In situ synthesis ZrB 2 /Fe cladding layer by PTA process

ZrB₂/Fe cladding layer was in situ synthesised by plasma transferred arc powder cladding on mild steel substrate using Zr and B₄C 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 ZrB₂ and iron. ZrB₂ particles have three morphologies: acicular, short rod and block. Reaction process could be divided into four stages according to the state of reactants. ZrB₂ particles gradient distribute in substrate from surface to bottom of the layer. Skeleton-like structure and cluster structure of ZrB₂ 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 ZrB₂ particles in comparison with the substrate.