Vol 39, No 3 (2018)

The effect of iron content on the strength and tribological characteristics of sintered tin-iron bronzes has been studied. It has been shown that the porosity has been reduced and the hardness monotonically increased with an increase in the iron content of the material. The strength dependence of the iron content is nonmonotonic, and the maximum strength increase took place at the iron content of 5%. The minimum coefficient of friction, the temperature in the friction zone and wear rate have been observed at iron content of 5–10%. In this case, the micropores and microlacunes have been formed on the friction surfaces that provide better lubricate conditions for the friction surfaces.

The modern development of automotive engineering and special-purpose machines has led to the need to increase the energy loading of friction units and provide smooth switching on and pulling away, as well as to prolong the service lives of vehicles. Domestic experience in using hydromechanical gear-boxes and oil-cooling brakes indicates that sintered friction powdered MK-5 material, a sintered blend of tin bronze reinforced with graphite particles, has become the most widespread material for this purpose. In the present work, various fibers of glass, basalt and carbon have been successfully applied as friction-purpose fillers for enhancing the tribotechnical characteristics of the material. The effect of nanoparticles as filler of sintered friction material has also been studied. In particular, embedding aluminum hydroxide (bumite) nanoparticles increases the coefficient of friction, while intermetallides (aluminides of nickel, iron and titanium) decrease the wear rate.

A unified analytical dependence for determining the full convergence at the contact between the sphere and flat surface of has been obtained and experimentally confirmed. It is valid both under the conditions of purely elastic deformation and elastoplastic deformation.

Experimental aluminum alloys with the addition of iron (about 1%) have been considered in order to simulate alloys obtained from secondary raw materials (wastes of domestic manufacture, scrap, etc.). In particular, the alloys have been studied using sclerometric tests according to a criterion of relative shear strength (τ/σ_mc). The tribological testing of the alloys has been also carried out according to the block-pad and ball–plane schemes of loading. A mathematical model of the wear process has been used to process the results of wear testing for the ball-plane scheme of friction contact. As a result, the wear law parameter K_w has been determined for all of the experimental alloys. The results of testing have confirmed that, in general, it is possible to use aluminum alloys that contain iron for manufacturing monometallic plain bearings. The structure and chemical composition of the surface have been studied for both the initial samples and the samples after testing.

Aluminum bronzes used in manufacturing ship propellers have been tested for cavitation wear using magnetostrictive vibrator in fresh water. The cavitation attack intensity was varied by changing the amplitude of horn end oscillations from 15 to 25 µm. It has been demonstrated that, within the incubation period of the cavitation wear, the arithmetic mean deviation R_a of the assessed profile, which is the parameter of roughness height, increases as linear function of the test duration. The R_a value that corresponds to the end of the incubation period is constant and does not depend on the cavitation attack intensity. The revealed characteristic properties allow the profile measurements to be used in predicting the duration of the incubation period for the cavitation wear of aluminum bronzes.

The research results of adhesive strength of single-layer coatings made of Cu, Ni, ВK6,Ti, Т15K6, W, Cr, 11Х15Н25М6АГ2 materials formed by electrospark alloying depending on the energy parameters of electrospark alloying process and subsequent ball rolling have been presented. The obtained results of comparative tests have shown the possibility of increasing the adhesive strength of the surface layer by 1.5 times.

Problems of increasing the effectiveness of edge cutting machining by cutting metals via improving the tribological properties of the multicomponent coatings to be deposited on the cutting tool have been considered. The results of experimental investigations of the wear resistance of the cutting tool, as well as the tribotechnical parameters of multicomponent coatings and their spectral analysis, have been presented.

The problems of making efficient rotor seals for turbomachinery has been outlined. A design of a seal with a sealing element made of metal-rubber elastic porous material has been proposed. A model of thermal processes in this seal during contact interactions with the rotor has been developed. The need to determine the range of changes in the parameters of the structure of the metal-rubber material, which makes it possible to use it as a sealing element for rotor seals made using existing technologies for structural damping systems, has been revealed. The results of studies of friction processes have been presented and the types of wear of the metal-rubber material in the rotor seal have been determined.