Numerical simulation and experimental study of cladding Fe60 on an ASTM 1045 substrate by laser cladding

Laser cladding is a dynamic physical metallurgy process. Laser cladding exhibits highly complex heat transfer and thermo-elastic-plastic-flow multi-physics field coupling changes, which are accompanied by such physical phenomena as melting, solidification and phase transitions in the metal powder. The temperature and flow fields in the melt pool affect convection, heat transfer, mass transfer, and solidification, which ultimately affect the quality of the cladding layer. It is notably difficult to dynamically track and identify the mechanisms of the multi-physics field coupling evolution process because the laser cladding pool has the characteristics of small volume, large temperature gradient and instantaneous characteristics. In this paper, a multi-field coupled 3D mathematical model for cladding Fe60 powder on an ASTM 1045 substrate was established. In the model, the interactions between the powder flow and the laser energy beam, the influence of the surface tension and the buoyancy on the fluid flow in the melt pool, and the instantaneous change in the shape of the cladding layer were considered. The physical parameters related to the temperature changes in the substrate and the powder were obtained by the CALPHAD (Calculation of Phase Diagram). Finally, the model was solved, and the distribution states and evolution laws for the temperature and velocity fields in the laser cladding process were obtained. The microstructure of the cladding specimen was analyzed by a Zeiss-ƩIGMA HD field emission scanning electron microscope. The experimental results were in good agreement with the calculated results, and the accuracy of the model was verified.