Improvement of operational parameters for precision rolling bearings by cleaning working surfaces from micro pollution of various nature

In manufacturing high-precision rolling bearings for aviation and urban machinery, the key tasks are to reduce the cost of production of such products, increase their efficiency and resource, and ensure their reuse after performing appropriate repair work. The results of many years of research show that these tasks can be successfully solved by cleaning the working surfaces of the parts of such precision tribonodes by non-contact pulse methods, particularly by using variable electromagnetic fields. The article describes the process of deep cleaning the working surfaces of parts of various high-precision ball bearings (from overall to miniature). During this cleaning, ferromagnetic and other impurities in the form of micro-, sub-micro- and nanoparticles were removed on a developed stand that can be used on an industrial scale. Further studies of cleaned bearings showed improved operational parameters such as reduced noise and vibration and the degree of magnetization. To achieve the specified results, appropriate cleaning methods were developed and tested

Resource testing of modified plain bearings for the aviation industry

The resource tests of plain bearings with metal-polymer tribo-systems developed for the aviation industry are presented. The purpose of the work is to determine the wear resistance of modern anti-friction polymer materials in plain bearings in comparison with metal fluoroplastic tape. The uniqueness of the tests lies in the use of a combination of high-performance polymer materials in a pair with chromium and molybdenum coating during the reversible movements of plain bearings. Since the use of such bearings is mass in nature, the use of titanium materials in the manufacture of bearing cages will allow to significantly reduce the weight of the aircraft and increase its efficiency. It was determined that a plain bearing with a polymer material of carbon and polyamide fibers and PTFE with functional additives shows a wear resistance 1.8-2 times greater on the segment of 40-100 thousand cycles than bearings with other materials during laboratory resource tests. Also, industrial tests have established that after 2 million cycles, a hinged bearing with a metal-polymer tape shows a result that is 1.2-1.5 times lower in wear resistance than polymer materials, but all these results are within the tolerances of normal bearing operation. Industrial tests have proven that at replacing the inner ring of a plain sliding bearing with a titanium alloy with a molybdenum coating, the wear resistance is almost the same or slightly lower than when the polymer rubs against steel. Technological recommendations have been developed and a new design and materials of plain sliding bearings with polymer anti-friction coatings for the aviation industry have been proposed. The implementation of technological recommendations in the production of bearings will allow to move away from the universality of the use of plain bearings and extend their wear resistance and durability in general due to the use of the full thickness of the polymer material and the development of bearings with predicted characteristics for a specific task

Tribomonitoring of the quality of aviation hydraulic oils according to lubricity and rheological indicators

The study proposes a diagnostic control method for assessing the quality of commercial batches of hydraulic oils based on the kinetics of changes in the thickness of lubricating layers, shear stresses of the lubricating material, and effective viscosity in tribotechnical contact. Timely and high-quality tribomonitoring of lubricants provides a perspective on their rational use and reduced wear of equipment parts. The developed methodology simulates the operation of gears in rolling conditions with a slip of 30% using a roller analogy. Samples of AMG-10 oil from two manufacturers were analyzed. For "Bora B" AMG-10 oil (sample 1) with gradients of the sliding speed of the lubricating layer in contact from 5.63·103 to 5.73·105 с-1, the effective viscosity is set at the level of 4249 and 5039 Pa·s at a bulk oil temperature of 20 and 100 oС, respectively, which indicates the resistance of oil components to destruction under conditions of increasing shear rate gradient. For AMG-10 oil (sample 2), the effective contact viscosity decreases by 1.53 times both at an oil temperature of 20 oС and at 100 oС and is 2764 Pa·s (at 20 oС) and 3309 Pa·s (at 100 oС), which indicates the destruction of the components of the lubricant. For "Bora B" AMG-10 oil, effective lubricating properties have been established both during the start-up period and at maximum revolutions in conditions of rolling with slipping. It was shown that at start-up, regardless of the temperature of the lubricant, the mixed lubrication mode dominates. At the maximum revolutions of the tested samples, the hydrodynamic lubrication mode dominates, which indicates the effective lubricating properties of the Bora B AMG-10 oil. According to the kinetics of changes in the rheological parameters of oils, it was established that the resistance of the lubricant's components to mechano-thermal destruction under non-stationary lubrication conditions contributes to the effective formation of a lubricating layer in contact with a high bearing capacit

Mechanisms of formation of wear-resistant dissipative structures in non-stationary lubrication conditions

The work aimed to determine the influence of the processes of supramolecular self-organization in the lubricating layer on the patterns of wear of friction pairs. The mechanisms of structural adaptability of tribocoupler elements were analyzed, and the regularities of the manifestation of a large-scale and energy jump, which characterizes the transition of the tribosystem to a metastable state, were determined. An evaluation of the tribotechnical characteristics of commercial transmission oils was carried out on a software-hardware complex that, using a roller analogy, simulates the operation of gears in conditions of rolling with slipping. It was established that the activation of contact surfaces in the mode of frequent starts and stops leads to active interaction of the lubricant's components and the metal's surface layers with the gradual formation of boundary adsorption layers. For transmission oil 'Bora B' T-Shyp, an increase in anti-friction properties has been established due to the effective lubricating ability of the oil when forming the hydro- and non-hydrodynamic components of the lubricating layer thickness. The effect of the chemical activity of the zinc dialkyl dithiophosphate antiwear additive and the hydrocarbon components of the base of transmission oils on the effectiveness of the formation of boundary films is considered. It was determined that the formation of stable boundary films of the lubricant is the leading process in manifesting their damping properties concerning the localization of elastic-plastic deformation along the depth of the metal. When boundary films are formed on 90-95% of the contact area, the change in the microstructure of the near-surface layers is fixed at a depth of up to 20 microns; when boundary films are formed on 20...50% of the surface area, the spread of elastic-plastic deformation reaches a depth of up to 50 microns. The kinetics of the formation of boundary films by the lubricant and the indicators of the specific work of friction in contact are correlated with the intensity of wear of the contact surface

Determination of the optimal parameters of the structure of functional gradient materials using mathematical modelling approaches

Purpose: Functioning of mechanical friction systems largely depends on the characteristics of the structure of their surface layers. By controlling these parameters, it is possible to significantly adjust the reliability and durability of parts under the conditions of contact interaction. Design/methodology/approach: he proposed approach, which is based on the principle of nonlocality of the operational properties of materials, allows determining the optimal microhardness values of the surface layers and the gradient of this parameter, at which the contact durability of friction pair elements significantly increases. Findings: It is established that by adjusting the ratios of the surface strength of materials and its gradient, it is possible to achieve a significant increase in the operational parameters of friction units. Practical implications: The engineering relationship considered in the work allows to establish functional distributions of microhardness in the structure of surface layers, at which their wear reaches minimum values. Originality/value: Mathematical approaches are proposed, which allow determining the parameters of the structure of the surface layers of parts to increase their durability under conditions of friction contact loads

Structura and phase transformations in coatings from ferritic and martensitic steels under gas-thermalspraing and modifying by electric-contact treatment

Исследован процесс формирования износостойких покрытий на железо-углеродистных сплавах при газопламенном и электродуговом напылении, и модифицировании поверхностных слоев напыленных покрытий, структурно-фазовые превращения в напыленных покрытиях при их модифицировании. Показано, что наиболее целесообразно высокую износостойкость, твердость и прочие свойства газотермических покрытий из сплавов на основе железа можно обеспечивать таким методом модифицирования, как электроконтактная обработка. In the initial state of gas-thermal coatings from steels of the martensite (FKh800) and ferritetypes, the matrix phase is the alpha-phase, which is formed independently of the productionmethod before electric contact treatment during the coating deposition at the stage of steel drophardening owing to its collision with the working surface due to the gamma-alpha transformationand is characterized by high hardness. Additionally, there are also some contents of ironoxides FeO; and Fe3O4, which arise in the course of coating deposition as a result of the interactionof melted iron particles of the steel with the oxygen of the working gas flow. The highcontent of carbon in steel 40Kh13 (0.48 at%) as compared to steel Sv-08 (0.06 at%) is relatedto the formation of residual austenite (gamma-phase) and high saturation of the alpha-phasewith carbon, which is confirmed by the increase in the alpha-phase lattice parameters in thecoatings from steel 40Kh13 comparing to steel Sv-08 as well as by higher microhardness(HV = 3000 and 1750 МPа, respectively). Moreover, the higher carbon content in coatingsfrom steel 40Kh13 is the reason of the appearance of residual austenite (gamma- phase) alongsidewith alpha-phase at the all stages of coating deposition. The intense thermal action of electriccontact treatment promotes the further increase in the carbon content in the alpha- phase.Also, the electric contact treatment of coatings from Sv-08 and 40Kh13 steels leads to decreasein porosity and increase in the content of oxygen in the surface layer. This is accompanied withincreasing microhardness after the treatment. In coatings from steel 40Kh13 the content ofresidual austenite decreases from the initial value 16 vol. % down to 8 vol. %, which is connectedwith the surface heating