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(FeNiCoCrTi0.5)Cx (x = 3 wt%, 6 wt%, 12 wt%) carbonized high-entropy alloy-based composite coatings, marked as C3, C6 and C12, were prepared on 45 steel by laser cladding. The macroscopic morphology, phase, microstructure, hardness and wear resistance of coatings have been investigated systematically. The results indicate that diamond content has a significant influence on the microstructure and mechanical properties of (FeNiCoCrTi0.5)Cx coating. (FeNiCoCrTi0.5)Cx coatings, without pores and cracks, are well metallurgically bonded with substrate. The coatings consist of BCC solid solution, Cr23C6 and TiC. The addition of diamond in (FeNiCoCrTi0.5)Cx coating leads to the instability of BCC solid solution and facilitates the precipitation of carbides, which causes carbides to become coarse and aggregate into large blocks. The hardness of (FeNiCoCrTi0.5)Cx coatings is much higher than that of the 45 steel, the average hardness of C12 coating is 4 times the hardness of substrate. Besides, the hardness of (FeNiCoCrTi0.5)Cx coating increases with the increase of diamond content. Nonetheless, compared to C6 coating, the C12 coating shows inferior tribological performance due to the brittleness. It is noteworthy that C6 coating with outstanding wear resistance has the potential to apply in various fields of machinery industry, marine engineering and aerospace.

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.