Probing superlubricity stability of hydrogenated diamond-like carbon film by varying sliding velocity

• Published in: Applied surface science 2018-05, Vol.439, p.976-982
• Main Authors: Liu, Yunhai, Yu, Bingjun, Cao, Zhongyue, Shi, Pengfei, Zhou, Ningning, Zhang, Bin, Zhang, Junyan, Qian, Linmao
• Format: Article
• Language: English
• Subjects: Diamond-like carbon film; Sliding velocity; Superlubricity; Transfer layer
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2018.01.048

H-DLC superlubricity achieved at low velocity and broke at high velocity. [Display omitted] •High sliding velocity will accelerate the superlubricity failure of H-DLC film.•Friction heat and hydrogen passivation is not the main reason for superlubricity failure.•Superlubricity failure was due to the absence of transfer layer on Al2O3 ball. In this study, the superlubricity stability of hydrogenated diamond-like carbon (H-DLC) film in vacuum was investigated by varying the sliding velocity (30–700 mm/s). The relatively stable superlubricity state can be maintained for a long distance at low sliding velocity, whereas the superlubricity state quickly disappears and never recovers at high sliding velocity. Under superlubricity state, the transfer layer of H-DLC film was observed on the Al2O3 ball, which played a key role in obtaining ultra-low friction coefficient. Although the transfer layer can be generated at the beginning of the test, high-velocity sliding tends to accelerate the superlubricity failure and leads to the severe wear of H-DLC film. Analysis indicated that the main reason for superlubricity failure at high sliding velocity is not attributed to friction heat or the break of hydrogen passivation but to the absence of transfer layer on Al2O3 ball. The present study can enrich the understanding of superlubricity mechanism of H-DLC film.