Enhancement in the tribological properties of Cr/DLC multilayers in methane: structural transformation induced by sliding

Diamond-like carbon (DLC) films respond as a lubricating material under some atmosphere conditions, such as N2, moisture. Nevertheless, incomplete knowledge about the key factors, which control the performances of film under distinct gases, limits the further use of them. Herein, the tribological properties of DLC film and Cr/DLC multilayers with different modulation periods were studied under methane. Frictional tests conducted under methane show that Cr/DLC film exhibits a great reduction in friction and wear compared to that of DLC film. An interpretation for tribological performances of films was proposed by considering repassivation and structural transformation taking place at the sliding interface. It is chemical passivation that plays a major role in the tribological properties of DLC film, while the Cr/DLC multilayers possess the lower friction coefficient because of the structural transformation induced by shearing. This study is important for broadening applications of DLC film in the industrial field and reducing energy waste.