Vol 38, No 1 (2017)

The tribotechnical properties of thin-film coatings obtained as a result of the tribomodification of 40Kh steel by various organic-inorganic tribotechnical materials (natural inorganic and synthetic polymers), as well as the compositions and composites created based on vermiculite are considered in the work. Comparative tribotechnical tests have made it possible to establish that the most promising materials for the tribomodification of the friction surfaces of steels are nanostructured composites based on vermiculite, which make it possible to get the minimum coefficient of friction and high wear resistance of the conjugation under the friction condition at boundary lubrication.

The article describes new mixed technology for increasing the wear resistance of parts of transport engines based on the example of a crankshaft. The basis of the new mixed technology is the heat treatment of crankshaft pins and the application of a multilayer antifriction coating in one technological cycle. Laboratory tests on mixed technology application revealed an increase of wear resistance of crankshaft pins, a reduction in the coefficient of friction, a reduction in the running-in period, and an increase in the scoring resistance and operating life of the crankshaft.

A technique for the design calculations of the local strength, wear, and durability of tractive cylindrical double gear of VL-10 locomotive with angular tooth correction has been suggested. The technique allows for realistic engagement conditions (parity and wear-induced changes in the tooth profile curvature). The regularities of the effect that structural (angular engagement correction) and operational (linear tooth wear) factors have on these parameters for triple–double–triple tooth engagement in this gear have been revealed. It has been established that, when considering tooth correction, there are certain optimum displacement coefficients that maximize the durability compared to the uncorrected gear. It has been shown that, if one allows for changes in the tooth-profile due to wear are allowed for, the actual durability and bearing capacity of the gear is higher. The results have been presented graphically in order to help establish regularities of the effect of engagement conditions on the tribotechnical characteristics.

The development of new compositions of sintered friction powders based on copper that operate in lubricated states should be based on deep knowledge of peculiar features of break-in and wear mechanisms of both counterbody and friction material. The obtained data have enabled the determination of the existence of the transferred bronze layer of friction material, the peculiarities of the generation of the surface microprofile of the counterbody during operation, these data can be useful upon assessing the thermal loading of the friction zone.

The results of an investigation of the influence of intensive friction interactions upon the transformation of a 20Х13 steel structure using optic metallography, scanning electron microscopy, and X-ray microanalysis have been described. It has been stated that, at a depth of 3 mm, structural changes connected with heating and intensive plastic deformation processes take place. Diagrams of chemical elements distribution show changes in the steel chemical composition in the surface layer up to 20 μm depth. An increase in microhardness to 5000 MPa has been observed at certain sections.

The results of an investigation of the effect of bulk quenching from temperature in the range of 760–1050°C, cryogenic treatment (–196°C) and surface plasma hardening on the abrasive-erosion wear of frugally alloyed V–Cr–Mn–Ni cast irons with spheroidal vanadium carbides have been presented in this article. It has been found that cast irons containing 5.0–7.5% V, 4.5–9.0% Cr, and 5.5–5.7% (total) of Mn and Ni after heat treatment have a 2–3-fold advantage in wear resistance compared to the prototype high-vanadium cast iron (11.9% V, 12.9% Mn). The maximum wear resistance of cast irons studied is achieved by quenching at 760°C followed by plasma surface hardening, as well as quenching at 840°C, followed by cryogenic treatment. These treatments result in the formation of an optimum microstructure that consists of spheroidal vanadium carbides, eutectic carbides M₇C₃, and a martensite-austenite matrix reinforced by secondary carbides. The increase in quenching temperature leads to an increase in the amount of residual austenite and decrease in the erosive wear resistance of cast irons.

The purpose of this work is to develop an express method of evaluating the coefficient of internal friction and cohesive strength of molding material briquettes. Advantages and disadvantages of modern evaluation methods of internal friction parameters in particulates have been considered, and the need to improve them has been substantiated. An alternative method based on measuring the position of shear planes and the briquette cracking pressure in uniaxial compression strength tests has been proposed. The theoretical justification of the method has been provided, and examples of implementation have been given. The research results may be used in the process of educating students of technical specialties, as well as at research and design organizations.

Tribological investigations of polymers and polymers with additives, using the SMC-2 device, were showed in the present work. Friction coefficient and contact temperature of sliding friction couples, containing different basic materials (PA66 and POM, with two types of nanoparticles, with five different concentrations 0; 0.5; 3; 7.5 and 15% by volume) were investigated. Self-lubricating polymers and steel friction couples have been tested without any lubrication. Research has shown, that the concentration of copper and graphite nanoparticles exceeding 5% leads to coagulation part, that reduces frictional properties of the base material.