Synergistic lubrication behavior of TiN coatings integrated with CNTs for oil and water lubrication

The titanium nitride (TiN) coating was deposited on the M50NiL substrate by using a multiarc ion plating technique to enhance tribological performance under high contact stress. The microstructure and mechanical properties of the TiN coating were characterized and results demonstrated that the hardness and modulus of elasticity were enhanced to 33 GPa and 400 GPa, respectively. The tribological behavior of TiN coatings sliding against Si₃N₄ ceramic was investigated by using a ball-on-disc tribometer. Under dry friction, the wear resistance property was improved by 60.5 % after TiN deposition at high contact stress of 2.3 GPa. Meanwhile, carbon nanotubes (CNTs) nano-lubricants with good dispersion stability were prepared. Under aqueous lubrication, the coefficient of friction (COF) and wear scar diameter (WSD) decreased by 15.6 % and 8.7 %, respectively, after adding 0.2 wt% CNTs when TiN coatings slid against Si₃N₄ ceramic. Under oil lubrication, the COF and WSD decreased by 5.5 % and 12.6 %, respectively with the addition of CNTs. The findings contributed to the practical application of CNTs as additives in hybrid ceramic bearings lubrication.