Effect of electrostatic field on microstructure and mechanical properties of the 316L stainless steel modified layer fabricated by laser cladding

In the present research, the laser cladding 316 L stainless steel layer with and without exerting electrostatic field were investigated. The microstructure and mechanical properties analyses reveal that the high solidification rate and specific convection result in the grain coarsening by stages and the crystal tends to grow paralleling with the laser scanning direction. Moreover, the rapid solidification also leads to the micro-segregation inside grain. The exerting of electrostatic field opposite to laser scanning direction promotes the elements diffusion and convection in the molten pool, which benefits the directional solidification of the laser cladding layer and produces the columnar grains. In addition, the accelerated diffusion eliminates the micro-segregation but induces the formation of stacking faults inside grains. The exerting of electrostatic field consistent with laser scanning direction restricts the elements diffusion and convection in the molten pool, which results in the ordered mushy solidification and ultrafine grain structure in whole cladding layer. Moreover, the existence of electrostatic field consistent with laser scanning direction promotes the micro-segregation and precipitation of small MC carbides. Compared with the laser cladding layer, the exerting of electrostatic field could decrease the porosity and improve the modulus and hardness of the laser cladding layer except the hardness of dendritic region. The interdendritic region in laser cladding layer with exerting of electrostatic field opposite to laser scanning direction obtains the highest modulus and hardness.