Roughness-dependent tribological characteristics of water-based GO suspensions with ZrO2 and TiO2 nanoparticles as additives

Hybrid nanosuspensions were synthesised through ultrasonically dispersing ZrO2 or TiO2 nanoparticles into graphene oxide (GO) nanosheet solutions for water-based lubrication. The effect of contact pair roughness on the tribological behaviours of the ZrO2/GO and TiO2/GO hybrid nanosuspensions were investigated using a block-on-ring testing approach. With a relatively smooth ring, the use of the nanosuspensions could reduce abrasive wear, and hence improve worn surface quality, owing to the relieved asperity ploughing. With a ring of moderate roughness, the use of the nanosuspensions suppressed the occurrence of adhesive wear through relieving the effect of asperity contact. With a relatively rough ring, the nanosuspensions generated a deposited layer of hybrid nanoparticles at the contact area that can prevent surface asperities from direct contact, thus leading to lower adhesive wear and friction.