Effect of Si on microstructure and properties of Fe-Cr-C-B self-shielded open arc hardfacing alloys

Fe-Cr-C-B-Si wear-resistant alloy was deposited on Q235 base metal by flux-cored wire self-shielded open arc welding.With the addition of ferrosilicon powders,the effect of silicon content on the microstructure and the properties of hardfacing alloys were researched by optical microscopy (OM), scanning electron microscopy (SEM),X-ray diffraction (XRD) and hardness measurement.The results show that silicon content has a significant effect on the morphology,the distribution and the size of the carbides.With higher silicon content,it appears the white nodular phases with 9.75-13.54 GPa in hardness, which becomes bigger in size and is congregating distributed.The analyses results by back-scattered scanning electron images as well as energy dispersive spectrometer (EDS) and microhardness shows that these nodular phase grains are two-phase complex carbide,in which the inner M₂₃ C₆ are enclosed by the carbide with lower chromium and carbon content.Furthermore,the results of wet sand rubber wear tests indicate that proper silicon content significantly improves the abrasion resistance of hardfacing alloys.The size and the microhardness of the contained M₂₃C₆ phases have a direct effect on wear mass loss.