Aluminum Composite Materials Providing Extended Service Life

Hardness and tribotechnical characteristics were investigated under conditions of dry sliding friction on steel obtained by liquid-phase mixing of Aluminum-Matrix Composite (AMC) materials based on aluminum alloys AK12, D16, V124, AL9, AL25, reinforced with silicon carbide SiC particles with a size of 28 μm with a content of 5, 10 or 15% by volume. AMC performed better than matrix alloys and the commonly used antifriction aluminum alloy AOM 2-1. The dry friction coefficient was 1.5-3 times lower on average, and the volumetric wear rate was 5-9 times lower. An increase in the content of SiC particles in the composite from 5 to 20 vol.%. As a rule, leads to an improvement in the tribotechnical characteristics. The composites obtained have shown a sufficiently high operational suitability for work in friction units with steels both in dry friction and in friction with lubrication.

Forecasting the properties of linear block-copoliurethanes based on oligoesters of regular structure

We showed that the development of recommendations for a reasonable choice of linear block copolyurethanes that would be optimal for given operating conditions is still intuitive and does not consider the features of the molecular structure and the nature of initial components. We suggested a new scientifically grounded approach to the creation of linear block-copolyurethanes with increased wear resistance in relation to strength, deformation, thermophysical and tribotechnical characteristics. To simplify analysis of the properties of the studied materials, a mathematical model was developed, which describes the relationship between all considered properties of materials and their structure. We proposed to assess the relationship between structure and properties of the investigated materials by using quality indexes. Maximum values of quality indexes, depending on the operating conditions, correspond to different contents of hard blocks (Pc), and, consequently, to different molecular structure of the studied polyurethanes. Thus, it is reasonable to use block-copolyurethanes based on OBGA500 with a maximum content of hard blocks (Рс>60%) for operating conditions where it is necessary to provide high strength characteristics. Polyurethanes synthesized with the formation of clusters of hard blocks in the range of 45–55% are recommended for the use as wear-resistant materials.

STRUCTURE AND PROPERTIES OF THE АК12М2МгН (AlSi12Cu2MgNi) PISTON ALLOY FORMED UNDER THE INFLUENCE OF A COMPLEX MODIFYING ADDITIVE OF FULLERENE-CONTAINING SOOT AND COPPER

The article presents the study results of the complex modification of eutectic silumin АК12М2МгН (AlSi12Cu2MgNi) with additives of fullerene-containing soot (FCS) and copper. It is shown that the effect on the alloy structure is caused by the introduction of carbon nanoparticles into the melt and is manifested in the dispersion of the structural phases and their uniform distribution in the casting volume. At the same time, the use of dispersed copper powder provides wetting of aluminum carbon particles with the melt and additional alloying of the melt. The formation of a dispersed structure leads to an increase in the mechanical and tribotechnical characteristics of the alloy: an increase in the ultimate strength (by 1.3–1.6 times) with a simultaneous increase in the relative elongation by up to 3 times, a significant decrease in the coefficient of friction (by 1.1–1.7 times) and the intensity of wear. The lowest coefficient of friction and high wear resistance are achieved at small fractions of FCS (0.05–0.1 wt.%) and the copper content in the modifier is not more than 0.5 wt.%.

Regulation Features of Structure of Linear Block-Copolyurethane Composites of High Wear Resistance

The influence of the main structural parameters (molecular weight and hard blocks content) as well as methods of filling linear block-polyurethanes and their compositions on their strength, deformation, rheological and tribotechnical characteristics has been studied. A complex approach to produce polyurethane compositions of improved wear resistance has been suggested.

Influence of the initial roughness of the antifriction carbons surface on tribotechnical characteristics and running-in coating efficiency

The roughness of the friction surface of antifriction carbons used in sliding friction units lubricated with water affects the tribotechnical characteristics during the running-in process. This article experimentally substantiates the range of optimal surface roughness formed during mechanical cutting of carbon plastics in terms of tribotechnical efficiency. The results of a series of tribotechnical tests using various methods under various conditions (contact pressure, sliding speed, counterbody materials) are presented. The relationship between the initial roughness and the effectiveness of a running-in coating based on FORUM® polytetrafluoroethylene powder is established.

Thermochemical synthesis of tribotechnical coatings based on molybdenum diselenide MoSe2 on structural steels

The study results of the influence of parameters of the process of chemical-thermal treatment in selenium vapor during the preparation of solid lubricating coatings from molybdenum diselenide on specimens of structural steels with a plasma Mo-coating are presented. An empirical mathematical model of the temperature-time parameters of the Mo selenization process is proposed, which makes possible to control the quality of the obtained coatings depending on requirements for their tribotechnical properties. An assessment of their tribotechnical characteristics in air and in vacuum in the temperature range 20—600 °С has been carried out.

Study of operational properties of steel friction pairs with antifriction coating from copper alloys produced by electric spark alloying

Improving the reliability, durability and safety of operation of heavily loaded friction units is an urgent problem in physics, chemistry and surface mechanics. The tribotechnical characteristics of coatings made of bronzes BrAZhMts10-3-1.5 and BrMtsF3-6, applied by electrospark alloying on bushings made of structural steel 30KhGSN2A for operation under conditions of high contact pressure under friction without lubrication, have been investigated. Modes of coating deposition from the standpoint of tribology (the value of the electric discharge current in a pulse, the value of the longitudinal electrode feed per one rotation of the part, the rotation speed of the workpiece, the number of passes during processing, finishing of the coating) have been developed. It was found that when applying bronze BrMtsF3-6 to obtain a high-quality coating, the process must be performed in a protective atmosphere of argon to prevent phosphorus burnout. The tribotechnical efficiency of coatings when working under dry friction conditions is shown. For the steady-state wear mode, the friction coefficient is 0.10 – 0.13 at a pressure of 200 – 250 MPa, the wear resistance of coated steel is doubled. Steel with a bronze coating BrAZhMts10-3-1.5 has a higher bearing capacity, with BrMtsF3-6 coating — a higher antifriction. The ways of increasing the service life of steel-coated steel friction pair are analyzed.