Formation of Surface Structures under Friction in Synthetic Oils
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ation of Surface Structures under Friction in Synthetic Oils A. V. Sidashova, *, M. V. Boikoa, A. T. Kozakovb, and V. V. Lesnyakc aRostov
State Transport University (RSTU), Rostov-on-Don, 344038 Russia Scientific Research Institute of Physics, Southern Federal University, Rostov-on-Don, 344090 Russia c Don State Technical University, Rostov-on-Don, 344000 Russia *e-mail: [email protected]
b
Received February 5, 2020; revised July 5, 2020; accepted July 7, 2020
Abstract—The interaction of transmission oils based on pentaerythritol esters and organosiloxane liquids with a surface of AISI 420S steel was studied. It was found that during friction, the lubricant interacts with the iron of the steel surface, resulting in the formation of protective surface films of sulfur and silicon compounds. The features of formation of protective surface films during friction with lubricants based on pentaerythritol esters and organosiloxane liquids are determined. It is noted that the formation of protective films when using a lubricant composition of pentaerythritol esters occurs with the participation of nonoxidized iron, and when using organosiloxane liquids with the participation of iron oxide, the main element of the metal counterbody. Keywords: friction, surface, gear oil, synthetic oils, surface films, X-ray photoelectron spectroscopy DOI: 10.3103/S1068366620050165
INTRODUCTION The development of technology creates more stringent demands on the quality and performance of lubricants [1, 2]. For the production of modern types of gear oils with improved low-temperature properties, workable in the Far North and the Arctic, synthetic base stocks are used [3, 4]. Such oils have high lubricity and thermo-oxidative stability and provide minimal friction losses. An essential aspect influencing the performance properties of oils is their ability to change the strength properties of the metal bodies of the friction unit. There is evidence that during friction, degradation of lubricant occurs, and the products formed in this case interact with the metal, causing a decrease in microhardness and an increase in surface roughness, which leads to a decrease in the wear resistance and durability of the friction unit [5]. The course of such processes must be considered to prevent premature failure of the friction units. Currently, an urgent task is to create a new lubricant for heavily loaded friction units of aircraft, eliminating the occurrence of negative segregation processes in tribocontact and providing formation of a protective surface film on the friction bodies. To solve it, transmission oils have been developed for the tail gear of a helicopter based on synthetic pentaerythritol esters (ТМ1 RSTU) and organosiloxane liquid (ТМ2 RSTU). The composition and results of physicochemical testing of TM1 RSTU is given in [6]. Both lubricating compositions contain sulfur-containing
additives; in ТМ2 RSTU, it is ashless dialkyldithiophosphate. Aim of this study: to establish of a mechanism for the formation of a modified surface layer under
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