A cobalt-based alloy coating was prepared on the surface of 300 M steel using magnetic field-assisted laser cladding technology. The effects of different frequencies of an alternating magnetic field on the properties of the coating, such as the microstructure, phase characteristics, mechanical properties, thermal stress, and wear and corrosion resistance were investigated. The results showed that the electromagnetic field optimized the microstructure of the coating, and the microstructural refinement was most significant at a magnetic field of 65 Hz. As the magnetic field frequency increased, the degree of microstructural refinement decreased. Modification of the magnetic field frequency did not produce any change in the phase composition of the laser cladding coating. However, the application of a magnetic field reduces the thermal expansion coefficient and elastic modulus of the coating, thus decreasing its thermal stress. The laser cladding coating formed in a magnetic field exhibited enhanced resistance to wear and corrosion. In particular, the coating formed in a magnetic field with a frequency of 65 Hz exhibited a lower friction coefficient and less surface plastic deformation. Further, the corrosion resistance of the coating improved significantly owing to the magnetic field effect, leading to a substantial improvement in the mechanical performance of the laser cladding coatings.
