Study on the influence of shielding effect for plasma cloud on multi-field coupling mechanism during laser cladding

Laser is a kind of electromagnetic wave. During laser cladding, metal vapor will be produced when the temperature reaches the material sublimation point, and plasma clouds will be produced after vapor atoms are ionized by laser. When the laser beam passes through the plasma cloud, it will be absorbed or refracted, resulting in the decrease of laser energy reaching the substrate surface. Plasma cloud shielding effect will directly affect the multi-field coupling behavior during laser cladding. It is significant to quantitatively reveal the influence mechanism of plasma cloud on multi-field coupling during laser cladding for improving the cladding layer quality. In the paper, a multi-field coupled numerical model for laser cladding of Fe60 with ASTM 1045 disk laser was established. The interaction between the waist beam of cladding powder jet, plasma cloud and laser beam was considered in the modeling. The influence of plasma cloud shielding effect on transient evolution for the temperature field, flow field, and stress field during laser cladding was compared and analyzed. The results show that the maximum temperature of molten pool is less than 2700 K, no plasma cloud will be produced during cladding. When the temperature is higher than 2700 K, the plasma cloud initiates. Under the same conditions, the molten pool temperature slightly decreases, the velocity decreases, and the stress increases slightly due to the shielding effect of the plasma cloud. And with the increase of laser power, the shielding effect of plasma cloud is more and more significant.