Tribological Behavior of In Situ TiC/Graphene/Graphite/Ti6Al4V Matrix Composite Through Laser Cladding

Abstract

The TiC/graphene/graphite/Ti6Al4V composite coating was prepared by laser cladding. The microstructure and tribological behavior of the coating were studied. The in situ reaction between graphene and Ti occurred, and feathery TiC was formed. The feathery TiC was homogeneously distributed between α' acicular martensites which was refined with the addition of graphene. Some graphene was transformed into allotrope graphite under the laser irradiation. The TiC hard particles and the self-lubrication of graphene/graphite improved the wear resistance of composite coating. The wear rate and friction coefficient of TiC/graphene/graphite/Ti6Al4V composite coating decreased with the increase in sliding speed, a mechanical mixing layer (MML) was formed on the wear surface of the composite coating under the frictional heat, which protected the substrate and reduced the contact. Because of the self-lubricating properties of graphene/graphite, interlayer sliding occurred easily, which also effectively reduced friction. The wear rate of TiC/graphene/graphite/Ti6Al4V composite coating increased with the increase in load, but the friction coefficient decreased. The plastic deformation of subsurface layer was more serious under high load, and a stable self-lubricating MML with a protective effect was formed between the wear interfaces, which reduced the friction coefficient. With the increase in load, the wear mechanism changed from abrasive and oxidation wear to delamination, fatigue and oxidation wear.