Study on the tribological properties of surfactant-modified MoS2 micrometer spheres as an additive in liquid paraffin

Tribological properties of MoS2 micrometer spheres modified by self-prepared surfactant as an additive in liquid paraffin (LP) are studied and compared with those of the commercial colloidal MoS2 on a four-ball tester and an Optimol SRV oscillating friction and wear tester. The worn surfaces are examined with SEM and XPS, respectively. Results show that MoS2 micrometer sphere is a much better extreme-pressure additive and anti-wear and friction-reducing additive in LP than the commercial colloidal MoS2. The boundary lubrication mechanism can be deduced as an effective chemical adsorption protective film formed by the long chain alkyl and active elements (S and N) in the prepared surfactant and tribochemical reaction film composed of the tribochemical reaction products of the additive. Moreover, sliding and rolling frictions exist simultaneously in the MoS2 micrometer spheres /LP lubricating system, which also do more contributions to the good tribological properties.