An investigation of the wear track on DLC (a-C:H) film by time-of-flight secondary ion mass spectroscopy

Tribological behaviors of diamond-like carbon (DLC) on steel under ambient air without lubricant were investigated. DLC (a-C:H) film was prepared on a cemented carbide substrate by radio frequency (r.f.) plasma assisted chemical vapor deposition (PACVD) using a methane (CH4) precursor. The hydrogen content in DLC film was approximately 35 at.%. Pin-on-disk experiments were conducted on DLC-coated disk at the sliding velocity of 52 mm/s under 10 N loading using a steel ball (AISI 52100, 6 mm in diameter) as the pin material. After the evaluation of friction coefficient and wear resistance, the transferred layer and wear debris on the wear track of DLC film were investigated using Time-of-Flight Secondary Ion Mass Spectroscopy (TOF-SIMS). The data of TOF-SIMS show the existence of hydrocarbon macromolecules (CnHm) inside the wear track. This result suggests there is a formation of some kind of lubricant materials containing polymer (macromolecule of hydrocarbon), which is generated by the polymerization of DLC film during the tribo-test, contributing thus, to the low friction performance of DLC film.