Multicomponent multiphase modeling of dissimilar laser cladding process with high-speed steel on medium carbon steel

During a laser cladding process, the transport phenomena in the molten pool, including rapid solidification, strong fluid convection, and species diffusion are complex, and determine the microstructure and composition of the cladding layer. In this study, a three-dimensional transient multicomponent multiphase model was proposed to simulate the dissimilar laser cladding process with T15 powder and T15/CeO2 mixed powder on 42CrMo substrate. The position and expression of the source terms on energy and mass were clearly defined. The model was validated by comparing the morphology of the cross section with single-track cladding experiments. The simulation results indicate that the molten pool is dominated by a strong Marangoni flow that results in a fully mixed cladding layer and a narrow transition zone at the bottom. The molten pool exhibits an inward flow pattern with pure T15 powder and an outward flow pattern with T15-CeO2 mixed powder. The content of the elements and the microstructure of the cladding layer were investigated by using an electron probe micro-analyzer and a scanning electron microscope. The microstructure evolves from planar to cellular, and to equiaxed dendrites from the substrate–clad interface to the top surface. The transition zone comprised of planar and cellular grains. The solidification characteristics calculated from the numerical model were associated to the grain morphology.