Friction and Wear Properties of Cyanex 302-Modified MoS2 Micro-Sized Spheres as Additive in Liquid Paraffin

Abstract

The friction and wear properties of MoS 2 micro-sized spheres (MS-MoS2) modified by Cyanex 302 (bis(2,4,4-trimethylpentyl) monothiophosphinic acid) as additive in liquid paraffin (LP) were studied and compared with those of commercial colloidal MoS 2 (CC-MoS 2 ) on a four-ball tester and an Optimol SRV oscillating friction and wear tester in a ball-on-disc contact configuration. The worn surfaces were examined with SEM and XPS, respectively. The results showed that the Cyanex 302-modified MS-MoS 2 was a better extreme-pressure and antiwear and friction-reducing additive in LP than CC-MoS 2 . The boundary lubrication mechanism could be deduced as the effective chemical adsorption film formed by the alkyl and active elements (S, O, and P) in Cyanex 302 and tribochemical reaction and deposition film containing MoS 2 , Fe 2 O 3 , and FePO 4 . Moreover, the coexistence of sliding and rolling frictions in the lubricant of MS-MoS 2 /LP also contributed to the enhanced tribological properties.