Characterization of laser-powder interaction and particle transport phenomena during laser direct deposition of W‒Cu composite

Abstract

Abstract The laser direct deposition, one kind of additive manufacturing technologies, was used to produce W‒Cu composite material. To explain the formation of the deposited microstructure, the process of laser-powder interaction and particle transport phenomena during laser direct deposition were investigated through experiment and simulation works. The parameters of the coaxial powder flow (the distribution and the velocity of flying particles) and the particle motion on the melt pool were demonstrated with high-speed imaging. By using these parameters, a laser-powder flow interaction model was established to calculate the laser intensity attenuated by the powder flow and the temperatures of W and Cu particles. Based on the calculated results, a three-phase fluid dynamics model was constructed to simulate the transport phenomena of W and Cu particles on the substrate surface during laser deposition. The calculated results indicate that the temperatures of W and Cu particles were mainly in the solid state but with huge difference in temperature while arriving at the deposition area. The captured images show that these solid particles can be deposited until the substrate surface was slightly melted. The simulation results suggest that the heat of W particles is conducted to Cu particles rapidly after being deposited on the substrate surface. Coupled with the laser irradiation, Cu particles are melted and form a melt pool. Subsequently, a fallen W particle can float on the melt pool since the inertial force of the falling W particle and the surface tension between Cu and W are roughly balanced. In comparison, if a Cu particle falls on a floating W particle, the Cu particle will be melted and then flow into the melt pool in 300 μs. The combination of high-speed imaging and our simulation explained the deposited microstructure, i.e., the distribution of W particles in the deposition layer.