Preparation and tribological properties of dual-coated TiO₂ nanoparticles as water-based lubricant additives

Titanium dioxide nanoparticles (TiO₂) were synthesized and then dual-coated with silane coupling agent (KH-570) and OP-10 in sequence in order to be dispersed stably in water as lubricant additives. The tribological properties and the application performance in Q235 steel machining of the nanoparticles as water-based lubricant additives were investigated on an MSR-10D four-ball tribotester and on a bench drilling machine, respectively. Scanning electron microscope (SEM) and atomic force microscope (AFM) were used to analyze the worn surface. The results show that the surface-modified TiO₂ nanoparticles can remarkably improve the load-carrying capacity, the friction reducing, and anti wear abilities of pure water. The wear scar diameter and the coefficient of friction of the water-based lubricating fluids with TiO ₂ nanoparticles decreased, and the thick deep furrows on the surface of wear scar also decreased obviously with the increase of TiO₂ concentration. The power consumption in drilling process was lower and the cutting surface was smoother using the water-based lubricating fluids added TiO₂ nanoparticles compared to the fluid without addition. The reason for nanoparticles improving tribological properties of water based lubricating fluid might be the formation of a dynamic deposition film during rubbing process according to analysis of the worn surface.