Tribological properties of graphene-reinforced graphite in high-temperature and high-pressure water

It is of great significance to ensure the stability and life of graphite counterparts under severe operating conditions in high-temperature and high-pressure water. In this study, the tribological properties of original graphite and graphene-reinforced graphite against Stellite 12 alloy are investigated on a disc-on-disc configuration under pv factors ranging from 0.2 to 13.0 MPa m/s at applied load p of 900 N with spindle speed v from 100 to 6500 rpm in a 70 °C and 2 MPa water environment, respectively. As the pv factors increase, the wear depth and surface roughness of both graphite are found to be decreased, while the residual compressive stresses on Stellite 12 alloy are elevated, because the friction pairs bear the boundary, mixed and hydrodynamic lubrication regimes, respectively. The pairs of original graphite against Stellite 12 alloy undergo abrasive wear, adhesive wear and fatigue wear simultaneously under the boundary lubrication, whereas the positive obstructing effect of graphene filler on the lamellar graphite being teared, enabling the fragmented abrasive debris to stabilize the vibration of friction counterpart and inhibit the propagation of fatigue wear. Both sets of friction pairs are subjected to fatigue wear under long-term high-cyclic alternating stresses from the water film under the hydrodynamic lubrication, the addition of graphene filler enables a significant increase in the loading capacity of graphite in high-temperature and high-pressure water, as well as a reduction in COF and wear depth.