A tribological behavior assessment of steel contacting interface lubricated by engine oil introducing layered structural nanomaterials functionalized by oleic acid

Traditional lubricating oil in the lubrication process leads to oil film rupture and lubrication failure due to thermal instability under high temperatures. Tribological characteristics of synthetic oil (5W-40) can be potentially improved by the application of layered nanoparticles (h-BN and MoS2 NPs). The tribological properties of base oil, MoS2, and h-BN nanolubricants (NLs) were comprehensively investigated under varying loads, rotating speeds, and temperatures using a four-ball tribometer. Moreover, this study confirmed that the COF and wear rate values of wear scar lubricated by h-BN NL and MoS2 NL decreased by approximately 21.5% and 13%, 91.6% and 90.9%, respectively, compared with base oil, showing the brilliant tribological performance following the introduction of NL. The results showed the wear interface lubricated by NL with oleic acid (OA) functionalization contributed to the appearance of tribo-film along with chemical absorption film due to the complicated oxidizing reaction. Eventually, the synergistic role between OA and nanomaterials responsible for the increasing tribological properties is elaborately elucidated.