Journal of Friction and Wear最新文献

The properties of a semi-liquid lubricant (Lb) with additives were tested using a KT-2 oil testing machine; its stability and influence on the ‘wheel flange—rail’ friction pair was assessed. The analysis is based on laboratory wear tests of locomotive wheel flanges. Investigation of lubricants with additives showed their low colloidal stability, the highest oil release being observed with the addition of sulfo compounds and phospho additives. The thermal stability of lubricants with additives shows that at approximately 220°C the lubricants melt completely and turn into a liquid state. After conducting tribological tests on a KT-2 oil testing machine of a lubricant with a hydroquinone additive, white crystals formed on the surface of the facility. The dependence of the friction coefficient on the test temperature of the studied lubricant with additives was obtained. X-ray fluorescence analysis of the locomotive wheel flange surface showed a change in the concentration of chromium and manganese in the surface layer of the sample before and after bench tests, which may indicate the formation of a stable transfer layer providing good tribological properties. Empirical coefficients were obtained to determine the wear rate of the locomotive wheel flange for the studied additives.

The tribomechanical properties of UPA-6130UV antifrictional polyamide composite filled with short carbon fibers have been studied in relation to metal-polymer bearings, gears, etc. The “pin-on-disc” setup was used to determine the macroscopic characteristics, and contact indentation and scratch testing, were employed to find submicroscopic parameters of the surface layer of this material before and after friction. It has been found that the tribological properties of studied carbon-filled polyamide are superior to those of glass-filled polyamide. With increase in the specific load, the mass wear of the UPA-6130UV composite increases less (from 0.0012 g at 10 MPa to 0.004 g at 40 MPa) and is significantly smaller than that of the PА6-L-SV30-1 glass-filled composite, the wear of which is 0.003 g at 10 MPa and 0.042 g at 40 MPa, respectively.

In this paper, we study the effect of corrosion inhibitors in compositions of friction composites on corrosion processes and noise generation in friction units. Model composites containing complex corrosion inhibitors as target additives were prepared. Tribological tests of the friction composite were performed using the “plane-to-plane” scheme. Transfer films on the surface of a steel counterbody are shown to be formed predominantly by laminar wear particles of the composite with sizes up to 50 μm. X-ray photoelectron spectroscopy data confirmed the presence in the transfer films of all elements related to the main components of the friction material, including corrosion inhibitors. Climatic tests were carried out. In a friction pair with a composite containing no corrosion inhibitor, continuous corrosion of the metal counterbody is shown to be predominant while pitting actively develops over time. The degree of corrosion damage to the surface reaches 90–95% of the nominal contact area. The introduction of a complex corrosion inhibitor into the composition of friction composites in an amount of 1.5–3.0 wt % was established to reduce the degree of corrosion damage to the nominal friction area of the metal counterbody by 20–35%. Outside the nominal friction area, the effect of reducing the degree of corrosion damage to the surface area of the metal counterbody by 50–60% was found. Triboacoustic tests were carried out on metal counterbodies subject to corrosion during climatic tests. Levels of sound pressure produced by the friction pair in the frequency range of 50 Hz–20 kHz are determined. The use of corrosion inhibitors was found to lead to a decrease in noise levels while the most significant decrease of 7–30 dB occurs in the high-frequency region of 6–20 kHz.

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.

Microcapsules consisting of only a gelatin shell, a gelatin shell with magnetite, and a gelatin shell filled with ozonated water (ozonated water in the microcapsule core was adsorbed by activated carbon), a gelatin shell treated with ozone, a gelatin shell with ozone-treated magnetite, and a gelatin shell containing magnetite and ozonated water were obtained by simple coacervation method. The effectiveness of using aqueous emulsions of the shells as production lubricants and coolants during cutting in turning operations on a 16K20 screw-cutting lathe using side cutters made of high-speed R6M5 steel was investigated. The set of processed materials included 12Kh18N10Т stainless steel, 40Kh chromium steel, and VT5-1 and VT-6 titanium alloys. The introduction of ozone into the composition of microcapsules is shown to increase the period of normal wear of the cutting tool. In addition, the duration of the initial wear-out period increases. It was revealed that the wear resistance of cutting tools increased most strongly if microcapsules with gelatin shells filled with magnetite and ozonated water are used. The increase in the wear resistance of a cutting tool can be explained by the formation of lubricant films at the interface between the tool and the material being processed; the films may include metal polymers and complex compounds of atomic iron, covering surface irregularities that are sterically inaccessible to metal polymers. Based on this hypothesis, an approach has been proposed, which enables predicting the potential effectiveness of production lubricants and coolants using quantum chemistry methods.

The results of a study on the influence of the modes of obtaining sintered BrO12 bronze on its structure, phase composition and tribological properties during friction with a lubricant are presented. It is shown that the phase composition of BrO12 bronze sintered for 5 min consists of a solid solution of tin in copper and inclusions of intermetallic phases δ-Cu41Sn11 and Cu81nSn22. An increase in the exposure time during sintering leads to an increase in the homogeneity of the solid solution of tin in copper, a decrease in the crystal lattice parameter of copper from 3.69 to 3.68 Å, an increase in the grain size from 2–5 µm at 5 min of sintering to 15–46 µm at 120 min, a decrease in the content of the intermetallic phase δ-Cu41Sn11, and the disappearance of the Cu81nSn22 phase at 60 min of sintering and the virtual absence of intermetallic compounds after sintering for 120 min. Tribological tests have shown that the friction coefficient of bronze sintered for 5 min at a pressure of 4 MPa varies from 0.08 to 0.03, and at 20 MPa, from 0.105 to 0.04, the average wear value at a pressure of 4 MPa and 20 MPa was 2.0 µm. The coefficient of friction at the above pressures of bronze sintered for 60 min was 0.11–0.036 and 0.095–0.023; 0.045 and 0.12–0.5, respectively, wear was 6.3 µm.

Carbon–carbon composite materials (CCCMs) are used in brake systems and in movable sealing joints, since they can have both frictional and antifriction properties, depending on their structure. In recent studies, data were obtained on the thermal properties of various CCCMs and the coefficient of friction in a pair with various counterbodies as a function of temperature. In this case, the nature of the dependences of the friction coefficient and the coefficient of linear thermal expansion on temperature is similar and has close critical points. The paper investigates the contact interaction of a heated heat-insulated annular punch with a half-space, the thermal expansion coefficient of which depends on temperature. Analytical expressions are obtained for calculation of the contact pressure and the penetration of the punch for various temperature distributions over the contact area. To take into account the uneven heating of the contacting surfaces, the temperature distribution under the annular punch was calculated during its frictional interaction with the elastic half-space. The case of temperature distribution during heating from spinning friction, which is typical for tribological tests and operation of interfaces made of CCCMs, is considered. It is established that in the considered case the temperature increases from the inner radius of the annular punch to the outer one. The joint effect of the ring width and temperature distribution on the value of contact pressures is studied. Calculations show that taking into account frictional heating is more important for narrow punches, while the minimum pressure in the contact area can significantly decrease at a fixed value of the external load.

The aim of this study is an experimental-based analysis of the effect of surface treatment, leading to the formation of carbonized layers, on the coefficient of sliding friction of two polyurethane materials that differ in mechanical and rheological properties. The properties were determined by the results of indentation on a NanoScan-4D scanning nanohardness tester. A ceramic ball with a diameter of 2.1 mm was used as an indenter, which was pressed into the samples at a given linear velocity. The indentation curves at low and high indentation velocities were used to calculate the longitudinal and instantaneous reduced modulus of elasticity. It was found that the longitudinal elastic moduli differ by more than seven times, and the rheological properties of a more rigid material are weak. Tribological tests were performed on a UMT-3 friction machine in the mode of unidirectional sliding friction at a constant load and velocity. Based on the data, regression equations were calculated and the dependences of the friction coefficient on the load and sliding velocity were obtained. The influence of the surface treatment fluence on the surface roughness, adhesion, and deformation friction force is analyzed, data are correlated with the known experimental and theoretical results. It is shown that surface treatment with a relatively small fluence gives fundamentally different effects for the two studied materials: a slight change in roughness and decrease of friction coefficient for the more rigid polyurethane; a significant increase in roughness and a consistently high coefficient of friction, which varies slightly in the considered ranges of loads and velocities. Thus, surface treatment can be used for controlling the coefficient of friction of polyurethane and ensuring its consistently high frictional properties.

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.

The features of the structural and tribotechnical characteristics of copper alloys and coatings during friction of a steel–steel pair are analyzed. Copper-based coatings obtained by gas-dynamic spraying have been experimentally studied. The wear resistance and microgeometric characteristics of the surface of steels with coatings of the composition Cu : Al₂O₃ = 55 : 45 (wt %) and Cu : Zn : Al₂O₃ = 35 : 35 : 30 (wt %) are determined. A coating is formed from a powder mixture of copper and corundum, mainly consisting of copper. Corundum is present in the form of particles with a size of 0.05 μm² in an amount of less than 1%. The coating has a high performance when tested under friction and wear conditions: wear intensity I_h (coating) ≈ (1.1–1.5) × 10^–10 and I_h (counterbody) ≈ (0.3–0.4) × 10^–11 under friction in I-20A mineral oil; I_h (coatings) ≈ (2–5) × 10^–10 and I_h (counterbodies) ≈ 0.2 × 10^–11 during friction in Litol-24 grease. Heat treatment of such a coating causes diffusion of zinc into copper with the formation of a solid solution of zinc in copper (α-phase) and an electron-type solid solution based on CuZn is also formed. The mechanism of contact interaction of steel coated with Cu–Zn–Al₂O₃ in a pair with ShKh15 steel is based on the process of mass transfer in the zone of surface plastic deformation, which minimizes the level of surface destruction of the pair as a whole, reducing it to practical wearlessness at high external pressures. Deformation, diffusion, and mass transfer in the zone of contact interaction during friction point to the effect of “classical wearlessness,” a distinctive feature of which is the formation of a copper-zinc third body interspersed with corundum, which has the ability to transfer from the sample on the counterbody and vice versa, providing protection of the surface layers from destruction but not a servovite copper film (with a special structural state). High wear resistance of friction pair materials is achieved due to frictional mass transfer films.