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Influence of Fluid Convection on Weld Pool Formation in Laser Cladding

Laser cladding is a relatively fast and precise metal deposition process that has been widely applied to deposit coatings to protect parts from wear and/or corrosion and to rebuild worn surfaces of expensive components such as jet engine turbine blade tips. Economic development of laser cladding process applications is impeded by lack of a capability to accurately predict the results of complex physical phenomena associated with this process. In this paper, a transient 3D transport model was used to generate insight into details of melt pool formation, fluid convection, and solidification in Inconel® 718 laser claddings. The predicted melt pool geometry was validated by comparison to corresponding experimental data. Simulation results showed a notable flat temperature profile in the liquid ahead of the rear melt pool boundary was induced by Marangoni flow. Also, convection patterns associated with the switching of surface tension gradient from positive to negative at a region behind the laser beam focus spot caused the deepest weld pool penetration to be at this location. Temperature gradients (G) and solidification rates (R) in the liquid on the solidification boundary at the back of the melt pool were quantified and solidification mode was predicted by these values. The results illustrated the key role played by fluid convection in the laser cladding process.