Tribotechnical Characteristics of Mated Metals in Lubricants Containing Cholesterol Compounds
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otechnical Characteristics of Mated Metals in Lubricants Containing Cholesterol Compounds S. F. Ermakova, *, E. B. Shershneva, A. V. Timoshenkob, and P. V. Medvedeva aFrancisk
bGomel
Skorina Gomel State University, Gomel, 246019 Belarus branch of the Belarusian Railway, Locomotive depot, st. House Alley, 1, Gomel, 246014 Belarus *e-mail: [email protected] Received February 19, 2020; revised April 24, 2020; accepted April 29, 2020
Abstract—It was found that during the friction interaction of 45 grade steel on 45 grade steel, the behavior of the friction coefficient and temperature in the dynamic contact area directly depends ent the concentration of cholesterol esters in the lubricant medium and the contact time of the mating surfaces. It is noted that the lowest values of the studied values are realized with an increase in the concentration of cholesterol esters in the lubricant medium, namely, at their 100% concentration in the lubricant composition. Keywords: mated metals, tribological properties, lubricating compositions, cholesterol esters DOI: 10.3103/S1068366620040054
INTRODUCTON Analysis shows that at the present stage, the creation and rational use of lubricant compositions (LC) with high antifriction characteristics is becoming increasingly important for reducing energy intensity and increasing the resource capacity of friction units [1, 2]. One way to increase such LC characteristics is to use both organic and inorganic additives with various natures and properties [1–5]. Therefore, the use of organic liquid crystals, e.g,, cholesterol esters (CE), as universal additives is becoming increasingly important, since such compounds are quite soluble in mineral and synthetic oils, leading not only to improved antifriction, but also load characteristics of friction units in machines and mechanisms [3–5]. However, despite significant advances in this area of research, analysis shows that at present, the influence of the concentration of mesogenic CE in LC on the tribological characteristics and microrelief of mating metal surfaces has not been studied. Objective—To establish the patterns of influence of the concentration of cholesterol compound additives in LCs on the friction of metal friction units. MATERIALS AND METHODS Studies of the friction and wear of metal joints based on 45 grade steel were carried out according to the traditional shaft–partial liner test scheme on an SMT-1 friction machine under a load of 3.5 MPa and a sliding speed of 0.5 m/s. In the studies, an LC based on petroleum jelly (PJ) was used. The EC concentration in the PJ varied from 0.5 to 100 wt %. Mesogenic
ECs were added to the PJ and mixed at 110°C, then the compositions were cooled to room temperature and tests were performed. The microrelief of mating surfaces before and after friction was studied using a Caliber-VEI profilograph-profiler adapted with an SM-1 type computing device [6, 7]. The three-dimensional topography of surfaces after friction was studied using a laser scanning differential-phase microscopeprofilometer. RESULTS
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