Microstructure and properties of laser cladding NiCrBSi coating assisted by electromagnetic-ultrasonic compound field

Abstract

To improve the defects of element segregation and the uneven microstructure of the laser cladding layer, the direct current electric field, alternating magnetic field, and ultrasonic field are innovatively coupled to assist the laser cladding process. The contrast experiments of no-auxiliary field and auxiliary field assisted laser cladding are carried out. The finite element simulation method is also used to study the influence of the auxiliary field on the flow behavior of the molten pool. The simulation results suggest that the fluid flow speed increased with the assistance of auxiliary fields. On the one hand, the electromagnetic force exacerbates the convection of the molten pool. And on the other hand, the acoustic streaming effect changes the macroscopic flow of the melt. These two effects all enhance the flow behavior in the molten pool. The experimental results show that the microstructure of the cladding layer fabricated with auxiliary fields is refined, and the elements diffuse uniformly. Due to the enhanced convection in the molten pool, the element segregation is inhibited, and the dendrites are broken up, further making the microstructure refined. Among the cladding layer fabricated with the assistance of the auxiliary field, the laser cladding layer assisted by the electromagnetic-ultrasonic compound field has the highest microhardness and the lowest wear volume. Under the action of the compound field, a cladding layer with fine structure, low element segregation, and good mechanical properties is successfully obtained.