Influence mechanism of active elements on multi-field coupling in laser cladding Fe60 process

During the laser cladding process, the flow rate and direction of the molten metal significantly affect the shape of the molten pool and the solidification process. The addition of active elements to the molten pool will change the temperature coefficient of surface tension, causing variations of the Marangoni convection in the molten pool to affect the flow, solidification of molten metal, and the molten pool formation. It is difficult to track the transient evolution of the molten pool in real time by the experimental method, and the numerical simulation can effectively reveal the evolution mechanism of the multi-field coupling in the cladding process. In this study, the thermophysical parameters of the material were calculated by the CALPHAD method, and a multi-field coupling three-dimensional numerical model of Fe60 cladding by a disk laser is established. The transient evolution behavior of the temperature, flow, and stress field during the cladding process was analyzed, and the effect of sulfur element on the heat transfer and convection behavior of the molten pool was revealed. The calculation shows that sulfur element has little effect on the temperature field and stress field. In the molten pool without sulfur, the molten metal flows from the center to the edge of the molten pool to form a “double-eddy like” Marangoni convection. When adding sulfur to the molten pool, the direction of Marangoni convection changes and the molten pool is deeper. With the increase of sulfur content, the flow rate of molten pool increases gradually.