Vol 39, No 2 (2018)

The influence of substrate temperature and bias voltage on the structure and tribomechanical properties of the Ti–Al–N coatings obtained by reactive magnetron sputtering technique has been investigated. The structure and elemental and phase compositions have been studied by scanning electron microscopy, Rutherford backscattering, and X-Ray diffraction. The results of friction and wear experiments indicated that the lowest coefficient of friction (three times lower than 12Cr18Ni10Ti) corresponded to a coating deposited at a bias voltage of–200 V and a substrate temperature of 340°С, while the most wear-resistant coating (under a load of 700 mN and the testing time of 1080 s) was Ti–Al–N sputtered at a bias voltage of–200 V and a substrate temperature of 440°С.

The development and implementation of novel galvanic coatings with abnormally high microhardness, wear resistance, and corrosion resistance are the focus of modern machine-building. The galvanic deposition of composite electrolytic coatings (CECs) is an efficient method of improving their properties. In this paper, a chloride-containing electrolyte has been proposed for obtaining a wear-resistant nickel–cobalt–polytetrafluoroethylene CEC. The effect exerted by electrolysis modes and electrolyte compositions on some physicomechanical properties (wear resistance and corrosion resistance) of a nickel–cobalt–polytetrafluoroethylene composite electrolytic coating deposited from chloride-containing electrolyte has been studied. The potentialities of using the deposited layer as wear- and corrosion-resistant coating.

The effect of the molecular weights of amorphous polyarylene ether ketone (PAEK) synthesized by the reaction of 4,4'-difluorobenzophenone with 2,2-bis (4'-hydroxyphenyl) propane (bisphenol A) potassium diphenolate on its tribological characteristics has been studied. In the case of the friction of a sample with M_w < 200 × 10³ Da, its high wear resistance and the coefficient of friction decreased to 0.4, even at high pressures of up to 10 MPa. These properties of high-molecular-weight PAEK are due to the high contribution of the weak dispersion forces into the intermolecular interaction energy of the polymer. Low wear determines the nature of tribodestruction, which, during the process of self-organization, leads to the appearance of a positive gradient in the physicomechanical properties in the surface layers. The XPS study shows that, during PAEK pressing at 260°C, the intensive oxidation of a thin surface layer occurs.

An experimental methodology for constructing a 3D friction map, which depends on normal pressure, sliding velocity, and temperature, for tire tread rubber has been presented. The methodology of constructing a 3D friction map is based on the principle of temperature–velocity superposition, which makes it possible to combine the obtained experimental data into one sculpted surface. Two types of the tread rubbers were investigated that are used in summer passenger tires and heavy-loaded all-metal tires. The results of analyzing the obtained 3D friction maps have been presented. The influence of normal pressure and sliding velocity to the amount and position of the values of coefficient of friction of the rubber sliding over the sandpaper surface with the specified abrasive grit has been considered.

In the article, the structure of a bench for testing the friction characteristics of a friction pair of centrifugal brake rollers has been considered. The dependences of the coefficient of friction and wear on the temperature of the materials of the friction pair, viz., a brake insert manufactured by Huzhou Jiutong Logistics Machinery Co., Ltd (China) and a domestic friction pair of the 6KV-10 rolled brake band of the EM-2 grade over St.3 steel grade (A537Gr.58), were obtained for temperature ranges that do not exceed 100°C. It has been shown that the rubber–PA6 friction pair widely used in brake rollers of foreign manufacture cannot be employed at high values of the slip velocity and the normal force applied to the friction lining, as it results in rapid heating to the critical temperature and, as a consequence, intensive wear. The domestic 6KV-10 brake band of the EM-2 grade, along with a metallic roller shell is proposed as the material of the friction pair. The frictional material proposed for the friction lining has a high coefficient of friction and a high wear resistance in a wide range of operating temperatures, normal forces, and temperatures of the frictional contact.

The article presents the results of metallographic study of low-carbon 20 steel grade and high-carbon 70 and 65G steel grades upon carburizing, heat treatment, and laser hardening. The change in the microhardness through the depth of the surface layer of steels and their abrasion resistance upon hardening under different conditions has been measured. Optimal hardening conditions have been proposed for steels for cutting blades of tillage machines that enable the durability of the blades to be improved.

In the paper, we have presented experimental results on the real-time triboacoustic control of the integrity of a nominally motionless friction joint under fretting conditions. The disturbance in the integrity of the tribosuppression as a result of wear has been reliably detected both by the change in the shape of the acoustic histograms of the operating noise and by the change in the noise spectrum due to the appearance of strong mid-frequency modes of the contact gap. The appearance of two oppositely directed wave energy cascades in the regime of fretting has been observed, i.e., the direct cascade from the pumping modes toward the high frequencies and the reverse cascade toward the low infrasonic frequencies. The former has been associated with microplastic deformations in the zones of actual contact, while the latter has been associated with the dynamic generation of slow angular motions in the friction system.