Effects of graphite content on microstructure and tribological properties of graphite/TiC/Ni-base alloy composite coatings

In order to reduce the friction coefficients and further improve the anti-wear properties of Ni-base alloy coatings reinforced by TiC particles, graphite/TiC/Ni-base alloy (GTN) coatings were prepared on the surface of 45 carbon steel. The effects of graphite content on the microstructure and tribological properties of the GTN coatings were investigated. The results show that the addition of graphite to the GTN coatings may greatly reduce the friction coefficients and improve their wear resistance. The 6.56GTN and 12.71GTN coatings exhibit excellent integrated properties of anti-friction and wear resistance under low and high loads, respectively. Under a low load, the wear mechanisms of the GTN coatings are mainly multi-plastic deformation with slight abrasive wear and gradually change into mixture of multi-plastic deformation, delamination and micro-cutting wear with the increase of graphite fraction. As the load increases, the main wear mechanisms gradually change from micro-cracks, micro-cutting and adhesive wear to micro-cutting and micro-fracture with the increase of graphite fraction.