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Laser cladding, as one of the most promising surface modification technologies, is being widely applied in industry to improve the wear and corrosion resistance of components. The high energy input and high cooling rate during the cladding process lead to severe metallurgical reactions that determine the microstructure and properties of the cladded layer. In this study, a 3-dimensional (3-D) finite element (FE) model was developed to study heat transfer during laser cladding of 420 stainless steel+ 4% molybdenum on mild steel A36. In this model, the effects of laser-powder interaction, temperature-dependent material properties, latent heat, and Marangoni flow were considered. A method based on mass balance was adopted to predict the clad geometry. The thermal results such as the temperature history, temperature gradient, and solidification rate were investigated. Based on the simulated thermal results, the microstructure and Mo distribution in the clad layer were studied. In order to verify the established model, a series of experiments was conducted by using an 8-kW high-power direct diode laser (HPDDL). Thermocouples and a CCD camera were used to monitor the temperature history and molten pool size. The predicted clad height and width showed a good agreement with the experimental results.

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