Effect of surfactant on tribological performance and tribochemistry of boric acid based colloidal lubricants

Abstract

This study demonstrated that surfactants can significantly improve the dispersion stability of milled boric acid particles over a broad range of operating temperatures. The tribological performance of boric acid and surfactant [sorbitan trioleate (STOMO)] mixed in the base oil was investigated under cylinder-on-plate line contact set-up using a reciprocating tribological test rig. Several characterisation techniques were used to understand particle distribution and size and composition of tribofilms that resulted from sliding contact. The results showed that surfactant prevented agglomeration of boric acid particles after the milling process and thus, provided good dispersion stability at elevated temperatures. The addition of surfactant in the base oil decreased the friction coefficients by 58 and 42% respectively, and reduced the wear scar diameter by 48 and 34% respectively, as compared to the base oil and fully formulated oil. In addition, the presence of a boron rich boundary film resulting from decomposition of boric acid compounds were detected by XPS and Auger in the wear track inside the wear tracks.