Atomic scale mechanisms of friction reduction and wear protection by graphene.

We study nanoindentation and scratching of graphene-covered Pt(111) surfaces in computer simulations and experiments. We find elastic response at low load, plastic deformation of Pt below the graphene at intermediate load, and eventual rupture of the graphene at high load. Friction remains low in the first two regimes, but jumps to values also found for bare Pt(111) surfaces upon graphene rupture. While graphene substantially enhances the load carrying capacity of the Pt substrate, the substrate's intrinsic hardness and friction are recovered upon graphene rupture.