Abstract

Friction and wear are key factors leading to energy loss and shortened part life in mechanical systems. Achieving superlubricity (mu < 0.01) is critical for advancing high-efficiency, long-lifespan equipment. In this study, B/Al co-doped hydrogenated amorphous carbon (BAl/a-C:H) films were prepared using unbalanced magnetron sputtering technology. The effects of trace B and Al co-doping on their structure, mechanical properties, and tribological behavior were systematically investigated. The results indicate that B/Al co-doping exerts a synergistic modulation effect on the carbon network structure: Al promotes the formation of sp(2) C clusters, while B introduces strong C-B bonds and forms C-O-B structures at the interface, enhancing the stability of the transfer film. By precisely controlling the Al target sputtering current during deposition, we obtained a series of B/Al co-doped films. Among these, the optimized film deposited with an Al target current of 0.6 A (designated as BAl-0.6/a-C:H) achieves long-term superlubricity (>500,000 cycles) in a dry N2 environment, with an 87% reduction in wear compared to the undoped a-C:H film. Microstructural analysis reveals the formation of a hydrogen-and oxygen-enriched amorphous low-shear passivation layer on the counterpart surface and a shear-induced sp3-rich layer on the wear track surface. This establishes a quasi-incommensurate contact at the friction interface, maintaining a stable low-shear state and thereby enabling prolonged superlubricity. This work provides an innovative method for designing carbon-based films that combine superlubricity and long service life through trace multi-element doping.

Keywords Plus: ULTRALOW FRICTION，BIAS VOLTAGE，DIAMOND，AL，MICROSTRUCTURE，MECHANISM，DLC

Published in TRIBOLOGY INTERNATIONAL，Volume221；10.1016/j.triboint.2026.112077，SEP 2026