Effects of High Carbon Ferrochrome Additions on the Microstructure and Properties of Fe-C-Cr-Nb Hardfacing Alloys

Fe-Cr-C-Nb hardfacing alloys composed of 1.07-1.33 wt% C, 0.08-2.61 wt% Cr, and 4.55-4.98 wt% Nb were prepared on C45E4 steel surfaces using alloy steel flux-cored wires. The alloy microstructures were studied by optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) and the effects of the alloying elements on the hardfacing properties were determined. The results indicate that these alloys contain martensite, austenite and NbC phases. As the C，Cr and Nb mass fraction in the surfacing material increases, the austenite and NbC contents increase, and the martensite content decreases. The NbC crystallite size in the surface layer affects its hardness and thus its wear resistance. The wear resistance first increases and reaches to its maximum value which is 5.7 times higher than that of the C45E4 steel substrate, while by higher increasing of the mentioned elements, it decreases.