Abstract
ZrB2/Fe composite coating was in situ synthesised by gas tungsten arc welding cladding process on AISI 1020 steel. Zr, B4C and Fe–B alloy powders were used as precursor powders. The phase composition and microstructure were investigated by X-ray diffraction analysis, optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. Microhardness of ZrB2/Fe composite coating at room temperature was examined. Main phases obtained from Zr and B4C precursor are ZrB2 and α-Fe, and those obtained from Zr and Fe–B precursor are ZrB2 and FeB. In the upper part of these composite coatings, ZrB2 phase mainly grows along temperature gradient direction. The middle part of these composite coatings has the highest ZrB2 content and highest microhardness. Gradient dispersions of ZrB2 reinforcements appeared in the composite coating from the middle to the bottom, leading to gradient dispersions of microhardness. With decreasing dilution rate, ZrB2 content and microhardeness increase.
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