Modulation of Si on microstructure and tribo-mechanical properties of hydrogen-free DLC films prepared by magnetron sputtering

Abstract

Modulation of Si on microstructure and tribomechanical properties of hydrogen-free DLC films was studied by preparing Si-DLC films through a hybrid HiPIMS and middle-frequency magnetron sputtering deposition technique. Atomic force microscope, scanning electron microscope, transmission electron microscope, Raman spectrometer and X-ray photoelectron spectroscopy were used to investigate film chemical composition and microstructure. Hardness and elastic modulus were characterized by a nanoindenter. Friction coefficient was measured by a ball-on-disk tribometer. 3D surface profiler, optical microscope and Raman spectrometer were applied to study the tribological behaviors of Si-DLC films. Films surface roughnesses (Ra) are in the range of 1.18–3.15 nm. Si-DLC layer presents a Si-rich/Si-poor multilayer microstructure with a period of about 4 nm. With the rise of Si content in Si-DLC film, sp3 content, hardness and elastic modulus increase. Most Si atoms are interspersed in the amorphous carbon matrix and bond with carbon atoms forming Si-C bonds. The lowest wear rate of 3.5 × 10-7 mm3/Nm is obtained as Si content in Si-DLC film is 14.8%. Varying Si contents in Si-DLC films generated different bonding states of wear tracks, leading to the different wear behaviors of Si-DLC films.