Superlubricity for hydrogenated diamond like carbon induced by thin MoS2 and DLC layer in moist air

Abstract

Hydrogenated diamond like carbon (H-DLC) films are widely used as solid lubricant because of its high hardness, wear resistance and superlubricity in high vacuum condition. However, it is challenging to achieve superlubricity for H-DLC in moist air because the moisture and other components in air have a negative influence on the coefficient of friction (COF) of H-DLC. In this work, H-DLC and its multilayer films with MoS2 and hydrogen-free diamond like carbon (DLC) were successfully prepared by plasma enhanced chemical vapor deposition and the magnetron sputtering system, respectively. The SEM, HRTEM, 3D-profilometer, ball-on-plane reciprocating friction tester and nanoindenter were used to characterize the properties of the films and their debris obtained after friction tests. The results demonstrate that the multilayer film with MoS2 and DLC layer on the H-DLC surface can reach superlubricity state with an average COF of 0.004 ± 0.001 in the stable friction period in moist air. And the lowest COF of this kind of multilayer film can reach 0.002. This study can provide a simple way to achieve superlubricity for H-DLC films in moist air.