Journal of Friction and Wear最新文献

To study such characteristics of sulfonate greases as the lubricity during friction of solids in the mode of boundary lubrication and the protective properties of these lubricants in corrosive environments. A common requirement for the implementation of these indicators is the formation of strong lubricating layers that protect the surfaces of parts from destruction. For each of the studied sulfonate greases with various thickeners and dispersion media, based on the analysis of experimental temperature dependences of the friction coefficients in the temperature range of 30–300°C, the values of the activation energies of the boundary layers destruction were calculated, and the values of Т_cm were estimated. The conducted research has shown that for the examined sulfonate greases, there is a qualitative correlation between the values of temperature-energy criterion π_D with the experimentally obtained values of the corrosion rates of the steel surface in a corrosive environment under the films of sulfonate greases.

TiN coatings have been deposited using cathodic arc deposition at various nitrogen pressures and deposition temperatures. The structure and elemental coating composition are analyzed using a scanning electron microscope and an energy dispersive spectrometer. The mechanical properties and adhesion strength of the coating are measured using nanoindentation and scratch testing. The degree of wear is investigated with a tribometer using the ball-on-disk test method. The analysis of the results is carried out by the methods of two-factor orthogonal experiment planning with optimization elements. The results show that the coating structure has a columnar (fibrous) morphology, the composition is close to stoichiometric. The moment of coating destruction, when determining the adhesive strength, occurs at a load of about 600 mN. On the basis of the obtained regression equations for the optimized values of hardness, plasticity index and wear degree, the values of the process parameters of deposition should be in intervals T = 350–430°С and P = 0.065–0.075 Pa.

The results of experimental studies of solid lubricating coatings for space applications, in particular, one of the most effective coatings EONIT-3, are presented. The coefficients of friction of coatings and wear resistance at temperatures from minus 150 to plus 400°C in air and in vacuum 10^–6 mm Hg were studied for various combinations of antifriction materials depending on the contact pressure, sliding speed, indenter—disk and shaft—sleeve test patterns. It is shown that in tribochemical process molybdenum disulfide, the main industrial solid lubricant, plays the role of an active catalyst. Optimal and stable antifriction and physico-mechanical properties of the EONIT-3 coatings are observed after two hours of heat treatment at 200°C.

The work of tillage machinery is accompanied by a natural process of abrasive wear of soil-cutting parts, which leads to a decrease in the quality of technological operations and requires consideration in the development of new designs of such parts. The application of the method of paired modeling of the tribological process of abrasive wear makes it possible to obtain the necessary data for choosing the forms of hardening of the friction surfaces of soil-cutting parts, providing them with the required working life. The pair model proposed here is based on a combination of the results of simulation modeling on bench equipment and the values of the measured pressures in real soils in the zones of subsequent operation. Simulation modeling was carried out on a soil background corresponding to medium loamy soils, and during loading, the values of normal pressures were measured at different points of the friction surfaces and geometric shapes of normal pressure plots were built on the entire friction surface of the part. The measurement of the pressures of real soils was carried out by dynamometry of soil-cutting parts on soils intended for operation with the determination of power equivalents of total loading cutting parts on soils intended for operation with determination of power equivalents of total loading. In the paired model, a combination of simulation data and force equivalents of loading obtained under dynamometry conditions is performed, which allows us to have reliable values for the exact selection of materials and geometric shapes of soil-cutting parts focused on the guaranteed service life.

The structure and properties of powder steel–copper alloy antifriction pseudo-alloys infiltrated with materials of various compositions are studied, it is shown that mechanical and tribological properties are determined both by the composition and structure of the steel skeleton and, to a large extent, by the composition and structure of the infiltrate. It has been established that the limiting content of lead in the infiltrate, which ensures the absence of lead deposits on the sample surface and a large (10–15%) residual porosity, should not exceed 3%. The use of a mixture of copper powders and alloying additives for infiltration is more technologically advanced than atomized bronze powders. It is shown that the wear resistance of pseudo-alloys with a chromium steel skeleton depends to a lesser extent on the composition of the infiltrate, since the main contribution to wear resistance is made by a hard steel skeleton. The introduction of 3–5% ultrafine aluminum oxide powders into the infiltrate leads to an increase in the seizure pressure by 1.2 MPa and wear resistance by 20–30% due to the refinement of the copper alloy structure and the deceleration of dislocations that arise during deformation due to friction. It is shown that during the wear of pseudo-alloys in the surface layer the structure is refined, martensite is formed in the skeleton, and, accordingly, the microhardness increases by 720–760 MPa.

The following carbon nanostructures (CNSs) are used: shungite nanocarbon (Sh), multilayered graphene oxide (GO), multiwalled carbon nanotubes (Taunit-M), and fullerene C60. Medical Vaseline (MV) free from any additives or thickeners is used as a lubricant base. Tribological tests are carried out using a 2070 SMT-1 friction machine at a load of 2000 N. The roughness parameters of steel rollers before and after the tests are studied by profilometry. Detailed characteristics of contacting surfaces before and after friction are obtained by scanning and transmission electron microscopy. The experimental data are analyzed using the Hertz and Johnson–Kendall–Roberts models. According to the data on efficiency coefficients k_ef, the studied dispersions are ranked as follows in the order of deterioration of antiwear properties: MV/GO (0.5 wt %), k_ef of 50% > MV/Taunit-M (1.5 wt %), k_ef of 40% > MV/C60 (0.5 wt %), k_ef of 15% > MV/Sh (0.5 wt %), k_ef of 5%, which is in agreement with the above-mentioned sequence of CNSs at low loads. The reason for the best and worst wear factors upon using CNSs in the dispersions under study and factors affecting the values of wear in the hard friction mode are considered. The results of the study can be a basis for the development of new plastic lubricating compositions with carbon nanostructure additives for use in heavily loaded friction units.