Development of Metal Cladding Additives for Agricultural Machinery Friction Unit Parts

The choice of materials for the formulation of the metal cladding additive has been theoretically substantiated. A process has been developed and a copper-containing lubricant composition has been synthesized. It is shown that the use of a metal cladding additive having antifriction and antiwear properties reduces 2.9 times the part wear rate. The effect of the additive on the anticorrosion properties and thermal-oxidative stability of the base oil has been studied.

Asperity level frictional interactions of cylinder bore materials and lubricant composition

Parasitic frictional losses in internal combustion engines of race vehicles adversely affect their performance. A significant proportion of these losses occur within the piston-cylinder system. This paper presents a study of the compatibility of cylinder bore surface materials with typical lubricant base constituent stock (poly alpha olefin and polyolester) as well as a fully formulated lubricant. Nanoscale boundary friction is measured using lateral force microscopy. The effect of material properties, nanoscale roughness and lubricant species upon underlying mechanisms of generated friction is presented. Advanced cylinder materials and coatings and lubricant molecular species used for high performance engines are investigated, and an integrated approach not hitherto reported in literature.

Tribocontact surface exploration after friction in hexanoic acid solution

Introduction. The paper considers the evolution of friction coefficient of the pair of copper - steel alloy under friction in a hexanoic acid solution in various concentrations, and antiwear properties of the steel-steel friction pair in an oil-acidic medium. The work objective is to explore the effect of hexanoic acid additives on the tribological characteristics of friction pairs under the friction interaction in waterborne and paraffin-based formulations. Materials and Methods. Tribological studies of a brass-steel friction pair were carried out on the AE-5 end-type friction machine. Antiwear characteristics were explored on a four-ball friction machine (FBW) in accordance with the standard GOST 9490–75. When tested at the FBW, the objective parameters of the lubricity of the oiling compositions were: welding load (Рс); wear spot diameter (Dн), critical load (Рк). Roughness parameters of the servovite film were determined through the optical profilometry; its microgeometry and structure at the nanoscale – through the atomic force microscopy. Research Results. Tribological properties of the brass-steel tribocoupling in aqueous media and steel-steel one in petroleum paraffin-based media are studied. The dependence of the frictional characteristics of the brass-steel friction pair on the concentration of carboxylic acid is established. Its optimum concentration is specified, which provides the effect of wearlessness. A decrease in surface roughness is revealed as a result of the frictional interaction of a brass-steel friction pair in the hexanoic acid solution compared to the initial friction surface due to the formation of a sufficiently dense layer from fine-grained copper clusters with tight particle-size dispersion. The tribological characteristics of a steel-steel friction pair were found to depend on the composition of the lubricant. It is shown that the dependence of the size of the wear scar diameter (WSD) on the acid content in the base oil is nonmonotonic in nature with a pronounced minimum at a concentration of 0.1 mass. %. The critical load (Pк) at a content of 0.05 and 0.1 mass. % increases by 32%, welding load (Pc) - by 27%.Discussion and Conclusions. As a result of the tribological studies of a brass-steel friction pair in the hexanoic acid solution, it has been found that the optimum acid molar concentration in the lubricant composition is 0.1 mol/L. Under the frictional interaction of a brass-steel pair in the hexanoic acid solution, an antifriction copper film is formed on the friction surfaces, which contributes to a sharp decrease in the friction coefficient to 0.007 and metal wear of the friction pair to 25 times. As a result of the frictional interaction of a brasssteel friction pair in the hexanoic acid solution, a decrease in roughness is revealed compared to the initial friction surface. It is found that the frictional interaction of a brass-steel pair in the hexanoic acid solution causes a significant modification of the friction surface as a result of the deposition of finely dispersed copper clusters occurring in the lubricating medium composition and forming a servovite film. As a result of studies, it is found that the dependence of the WSD size on the acid content in the base oil is nonmonotonic in nature with a significant minimum at a concentration of 0.1 mass. %. It is shown that the addition of 0.1 mass. % of hexanoic acid into the lubricant composition exhibits the smallest wear of the steel-steel tribological pair, the WSD decreases to 0.497 mm, the critical load (Pк) and the welding load (Pc) increase by 32% and 27%, respectively.

THE EFFECT OF GRAPHENE ADDITIVE ON THE TRIBOLOGICAL PROPERTIES OF BIONIC LUBRICANT COMPOSITIONS TESTED BY THE SRV METHOD

The aim of the study was to investigate the effect of the addition of graphene dispersion on anti-wear properties of bionic lubricant compositions based on aqueous sodium hyaluronate solutions. Tribological tests were carried out using a SRV tester, enabling the tests to be carried out in conditions of linear oscillating movement of the bullet-shield type association in which the ball was made of aluminium oxide and the disc was made of bearing steel 100Cr6. For research, a 0.5% solution of sodium hyaluronate in water (composition BSS2) was chosen, which was the base to which the graphene additive was introduced. During the main stage of work, three lubricant compositions were tested, i.e., as well as BSS2 solution, into which 0.05% m/m or 0.1% m/m graphene oxide was introduced, respectively. The study allowed the observation of a clear anti-wear effect associated with the introduction of graphene preparations into the hyaluronan base, manifested in a change in the trend of the graph of the coefficient of friction over time. In addition, a reduction in the volume wear of friction node components was found. Based on the analysis of tribological research results, it was found that the anti-wear effect of the lubricant on the friction elements of the steel-ceramic material combination increases with increasing the content of the graphene preparation in the lubricant composition.

In-situ-determination of tribologically induced hydrogen permeation using electrochemical methods

White etching cracks are one of the possible causes of bearing damage, which can lead to the failure of wind turbines. The mechanisms of hydrogen diffusion in bearings are not yet fully understood, but it is assumed under tribological loading that the lubricant degradation releases hydrogen which diffuses into the contacting surfaces (i.e. steel). This leads to hydrogen-induced cracking and damage to the bearings. In order to better understand these mechanisms, it is necessary to investigate the influence of tribological loads and lubricant composition on hydrogen release. For this purpose, a test setup was developed for the analysis of tribologically induced hydrogen permeation by means of a ball-on-plate test. The diffused hydrogen was measured with an electrochemical three-electrode setup. The results showed a direct correlation between the amount of hydrogen released and the applied normal load. Furthermore, an increased velocity resulted in enhanced diffusion of hydrogen through metal. In addition, the tribological contact surface was decisive for hydrogen permeation. The higher velocity and the larger contact area result in an activated nascent iron surface which promotes hydrogen penetration. The results show that lubricants can be classified as critical for the formation of hydrogen embrittlement in tribological contacts.

OPTIMIZATION OF THE COMPOSITION OF THE ELECTRICAL CONDUCTING LUBRICATING COMPOSITION FOR OPERATING APPLICATION IN THE BATTERY-BRUSH ASSEMBLY OF THE ELECTRIC MOTOR

A large number of methods for improving the efficiency of collector-brush units, a common feature of which is the creation of thin transition layers on the contact surface of materials that do not affect the current flow in contact and reduce the intensity of mechanical wear, have been studied. The data obtained in the course of the work showed that the electrically conductive lubricant composition helps to reduce the coefficient of friction to increase the wear resistance of the brush material and improve the switching conditions of the entire collector-brush unit. Considered the issue of optimization of the composition of the electrically conductive lubricating composition to the collector-brush Assembly of a traction motor. Providing with minimal costs the required composition of the conductive lubricant composition that meets the operating conditions is a difficult task and depends on a number of parameters of the components used. By using the generalized parameter of optimization of the desirability function of E. Harrington the optimal chemical composition of the conductive lubricant composition is obtained. Application of method E. Harrington to optimize the composition of the lubricant composition, allowed to meet the antagonistic requirements for its composition by mechanical and electrical characteristics, which had a positive impact on improving the performance and reliability of not only the collector-brush unit, but also the entire traction motor of the locomotive in operation.

Development of the lubricant for side-mounted rail flange lubricators for traction rolling stock

Specificity of operating conditions of the rolling stock defines a number of requirements for lubricants intended for the wheel-rail tribosystem. Lubricants are used for “wheel — rail” contact, the aggregate state of which varies from liquid to solid. When evaluating the lubrication properties of these materials, a significant number of factors must be taken into account, in particular, influence of the environment, method of application, condition of the rail surface. The paper discusses the main operational requirements for lubricants operating in a wheel-rail tribosystem. Temperature ranges of the lubricants used for the “wheel — rail” contact on the railway network of the Russian Federation are given. As a result of the research, it was determined that none of the materials used for lubrication of the wheel-rail system satisfies the operating temperature conditions of the traction rolling stock. To solve this problem a lubricant was developed and tested in an industrial environment at the Rostov State University of Railway Transport. Its lubricant composition allows to significantly expand the temperature range of the lubricant. Complex of experimental studies and method of orthogonal central composite plan of the 2nd order established the optimum values of the thickness of the working shell of the 0.846 mm lubricating rod and the 50.411 % percentage of plastic lubricant, allowing to extend the temperature range of lubricant rods and, in particular, completely eliminate the lubricant flow to achieve a temperature of 126.034 °C. Proposed composition of the lubricant was tested on a freight electric locomotive of the VL80T series, equipped with non-power lubricators, under the conditions of the Bataysk — Likhaya section of the North Caucasus Railway. Intensity of wear of the wheel flanges of the traction rolling stock lubricated by the proposed material, compared with the intensity of wear of the wheel flanges without the use of lubrication systems is reduced by 2 times.

THE EFFECT OF THE TYPE OF WALL MATERIAL AND GREASE COMPOSITION PAIRING ON SHEAR STRESSES IN BOUNDARY LAYER

The paper presents the results of research on the influence of fillers introduced into plastic greases on the rheological properties of the boundary layer of the resultant lubricant compositions. The fillers were PTFE and MoS2 powders. They are added to lubricants to improve their tribological properties; however, these fillers also affect the rheological properties of the composition. This affects the change of the shear stress value in the lubricant during its flow in the lubrication system. Knowledge of this value, especially during the flow of the lubricant composition in the boundary layer, has a significant impact on the operation of automated central lubrication systems in which these compositions can be used. Measurements were carried out by means of a rotary rheometer (Rheotest 2.1). Tests were performed on lithium and bentonite greases (without additives) as well as compositions of these greases containing various percentage of the fillers mentioned above. Test results showed that both the type of grease and the type of filler introduced into this grease affect the rheological properties in the boundary layer of the produced lubricating compositions.