Numerical Simulation and Experiment of Thermo-Elastic-Plastic-flow Multi-field Coupling in Laser Cladding Process

Laser cladding exhibits highly complex heat transfer and thermo-elastic-plastic-flow multi-physics field coupling changes. The temperature and flow fields in the melt pool influence the convection, heat transfer, solidification and phase change. The quick cooling and rapid heating of the laser cladding process cause complex residual stress and deformation, producing cladding cracks and affecting the quality of the cladding layer. It has been revealed that the mechanism of multiphysics field coupling in the laser cladding process is the key to control and avoid cladding cracks. The material's temperaturedependent physical parameters were obtained by the CALPHAD method and a multi-field coupling model for a 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 the 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 of instantaneous change for the temperature, flow and stress fields in the cladding process were obtained. The microstructure of the cladding layer was observed by a Zeiss.IGMA HD field emission scanning electron microscope, and the accuracy of the model was verified. Results show that an ellipsoid melting pool approximating 2 mm x 1.5 mm x 1 mm is formed, and the maximum temperature is at the back of the spot center. After 700 ms, the equivalent thermal stress is about 548 MPa, and the maximum thermal stress is at the bottom of the melting pool. This provides an effective way to reduce and eliminate residual stresses.