Effects of graphite and graphene spatial structure on the TiC crystal structure and the properties of composite coatings

Abstract

To investigate the uniqueness of graphene, compared with graphite, in the preparation of TiC reinforced composite coating, the composite coatings were obtained from Ni-Cr-Ti-graphene/graphite powder by laser cladding. The phase composition and microstructure of composite coatings are detected by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive spectrometry (EDS), respectively. The phase composition of the composite coatings both mainly consist of Ni-Cr-Fe, Ni3Ti, Cr2Ti and TiC. The research results indicate that the crystal structures of in-situ synthesized TiC in the composite coatings have great difference, in detail, TiC crystals in the graphene-coating and the graphite-coating are dominated by equiaxed and dendrite crystals, severally, which is due to the reaction of two-dimensional graphene with Ti has better diffusion kinetics than that of three-dimensional graphite under rapid solidification of molten pool. The maximum microhardness of graphene-coating is 1000.3 HV0.1, which is about 4 times as hard as the substrate. The composite coatings show significant improvement in hardness and wear resistance than the substrate. The graphene-coating possesses more uniform hardness distribution and better wear resistance than that of graphite-coating, which is benefited from the uniform distribution of TiC equiaxed crystals in the graphene-coating.