The influence of self-assembled monolayers on tribological properties of Si-DLC coatings

Abstract

The tribological properties of diamond like carbon (DLC) and silicon-incorporated diamond like carbon (Si-DLC) coatings in contact with Si3N4 counterbody were investigated using a ball-on-disc tribometer. The effect of modification by perfluoro and alkylphosphonic self-assembled monolayers was evaluated in terms of lowering the coefficient of friction (CoF) and wear rate. The tribological tests revealed that the presence of silicon decreases the CoF and slightly increases the wear rate of Si-DLC coatings in comparison with DLC. Further decrease of CoF was achieved for Si-DLC coatings after self-assembled monolayers deposition. The effectiveness of modification, stability on ultraviolet (UV) irradiation and characterization of all coatings was monitored by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman spectroscopy and measurements of the surface free energy (SFE). The obtained study demonstrated that self-assembled monolayers reduce friction and are highly promising candidates as a good lubricant for tribological and mechanical systems.