Analysis on microstructure of particles reinforced Fe-based layers by plasma spray welding

The WC reinforced Fe-based alloy composite coatings were prepared on the surface of 45 steel by back feeding equipment of plasma spray welding.Scanning electron microscopy(SEM), X-ray diffraction(XRD) and energy diffraction spectrum(EDS) were used to analyze the microstructures and compositions of the coatings.The results show that WC particles are mainly distributed on the top of the coating, and less in the middle and bottom of coating.There are planar crystal, celluler crystal, dendritic crystal and equiaxed crystal from the interface of coating/substrate to the top of the coating.The surface of the coatings has a microstructure consisting of WC, Fe₂₃B₆, Cr₂₃C₆, Cr₇C₃, SiC, W₂B₅ and FeW₂B₂.The WC particles have dissolution in the spraying process.The dissolution at the top of the coating is higher.The hardness increases from the matrix to the surface of coatings, which is up to 2218 HV.