Influence of AC Magnetic Field on Microstructure and Wear Behaviors of Laser Cladding Fe-Based Composite Coating

Fe-Cr-Si-B-C composite coatings were fabricated on 45 medium carbon steel substrate using electromagnetic control assisted laser cladding process. The microstructure, phase composition, friction and wear behaviors of the composite coatings were investigated by X-ray diffraction, scanning electron microscopy, energy dispersespectroscopy, and a pin-on-disc tribometer. The results indicate that AC magnetic field can reduce the liquid phase temperature gradient of laser molten pool solid -liquid interface and increase the heterogeneous nucleation rate. Consequently, coarse columnar grains into uniform and fine equiaxed grains was prompted and the pores and cracks defects in the composite coatings were eliminated. However, it had no distinct effect on the phase composition of the composite coatings. The coatings were mainly composed of γ-(Fe, Cr) solid solution, γ-(Fe, Cr) eutectic and a small amount of Fe₃(B,C), Cr₇(B, C)₃ and CrFeB compounds. The friction and wear behaviors of the composite coatings treated by AC magnetic field were much better than that of untreated coatings. The wear of the electromagnetic control assisted laser cladding coatings was 50% of that of the non-magnetic field coatings, and the fluctuation of friction coefficient was low.