I. A. Buyanovskii

ORIENTATION ORDERING OF BOUNDARY LAYERS AND LUBRICITY OF OILS

A computer model of the adsorption process of lube oil molecules on friction surfaces reveals that carbon monocrystalline coatings with a strongly orientating effect promote the level of molecular orientation in boundary layers contrary to the amorphous ones because there is no essential orientating effect on these layers. The results of lab tribological tests of carbon coatings deposited on steel surfaces in some model oils corroborate that the coatings with a higher level of orientation ability yield better lube properties.

Boundary lubrication by an adsorption layer

Some key directions of study of the friction and wear of solids under conditions of boundary lubrication by an adsorption layer are analyzed. The ideas and methods of the studies are considered in sequence starting from works of the founder of the boundary lubrication concept W. Hardy and proceeding to the results of the outstanding scientists of the following generations—F.P. Bowden, D. Tabor, B.V. Deryagin, A.S. Akhmatov, G.I. Fuks, R.M. Matveevskii, and others—and then to those of contemporary researchers. Tribochemical aspects of lubrication by an adsorption layer are discussed. Special attention is paid to attempts to develop physical and mathematical models of the boundary lubrication process.

Effect of orienting coatings on the apparent activation energy of boundary film destruction

The apparent activation energy of seizure in boundary lubrication was calculated using the temperature-kinetic approach to the description of boundary lubrication. The tests were carried out with the ball-on-disc machine. The ball was made of chromium ball-bearing steel and the disc was made of stainless steel. Discs made of stainless steel coated with aluminum nitride and high-ordered polycrystalline carbon were also used. The pair was lubricated with model lubricants. It was shown that the apparent activation energy of seizure in friction against steel coated with carbon is by almost an order of magnitude higher than in friction against uncoated steel.

On the durability prediction for an elastic cylinder-elastic layer pair reinforced by thin coating according to the wear criterion

The plane (plane-deformation) wear contact problem of elasticity theory concerning the interaction of a cylinder and a thick layer reinforced by a thin coating along the boundary is considered. The cylinder glides on the coating surface with a low speed (sufficient for neglecting inertia effects of the contacting bodies), which leads to the wear of their surfaces. The problem is traced to the solution of a nonlinear integral equation relative to the unknown contact pressure and size of the contact area depended on the cylinder pressing force. In case of the soft coating in relation to the cylinder and coating layer and the abrasive character of wear, actual solutions of the problem in quadrature are developed. Variants of the low and high wear of the coating are discussed. It is noted that the proposed method may be used for the investigation of the contact problem concerning pressing a smooth indenter into the thin viscoelastic coating on a rigid base.

Effect of structure and composition of solid carbon coatings of steel parts on the lubricating properties of synthetic oil

The authors studied the friction and wear properties of PAOM-4 synthetic oil under the friction of steel samples, the working surfaces of which are coated by a thin layer of hard carbon coatings of different composition and structure. It was found that some of them result in improved antiwear and antifriction behavior of the test oil. The polyalphaolefin oil shows the highest lubricity when steel rubs against carbon diamond-like coatings, namely, monocrystalline tungsten-alloyed coatings and amorphous coatings with increased sp3 phase.

Laboratory tribotests of thin carbon coatings in lubricants

The basic means and methods for tribotests of modern thin coatings in lubricants are considered. The ball-on-disk, cylinder-on-plane, and ring-on-ring arrangement are used.

Nanostructured carbon coating-orientant and its interaction with boundary lubricating layers

In previous works we have shown that to improve oil lubricity one should increase the orientability of the working surfaces of solid bodies. This can be achieved by applying special carbon orientant coatings to ensure the formation of highly oriented boundary layers whose molecules acquire some orientation under the effect of the solid-phase force field. The level of the orientation effect and coating characteristics are dependent on its synthesis parameters, which makes it possible to regulate them during coating application. It is shown that with increasing structural ordering of the boundary layers, the friction coefficient decreases, thus widening the limits of resistance to temperature. In contrast, tribological tests of traditional carbon coatings of the amorphous structure are devoid of the above-described effect. The estimate of the total activation energy of failure of the boundary layers for steel samples with a polycrystalline coating-orientant has proved this value to be much higher than for the same steel with a coating without the orientant coating properties.

Reduction of amount of tribotests of lubricants with four-ball machine

The paper shows the possibility of reducing the labor-consumption of tribotests of lubricants with the four-ball machine according to the Methodical Recommendations Pд 50-531-85. The amount of experiments can be reduced by replacing testing of several specimens with averaging data over the set of realizations with one process of a quite long duration provided that the informative content of the experiment is retained.

Wear of the Counterbody at the Research Friction on Carbon Coating–Orientant in Lubricant Environments

The profile wear scars on steel balls are analyzed upon their friction in lubricant against steel coated with monocrystalline carbon doped by tungsten. Bond of ball wear with the lubricant composition and the range of test loads has been established.

Minimizing the number of experimental tribological tests on the friction machine of reciprocating motion

The theory of the equivalence of friction units tests for a large number of samples to lengthy tests of one sample for friction machines of reciprocating motion based on the Birkhoff-Khinchin theorem for processes that meet the criteria of ergodicity and stationarity has been developed. It has been established that a large part of the examined friction pairs under the indicated test conditions meets the specified criteria.