The Frictional Properties of Diamond-Like Carbon Films Deposited on a 45 Steel Substrate

The aim of this work is to synthesize diamond-like carbon (DLC) films using physical vapor deposition (PVD), determine their sp²/sp³ phase composition, and investigate the tribological properties of a multilayer system consisting of DLC layers and titanium/titanium nitride adhesion sublayers on a steel 45 substrate. Two DLC films were produced using the BRV600 magnetron sputtering system, one in a hydrogen atmosphere and the other without hydrogen addition to the process chamber. XPS analysis of these films revealed that the sp²/sp³ phase ratio was approximately 0.2 for the film synthesized with hydrogen and 0.02 for the one without it. The tribological behavior of these DLC films depended on the sp²/sp³ ratio hybridized bonds and the gas atmosphere during synthesis. The interaction between the test ball and initial surface of a film formed in a hydrogen free atmosphere started with a friction coefficient of 0.45, while it started at 0.35 for a film formed under hydrogen conditions. After 1,000 cycles, graphitization of the surface occurred in both wear tracks accompanied by transformation of sp³ into sp². This led to an increase in the sp²/sp³ phase ratio within the wear tracks, reaching a value of approximately 2 for both films after 6,000 cycles. At this sp²/sp³ ratio, the friction coefficient dropped to approximately 0.1.

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