Nanoindentation and nanofriction on DLC films

Diamond-like carbon (DLC) coatings have been studied for many years as wear-resistant and low friction materials. Their tribological behaviour depends on the nature of the coating, which is determined by the deposition process. It is also strongly affected by environmental conditions. In this study, the nanomechanical properties and the nanofriction behaviour of two aC:H coatings deposited on silicon substrate and exhibiting different macroscopic friction behaviours were investigated using a three-axial surface force apparatus equipped with a diamond tip. The hardness, Young's modulus and Poisson's ratio of the two coatings were determined. Viscous recovery of the indents was observed a few days after the indentation tests. Low friction coefficients (around 0.06) were measured for the coating which exhibited macroscopic low friction. For the coating which exhibits a higher friction coefficient, the dissipative behaviour measured during nanofriction test was enhanced by sliding, compared to the dissipative behaviour measured during normal indentation, suggesting a link between normal viscous dissipation at nanoscale and high friction.