Tribological Performances of Graphite and Hexagonal Boron Nitride Particles in the Presence of Liquid

Abstract This article focused on the effects of the presence of liquid on tribological performances of graphite and hexagonal boron nitride (hBN) particles at ambient atmosphere. Two tribological tests conditions have been evaluated with AISI 52100 steel materials. In dry conditions for lubrication tests with pure particles and liquid conditions a drop of liquid is added before or during the friction tests. In dry conditions, graphite and hBN have two different tribological performances, while whatever was the type of liquid in liquid conditions, they are similar: μpure graphite ≈ 0.09 and μpure hBN ≈ 0.42, while μgraphite+liquid ≈ μhBN+liquid ≈ 0.06. Raman spectroscopy and scanning electron microscopy (SEM) investigations bring out weak influence of sliding mechanical constraints for tribofilms built in the presence of the liquid. Different hypotheses have been investigated; tribo-intercalation, influence of adsorption, lubrication by hydrogen, and action of the liquid. The simultaneous presence of liquid and particles induces friction mechanism inside the tribofilm reducing friction due to its nanostructuration.