In situ synthesis ZrB_2/Fe cladding layer by-PTA process

摘要

ZrB_2/Fe cladding layer was in situ synthesised by plasma transferred arc powder cladding on mild steel substrate using Zr and B_4C as the precursor powders. The phase composition and microstructure were investigated by X-ray diffraction analysis, optical microscope, scanning electron microscopy and energy dispersive spectrum. Microhardness of the layer was examined at room temperature. The results show that the phases of the cladding layer are ZrB_2 and iron. ZrB_2 particles have three morphologies: acicular, short rod and block. Reaction process could be divided into four stages according to the state of reactants. ZrB_2 particles gradient distribute in substrate from surface to bottom of the layer. Skeleton-like structure and cluster structure of ZrB_2 are formed in the surface part, and particulate reinforced structure is formed in the middle and bottom part of the layer. The microhardness was greatly improved due to the presence of ZrB_2 particles in comparison with the substrate.