Numerical simulation of heat transfer and flow behavior of molten pool under figure-8 oscillating laser cladding

The figure-8 oscillating laser can improve the quality of cladding and has great value for industrial applications, but its molten pool heat transfer and flow behavior are poorly known and seldom reported. For this reason, an in-depth understanding of the heat flow characteristics of the molten pool in this special laser mode is of great significance to the molding law of microstructure as well as the regulation work. In this work, a finite element model of laser cladding with multi-physical fields is established to investigate the effects and laws of different oscillation frequencies and amplitudes on the size of the cladding layer, heat transfer, and the fluid flow. The reliability of the numerical model is verified through experiments. The results show that the introduction of the figure-8 oscillation mode expands the range of the effective heat source, and the depth-to-width ratio of the molten pool is decreased. The temperature distribution is more uniform, and the nodal temperature values show periodic fluctuations consistent with the frequency. The complex laser overlap path periodically generates vortices that interfere with the Marangoni effect, and the flow of the molten pool becomes more complex. The microstructure of the cladding layer is refined due to sufficient mixing of the molten material, and the hardness is more uniform along the depth direction. This work provides insights and guidance for understanding the characteristics of the figure-8 oscillating laser cladding process and controlling metallurgical defects.