Simulation and experimental investigations on the effect of Marangoni convection on thermal field during laser cladding process

Abstract

Laser cladding process consolidates powder or wire materials into a dense metal part with the assistance of laser energy source. Simulation of temperature distribution and fluid flow of the laser cladding process was carried out using the finite volume method (FVM). The influence of the Marangoni convection on the dimensions of the melt pool was investigated. A double peak phenomenon of flow velocity on the surface of the molten pool was induced by the Marangoni convection. The heat and mass transfer in the molten pool caused by the Marangoni effect was measured by the Peclet number. Temperature gradient (G) and solidification rate (S) were calculated to predict the morphology and size of the solidification microstructures. During the solidification process of the molten pool, the cooling rate (G×S) declines from the top region of the cladding layer, and the solidification rate of the cladding layer gradually decreases from the top to the bottom. The corresponding microstructure is in a good agreement with the experimental results. The metallurgy bonding between the substrate and the cladding layer is not very well when the simulated molten pool depth is smaller than the thickness of the pre-placed powder bed.