Effect of Y2O3 content on the microstructure and wear performance of plasma-sprayed Cr2O3–Y2O3 composite coatings

Abstract

As the inner working surface of a diesel engine, the cylinder liner is subjected to a harsh frictional wear environment, which can lead to performance degradation and ultimately affect the engine's service life. Ceramic coatings can improve the wear resistance of the cylinder liner, thereby enhancing the reliability and stability of the diesel engine. In this study, Cr2O3–Y2O3 ceramic composite coatings were deposited on the substrate of 304 stainless steel by atmospheric plasma spraying (APS). The influence of Y2O3 content on the microstructure, porosity, phase composition, microhardness and wear performance of the composite coating was investigated. The results showed that the composite coatings exhibited a typical layered structure, and Y2O3 and Cr2O3 were dispersed relatively evenly. When the Y2O3 content was 10 %, the coating had the lowest porosity rate of 5.41 % and the highest hardness of 1094.6 HV1. As the Y2O3 content increased, the coating exhibited an increase in porosity and a decrease in hardness. Under dry friction conditions, the friction coefficient curve underwent a rapid increase phase, followed by stabilizing within the range of 0.29–0.40. When the Y2O3 content is 10 %, the coating exhibits the best wear resistance, including the lowest coefficient of friction, wear rate, and scratch depth. However, the composite exhibits the worst wear resistance when the Y2O3 content reaches 50 %. The wear mechanism was altered by the addition of Y2O3. At lower Y2O3 content, the predominant wear mechanism was abrasive wear resulting from particle refinement. Conversely, at higher content, adhesive wear caused by wear transfer from the milling balls became more prominent.