Abstract

Critical components in advanced engineering systems are frequently exposed to severe service friction and wear conditions, including heavy loading and chemically aggressive environments. Ceramic protective coatings are widely employed to mitigate surface degradation and extend operational lifespan of those equipment. Highentropy ceramics (HECs), distinguished by their compositional complexity, exhibit remarkable chemical stability while offering a more favorable balance between strength and toughness compared with conventional ceramics. In this work, the tribological behavior of (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Ce2O7 (LECO) coatings was examined against three representative counterparts spheres-316 L stainless steel, Si3N4, and WC-in both ambient air and HCl environments. Under dry sliding conditions, contact with 316 L steel promotes oxidative reactions at the interface, leading to the generation of hard debris that intensifies abrasive wear. In contrast, sliding against Si3N4 results in progressive smoothing of surface asperities. This evolution is accompanied by the formation of an amorphous silica-based transfer layer, which contributes to a gradual reduction in friction. When the environment is switched to an acidic medium, the liquid phase not only removes loose debris but also modifies interfacial processes. Although this leads to a lower friction level, it simultaneously accelerates localized corrosion on the 316 L surface, particularly after disruption of the passive film. For WC counterparts, the presence of a 6% Co binder makes the material susceptible to chemical attack, which in turn increases material loss. A distinct behavior is observed in the Si3N4 system under acidic conditions. The combined effect of H+ and frictional heating promotes hydrolysis reactions, producing a SiO2 & sdot;nH2O layer at the interface. This gel-like film acts as an effective lubricant, markedly reducing both friction and wear. Overall, the observed tribological responses arise from the interplay between mechanical interaction and environment-assisted chemical transformations at the sliding interface.

Keywords Plus: GLOBAL ENERGY-CONSUMPTION，WEAR

Published in TRIBOLOGY INTERNATIONAL，Volume224；10.1016/j.triboint.2026.112366，DEC 2026