Problems of Tribology

Development of Plasma-Sprayed Copper Alloy–Nickel-Clad Graphite Composite Coatings with Enhanced Tribological Properties

O. Terentjev — 2025-12-15

This study is focused on the development of composite plasma-sprayed coatings with a low coefficient of friction based on copper alloys with additions of nickel-clad graphite and on the investigation of their physicomechanical and tribological properties. Composite coatings were produced by atmospheric plasma spraying (APS) from agglomerated powders of copper alloys with the following compositions: BrONG-30 (70 wt.% BrOF10-1 + 30 wt.% nickel-clad graphite), BrOSNG-30 (70 wt.% BrOCTS5-5-5 + 30 wt.% nickel-clad graphite), and LNG-30 (70 wt.% L63 + 30 wt.% nickel-clad graphite). The application of graphite in a nickel shell improves its wettability by the metallic matrix and enhances adhesion. The obtained coatings exhibit high adhesion strength to the substrate (33–38 MPa) and density (94–97%). Tribological tests demonstrated that the LNG-30 – steel 45 friction pair showed the best performance. The inclusion of nickel-clad graphite reduced the friction coefficient by up to 1.5 times and increased wear resistance by up to 3.8 times. Using EDS and Auger spectroscopy, it was established that during friction in the LNG-30 – steel 45 pair, a film consisting of graphite (16–17 nm thick) and oxides of copper, zinc, nickel, and iron is formed on the counterbody wear track. The presence of such oxide films indicates a predominantly oxidative mechanism of friction, with minor adhesive interaction. The proposed coatings are promising for application in friction units, particularly under conditions where the use of liquid lubricants is limited or impossible

Initiation of a data bank of activation energy values for tribo-reaction wear and modification of Shkh 15 and Steel 45 steels in the environment of hydrocarbon liquids

O.I. Bogdanovych — 2025-12-15

The kinetic technique, which is developed on the basis of the kinetic three-stage model of normal mechano-chemical wear, is considered. The values of the activation energy of wear of secondary structures of structural steels in the medium of hydrocarbon liquids are obtained by the experimental-calculation method. The obtained results of the assessment of the energy of activation of wear and chemical modification of structural steels in the media of hydrocarbon liquids allow us to establish a data bank of anti-wear and modification properties of secondary structures, which can serve as reference data on the anti-wear and modification properties of secondary structures on structural steels in the media of hydrocarbon liquids

Modifying NiAl intermetallic powder by phosphorus cladding for plasma-sprayed coatings and studying their structure and tribological properties

T. Levchuk — 2025-12-15

This article examines the impact of adding phosphorus to NiAl intermetallic powder on the structure, microhardness, and tribological properties of plasma-sprayed coatings, which are suitable for use under dry friction conditions. A composite powder designated NiAl+P was obtained by cladding NiAl powder with phosphorus-containing compounds. It was found that the addition of phosphorus promotes the formation of phosphate phases in the coatings, which reduces microhardness but significantly increases wear resistance. In the NiAl+P coating, a protective phosphate film forms on the friction surface during tribological tests, acting as a solid lubricant that reduces the wear rate by almost 2.5 times. The results demonstrate the effectiveness of phosphorus as an alloying element for enhancing the service life of NiAl-based coatings in tribological assemblies.

Optical interferometry for assessing lubricating film properties

V. Akhmatov — 2025-12-15

The study investigated the influence of rolling speed and lubricant properties on the formation of a lubricating film in point contacts. The film thickness was measured using optical interferometry, which provides high-precision, real-time data. Experimental tests were conducted on a specially designed rig simulating rolling conditions in bearing assemblies. Analysis of various lubricants showed that kinematic viscosity, base oil type, and chemical composition significantly affect the lubrication behavior and film formation regime. It was found that increasing rolling speed leads to a transition from boundary to hydrodynamic lubrication, with substantial changes in film thickness. The results can be applied to optimize lubricant selection in bearings of precision mechanisms

The influence of high-entropy alloys on the abrasive wear index of ultra-high-molecular-weight polyethylene

А.-М.V. Tomina — 2025-12-15

This work examines the influence of high-entropy alloys Fe₂₀Ni₂₀Co₂₀Be₂₀Si₁₄B₆ and : Al₄₀Co₁₂Cu₁₂Cr₁₂Ni₁₂Fe₁₂ on the abrasive wear index of ultrahigh-molecular-weight polyethylene. The effective filler content that ensures the minimum wear rate has been determined. For the Fe₂₀Ni₂₀Co₂₀Be₂₀Si₁₄B₆alloy, the optimal concentration is 25 wt.%, whereas for the: Al₄₀Co₁₂Cu₁₂Cr₁₂Ni₁₂Fe₁₂ alloy it is 20 wt.%. The overall improvement in abrasive resistance reaches 35–45% compared to unfilled polyethylene. The enhancement in wear resistance is attributed to the strengthening of the polymer matrix by hard particles of the high-entropy alloys, whose microhardness exceeds 10000 MPa. Their introduction significantly increases the material’s ability to resist mechanical degradation of the surface layers during friction against rigidly fixed abrasive particles. The obtained results confirm the feasibility of using high-entropy alloys as effective functional fillers for the development of wear-resistant polymer composites based on ultra-high-molecular-weight polyethylene and open up promising directions for further research in this field.

https://doi.org/10.3103/S106836662201010X

A. Gypka — 2025-12-15

The article investigates the causes of surface degradation in the “stationary shaft–bushing” tribological pair of the roller assembly of a diesel engine fuel pump plunger in a heavy-duty truck, operating under increased loads and boundary lubrication conditions. A surface damage passporting methodology was applied, including analysis of microhardness, surface roughness, geometrical accuracy, and structural transformations within surface layers of the components, supplemented by elements of X-ray diffraction analysis.

It was established that the dominant wear mechanism is hot scuffing (adhesive wear of the second kind), driven by irregular lubricant supply, chemical affinity of the materials of both components (bearing steel 100Cr6/ШХ15), localized load concentration, and the stationary configuration of the shaft. The formation of secondary hardened “white layers” was observed, indicating thermal overloading and a reduced load-bearing capacity of the surface layers after prolonged service.

A set of design, technological, and operational measures is proposed to improve the reliability and durability of this friction pair.

Enhancement of corrosion–mechanical wear resistance of metallic alloys by glow-discharge nitriding

M.S. Stechyshyn — 2025-12-15

The aim of this work is to provide a comprehensive analysis of hydrogen-free nitriding and nitrocarburizing processes in a glow discharge, to summarize the regularities of nitride and carbonitride layer formation on steels and titanium alloys, and to evaluate their corrosion–mechanical wear resistance under conditions of sliding, fretting, cavitation, and exposure to aggressive media. Particular attention is given to the application of model for interpreting the kinetics and energy mechanisms of diffusion processes. The study presents a comparative analysis of the structural–phase transformations during nitriding and nitrocarburizing in a hydrogen-free glow discharge and systematizes experimental data on microhardness, electrochemical behavior, and corrosion–mechanical wear resistance.

The methodological basis of the theoretical part is the energy-exchange model, which describes the influence of active plasma species on the diffusion rate and phase formation. It is shown that hydrogen-free nitriding provides intensified nitrogen diffusion, the formation of stable nitrides TiN, Ti₂N, ε-(Fe₂–₃N), γ′-(Fe₄N), and the elimination of hydrogen embrittlement. It is established that nitrocarburizing produces multilayer carbonitride structures with hardness values of 900–1300 HV and high adhesion to the substrate. The modified layers demonstrate a 3–6-fold increase in wear resistance, a 2.5–4-fold reduction in cavitation damage, and a significant decrease in corrosion current in NaCl and NaOH solutions. A transition of the dominant failure mechanisms from brittle and adhesive to plastic-deformation dominated modes has been identified. The obtained results confirm the experimentally observed regularities of carbonitride-layer formation and demonstrate the key role of ion bombardment in generating the defect-subzone .

Influence of surfacing modes on the properties of high-carbon coatings

V. Shenfeld — 2025-12-15

The paper presents the results of a study of the influence of surfacing modes on the hardness and wear intensity of high-carbon coatings under dry friction. The coatings were deposited by electric-arc surfacing using carbon fibrous materials. A mathematical model is proposed that describes the influence of the selected parameters (v_н, U, І) on the hardness of the surfaced layer (HRC) and the wear intensity І_З. Using the obtained mathematical models, it is possible to solve current problems of obtaining coatings with a given hardness and wear resistance, which arise during the design of technological processes that use the deposition of coatings. For real technological processes, the problems should be solved by the graph-analytical method or linear programming methods using response surfaces. Analysis of response surfaces showed that increasing the deposition rate increases the hardness of the deposited coating and the intensity of wear under dry friction conditions.

Analytical study of an improved mathematical model of the hydraulic drive of the garbage truck’s sealing plate mechanism, taking into account the wear of its hydraulic cylinder

O.V. Bereziuk — 2025-12-15

The article is dedicated to the analytical study of the improved mathematical model of the hydraulic drive of the garbage truck’s sealing plate mechanism, in which the influence of the wear of the hydraulic cylinder on its operation is additionally taken into account. On the basis of the numerical studies of the improved nonlinear mathematical model of the hydraulic drive of the garbage truck’s sealing plate mechanism, which takes into account the wear of the hydraulic cylinder, its linearized modification was created, presented in the form of a system of ordinary linear differential equations of the second order. To perform design calculations of new modifications of garbage trucks, approximate analytical expressions were obtained that describe the change in time of the pressure in the hydraulic cylinder’s pressure line, as well as the speed and movement of the sealing plate based on the proposed linearized mathematical model of the hydraulic drive of the garbage truck’s sealing plate mechanism, taking into account the wear of the hydraulic cylinder. The obtained regression equation that provides the possibility of an approximate determination of the duration of the process of compacting municipal solid waste in a garbage truck, taking into account the wear of the hydraulic cylinder.

Enhancing the reliability and wear resistance of high-speed cutting tools through the use of ionized air-oil lubrication media in machine part restoration

D.D. Marchenko — 2025-12-15

A comprehensive analysis of the wear processes of high-speed cutting tools and methods of improving their performance during machining has been carried out in this work. An analytical review of scientific sources on modern methods of supplying lubricating and cooling technological means (LCTM) was performed, including the activation of air and air–oil flows and their influence on friction and cutting processes. Special attention is given to the micro-dosed supply of industrial oil Mobil DTE 22 in the form of sprayed air–oil mixtures activated by the electric field of a corona discharge. A nozzle device for the metered supply of viscous fluids with subsequent activation of the air stream has been developed and investigated, ensuring reduced operating pressure and improved operational safety. A tribometric test stand was designed and used to study the lubricating ability of activated LCTM and to determine the friction coefficients of various materials. It was established that ionized air–oil media significantly reduce friction torque, stabilize contact interaction, and decrease surface roughness. Experimental studies of the cutting process demonstrated a substantial increase in the tool life of high-speed steel cutters when using ionized air–oil flow: up to three times compared with dry cutting and up to 2.5 times compared with free oil flooding. The application of the desirability function enabled a comprehensive evaluation of the effectiveness of different LCTM options, showing an increase in machining efficiency of up to 40%.