Nano-mechanical behaviour of the 3rd body generated in dry friction—Feedback effect of the 3rd body and influence of the surrounding environment on the tribology of graphite

Wear particles often agglomerate into cohesive transfer films (so-called 3rd body) during dry friction. Although described in terms of load carrying capacity and velocity accommodation, the 3rd body finally became a kind of black box where the comprehension of the real interactions, which occur in the tribocontact, can be unknown. We study the behaviour and the mechanisms of action of the 3rd body in a graphite/steel dry contact. Our experimental approach simultaneously involves the determination of the mechanical properties, the topography and the microstructure of transfer films in order connecting them to the fundamental tribological parameters (surrounding environment, load carrying capacity, friction and wear). In this paper, a methodology combining nano-indentation and AFM is developed. The results explain the various links between the effect of the environment on 3rd body generation and related friction and wear by taking of account the detachment mechanisms, the agglomeration mechanisms and their evolution during friction.