Running-in behavior of a H-DLC/Al2O3 pair at the nanoscale

Diamond-like carbon (DLC) film has been developed as an extremely effective lubricant to reduce energy dissipation; however, most films should undergo running-in to achieve a super-low friction state. In this study, the running-in behaviors of an H-DLC/Al 2 O 3 pair were investigated through a contr...

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Bibliographic Details
Published in:	Friction 2021-12, Vol.9 (6), p.1464-1473
Main Authors:	Shi, Pengfei, Sun, Junhui, Liu, Yunhai, Zhang, Bin, Zhang, Junyan, Chen, Lei, Qian, Linmao
Format:	Article
Language:	eng
Subjects:	Aluminum oxide Atomic force microscopes Atomic force microscopy Coefficient of friction Corrosion and Coatings Design optimization Diamond-like carbon films Energy dissipation Engineering Friction Friction reduction Hydrogen bonds Lubricants Mechanical Engineering Nanotechnology Physical Chemistry Research Article Substrates Surfaces and Interfaces Thin Films Tribology
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Summary:	Diamond-like carbon (DLC) film has been developed as an extremely effective lubricant to reduce energy dissipation; however, most films should undergo running-in to achieve a super-low friction state. In this study, the running-in behaviors of an H-DLC/Al 2 O 3 pair were investigated through a controllable single-asperity contact study using an atomic force microscope. This study presents direct evidence that illustrates the role of transfer layer formation and oxide layer removal in the friction reduction during running-in. After 200 sliding cycles, a thin transfer layer was formed on the Al 2 O 3 tip. Compared with a clean tip, this modified tip showed a significantly lower adhesion force and friction force on the original H-DLC film, which confirmed the contribution of the transfer layer formation in the friction reduction during running-in. It was also found that the friction coefficient of the H-DLC/Al 2 O 3 pair decreased linearly as the oxygen concentration of the H-DLC substrate surface decreased. This phenomenon can be explained by a change in the contact surface from an oxygen termination with strong hydrogen bond interactions to a hydrogen termination with weak van der Waals interactions. These results provide new insights that quantitatively reveal the running-in mechanism at the nanoscale, which may help with the design optimization of DLC films for different environmental applications.
ISSN:	2223-7690 2223-7704