Improved lubrication performance of MoS2-Al2O3 nanofluid through interfacial tribochemistry

Nanofluids containing nanocomposite materials have broad application prospect in lubrication . In the present study, MoS 2 -Al 2 O 3 nanocomposite was synthesized by solvothermal method . Then water-based nanofluid containing MoS 2 -Al 2 O 3 nanoparticles was prepared and it exhibited optimal stability and wettability . The tribological properties of MoS 2 -Al 2 O 3 nanofluid under steel/steel contact were investigated. Through chemical analysis of worn surface, tribochemical reactions occurred and tribofilm generated at friction interface were studied to reveal the lubrication mechanism. The results showed that MoS 2 -Al 2 O 3 nanofluid exhibited outstanding effect on reducing the friction force and wear rate of friction pairs. The superior lubrication performance was partly attributed to the entry and movement of nanoparticles at friction interface. More importantly, due to interfacial tribochemistry , a tribofilm with double layer structure composed of adsorption film and reaction layer was formed on the metal surface , preventing the direct contact of steel surfaces. The adsorption film with a thickness of about 16 nm was predominated by amorphous substrates and crystal phases (ultrafine Al 2 O 3 and MoS 2 debris) embedded in the top. And the reaction layer beneath adsorption film contained high mechanical properties iron oxides (mainly Fe 3 O 4 and Fe 2 O 3 ) and self-lubricating Fe 2 (SO 4 ) 3 , which further alleviated friction and enhanced the wear-resistance of materials.