Effect of alternating current electric field on microstructure and properties of laser cladding Ni–Cr–B–Si coating

The effects of alternating current (AC) on the morphology, microstructure and property of the laser cladding Ni–Cr–B–Si coatings were studied. The experimental results showed that the surface morphology of the coating was wavy due to the skin effect and the alternating electromagnetic force produced on the surface of the molten pool under the action of the AC. Electric field could increase the nucleation rate and refine grain size, thus the structure in the bottom of the coating transformed from dendrite to equiaxed crystal. However, alternating current did not change the phase type in the coating. Furthermore, due to the refinement of the grain structure at the bottom of the coating, the number of cracks in the coating was reduced by 60%. The average microhardness of the coating increased, and the corrosion resistance was also improved under the AC electric field.