Comparison of graphene as an oil additive with conventional automotive additives for the lubrication of steel and DLC-coated surfaces

The present work is focused on comparing the tribological behaviour of graphene platelets and commercially available automotive additive package, combined with glyceryl isostearate (GIS) as a friction modifier. The investigation was performed with steel/steel and DLC/DLC contacts, at 25 °C and 100 °C, in all lubrication regimes and by considering the running-in effect. Under all the investigated conditions the graphene platelets provided the lowest friction in the ML and BL regimes. This is the result of forming graphene-based tribofilms which, unlike for the other tested lubricants, is relatively insensitive to temperature, tribochemical activation and the conditions before or after the running-in. By combined the use of graphene platelets and conventional additives some interactions in their tribological behaviour were also observed.