Precipitation behavior of carbide in hardfacing coating containing Nb

Three kinds of flux-cored wires were designed for hardfacing continuous casting roller. The microstructure and fractograph were observed by metallographic microscope, Scanning Electron Microscopy(SEM). The phase structures were determined by X-ray Diffraction (XRD). The thermodynamic precipitation of the hardfacing coating with Nb content was calculated by Thermo-Calc software. The results show that, the microstructures of the hardfacing metals are ferrite, M₂₃C₆ and MC. With the increase of the Nb content, the microstructure is refined and the NbC precipitates along the grain boundary. Thermodynamic calculations show that, the precipitated carbides are mainly MC and M₂₃C₆. With the increase of the Nb content, the amount of MC precipitated in the steel increases gradually while that of M₂₃C₆ decreases. MC mainly contains V and Nb element, and dissolves a certain Mo, Cr and Fe elements and M₂₃C₆ mainly contains Fe and Cr elements;Nb content mainly affects MC.