Formation mechanism of Cr₇C₃ hard phase under magnetic field

Longitudinal magnetic field was applied to the plasma arc surfacing of Fe-based alloy powder. The morphology and distribution of hard phase in surfacing deposit was changed by magnetic field. The microstructure and orientation of Cr₇C₃ hard phase in the Fe5 surfacing layer were tested by using the optical microscopy and X-ray diffraction. The results show that obvious orientation behavior of Cr₇C₃ hard phase with paramagnetism in the process of nucleation and growth under the effect of external magnetic field. When driving current of magnetic field is 3A,the distribution of Cr₇C₃ hard phase is optimum,which is fine and shown as "the hexagon" in the surfacing layer. The hardness and wear resistant are improved by the Cr₇C₃ hard phase. The formation mechanism of Cr₇C₃ hard phase is that revolution orientation during high temperature and preferential growing during low temperature.