Modeling for evaluating the effect of powder flow during laser cladding process: From thermal and flow fields to microstructure of the molten pool

During the laser cladding process, the mass, energy and momentum inputs of the powder flow play a significant role in the evolution of the molten pool and microstructure. Considering the mass, energy and momentum inputs of the powder flow can significantly improve the accuracy of the simulation. In this study, an integrated modeling framework containing a computational fluid dynamics (CFD) model with the powder source described by ray tracing method and a cellular automata (CA) model was established to investigate the effects of powder flow on the evolution of the molten pool and microstructure during the laser cladding process. The accuracy of the modeling framework was verified by experiments with different powder particles velocities. The results indicated that the powder flow impact changed the vortices of the molten pool, resulting in less high–temperature molten metal flowing into the tail but more high–temperature metal accumulating at the bottom of the molten pool, thus decreasing the height but increasing the depth of the cladding layer. And the tail of the molten pool is more easily to be nucleated than other zones for the same reason. Increasing the powder particles velocity increases the percentage of equiaxed grains in the cladding layer from 46.21 % to 52.64 % and the aspect ratio of the grains at the top of the cladding layer decreases by 16.92 %. This study helps to optimize the laser cladding process and provides a basis for regulating the microstructure by controlling powder flow.