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The results of a study of the tribological properties and microstructure of rapidly solidified Al–12.2 wt % Si–0.2 wt % Fe (AK12vp) and Al–12.5 wt % Si–0.8 wt % Mg–0.4 wt % Mn–0.7 wt % Fe–0.9 wt % Ni—1.7 wt %, Cu (Al–Si–M) alloys are presented. The effect of multicomponent alloying on the microstructure of near-eutectic silumin was studied using scanning electron microscopy and X-ray spectrometry. Multicomponent alloying of the Al–Si eutectic alloy with magnesium, manganese, iron, nickel, and copper leads to a reduction in the size of the primary α-Al dendrites to 3–4 μm. Tribological tests carried out under conditions of dry friction with reciprocating motion of the indenter showed that alloying by metals of rapidly solidified eutectic silumin leads to a reduction in the coefficient of friction by 25%. An analysis of the surface state of the track showed that, as a result of deformation heating, the oxidation of the α-Al phase occurs, the destruction of the oxide film, which represents the third body, and its removal beyond the track. The fragmentation of silicon plates in the track area into nano-sized particles was also obtained. The impact of the indenter also leads to a uniform distribution of equiaxed particles of intermetallic compounds while maintaining their phase composition. [ABSTRACT FROM AUTHOR]

The study compared properties of carbon–carbon composites for manufacturing aircraft brakes. Composites based on various graphitized and carbonized fibers, coal, tar pitch, and pyrocarbon matrices were considered. Friction tests were carried out on full-size brake discs (three-disk stand) and on model samples (UTM-2168 testing machine). A significant wear increase of composites based on a pyrocarbon matrix was found during taxi braking in the temperature range of 50–250°C. Wear of composites based on a coal tar pitch matrix did not depend on the temperature of the friction surface. It was found, that the "third body" of composites based on pyrocarbon has a coarse rough structure with distinct individual abrasive particles; its hardness is more than twice as high as the hardness of the third body of composites based on pitch matrix. The size distribution of pores for composites based on different matrices is given, the difference in the quantity and size of structural defects is illustrated. The variation in wear of materials during taxi braking is explained. The increase of degree of anisotropy of the pitch matrix, provided the decrease of wear of the material. The wear was measured during taxi braking of specimens with a hybrid matrix having a different ratio of coal tar pitch and pyrocarbon components. Carbon–carbon composites containing 45% or more of the pitch component in matrix have stable reduced wear during taxi braking, regardless of the reinforcement scheme. The possibility of reducing wear during taxi braking of composites on pyrocompacted matrices by modifying the matrix with pitch is shown. [ABSTRACT FROM AUTHOR]

This paper presents the results of tests of EPAN coatings, a composite material based on carbon–carbon fibers. It uses fine molybdenum disulfide as the main lubricant and for binders, phenol, peroxide, and silicone resins. The tests were carried out on microarc oxidation (MAO) coatings. For comparison, the tribological characteristics of EPAN under friction on steels, as well as molybdenum disulfide composites are given. The friction coefficients of EPAN coatings on MAO coatings according to the "shaft–bushing" scheme do not exceed 0.05 at pressures of 10–20 kg/cm2 and shaft rotation speeds from 130 to 600 rpm. The advantage of such combinations of materials is the use of a light alloy, aluminum with MAO coating, for the counterbody to the EPAN coatings, which is important for space products. The creation and testing of solid lubricating coatings for modern space technology is a task of extreme importance, because in many developments of space products, low-temperature plastic lubricants continue to be used, which are operable up to subzero temperatures of –90 to –110°C. Such solutions require the use of thermal insulation and heating for mobile interfaces and friction units of machines, mechanisms, and devices. The result is a serious complication of structures and an increase in their weight. The tests of EPAN coatings on MAO coatings carried out in the work open new possibilities in the combination of materials for space technology. Having a coefficient of friction of 0.05 and high wear resistance, they allow you to create movable joints, first of all, sliding bearings, for operation on Earth sensing satellites, as well as mechanisms on the Moon. [ABSTRACT FROM AUTHOR]

The work is devoted to the study of the tribological properties of functional coatings based on the FeO oxide matrix, additionally doped with boron oxide B2O3 and zirconium dioxide ZrO2. The coatings are obtained by highly concentrated short-pulse laser processing of powder compositions previously applied to metal surfaces. The resulting coatings are subject to wear tests under conditions of dry sliding friction with fixation of the friction coefficient, depending on the applied load and the composition of the powder composition. The results give an idea of the degree of change in the coefficient of friction of coatings depending on the powder compositions, as well as their alloying. It has been confirmed that additional alloying with boron oxide has a positive effect on the tribological performance of the coating; in particular, the introduction of 4% boron oxide reduces the coefficient of dry sliding friction to a unique 0.09–0.10. At the same time, a more stable scuffing resistance of friction surfaces is observed, confirmed by studies of surface roughness after testing. A feature of the tribological behavior of the coatings under study is the excessively high temperature background of the tests, reaching 300°C. High temperature and the presence of oxide structures are a catalyst for the formation of stable tribological structures between the rubbing surfaces. The nature of the tribostructures is self-organizing in a "glaze" type and has the property of recovery under friction conditions. After the formation of tribostructures in the friction zone, a significant decrease in temperature and an abrupt decrease in the friction coefficient are observed. With an increase in the amount of boron oxide, the friction coefficient does not decrease so significantly and the minimum value of the dry friction coefficient corresponds to 0.14–0.15, which is caused by a decrease in the cohesive strength of the coating. [ABSTRACT FROM AUTHOR]

The study of the structural-phase state and tribotechnical properties of antifriction gas-thermal coatings made of aluminum alloy AlSi12, welding bronze CuSi3Mn1, as well as composite material CuSi3Mn1 + AlSi12 and a coating of bronze CuSn10P1 obtained by centrifugal induction surfacing was carried out. It is shown that composite gas-thermal coatings from CuSi3Mn1 + AlSi12 after spraying include Cu, Al, Cu9Al4, CuAl2, Cu3Al, Si, and Al2O3 phases. The matrix phase of the bronze interlayers is doped with aluminum, while the Al interlayers are doped with copper. It has been established that annealing of coatings CuSi3Mn1 + AlSi12 at temperatures of 175 and 225°С for 2 h leads to the release of an additional amount of intermetallic compounds in them and an increase in their microhardness. It is shown that composite gas-thermal coatings have ≈1.2–1.7 times higher wear resistance in the environment of I-20A and Litol-24 lubricants compared to coatings of CuSn10P1 bronze. Annealing of composite coatings from CuSi3Mn1 + AlSi12 leads to an increase in their wear resistance in the environment of I-20A liquid lubricant up to 30% and Litol-24 up to 20% compared to the initial state. The coefficients of friction of all antifriction coatings based on copper in the environment of the I-20A lubricant did not exceed 0.08, and in the environment of the Litol-24 lubricant, 0.10. [ABSTRACT FROM AUTHOR]

The main regularities of friction and wear of surface layers of composite materials for antifriction and friction purposes have been established. It has been shown that mineral fillers modified with an organic lubricant (travertine, bentonite, tuff, marble, basalt) have a significant effect on the structure and properties of heterochain polymers based on a copolymer of formaldehyde, polyamides, and polyphenylene oxide. The developed composites are characterized by high wear-resistance (1.43–1.9 times), improved strength properties (1.5–2.0 times), and decreased friction coefficient (1.17–1.4 times) compared to the initial polymer materials that extend the opportunities of their application in modern friction units. The main mechanism of fatigue-delamination high-temperature wear of brake friction composite materials with mineral additives is revealed and based on it a physical model of the surface layer destruction is developed. It was established that the performance of these materials under conditions of high-temperature wear is determined by the stress-strain state of thin surface layers, in which tensile and compressive stresses exceeding the ultimate strength at shear act. At the stage of designing brake devices an analytical method to predict the wear resistance of friction linings was developed. [ABSTRACT FROM AUTHOR]

The present study analyzed the effect of protective coatings of replaceable hard-alloy plates on cutting forces when milling austenitic high-manganese Hadfield (110G13L) steel. S30T, 1130, S40T, and 4240 hard alloys with PVD and CVD coatings were explored. The analysis was conducted on a milling machining center with a dynamometer plate installed on the table. The experiment was based on the orthogonal planning matrix. The Taguchi method was employed to identify a coating with the best properties. The analysis of variance showed that the tool feed has the greatest effect on active cutting forces. The specific feed gravity was 65.22%. The regression analysis revealed that to minimize and predict cutting forces for the entire range of cutting conditions, S30T alloy with a protective TiAlN PVD coating is preferable in machining austenitic 110G13L stainless steel. The results can improve the machining efficiency for Hadfield steel products produced by machine-building enterprises. [ABSTRACT FROM AUTHOR]

An experimental and theoretical method of triboanalysis is proposed to characterize the antifriction properties of polyamides and composites based on them, used in self-lubricated metal-polymer sliding bearings. The indicators of wear resistance of the materials are determined experimentally. The generalized parameters of the mathematical model of wear used in the design of metal-polymer bearings are calculated. The dependences (diagrams) of wear resistance of unfilled polyamides PA6, PA66, and polyamide composites PA6 + 30GF, PA6 + 30CF, PA6 + MoS2, and PA6 + oil paired with steel 45 on specific friction force are obtained and a comparative assessment of the wear resistance is given. The influence of contact pressure on the friction coefficient is studied and a significant decrease in the latter with increasing contact pressure is shown. A decrease in the Vickers hardness and elastic modulus of the surface layer of the studied materials during wear is also established. It is more significant for unfilled polyamide PA66 (by 1.66 times), PA6 + 30CF (by 1.5 times), PA6 + MoS2 (by 1.41 times), and less noticeable for polymer composites PA6 + 30GF and PA6 + oil by 1.21 and 1.09 times, respectively. The fact should be taken into account in tribological calculations of metal-polymer sliding bearings. The research results are presented in the form of diagrams, which allow one to compare the wear resistance of the investigative materials in a wide range of specific friction forces. Thus, the practical significance of the results lies in the possibility of their use in tribological engineering to predict the service life of metal-polymer plain bearings and validate the choice of antifriction materials for their manufacturing. [ABSTRACT FROM AUTHOR]

The article suggests a disc brake design with carbon friction materials (CFMs). The principle of the method is to create two friction units in the disc brake with materials placed in them that have different frictional properties. The two friction units are created by separating the brake disc with a thermally insulating screen. One friction unit (friction unit A) has CFMs installed having a low friction coefficient in the initial temperature mode and a high friction coefficient at a temperature of 300°C or higher. The other friction unit has a premium-class car block (CB) and a steel disk (35GS steel) the friction coefficient of which does not depend on temperature (friction unit B). The experiment conducted justifies the creation of a disc brake based on the described principle. The experiment was carried out on a testing bench that simulates the interaction of the disc brake as per the load-speed criteria. The testing bench creates conditions for a constructive separation of the brake disc into friction units A and B. As an example of two friction units: CFM–CFM (friction unit A) and CB–steel 35GS (friction unit B). The experimental performance of the friction coefficient versus temperature obtained on the testing bench in relation to friction units containing friction materials CFM–CFM and CB–steel 35GS showed that the friction coefficient of the disc brake takes high values in the entire range of temperatures tested during braking. The article offers a promising design of a disc brake with thermally insulated friction units. The design consists of two brake discs and a central part, which is thermally insulating. All parts are glued together. [ABSTRACT FROM AUTHOR]

This study proposes to use synthetic discrete refractory fiber, grade NDA-17-42-2, based on alumina and silica (in the weight ratio 85 and 15%, respectively) with a diameter from 1 to 3 μm as a friction component in tribotechnical materials. Due to high hygroscopy in combination with a high specific surface area up to 400 m2/g (comparable to asbestos) it is possible to expect high efficiency as a tribotechnical additive to frictional materials. Specimens based on iron, bronze, and copper with addition of fibers have been produced using the methods of powder metallurgy. Tribotechnical behavior of iron and copper-based specimens is comparable both in terms of functions of sliding speed and load on friction contact, and of respective values. Tests of copper-based specimens have demonstrated decrease in the coefficient of friction from 0.44 for pure copper to 0.18 and its stabilization. In addition, despite lower mechanical strength of the copper specimen with fibers in comparison with bronze and iron ones, its wear is not higher and in certain regimes is even significantly lower. It has been established that tribotechnical behavior of copper-based specimens with frictional additive of fibers qualitatively differs from that of iron and bronze-based specimens with the same frictional additive of alumina-based fibers. The difference in tribotechnical behavior of copper-based specimens with fibers is related to formation of an adhesive ceramic layer on the friction track. Formation of a similar layer on iron and bronze specimens is not observed. The formed ceramic layer separates friction surfaces, preventing formation of scores, sticking of friction materials, the coefficient of friction is stabilized, and the wear decreases in wide range of sliding speeds and loads. As a consequence, the operation ranges regarding the allowable sliding speed and loads are significantly expanded. [ABSTRACT FROM AUTHOR]

A polymer–polymer tribological pair made of antifriction ultrahigh molecular weight polyethylene (UHMWPE) and high-strength polyetheretherketone (PEEK) composites was proposed and tested in various operating conditions (lubrication medium and dry friction at a deficit of synovial fluid in the joint). The selection of fillers for UHMWPE and PEEK was substantiated in steps proceeding from the data of systematic mechanical and tribological tests. The optimal composition of the composites, suggesting the possibility of manufacturing customized joint prosthetic implants using additive manufacturing technologies, is determined. It was shown that the PEEK (pin)-on-UHMWPE (disk) tribological pair is well compatible, characterized by a low coefficient of friction (f = 0.02), and zero wear found by optical microscopy observations. The friction of non-filled UHMWPE on PEEK reinforced with two types of carbon fibers (milled carbon fibers, 30 wt % and CNT, 2.5 wt %) is checked. It is shown that carbon nanotubes are efficient fillers for PEEK in the UHMWPE–PEEK tribological pair under dry sliding friction at a deficiency of synovial fluid. [ABSTRACT FROM AUTHOR]

The results of the study of the effect of adding colloidal graphite powder in a composition of a carbon-containing additive on the tribotechnical properties of a sintered friction material based on copper operating in the presence of a lubricant are presented. It has been established that the method of introducing colloidal graphite into the composition of friction material affects the tribotechnical properties. With joint mixing of the components of the charge of the friction material, the coefficient of friction was 0.052–0.068. In the case of preliminary mixing of the batch without adding GE-1 graphite, the value of the friction coefficient was 0.045–0.068. It was found that a content of colloidal graphite of more than 15 vol % leads to a significant decrease in the value of the coefficient of friction, and an increase in wear. Compressive strength of material from 30 vol % of the carbon-containing additive in the form of GE-1 graphite is 340 MPa. Introduction of 5 vol % addition of colloidal graphite to GE-1 graphite practically does not ultimately affect the value of the strength, while a 10 vol % addition leads to a decrease in the ultimate strength by 20–30 MPa, and a 15 vol % addition, to a decrease to 270 MPa. The research results can be used in the development of new compositions of friction and antifriction materials obtained by the method of powder metallurgy, used for friction units of automotive vehicles and special purpose vehicles. [ABSTRACT FROM AUTHOR]

This paper discusses the topical issue of the general compatibility of tribological pairs from the point of view of wear resistance when using various electrospark coatings. For investigation, steel segments were coated with bronze, Mo, and combined Ti + Al + C coatings by electrospark treatment. Coated segments and uncoated control segments were studied in a friction pair with an unhardened C45 steel roller (15HRC) at loads of 300 and 600 N in a lubricant medium. Throughout the test, the coefficient of friction was measured, the wear rate of the tested tribo-pairs was estimated, and the nature of the wear of the friction surfaces after testing was analyzed using optical and scanning electron microscopy (SEM). The results have shown that the most compatible tribo-pairs were steel 45/Bronze and steel 45/Mo, since they have exhibited the best resistance, i.e., the least wear under both loads tested. [ABSTRACT FROM AUTHOR]

The results of studying the effect of the additive powder of the iron-chromium alloy PH-30 on the tribological properties of a composite friction material based on copper operating in the conditions of boundary friction are presented. It is shown that the introduction of 10 to 40 vol % PH-30 powder helps to increase the coefficient of friction from 0.042 to 0.075. It is found that at 10 vol % PH-30 the material's wear is minimal and is 4 μm/km, while at 40 vol %, catastrophic wear is observed, exceeding 20 μm/km. The limit value of the material's wear of 9 μm/km is noted with the powder content of PH-30 of less than 28 vol %. The increase in the tribotechnical properties of copper-based friction material with the addition of PH-30 powder is explained by the action of not only the PH-30 powder itself but also Fe4Cu3, FeSn intermetallide, and solid ceramic particles of chromium carbide Cr23C6 formed on the surface after sintering. [ABSTRACT FROM AUTHOR]

The possibility for predicting tribological characteristics of polymer nanocomposites was studied with the example of nanocomposite poly (ether ketone)/graphene. It has been shown that the "escapement" effect of polymer matrix macromolecules by graphene surface essentially reduces (a several times) the indicated characteristics. The proposed simple structural model describes the obtained results through experiments. The fulfilled estimations indicate that the "escapement" effect of macromolecules by graphene surface results in a loss of 60–86% of the initial area of contact polymer matrix-nanofiller with a growth of graphene content up to 10 mas %. Thus, the improvement of the indicated contact (i.e., by nanofiller functionalization) likely leads to essential improvement of tribological characteristics of nanocomposite. [ABSTRACT FROM AUTHOR]

The paper presents the study results of the effect of carbon fibers with mechanically activated bentonite on the physical and mechanical properties, and tribological characteristics of polytetrafluoroethylene. It is shown that the introduction of combined fillers (carbon fibers with bentonite) in polytetrafluoroethylene leads to a significant improvement in the wear resistance of the material while maintaining a low friction coefficient. Structural studies of a worn surface by IR spectroscopy and scanning electron microscopy indicate: the localization of carbon fibers and activated bentonite particles on friction surfaces with the formation of wear-resistant secondary structures; the progress of tribochemical reactions with the oxidation of fragments of the PTFE tribodecay; and the subsequent structuring of surface layers. [ABSTRACT FROM AUTHOR]

The temperature stability of bentonite greases based on petroleum (I-40A) and synthetic (PAO-10) oils with the addition of PTFE, molybdenum disulfide, and boron nitride were evaluated. It was found that bentonite lubricants prepared on the basis of industrial oil I-40A have a higher lubricating ability than compared greases based on polyalphaolefine oil PAO-10. [ABSTRACT FROM AUTHOR]

The effect of the introduction of ultrafine particles of alumina, nickel oxides and a mixture of their oxides on the mechanical and tribological properties, structure and wear characteristics of powder tin bronze is studied. The increase in the content of alumina from 2 to 5 wt % leads to a decrease in strength by 1.2–1.4 times, and from 5 to 10 wt % it does not affect the change in the tensile strength of powder bronze and leads to a slight decrease in the compressive strength. With an increase in the alumina content from 2 to 10%, the coefficient of friction and the wear rate of powder bronze decrease, and the seizure pressure increases. The addition of nickel oxide to alumina promotes the formation of a homogeneous structure, lower porosity and smaller pore size, an increase in strength, a decrease in coefficient of friction of powder bronze from 0.028 to 0.022, by 2.5 times of wear rate, as well as an increase in seizure pressure from 4 to 7.0 MPa. [ABSTRACT FROM AUTHOR]

ZrN coatings were formed by magnetron sputtering at various rates of nitrogen flow in the reaction chamber: 3, 4, 5, and 6 cm3/min. The thickness of the ZrN coatings was approximately 3 μm. Using atomic force microscopy (AFM), we studied the surface morphology; roughness; coefficient of friction Сfr; specific volumetric wear ω of ZrN coatings with the construction of Сfr dependencies on the number of scan cycles; and specific volumetric wear on load, probe speed, number of scan cycles. It was found that the coating obtained at a nitrogen flow rate of 3 cm3/min has the lowest values of Сfr and ω. [ABSTRACT FROM AUTHOR]

The results of a study of the noise generating mechanism during the application of disk brakes on rolling stock are presented. It is shown that one of the main sources of noise generation is the deformation of the microgeometry of the surface layer and its elastic recovery, which occurs under the influence of the interaction of the working elements of the disk brake. The influence of the ratio of the working areas of the friction elements that model the brake pad and brake disc on the noise intensity during their interaction is estimated. A design and technical method is proposed for reducing the noise level of a disk brake during braking, which consists of increasing the ratio between the working areas of the brake pad and brake disc. [ABSTRACT FROM AUTHOR]

Abstract—This article sets out the basic principles and approaches to modernizing a friction testing machine. The advantages and disadvantages of existing devices for tribotechnical testing of friction pairs are investigated. It is noted that friction machines manufactured by OAO TOChPRIBOR, Ivanovo, including the 2070 SMT-1 friction testing machine, were the most widespread in the Russian Federation. However, in modern conditions, these are outdated and cannot solve problems efficiently. The Department of Technical Service of Machines National Research Mordovia State University has developed and manufactured a new device for tribotechnical testing of friction pairs; it has a modern element base, including a digital signal processing system and specialized software for controlling the test process. The new device yields basic tribotechnical characteristics in real time; test results can be analyzed on a PC. The results of the study are used to increase the reliability and accuracy of tribotechnical tests of friction pairs from structural materials. [ABSTRACT FROM AUTHOR]

This study focuses on the tribological properties of superhard and functional coatings on the basis of carbide and boron nitride, which were optionally doped with powdered graphite and molybdenum disulfide. Coatings were obtained by highly concentrated short-pulse laser treatment of powder compositions on metal surfaces. The resulting coatings were subjected to wear tests under conditions of dry sliding friction with friction coefficient fixation, depending on the applied load and the composition of the powder composition. The results provide an idea of the degree of change in the coefficient of friction of coatings from the composition of powder compositions, as well as their alloying. The features of the behavior of boron carbide and nitride at high temperatures and their influence on the coefficient of friction are presented. [ABSTRACT FROM AUTHOR]

Abstract—It has been shown that the tribological characteristics of nanocomposites of polymer/carbon nanotubes are determined by the same parameters as the other properties of these nanomaterials. These parameters are the properties of the matrix polymer, structure, and nanofiller contents. In turn, the structure of nanofillers, treated as annular formations of carbon nanotubes, determines both their degree of aggregation and level of interphase interactions. This leads to a change in the control tribological characteristics of nanocomposites via a target-oriented change of the nanofiller structure, for example, by functionalization. [ABSTRACT FROM AUTHOR]

The effect of carbon nanomaterials (CNMs) of various structures (multi-layered oxidized graphene, single-walled and multi-walled carbon nanotubes, schungite carbon nanoparticles) on the friction coefficient and scoring resistance of industrially manufactured imported and domestic plastic lubricant materials (PLMs) has been experimentally investigated. It is shown, that the addition of CNMs to domestic PLMs leads to an increase in durability, and the resulting effect on the friction coefficient depends on different factors, such as the type of base PLM, the structure of CNMs, the concentration of CNMs, and the load. [ABSTRACT FROM AUTHOR]

Based on the interpretation of the laws of friction of Amontons and Coulomb as equations of linear regression of the friction force on the normal pressure force corresponding to the statistical processing of the experimental results, the values of the friction coefficients for six metal pairs are calculated. The principal difference between the values of the friction coefficient calculated in this way and the values calculated by simply dividing the friction force by the normal force is emphasized. Quantitatively, the difference can be more than twofold. [ABSTRACT FROM AUTHOR]

The results of studying the improvement of tribological properties of polyethylene products by modification with Nd and Al chelate complexes containing bulky tert-butyl groups in the ligand surrounding are given. The effect of additives on the coefficient of friction and wear of friction parts under static load is studied. The influence of coordination compounds on thermomechanical characteristics of polymers is studied. It is shown the treatment of polyethylene with Nd and Al complexes gives rise to a 1.2- to 1.5-fold decrease in the coefficient of friction and a 1.5- to 2-fold increase in the wear resistance. [ABSTRACT FROM AUTHOR]

The rheological and tribological characteristics of greases based on a complex calcium thickener using lanolin as an antifriction additive were studied in this work. An increase in the rheological characteristics, a decrease in wear and a coefficient of friction, depending on the lanolin content in the lubricant, is shown, and its optimal concentrations have been determined. [ABSTRACT FROM AUTHOR]

The dependencies for determining the axial frictional force at rest in cylindrical joints assembled with a thermal tightness at different hardness ratios of the materials of the parts were investigated in this work. It is shown that the values of the friction coefficient may significantly differ depending on phenomena occurring in the contact of the microroughness of the mating rough surfaces of the parts. The obtained dependence for the determination of the friction force was experimentally proved. The application of the developed method for determining the friction force at rest allows reliable values of the bearing strength of the pressure joint to be obtained and reveals the unused reserves of the bearing strength. The developed method may be used in the design of pressure joints. [ABSTRACT FROM AUTHOR]

Abstract—The results of friction-wear tests of rolled friction-polymer materials (FPM) of two types using the operating modes of the friction brake of a centrifugal type roller are presented in this work. The tests were performed on the Nanovea T50 tribometer according to the pin-on-disk scheme. Experimental dependences of temperature, coefficient of friction and wear on the pressure on the friction lining have been obtained. The stability of the coefficient of friction of the FPM/Steel friction pair was evaluated. Comparison and analysis of the results have been performed and recommendations on the application are presented. [ABSTRACT FROM AUTHOR]

The behavior of the friction coefficient for the initial and modified surface of butadiene-nitrile rubber with respect to a counterbody in the course of tribological tests is considered. The adhesion and hysteresis loss occurring under friction are estimated. It is shown that in the course of friction of the modified surface, the contribution of the loss of hysteresis to the friction coefficient is almost constant, whereas the adhesive component of the friction force exhibits an increase. [ABSTRACT FROM AUTHOR]

The results of the investigation of the microstructure, crystal lattice parameter, roughness, microhardness, elasticity modulus, friction coefficient, specific volumetric wear, and adhesion strength for CrN, ZrN, Zr–O–N, and Cr–O–N coatings are presented. The coatings are formed by cathodic arc evaporation and have a cubic lattice. Addition of oxygen to the nitride CrN and ZrN coatings leads to the lattice parameter increasing and the crystallite size decreasing simultaneously. The oxynitride coatings, Cr–O–N and Zr–O–N, possess improved tribological properties in comparison with nitride coatings. [ABSTRACT FROM AUTHOR]

The results of a study on the development of tribological materials based on polytetrafluoroethylene and carbon-fiber-activated material of the UVIS-AK-P brand are presented. The effect of mixing technologies on the physicomechanical and tribological characteristics of polymer composites is studied. [ABSTRACT FROM AUTHOR]

Abstract—: This article investigates the main tribotechnical properties of high borides of rare-earth metals with a UB12-type structure. The experiments have demonstrated that ZrB12, DyB12, and TmB12 dodecaborides during friction are characterized by a rather low weight wear of 10-3 mg/m, coefficient of friction f = 0.2-0.5 and are highly wear-resistant materials, as well as that porous dodecaborides with lubricants can operate for a long period of time at a low coefficient of friction as tribometric couples. [ABSTRACT FROM AUTHOR]

Abstract: This paper concerns the development of oil-filled, heat-resistant aromatic polyamide Phenilon C-2-based composites with high physicomechanical characteristics, an advantage that can withstand loads of up to 25 MPa and operating temperatures of up to 250°C in friction units. When producing oil-filled, Phenilon C-2-based nanocomposites with 300-320°C molding temperature, the choice of oils is limited and depends on their ability to maintain lubricating properties at high temperatures. The physicomechanical and tribological test results using different friction machines prove oil filling’s high efficiency in creating a stable lubricating film on a tribocontact and in improving the tribological properties of polymer composites. Research results helped outline the range of the most promising hybrid fillers for Phenilon C-2-based polymer composites and lubricants for oil filling, which contribute to the formation of a long-lasting lubricating film on a tribocontact. The combination of the experimental studies and a scientifically based approach to predicting the properties of polymer nanocomposites makes possible expedited development of new materials with high target characteristics. The technology of the production and use of these oil-filled polymers refers to nontraditional areas of plastic processing; however, the world statistics of production and consumption of polymeric friction and wear inhibitors shows that these materials are one of the most promising ways to reduce operating losses. [ABSTRACT FROM AUTHOR]

Temperature relationships of the maximum coefficient of static friction, maximum specific static friction force, and its parameters τ0 and β at the ball-plane contact are experimentally investigated. A ball indenter with a radius of 0.5 mm made of ZlM80 alloy contacted a flat gold sample (99.99%). The range of contact loads was 0.5-4 mN, and the temperature range was 24-160°C. The experiments have shown that the coefficient of friction, specific friction force, and parameter β increase with increasing temperature, while parameter τ0 decreases. [ABSTRACT FROM AUTHOR]

The modern development of automotive engineering and special-purpose machines has led to the need to increase the energy loading of friction units and provide smooth switching on and pulling away, as well as to prolong the service lives of vehicles. Domestic experience in using hydromechanical gear-boxes and oil-cooling brakes indicates that sintered friction powdered MK-5 material, a sintered blend of tin bronze reinforced with graphite particles, has become the most widespread material for this purpose. In the present work, various fibers of glass, basalt and carbon have been successfully applied as friction-purpose fillers for enhancing the tribotechnical characteristics of the material. The effect of nanoparticles as filler of sintered friction material has also been studied. In particular, embedding aluminum hydroxide (bumite) nanoparticles increases the coefficient of friction, while intermetallides (aluminides of nickel, iron and titanium) decrease the wear rate. [ABSTRACT FROM AUTHOR]

The effect of iron content on the strength and tribological characteristics of sintered tin-iron bronzes has been studied. It has been shown that the porosity has been reduced and the hardness monotonically increased with an increase in the iron content of the material. The strength dependence of the iron content is nonmonotonic, and the maximum strength increase took place at the iron content of 5%. The minimum coefficient of friction, the temperature in the friction zone and wear rate have been observed at iron content of 5-10%. In this case, the micropores and microlacunes have been formed on the friction surfaces that provide better lubricate conditions for the friction surfaces. [ABSTRACT FROM AUTHOR]

The tribotechnical characteristics of additives in compositions of modified I-40A oil with antifriction dopes in an optimal concentration (2%) have been investigated. Combined laboratory tests have been performed on an SMTs-2 friction machine to determine the optimal lubricity value and changes in the coefficient of friction. Tests have been carried under start-stop conditions under maximal contact stresses of about σmax = 550 and 680 MPa. It has been shown that the tribotechnical properties of I-40A oil improve in the presence of sulfur and phosphorus in the dopes. [ABSTRACT FROM AUTHOR]

In the article, the structure of a bench for testing the friction characteristics of a friction pair of centrifugal brake rollers has been considered. The dependences of the coefficient of friction and wear on the temperature of the materials of the friction pair, viz., a brake insert manufactured by Huzhou Jiutong Logistics Machinery Co., Ltd (China) and a domestic friction pair of the 6KV-10 rolled brake band of the EM-2 grade over St.3 steel grade (A537Gr.58), were obtained for temperature ranges that do not exceed 100°C. It has been shown that the rubber-PA6 friction pair widely used in brake rollers of foreign manufacture cannot be employed at high values of the slip velocity and the normal force applied to the friction lining, as it results in rapid heating to the critical temperature and, as a consequence, intensive wear. The domestic 6KV-10 brake band of the EM-2 grade, along with a metallic roller shell is proposed as the material of the friction pair. The frictional material proposed for the friction lining has a high coefficient of friction and a high wear resistance in a wide range of operating temperatures, normal forces, and temperatures of the frictional contact. [ABSTRACT FROM AUTHOR]

As a result of an analysis of the literature data on ground-space tribological tests of friction couples with solid lubricant coating (SLC) ARSRI PP 212, the dependences for evaluating the starting antifriction characteristics have been determined. The wear life and coefficient of friction have been compared. According to results, calculation algorithms of tribological characteristics of friction couples with SLC for considered operational conditions have been developed and implemented. [ABSTRACT FROM AUTHOR]

The dependence of the coefficients of friction of polyester fabrics with coatings based on telomeres of tetrafluoroethylene from species of telomeres has been investigated. The stiffness of coatings based on various telomeres of tetrafluoroethylene has been studied. The stability of tribological characteristics of the modified fabrics to operational impacts has been evaluated. It has been established that coatings based on tetrafluoroethylene telomeres synthesized in acetone have a low coefficient of friction and a high resistance to operational impacts. These coatings are characterized by low stiffness. [ABSTRACT FROM AUTHOR]

This article discusses the influence of the addition of vanadium nitride on the mechanical and operational properties of diamond composite material based on metallic bond comprised of iron, copper, nickel, and tin obtained by sintering in a mold at 800°C for 1 h with subsequent hot repressing. It has been established that the addition of vanadium nitride in the amount of 2 wt % to diamond-(51Fe-32Cu-9Ni-8Sn) increases the ultimate compressive strength from 846 to 1640 MPa and bending strength from 680 to 1120 MPa, as well as decreases the wear intensity of the composite material from 0.0069 to 0.0033 g/km. The mechanism of improving the tribological properties has been revealed. [ABSTRACT FROM AUTHOR]

It has been shown that the reinforcement of fluorine-containing thermoplastic polymers by carbon fibers enables a significant reduction (five- to tenfold) in their wear rate compared to steel in a mode that simulates the performance of stop valves under the conditions of dry friction with heavy loads. A positive effect has been observed for reinforcement by carbon fibers under the conditions of boundary lubrication by oil, but to a lesser degree (twofold increase in wear resistance). [ABSTRACT FROM AUTHOR]

The influence of substrate temperature and bias voltage on the structure and tribomechanical properties of the Ti-Al-N coatings obtained by reactive magnetron sputtering technique has been investigated. The structure and elemental and phase compositions have been studied by scanning electron microscopy, Rutherford backscattering, and X-Ray diffraction. The results of friction and wear experiments indicated that the lowest coefficient of friction (three times lower than 12Cr18Ni10Ti) corresponded to a coating deposited at a bias voltage of-200 V and a substrate temperature of 340°С, while the most wear-resistant coating (under a load of 700 mN and the testing time of 1080 s) was Ti-Al-N sputtered at a bias voltage of-200 V and a substrate temperature of 440°С. [ABSTRACT FROM AUTHOR]

The three-dimensional contact problem for rolling of a rigid sphere over a base, which consists of viscoelastic layer bonded to a rigid half-space has been considered. The thin viscoelastic layer simulates the action of a friction modifier. The Kelvin model has been used to describe the layer properties. The method of calculating the distribution of normal and shear stresses within the contact interaction area has been presented, the boundaries of traction have been determined, and the slip subareas have been studied. In addition, the influence of the viscoelastic layer properties on the distributions of contact stresses has been analyzed. [ABSTRACT FROM AUTHOR]

The paper treats the results of investigating asphaltenes, which present natural nanometer formations obtained by oil genesis. The use of asphaltenes as a filler for lubricating oils has been substantiated. Tribological properties of asphaltene fillers, the morphology of surface films and their chemical composition have been discussed and an attempt has been made to explain the mechanism of the friction surface cladding by the asphaltene structures. It has been proved that asphaltenes display satisfactory tribological and technical properties for their application in low-speed heavy-loaded friction joints. [ABSTRACT FROM AUTHOR]

The theory of the equivalence of friction units tests for a large number of samples to lengthy tests of one sample for friction machines of reciprocating motion based on the Birkhoff-Khinchin theorem for processes that meet the criteria of ergodicity and stationarity has been developed. It has been established that a large part of the examined friction pairs under the indicated test conditions meets the specified criteria. [ABSTRACT FROM AUTHOR]

Friction and wear regularities of the bronze-steel joint have been studied during continuous sliding and friction with recurrent start and stop periods. The test results for friction without cooling and constant temperature of the lubricating material have been compared. Under the conditions of the forced cooling of the oil, transfer from continuous to periodic sliding is accompanied by a growing coefficient of friction and the wear rate of the bronze counterbody. Under conditions without cooling and in certain loading modes, the reverse scenario is probable. [ABSTRACT FROM AUTHOR]

The paper presents the results of theoretical and experimental investigations in the effect of a partial heat energy removal in the friction contact zone upon the disc brake coefficient of friction during braking. A fluid cooling system for the disc brake friction elements has been proposed based on a recuperative liquidpneumatic heat-exchange apparatus. [ABSTRACT FROM AUTHOR]

The effect of Belum discrete carbon fibers on the service properties and structure of polytetrafluoroethylene has been studied. It has been shown that a filling of polytetrafluoroethylene with 1-5 wt % of carbon fibers does not worsen the stress-strain properties of composites. The introduction of carbon fibers improves the tribological characteristics of polytetrafluoroethylene. The thermodynamic and structural studied of polymer composites have been performed. [ABSTRACT FROM AUTHOR]