Numerical simulation and experimental study on the evolution of multi-field coupling in laser cladding process by disk lasers

摘要

Laser cladding exhibits highly complex heat transfer and thermo-elastic-plastic-flow changes. The multi-physics field coupling changes affect heat transfer, mass transfer, solidification, and phase transformation behavior. The quick cooling and rapid heating of the laser cladding process cause complex residual stress and deformation, which ultimately affect the quality of the cladding layer. It is notably difficult to reveal the mechanism of multi-physical field coupling in laser cladding by experiments. In this paper, the material's temperature-dependent physical parameters by the CALPHAD method were obtained and a multi-field coupling model for laser cladding process by disk lasers was established. In the mathematical model, the interactions between the laser beam and the powder flow, the influence of the surface tension and buoyancy on the liquid metal flow in the melt pool, and the instantaneous change in the shape of the cladding layer were considered. Finally, the laws for the temperature, flow, and stress fields in the cladding process were obtained. The microstructure of the cladding layer was observed by Zeiss-IGMA HD FESEM. The accuracy of the model was verified by comparing the growth morphology of the grain and the size of the cladding layer. The study provides an effective way to reduce and eliminate residual stresses.