Influence of the Structure of Perfluoroalkylsilanes Self-Assembled Monolayers on Tribological Properties of TiOx-Incorporated Diamond-like Carbon Coatings.

This paper reports the effects of formed perfluoroalkylsilane self-assembled monolayers (SAMs) on the tribological and corrosion properties of TiOx-incorporated diamond-like carbon (TiOx-DLC) coatings deposited on a Ti6Al4V substrate. The SAMs were formed using 1H,1H,2H,2H -perfluorodecyltrichlorosilane (FDTS) and (3,3,3 -trifluoropropyl) trichlorosilane (FPTS) compounds. Their presence was confirmed using techniques such as ellipsometry, time-of-flight secondary ion mass spectrometry, and Fourier-transform infrared spectroscopy. The results of the ball-on-disc test indicate the role of the structure of the created SAMs on their tribological properties. The FDTS compounds with longer alkyl chains favor the creation of a well-packed layer bonded to the TiOx-DLC coating. This hydrophobic structure allows for obtaining the lowest coefficient of friction (0.180) during tribological tests. The results of electrochemical tests indicate that the SAM modification reduces the barrier properties of TiOx-DLC and provides enhanced kinetic stability against carbon matrix oxidation at higher anodic potentials.