Tribological behaviors and self-healing performance of surface modification nanoscale palygorskite as lubricant additive for the steel pair

Palygorskite is an environmentally friendly, inexpensive, and promising silicate mineral. In this research, nanoscale palygorskite additive powders (NPA) were prepared by high energy ball milling with the modifier γ-aminopropyltriethoxysilane (KH550). The NPA was sustainably dispersed in base oil 150 N, exhibiting no particle sedimentation for one week. The self-healing behavior and tribological performance of NPA as lubricant additive were investigated by a ring-on-disc tribometer under different concentrations for 50 h. The results indicate that NPA possesses excellent friction-reducing and anti-wear performance. The 3.0 wt.% and 4.0 wt.% concentrations of NPA displayed the best friction-reducing and anti-wear effects, respectively. The average friction coefficient and wear mass loss decreased by 31.93% and 26.92%, in contrast to that of base oil 150 N. It was also found that different NPA concentrations possessed different friction states. A tribo-film with bilayer structure was formed during the friction process, the first one of which contained compound made up of multiple elements, and the second one of which contained NPA nanoparticles deposited on the friction interface. Moreover, the friction coefficient increased dramatically during the formation of the tribo-film. (paper)