Vol 39, No 5 (2018)

The effect of adhesive activation of polytetrafluoroethylene (PTFE) powder by sodium ammonia solution on the structure and tribological behavior of sintered polymer is studied. The friction coefficient of the adhesion-activated PTFE (PTFE-A) increases, while the rate of wear decreases compared to the original PTFE by about 50-fold on friction against 40X13 stainless steel and by up to 800-fold on friction against 40X chromium steel. The difference is attributed to the dependence of the rate of wear on activation of the tribochemical mechanism, which is responsible for chemisorption of the transfer film on the metal counterface and increases its life, wear resistance and, eventually, the wear resistance of PTFE-A. When the friction conditions preclude its activation (friction against 40X13 stainless steel), the modest improvement in wear resistance is achieved through increased intermolecular interaction in PTFE-A. On friction against corrosion-active 40X steel, an iron oxide layer facilitates chemisorption of the transfer film providing for additional reduction in the wear rate by more than an order of magnitude. Functionalization of PTFE-A also inhibits the dependence of the wear rate on the relative humidity of the surrounding atmosphere observed during friction of some PTFE-based composites, which may be useful for practical applications.

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.

The effect of temperature on the friction coefficient under boundary lubrication by cholesteric liquid crystal nanomaterials, as well as by their solutions in industrial oil, is studied. It is established that the minimum friction coefficient for the investigated substances is reached in the mesomorphic state. In the isotropic state, an insignificant monotonic increase in the friction coefficient with increasing temperature is observed. The friction coefficient also decreases with the increasing molecular weight of the lubricant. Under friction in solutions, an abrupt increase in the friction coefficient occurs when a certain critical temperature is reached, which could be caused by the temperature destruction of the adsorbed layer.

The tribotechnical characteristics of grease oxidized with ozone and modified with a carbon framework (CF) are studied. It is shown that, starting from the temperature of 150°C and up to 600°C, the ozone oxidation of compressor oil KS-19 (grease based) and the active components of a CF used as an additive have a favorable effect on the characteristics of the adhesive interaction under friction due to the low level of plasticity of the frictional contact.

A method for calculating the frictional moment in cageless rolling bearings has been developed. Test results of cageless bearings have been shown in the study and comparison of experimental data of frictional moments with theoretically calculated frictional moments has also been shown. A conclusion has been drawn about the correctness of the method based on the data collected from the experiments.

The contact problem concerning sliding of a solid surface with a regular relief along a fixed ring-shaped elastomer under normal load and rotational moment is studied. The concept of an effective (integral) coefficient of friction is introduced, and the aim of this study is to analyze the dependence of this value on the density of contact spots. The problem is solved by direct computer modeling in finite-element formulation. It is shown that dependences of an effective friction coefficient on time have a nonmonotonic cyclic character with transition to the steady-state regime. The amplitude values of an effective friction coefficient are higher for a lower density of contact spots at a fixed value of the normal load on the sample, whereas its averaged value is higher for a higher density of contact spots.

The microstructure, hardness, and wear resistance of surface deposited layers made of experimental 20Cr16 and 26Cr16 wires on 55Mn steel were investigated. It was shown that during crystallization, these deposited layers, having very high hardness, did not form cracks and/or other defects typical of high-strength deposits. The absence of dendrites and lack of significant chemical composition gradients across the overall section ensures that they are microstructurally uniform in depth, and therefore, their hardness and wear resistance is also independent of layer depth. The latter properties appeared to be only slightly dependent on the type of wires used, despite their significant difference in carbon content. The results make it possible to consider the designed experimental wires as highly promising for practical application in industry.

The technological features for magnetic lubricating oil synthesis with a carboxylic acid diester-based dispersion medium , and the study results of their properties are presented. Physicochemical and tribological features of diester-based magnetic lubricating oils are studied. The lubricating properties of magnetic oils under various friction conditions are investigated and their specific characteristics are established. An effect exerted on friction by a number of antiwear additives dissolved in oils is analyzed and their action mechanism is proposed.