THEORETICAL SUBSTANTIATION OF CAVITATION WEAR INTENSITY REDUCTION OF CYLINDER SLEEVE WALLS BY APPLICATION OF ANTI-CAVITATION COATING

Abstract

One of the ways to increase service life of internal combustion engines is to reduce cavitation wear intensity of the outer wall of the cylinder sleeves. The most promising, at present, method is application of anti-cavitation coating on the outer surface of the cylinder sleeve. The aim of the research was to establish theoretical dependencies that allow to substantiate the properties and thickness of the anti-cavitation material applied to the outer wall of the cylinder sleeve. Theoretical studies of cavitation wear intensity along the destruction depth of the cylinder sleeve wall established that when choosing cavitation-resistant materials, it is necessary to have regard to material structure and give preference to those materials that are characterized by high resistance to microvolumes of plastic deformation under microshock action and are capable of withstanding operating modes over a wide temperature range. The materials of the polytetrafluoroethylene group - fluoroplasts - most fully meet these requirements. Studies of the fluoroplastic coating applied to the outer wall of the cylinder sleeve, using the obtained theoretical dependencies, showed that the minimum wear rate of the cylinder sleeve of 0.0006 mm3/cycle is achieved with a fluoroplastic coating thickness of the outer surface of the cylinder sleeve with a thickness of 1.8 mm. In this case, the difference in heating of a typical sleeve and a sleeve with a fluoroplastic coating with an increase of the heating temperature of the inner wall of the sleeve decreases from 15% at a temperature of 50 °C to 5.7% at a heating temperature of 150 °C, that is, the application of a fluoroplastic coating on the outer wall of the cylinder sleeve does not lead to a change in the heat stress of the cylinder sleeve and will not affect the heat balance of the internal combustion engine. Thus, the obtained theoretical dependences make it possible to establish and justify not only the properties of the anti-cavitation material, but also the thickness of its application to the outer surface of the cylinder sleeve.