Mechanism of Antiwear Property Under High Pressure of Synthetic Oil-Soluble Ultrathin MoS₂ Sheets as Lubricant Additives

Abstract

Wear occurs between two rubbing surfaces. Severe wear due to seizure under high pressure leads to catastrophic failures of mechanical systems and raises wide concerns. In this paper, a kind of synthetic oil-soluble ultrathin MoS sheets is synthesized and investigated as lubricant additives between steel surfaces. It is found that, with the ultrathin MoS sheets, the wear can be controlled under the nominal pressure of about 1 GPa, whereas the bearable nominal pressure for traditional lubricants is only a few hundred megapascals. It is found that when wear is under control, the real pressure between the asperities agrees with the breaking strength of ultrathin MoS. Therefore, it is believed that, because of the good oil solubility and ultrasmall thickness, the ultrathin MoS sheets can easily enter the contact area between the contacting asperities. Then, the localized seizure and further wear are prevented because there will be no metal-to-metal contact as long as the real pressure between the asperities is below the breaking strength of ultrathin MoS. In this way, the upper limit pressure the lubricant can work is dependent on the mechanical properties of the containing ultrathin two-dimensional (2D) sheets. Additionally, ultrathin MoS sheets with various lateral sizes are compared, and it is found that sheets with a larger size show better lubrication performance. This work discovers the lubrication mechanism of ultrathin MoS sheets as lubricant additives and provides an inspiration to develop a novel generation of lubricant additives with high-strength ultrathin 2D materials.

A review of recent advances in tribology

“…At the same time, the nanocomposites significantly improve the lubricating properties of the base oil due to the synergistic lubrication between LDH and GO or MoS 2 . Chen et al [154] successfully prepared a synthetic oil-soluble ultra-thin MoS 2 sheet as lubricant additive and investigated the wear behavior under about 1 GPa pressure. Because of the uniform dispersion of molybdenum disulfide, wear can be controlled as long as the actual pressure is less than the fracture strength of MoS 2 .…”

Effect of Humidity on Friction and Wear—A Critical Review

“…The tribological applications of metals or alloys are usually associated with oil lubrications [234][235][236][237][238][239][240]; thus, studies on the effect of humidity on friction and wear behaviors of metallic substrates are conducted less extensively. Most research focuses on steel interfaces.…”

PEG‐assisted solvothermal synthesis of MoS2 nanosheets with enhanced tribological property

“…17 Meanwhile, it has been reported that ultrathin MoS 2 could significantly improve the lubrication property of oils, as they could be penetrated into the contact area easily. 18,19 In view of the above, it is highly desired to fabricate MoS 2 nanosheets with ultrathin shape and structure defects to apply as oil additives.…”