Vol 37, No 5 (2016)

The tribological properties of chromium-based coatings deposited by reactive magnetron sputtering in argon–acetylene–nitrogen and argon–acetylene–air mixtures of different volume compositions have been studied. The coatings acquired in acetylene–nitrogen gas mixture have DLC structure and demonstrate high mechanical characteristics and low coefficient of friction values in dry friction. Although the coefficient of friction of these coatings has a tendency to decrease with the increasing nitrogen volume concentration in the mixture (until the values below 0.1 in dry friction in pair with silicon nitride), their performance diminishes at high contact pressures. This decrease was maximal for coatings deposited in acetylene–nitrogen gas mixture, with 80 vol % of nitrogen. The substitution of nitrogen with air is shown to considerably improve the performance, but a further increase in the air volume fraction above 85 vol % provokes a drastic decrease in the efficiency, especially at high contact pressures. The possible mechanisms of these effects and the abilities of their elimination are discussed, as well.

The results of wear of four ceramic materials made of a partially stabilized zirconia (Y-TZP, YPCZ, Ce-TZP and Mg-PSZ) during friction against steel without lubrication are presented. It is shown that wear of ceramics from Y-TZP, Y-PSZ, and Ce-TZP occurs in two stages: first it’s a tear fracture and then it’s a shear fracture. The ceramics based on Mg-PSZ wears out by only the mechanism of shear fracture. Proceeding from the analysis, it was concluded that the wear mechanism of the ceramics under study depends on the grain boundary strength.

The questions of the changing tribological characteristics of filament yarn using lubricants have been discussed. Handling polyester filament yarn with lubricants based on polyethylene glycol PEG-400 allows one to change their friction and electrophysical properties due to the formation of the molecular boundary layers. The area of desired tribological characteristics for polyester filament yarn treated with experimental lubricants has been determined.

The efficiency of the work carried out efficacy and mechanism of the lubricating action have been determined and the anti-wear, extreme pressure, and anti-friction properties of the motor and gear oils with advanced friction modifiers have been defined in order to significantly increase the service lives of engine components and transmissions tracked vehicles, the results of which will comply with new requirements to the motor and gear oils that further bench and field tests carried out at specialized enterprises using the methodology developed by the authors.

Microstructures, coefficients of friction, and relative wear of composite coatings based on the PG-12N-01 nickel self-fluxing alloy and PG-19M-01 bronze have been considered. It has been found that composite coatings have a complex structure. The bronze coating, which is deposited on the fillets of the nickel alloy, crystallizes in a form of dendrites with axes arranged under an angle of 45°. The nickel alloy has a globular-dendritic structure with the eutectic component crystallizing between its branches. Momentary coefficients of friction in conditions of the concentrated load are independent of the cladding rate, and their values are 0.08–0.12 depending on the load. In this case, the wear rate of coatings depends substantially on the laser cladding. Under conditions of the distributed contact, bilayer coatings have a considerable advantage, and the relative wear is reduced by several tens of times compared with single-layer ones.

The results of an investigation of experimental aluminum alloys proposed for replacing the highcost bronzes in friction units have been presented. The alloys were preliminarily selected using sclerometric tests based on the criterion of relative shear strength τ/σ_mc as being more informative compared with contact microcutting stress smc. Tribotechnical tests of selected alloys have been performed according to the three pins-on-disc scheme, which imitates the operation of the plane journal bearing. The results of tests confirmed the possibility of using these alloys as bronze substitutes. The structure and chemical composition of the surface of both initial samples and tested samples have been investigated. The influence of the chemical composition of the alloy on the tribotechnical properties of alloys under study has been shown.

The operability of low-voltage sliding electrical contacts made of ZlM-80 and ZlKh-05 alloys has been investigated. The temperature-time parameters of thermal treatment, which ensures the improvement of the physicomechanical properties of alloys and the rise in the operability indices of low-voltage sliding contacts (LVSC), have been investigated. Applying the friction pair of ZlM-80 and ZlKh-05 alloys ensured operation under the conditions of the implementation of the elastic unconcentrated contact in the friction zone and the decrease in the wear rate of low-voltage sliding contacts

An energy-mechanical approach to developing analytical failure models of stationary tribological conjunctions has been suggested. The design calculation methodology of their durability prediction has been developed on its basis. The methodology was used to predict the durability of standard friction pairs of the disc–shoe type, abraded under different conditions of frictional interaction. To verify the theoretical results, the statistically significant experiment on an SMT-1 friction test machine was carried out. The effectiveness of polymeric and metal-polymeric coatings to increase the durability of the studied conjugations was evaluated using computer and laboratory experiment. The most effective solutions obtained in the experiment were introduced into industrial production.

The interconnection of triboelectric, segregation-diffusion and tribochemical processes at metal–polymer contact area have been revealed. A system approach allows the methods for control of friction properties of metal–polymer friction assemblies to be developed. These methods are based on data that describe the effect of the triboelectric field on diffusion processes in metal–polymer tribosystems and the formation of friction transfer film. The formation of the transfer film has been studied by IR-spectroscopy, and element content on the grain boundaries–by Auger-spectroscopy.