Improving the Wear Resistance of Piston Rings of Internal Combustion Engines when Using Ion-Plasma Coatings

Abstract

Modern designs of piston rings of internal combustion engines and wear-resistant coatings used for them are considered. It is noted that the upper (compression) ring undergoes the most intense wear. Among the traditionally used wear-resistant coatings of compression rings, galvanic chrome plating and thermal spraying with molybdenum are most often used. The paper proposes the use of the ion-plasma spraying method for applying hard wear-resistant coatings to the working surface of piston rings based on titanium and molybdenum nitrides. The specified method relates to vacuum coating technologies (PVD methods), in which layers of high-strength materials are sprayed directly onto the surface of the product. The present work aimed to carry out comparative tribotechnical tests of piston ring samples having hard coatings obtained by ion-plasma spraying and to compare them with traditional galvanic chromium plating. A technique has been developed for a comprehensive assessment of comparative tribological characteristics, including the critical load during testing, the specific load of seizing, the coefficients of friction, scoring resistance, and wear resistance. The test results of samples with the galvanic coating with chromium, ion-plasma spraying with titanium nitride, and molybdenum nitride are shown. In contrast, it is shown that samples with an applied ion-plasma coating surpass samples that are electrolytically chrome plated by all tribological parameters. The results obtained allow concluding that the ion-plasma coating of molybdenum nitride is promising for piston rings, as well as other critical parts of internal combustion engines.