surface roughness. To evaluate the friction and wear characteristics of the different specimens, a series of ball—disk tests were conducted under both dry friction and oil lubrication conditions. The results indicate that the surface subjected to ultrasonic impact treatment exhibited the lowest coefficient of friction, minimal surface wear, and a relatively moderate surface wear development rate under dry friction conditions. Specifically, the quenching process reduced the surface wear rate by 10.8 %, while the ultrasonic impact treatment led to a substantial reduction of 52.60 %. Under oil lubrication conditions, ultrasonic impact treatment decreased the surface wear rate by 18.26 %. Additionally, this research delves into the microscopic wear mechanisms and observed wear behaviors of the 1045 steel specimens under different lubrication conditions. It particularly examines how lubricating oils may adversely affect the tribological performance of ultrasonically treated steel surfaces. By providing a comparative analysis of the specimens subjected to ultrasonic impact treatment and those processed through traditional quenching, this paper aims to enhance the understanding of the effects of ultrasonic impact treatment on the performance of metal materials and to offer a reference framework for optimizing the tribological applications of such materials.