Problems of Tribology

Kinetics of heterogeneous chemical reactions, initiated by metal deformation

V.V. Shevelya — 2026-05-28

Topochemical processes in the air environment initiated by plastic deformation of the metal of various intensities and types were investigated : cyclic bending of the sample, rolling friction, sliding friction, cutting. It was established that during the cyclic loading of the metal, the concentration and composition of the air components in the test chamber change: a decrease in the content of the reagent - molecular oxygen and the appearance of the interaction product - hydrogen. The influence of the type of plastic deformation of the metal and the processes that occur during this on the kinetic dependences of the topochemical processes was revealed: damped, rectilinear and exponential. The dependence of the speed of topochemical processes on the intensity of plastic deformation was established. An indicator for assessing the competing effect of metal oxidation on the active centers of the surface subjected to plastic deformation was proposed. The results obtained reveal the nature of the friction and wear process and ways to increase the durability of friction units.

Increasing the durability of the Ti-GFRP/CFRP contact with a layer of wear-resistant polymer composite coatings under vibration load conditions

A. Khimko — 2026-05-28

The development of aviation and the improvement of the flight characteristics of aircraft and helicopters requires the use of CFRP carbon fibers and GFRP fiberglass in power structures. The vibration load factor is an integral part of the aircraft design. With vibrations, a contact that we thought was nominally stationary begins to move at the micro level over time. Movement between parts is sufficient for the catastrophic development of fretting-corrosion wear of contacting parts, followed by the development of fatigue cracks and structural failure. Therefore, it is very important to pay attention to increasing the durability of contact made of Ti-GFRP/CFRP materials under vibration loads, since as a rule, these are power parts of aircraft, damage to which significantly reduces the reliability of the structure and increases the risk of fatigue cracks, especially in parts made of titanium alloys. One method of increasing the durability of the Ti-GFRP/CFRP contact is the use of intermediate "sacrificial" materials that are triggered during operation and replaced during repairs, but protect the contact from damage. The paper analyzes wear-resistant composite materials and determines what materials F4К15М5 and ZX550 are most suitable for this. It was found that during tests in the Ti-F4К15М5-GFRP system, the metal surface is completely protected by spreading an intermediate material on the surface. The mechanisms of wear of intermediate materials and their effect on contact under vibration loads have been determined.

Technological features of forming regular micro reliefs on conical surfaces

V.O. Dzyura — 2026-05-28

The paper examines the technological features of schemes for forming regular micro reliefs on conical surfaces. A classification of these formation schemes is proposed according to the regularity of the generated micro relief and its geometric parameters. A set of possible groove configurations of the formed micro relief has been obtained, comprising 54 variants of geometric property combinations that integrate the shape of the axial line of the micro relief grooves, the pattern of variation of the groove geometric parameters, and the groove profile itself. The specific characteristics of each technological scheme are analyzed, and the principal analytical relationships are derived that determine the interdependence between the geometric parameters defining the shape of the micro relief groove elements-namely the pitch (T_k) and the amplitude (A_g); the groove arrangement parameter – the center-to-center spacing (S_o); and the parameters of the conical surface, including the cone angle (α_с) and the length of the axial line of the regular micro irregularities formed on the conical surface. The obtained relationships make it possible to ensure the regularity of the micro relief groove elements and to form a micro relief with the required geometric parameters. It has been established that the determination of the length of the helical line on the conical surface forms the basis for further calculations of the groove elements arranged along this line.

Effect of composition modification and heat treatment on the microstructure and wear resistance of plasma-sprayed nickel-based coatings for engine valves

O.V. Dykha — 2026-05-28

The work investigated the microstructure, phase composition and wear resistance of plasma coatings based on self-fluxing nickel alloys obtained from PG-10N-01 powder and intended for strengthening internal combustion engine valves. It was established that due to high heating and cooling rates during plasma spraying, a lamellar structure with the presence of amorphous and crystalline phases, oxide inclusions and pores is formed. It was shown that heat treatment provides partial crystallization of the amorphous phase, a decrease in porosity and an increase in the microhardness of the coating. The distribution of microhardness along the depth of the layer was studied, which is characterized by relative stability within the coating and a gradual decrease in the transition zone to the base. The effect of composition modification (introduction of ferrosilicon) on the structure formation and porosity of the coating was established. According to the results of tribological tests, an increase in wear resistance and a decrease in the coefficient of friction after heat treatment were determined. The adhesive wear mechanism caused by the structural heterogeneity of the coating is substantiated.

Construction and application of the limit strain surface for evaluating the plasticity of porous bodies

R. Sivak — 2026-05-28

Traditional failure criteria for solid materials are not applicable to powder materials due to the presence of porosity, which acts as a sink for dislocations, alters defect accumulation kinetics, and slows structural degradation. This study presents a comprehensive analysis of the deformation behavior of cylindrical porous iron-based samples. The deformed state on the sample surface was determined using the coordinate grid method, while displacement measurements were performed with a high-precision instrumental microscope, enabling the calculation of strain rate components at each stage up to macrocrack formation. To ensure a wide variation of the stress state index and the Nadai–Lode parameter, eight loading paths were implemented, including free upsetting under different friction conditions and deformation in steel shells. The parameters η₀ and μσ were calculated considering porosity functions, ensuring an adequate representation of void effects on the stress state. Experimental data were processed using successive approximation methods to identify key model parameters. As a result, an analytical expression for the limit deformation surface was obtained, describing the failure condition of the material. A significant finding is the confirmation of the invariance of the plasticity resource of the base material with respect to initial porosity, provided the matrix composition and structure remain unchanged. This enables the obtained surface to be considered a universal characteristic of sintered iron. The developed approach provides a reliable tool for predicting defect formation and optimizing powder metallurgy processes such as pressing, calibration, and bulk forming.

The effect of load and sliding speed on the wear rate of a metal-polymer composite containing an Al-Co filler

K.A. Mykyta — 2026-05-28

The paper presents the results of a study on the tribotechnical behaviour of a polymer composite material based on ultra-high-molecular-weight polyethylene, filled with 25 wt.% of a rapidly quenched binary alloy of the Al–10 wt.% Co system. The relevance of the study is due to the need to improve the wear resistance of tribological joints operating under conditions of intensive wear, high loads, and insufficient lubrication. The aim of the study is to develop a mathematical model describing the influence of sliding speed and applied load on the intensity of linear wear of the composite under dry friction conditions using a disk–pad configuration. The study was carried out using a full factorial experiment and a first-order regression model, which made it possible to quantitatively evaluate the influence of the experimental factors and their interaction. It was established that with increasing load, the intensity of linear wear increases significantly, while the influence of sliding speed is less pronounced and becomes evident in interaction with load. A synergistic effect of the combined action of the investigated factors on the linear wear intensity of the polymer composite was identified. The developed mathematical model was validated using statistical criteria and adequately describes the experimental data. The obtained results can be used to predict the wear resistance of the material and to determine rational operating conditions for tribological joints, thereby improving their durability and reliability

New anti-corrosion pigment based on natural aluminosilicate with a layered structure

M.-O.M. Danyliak — 2026-05-28

According to scanning electron microscopy results the montmorillonite particles are in the form of curved plates that tend to agglomerate. Using EDX analysis, it was established that the initial montmorillonite was Ca, Mg – form of montmorillonite. Due to the mechanochemical modification of montmorillonite, intercalation of Zn²⁺ cations into the layered structure of natural montmorillonite occurred, and phosphate anions were able to form surface adsorption complexes with positively charged edge surfaces of montmorillonite through the acidic environment of the crystal hydrate of the salt Zn(H₂PO₄)₂·2H₂O, while the content of zinc and phosphorus is ~5 wt. % and ~ 4 wt. %, respectively. It was established that the obtained pigment based on mechanochemically modified montmorillonite increases the corrosion resistance of the aluminium alloy in an acid rain environment with pH = 4.5 by potentiodynamic polarization and electrochemical impedance spectroscopy methods. The inhibitory effect of mechanochemically modified montmorillonite consists in the release of Zn²⁺ cations from montmorillonite containers, which, interacting with OH^– anions, form zinc hydroxides at the cathode sites, and the slowing down of electrochemical corrosion occurs due to the formation of phosphates at the anode sites of the aluminium alloy. It was established that the protection degree of the aluminium alloy in the acid rain environment with mechanochemically modified montmorillonite was above 90 %. Thus, montmorillonite, an aluminosilicate mineral of natural origin, is a promising material for obtaining new eco-friendly anti-corrosion pigments in paint and varnish coatings to ensure long-term protection of metal products

Hardening protective coatings on niobium alloys, their thermal-cyclic creep and long-term strength

L. Lopata — 2026-05-28

A solution to the problem of protecting niobium from high-temperature, highly intensive oxidation is considered. The isothermal and thermocyclic creep and long-term strength characteristics of a niobium alloy with three coating variants are determined at temperatures of 1400–250°C in air. A test methodology for niobium alloys with coatings under simultaneous loads, high temperatures, abrupt thermal cycles, and an oxidizing environment with radiant heating and non-contact cooling by focusing radiant energy is presented, ensuring reliable determination of mechanical properties. A comparison of ultimate strains, creep rates, and durability under isothermal and thermocyclic conditions for the three coating variants is conducted, demonstrating the advantage of a combined plasma-diffusion coating over silicide and borosilicide coatings. Differences in creep and long-term strength characteristics of the three coating variants are demonstrated, which are explained by the nature of crack development in the coating. The transition from single “sharp” cracks in the coating to regular cracks in the diffusion sublayer with rounded tops ensures an increase in the strength and durability of the niobium alloy.

Tribological information of contact electrical resistance parameters in the study of oxidation and metal plating processes

A. Gypka — 2026-05-28

The work investigates the regularities of the change in contact electrical resistance in heavily loaded tribosystems under the conditions of transition from oxidation processes to the formation of adaptive metal-clad tribofilms. It is proposed to consider contact electrical resistance as an integral kinetic criterion of the structural and energy state of the frictional contact, which reflects the processes of destruction of oxide and metal-clad layers, activation of friction surfaces, formation of electrically conductive adaptive tribostructures and transition to adhesive contact. The research was carried out according to a scheme that models the contact "camshaft cam - roller pusher" using 42CrMo4 and 16MnCr5 steels, typical for modern heavily loaded components of the gas distribution mechanism of internal combustion engines. It is established that the change in contact electrical resistance has a pronounced kinetic nature and reflects structural and phase transitions in the surface layers of the tribosystem. It is shown that high values correspond to the presence of oxide and tribochemical insulating layers, stable minimum values characterize the formation of adaptive electrically conductive metal-cladding tribofilms, and a sharp decrease in contact electrical resistance indicates the destruction of adaptive tribolayers and the transition to direct metal contact. Critical regimes of force loading and sliding speed are determined, under which the most stable conditions of structural and energy self-organization of surface layers are realized.

Solid lubricant nanocoating’s based on magnesium compounds

V.V. Shchepetov — 2026-05-28

The results of studies of friction and wear of detonation composite nanocoating’s based on the ternary compound aluminum-magnesium-boron under test conditions with constant load in the sliding velocity field are presented. Their structural-phase composition and passivating complex of surface oxide structures are determined using modern physical analysis methods. It is established that the parameters of wear intensity and friction coefficients are minimized due to the set of surface structures that regenerate a stable self-lubricating structured layer under friction conditions. Factors that influence the formation of dynamic equilibrium of a self-lubricating layer that has an effective ability to self-repair are determined. At the same time, a continuous protective layer screens the processes of molecular-adhesive interaction and blocks the development of unacceptable destruction phenomena.

Improved algorithm for calculating engineering parameters of a garbage truck compaction plate mechanism considering hydraulic cylinder wear

O.V. Bereziuk — 2026-05-28

The article presents a scientifically based, improved methodology for the design calculation of the parameters of a garbage truck’s sealing plate mechanism, developed through an analysis of scientific literature and taking into account the wear of its hydraulic cylinder, in order to determine the main geometric, force, and speed characteristics. The drive for the working components of the sealing plate mechanism is hydraulic and is powered by the garbage truck’s pump station. The application of the proposed improved engineering calculation methodology allows for a significant reduction in design time and avoids unnecessary costs associated with conducting complex experimental and theoretical studies. Using the developed methodology, the main geometric, force, and speed parameters of the garbage truck’s sealing plate mechanism were determined, taking into account the wear of the hydraulic cylinder. It has been established that further refinement of the engineering calculation methodology for the garbage truck’s sealing plate mechanism using a load-sensitive scheme requires additional research

Forecasting the resource of machine parts based on the dynamics of changes in the wear mechanism using the neural network method

V.V. Aulin — 2026-05-28

The problem of predicting the residual resource of tribocouplings of resource-determining parts of automotive and agricultural machinery under conditions of operational change of the dominant wear mechanism is considered. It is shown that in real operating conditions the wear mechanism does not remain static: degradation of lubricants, change of load-speed regimes and variability of soil conditions cause a transition from a regular mechanism to an emergency one, which is accompanied by a sharp reduction in the residual resource of machine parts. A two-stage system for identifying the change in the dominant wear mechanism is proposed, combining a classifier based on long short-term memory with an entropy transition detector, which develops an entropy approach to the analysis of tribosystems. The data set is formed on the basis of a modified Archard model with five calibrated coefficients for different lubrication modes and a Palmgren-Miner model in the form of an endurance curve with realistic values of the basic number of cycles 10⁸...10⁹for different materials of tribocoupling parts. Validation on eight scenarios of transition between wear mechanisms demonstrated reliable detection of the change in the dominant mechanism, the warning time for reaching a critical state of 229…593 hours for automotive parts and 13…21 hours for agricultural parts, which is 5.6…7.1% of the total resource and is sufficient for planning maintenance of machines

Mathematical modeling and optimization of wear-resistant material selection for technological tooling of internal combustion engines

I. Drach — 2026-05-28

The study develops an integrated approach for selecting wear-resistant materials for technological devices used in machining and repair of internal combustion engines, considering mechanical, thermal, economic, and reliability factors. KHVG and R6M5 steels were comparatively analyzed using modified abrasive wear models, Weibull reliability assessment, and Life Cycle Cost (LCC) analysis. The model accounts for temperature-induced hardness degradation, lubrication conditions, contact geometry, and coating adhesion. It was established that at temperatures above 400 °C and severe abrasive wear, R6M5 steel provides longer service life and reduces LCC by 6–19% compared to KHVG steel. Under moderate temperatures and impact loading, KHVG steel is preferable due to higher fracture toughness. Optimal heat treatment regimes were determined for both steels. Lubrication increases service life by approximately 66%, while risk mitigation measures are more effective than material substitution under high failure probability conditions. TiN coating is not recommended for rough surfaces because of delamination risk. The developed model enables improved engineering decision-making for wear-resistant tooling applications.