A ball-on-disk tribometer was employed to evaluate the lubrication performance and mechanisms of innovative TiO 2 nano-additive water-based lubricants. Two experimental methods were applied to determine the optimal mass fraction of TiO 2. In the method I, lubricants were added onto the worn disk tracks at a predetermined time interval. In the method II, the disks were immersed in the lubricants continuously during the whole process of tribological tests. The results both indicate that the water-based lubricants can significantly reduce the coefficient of friction (COF). The 0.8 wt% TiO 2 lubricant demonstrates excellent tribological properties including the lowest COF and the strongest wear resistance under all lubrication conditions. The lubrication mechanisms are attributed to the rolling and mending effects of the TiO 2 nanoparticles.

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Friction and wear characteristics of TiO2 nano-additive water-based lubricant on Friction and wear characteristics of TiO2 nano-additive water-based lubricant on ferritic stainless steel ferritic stainless steel

Graphene oxide (GO) and alumina (Al 2 O 3 ) nanoparticles were added in deionized water in order to synthesise a dimensionally integrated nanolubricant. Tribological tests were performed using an alloy/stainless steel contact pair. A 0.12 wt.% 1:1 GO-Al 2 O 3 lubricant produced 64% and 47% reductions in the COF as well as 63% and 60% improvements in the Ra compared with 0.06 wt.% Al 2 O 3 and 0.06 wt.% GO solutions. Analysis of the worn surface indicated that a thin film consisting of a layer of GO and a tribo-layer of Al 2 O 3 was formed during testing. The GO layer prevented the direct contact of surface asperities, leading to a low resistance to sliding, whilst the Al 2 O 3 tribo-layer acted as a load bearer to strengthen the GO layer.

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