Numerical simulation of thermal behavior and multicomponent mass transfer in direct laser deposition of Co-base alloy on steel

Abstract

a b s t r a c tDuring direct laser deposition process, rapid melting-solidification and addition of multicomponent powder lead to complex transport phenomena in the melt pool. The thermal behavior and mass transport significantly affect the solidified microstructure and properties of fabricated layer. In this paper, an improved 3D numerical model is proposed to simulate the heat transfer, fluid flow, solidification and multicomponent mass transport in direct laser deposition of Co-base alloy on steel. The solidification characteristics, including temperature gradient (G), solidification growth rate (R) and cooing rate (G Â R), can be obtained by transient thermal distribution to predict the morphology and scale of the solidification microstructure. Multicomponent transport equation based on a mixture-averaged approach is combined with other conservation equations. The calculated melt pool geometry and the composition profiles of iron (Fe), carbon (C), cobalt (Co) and chromium (Cr) are compared with the experimental results. The results show that in the initial stage of direct laser deposition, the rapidly mixture of substrate material and added material occur in the melt pool and conduct plays an important role in heat transfer due to the low Peclet number. As the melt pool is developed, the heat and mass transfer in the melt pool are dominated by strong Marangoni convection. An unmixed zone is observed near the bottom of melt pool where the convection is frictionally dissipated due to the presence of solidified dendrites. Since the G/R decreases and G Â R increases from the bottom to the top of the solidified track, the morphology of the microstructure changes from planar front to columnar dendrites to equiaxed dendrites and the grain size decreases.

Experimental and numerical study on laser keyhole welding of 42CrMo under air and argon atmosphere

“…Fluid dynamics in the laser-induced weld pool has been considered to be the important mechanism for the heat transport [14,[26][27][28][29][30]. Buoyancy effect and Marangoni effect due to temperature variation have been considered to be the driving forces for fluid flow.…”

Microstructure and properties of Fe–Cr–Ni alloy coatings on T10 steel by laser cladding

“…Figures 10(b) and (c) show the evolution from the equiaxed crystal to the columnar crystal in the middle of the cladding track. The crystal morphology evolution of the cladding track at the cross section was summarized in figure 11(a) [24]. When temperature gradient (G) decreases and the solidification rate (R) increased, the value of G/R would decrease and the solidification structure of laser cladding coatings would change from planar to cellular dendrites to columnar dendrites to equiaxed dendrites.…”

“…The crystal morphology evolution and the laser melted pool (a) The effects of the G and R on the morphology and scale of the solidified microstructure[24]; (b) The heat dissipating ways and the temperature gradient of the laser melted pool.…”

High-power laser resistance of filled sandwich panel with truss core: An experimental study

“…High-power laser-matter interactions have received increased attention in various conditions, including laser welding [1,2], laser drilling [3], laser cutting [4] and laser processing [5], as well as in the study of laser induced damages. When exposed to a high-power continuous wave (CW) laser, one of the most practical interests for structures used in the aerospace industry is the time that the melt front reaches the opposite surface.…”