Lubrication of DLC-coated surfaces with MoS2 nanotubes in all lubrication regimes: Surface roughness and running-in effects

It was realized that the addition of the nanotubes to the base oil lowered the coefficient of friction of the DLC by more than 50% for the smooth, DLC-coated surfaces and up to 40% for the rough, DLC-coated surfaces. The nanoparticles were the most effective under boundary-lubrication conditions and had a negligible effect in the EHL regime. The surface roughness has a notable and two-fold effect: while the friction was lower on the smooth, compared to the rough, DLC-coated surfaces, the rough surfaces were better able to retain the nanoparticles within the contact during the running-in.