Investigation on laser cladding Ni-base coating assisted by electromagnetic field

Laser cladding Ni-base coatings were prepared on pure iron assisted by an electromagnetic compound field. The microstructure, phase composition, crack and microhardness of the cladding coatings were investigated. Results indicated that laser cladding Ni-base coatings with and without the electromagnetic field was composed of γ-(Fe, Ni), CrB, Cr7C3, Ni3B and Ni2B. The electromagnetic compound field could promote the transformation of γ-(Fe, Ni) to equiaxed crystals. The volume fraction of hard phase CrB can be increased by electromagnetic field. Mechanical scouring effect of electromagnetic stirring makes hard phase Cr7C3 form an independent rod structure. The number of cracks in coatings is decreased under the electromagnetic field. The average microhardness of cladding coatings increased to 923.7 HV0.2. Under the combined action of the electromagnetic stirring and current thermal effect, the temperature gradient in the molten pool had an optimum value. That is, the value of AC current was 1200 A and magnetic flux intensity was 0.2 T.