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The cladding layer formed by laser cladding is formed by solidification of the molten pool. The quality of the cladding layer is directly determined by the evolution of the molten pool. The numerical simulation of the evolution of the molten pool is carried out, revealing the relationship between different powers and the evolution of the molten pool. The results show that the volume of the molten pool exhibits a nonlinear expansion of "expansion-shrinkage-re-expansion" before reaching the steady state, and the volume and expansion rate of the molten pool are determined by the laser power. In addition, the degree of shrinkage of the molten pool and the speed of convection can also be controlled by the laser power. When the laser power reaches a certain level, evaporation occurs on the surface of the molten pool. The convection pattern of the molten pool can be changed by evaporation. However, due to the impact of shielding gas and Marangoni movement, the effect of evaporation on the geometry of the cladding layer is limited. [ABSTRACT FROM AUTHOR]

Because the convection pattern inside the laser cladding transient molten pool is difficult to measure by experimental means, the numerical analysis model of the inside of the laser cladding molten pool was constructed, and the forming mechanism of the cladding layer was simultaneously analyzed. The internal convection pattern of the single-track, multi-track and multi-layer laser cladding molten pool was analyzed. The results show that the convection inside the laser cladding molten pool in different types is mainly annular convection. The fluid at the bottom of the molten pool flows to the surface of the molten pool, and the fluid on the surface of the molten pool flows along the sides to the bottom of the molten pool. Therefore, the cladding layer is mainly solidified by the fluid flowing from the bottom of the molten pool to the surface of the molten pool. [ABSTRACT FROM AUTHOR]

Due to the complex transient characteristics, it is difficult to directly measure the formation and development of a molten pool formed by laser cladding. Considering the change of thermophysical properties at high temperatures and the coupling between the heat source and the molten pool surface, a new numerical simulation method was proposed and verified. The thermal history and formation of the molten pool, the convective pattern, and the solidification morphology of the cladding have been analyzed. The results show that the molten pool can reach steady-state in a very short time, and both considerable temperature gradient and fast circular convection exist in the molten pool. The bottom of the molten pool mainly showed columnar growth, while the top was equiaxed. Columnar to equiaxed transition occurred at the center of the molten pool. • Established a multiphysics three-dimensional simulation model for laser cladding. • Two annular Marangoni convections were founded inside the molten pool. • Evaporation hardly affects the shape of the cladding. • CET occurs during solidification. [ABSTRACT FROM AUTHOR]