In situ Synthesizing Carbon-Based Film by Tribo-Induced Catalytic Degradation of Poly-α-Olefin Oil for Reducing Friction and Wear

Abstract

Reducing friction and wear in a convenient and economical way has always been desired for industrial production. Here, a carbon-based film with excellent friction-reducing and antiwear abilities was formed in situ from the degradation of poly-α-olefin oil (PAO10) on the friction interfaces of the MoN/Pt coating sliding against the Si 3 N 4 ceramic ball during the rubbing process. The MoN/ Pt coating was prepared on stainless steel by direct current magnetron sputtering, in which an active 10 nm Pt layer grew well on the MoN layer. The MoN/Pt coating, lubricated by trace amounts of 5 mL PAO10 oil, exhibited a super low friction coefficient of 0.042 and an extremely low wear rate of 1.08 × 10 −8 mm 3 (N m) −1 after a long duration of applied friction under a high Hertz contact stress of 1.7 GPa. Raman spectra and transmission electron microscopy images revealed that the carbon-based film was composed of amorphous carbon phase dotted with sporadic Pt, MoO 3 , and SiO 2 crystal phases. Molecular dynamics simulations illustrated that the MoN/Pt coating had catalytic action and resulted in the degradation of PAO10 during the rubbing process, which corresponded to the formation of the amorphous carbon-based film on the wear surfaces.

Achieving Ultralow Friction and Wear by Tribocatalysis: Enabled by In-Operando Formation of Nanocarbon Films

“…Notably, not only has the resulting wear rate of the materials been substantially reduced (to 1.08 × 10 −8 mm 3 (N m) −1 ), but the coefficient of friction also decreased from ∼0.15 for bare steel to ∼0.04 for the coating. 117 Further, a similar mechanism of the carbon-based film formation from oil was reported for MeN coatings with tribocatalytically active silver patches. 118 Alternatively, the MeN-Cu coatings demonstrated great potential for tribocatalytic activation of the protective tribofilms' formation in different alkane environments with the alkane molecule length and wetting characteristics affecting the effectiveness of the film growth and protection.…”

“…Xu et al . tried replacing the catalytically active copper in the MoN matrix with Pt and observed a similar formation of amorphous carbon inside the wear track during sliding of the film against the silicon nitride ball in the PAO10 synthetic oil.…”

“…Analysis of the wear track suggested that during sliding under the high Hertzian contact pressure of 1.7 GPa, the PAO10 oil underwent dehydrogenation and a carbon chain scission process leading to the formation of an amorphous carbon film in the wear track. Notably, not only has the resulting wear rate of the materials been substantially reduced (to 1.08 × 10 –8 mm 3 (N m) −1 ), but the coefficient of friction also decreased from ∼0.15 for bare steel to ∼0.04 for the coating . Further, a similar mechanism of the carbon-based film formation from oil was reported for MeN coatings with tribocatalytically active silver patches …”

“…Figure 10 provides the representative summary of the process of tribocatalysis on the MoNx-Cu surfaces from olefin molecules resulting in the formation of the DLC films. 92 Xu et al 117 tried replacing the catalytically active copper in the MoN matrix with Pt and observed a similar formation of amorphous carbon inside the wear track during sliding of the film against the silicon nitride ball in the PAO10 synthetic oil. Analysis of the wear track suggested that during sliding under the high Hertzian contact pressure of 1.7 GPa, the PAO10 oil underwent dehydrogenation and a carbon chain scission process leading to the formation of an amorphous carbon film in the wear track.…”

Effect of functional groups on tribological properties of lubricants and mechanism investigation

“…This indicates that the whole friction process is dominated by oxidative wear, which causes the friction coefficient to fluctuate violently (Fig. 3(a)) [40].…”