Tribological properties of Si-containing diamond-like carbon film under ATF lubricated condition

Abstract

Recent years have seen a rise in social needs regarding safety and the environment, and this has placed increasing importance on product development for automotive parts that leads to smaller sizes, higher capacity, and lower costs. Diamond-like carbon (DLC) coating technology is being focused on as an effective solution to such issues. This paper reports on the tribological properties of a Si-containing diamond-like carbon film under an automatic transmission fluid (ATF) lubricated condition, which dramatically improves the performance of an electromagnetic clutch used in electronically controlled All-wheel-drive (AWD) coupling. The Si-containing DLC film maintains its rough sliding surface while simultaneously exhibiting extremely low aggression against mating materials. Thus, the boundary lubrication state of the initial friction stage is maintained, while also displaying a positive μ– v slope with excellent anti-shudder performance and a satisfactory friction coefficient as demanded by the drive train. Based on time-of-flight secondary ion mass spectrometry (TOF-SIMS) of sliding surfaces, it was speculated that the mechanism behind the good tribological properties of a sliding material coated with Si-containing DLC film under fluid lubrication are in part connected to the material properties of the DLC-Si film and an adsorbate such as a succinimide-based dispersant.