Numerical simulation of thermal evolution and grain morphology of laser melted AlSiTiNiCo-WC composite coatings

Simulation of the geometry and internal grain size changes of laser cladding has been extensively studied, with the majority of such simulations focusing on pure metal powders. However, there are fewer simulations for aluminum-based composite coatings by laser cladding. In this paper, a new three-dimensional model of laser cladding composite coatings is proposed, which can accurately determine the geometrical size of the AlSiTiNiCo-WC cladding layer and the internal grain morphology and grain size changes of the cladding layer. The temperature-selective judgment mechanism and material thermal property calculation ensure the calculation accuracy of the composite coating, while the model accurately and intuitively determines the state changes of the composite coating in the process of laser cladding. Furthermore, the model verifies the feasibility of the exponential decay laser source in the simulation of composite cladding, and temperature field analysis accurately predicts the trends of grain morphology and grain size inside the cladding. The simulation results show that the variation of the laser scanning speed has a more pronounced effect on the depth of the cladding layer. The high-temperature gradient at the top of the molten pool is more likely to form fine grains, and the bottom of the cladding layer tends to form coarse columnar crystals with the increase in the internal temperature gradient at the depth. The simulation results were compared with experimental results to validate the accuracy of the simulation process.