Modeling analysis of laser cladding of a nickel-based superalloy

A novel numerical modeling simulation, involving an integration of computational fluid dynamics (CFD), a physical energy function and the finite element method (FEM) to investigate the thermal history experienced by the powder, deposited coating and substrate during the laser cladding of a nickel-based superalloy is performed. The laser cladding process is simulated in three sub-steps through different models. First, a CFD model is developed to track the trajectory of the powder during the feeding procedure before the powder particles merge into a molten pool of the substrate. Then, a physical energy function is used to compute the absorbed energy of the powder under laser irradiation. Finally, an FEM model is employed to investigate the addition of material and thermal history in the cladding structure. The simulation results are used to predict the solidification microstructure of the deposited coating and the dependence of the microstructure on the processing parameters, such as powder size, laser power and cladding speed. It is found that powder that is small in size is favorable for obtaining fine solidification microstructure in the laser deposited coating. However, the degree of influence of the powder particle size on cooling rate and resultant secondary dendrite arm spacing is weakened by a combined increase of the laser power and cladding speed at a fixed ratio of the laser power to cladding speed. This work contributes to the comprehensive understanding of laser cladding, as well as provides a fundamental basis for controlling the microstructure in laser deposited nickel-based superalloy coatings. (C) 2014 Elsevier B.V. All rights reserved.