OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 4 No. 4 2022 move at high speeds. These parts and assembles work satisfactorily only in the presence of lubrication. This often results in the re-lease of oil stains into the water, adversely affecting the fauna and flora. Ship shaft bearings (stern tube bearings) operate under extreme conditions. Solving the problem of its reliability and performance in water, especially at high pressures of the deep sea medium, is one of the difficult tasks of materials science [1, 2, 3]. Polyamides and compositions based on it have high wear resistance and a stable coefficient of friction in water and in other media; lubricants can reduce vibration loads and noise and ensure the environmental safety of the water basin. Despite the fact that the presence of a liquid medium, including water, leads to swelling of polymeric materials, it is found that exposure to water stabilizes its dimensions and improves tribological properties [4, 5]. At the same time, in the works by the school of Rehbinder and other researchers [6, 7, 8, 9] the adsorption effect of water and other liquids on the strength of solids due to a decrease in surface energy and its “wedging” effect on walls has become wide-spread. It is assumed that a decrease in the strength of polymers is caused by a change in the surface energy, which leads to a decrease in the critical stress at the crack tip. With this approach, failure is a critical phenomenon that occurs when the stress at the tip of the most dangerous crack reaches the strength of the material. An approach based on the kinetic concept of strength was developed in the works of Bershtein [10, 11, 12], who proceeded from the kinetic concept, according to which destruction occurs as a result of the accumulation of chemical bond breaks under the action of thermal fluctuations, i.e., the destruction in the presence of water molecules is a reaction of mechanically stimulated hydrolysis. In studies on the tribotechnical properties of polymer composite materials, we found [13, 14] that under the dry friction with an oscillating movement of the working surface, with unidirectional linear movement, in the presence of dynamic loading, in abrasive or chemically aggressive media, the leading wear mechanism is fatigue failure of the working layer. The state of the friction surfaces of the pair is characterized by the presence of a certain composition of surface films. In real air conditions, all microasperities and microcracks are almost instantaneously coated with oxide films and layers of adsorbed polymer sample molecules and fillers that are strongly bound to the metal. Typically, oxide layers are located above the juvenile (pure) surface. These films shield the working surfaces of the tribosystem thus contributing to the boundary friction mechanism in the absence of lubrication and “self-organization” of the steady-state friction [15, 16]. The materials used for the manufacture of friction parts should have low friction coefficient and high wear resistance, i.e., optimal basic informative tribotechnical characteristics. Besides, the tribotechnical composite materials require that the materials used as modifiers are able to form friction transfer films (graphite, carbon, polytetrafluorethylene, silicon dioxide, molybdenum disulfide, etc.) during friction and ensure a self-lubricating mode. These requirements can be met by the use of polymer composite materials (PCMs). Most polyamides are characterized by a good combination of these parameters; it retains its properties when exposed to aggressive media [3, 17, 18, 19]. The analysis of various studies shows the need for experimental verification of the behavior of polymer materials in the presence of sea water in the working contact. The purpose of this work is to study the tribotechnical properties of materials based on polyamide in a sea water simulant medium and to compare pure and filled polyamides in terms of its antifriction properties and fatigue wear resistance under various test conditions. This purpose requires the solution of the following tasks: 1) to choose the test materials on the basis of theoretical surveys; 2) to develop a test method and experimental equipment; 3) to perform laboratory tests of chosen materials; 4) to verify laboratory test methods in conditions simulating the actual operation modes of the product. To ensure high reliability of friction units operating in sea water, the correct choice of a friction pair is of great importance. The increased wear observed during the operation of functional units requires new polymer-based anti-friction materials, one of the representatives of which is a group of materials called “Maslyanit.” Due to its unique characteristics in water medium, Maslyanit materials have been widely
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