Optimum structure design of free-fall nozzle in preparation process of superalloy powders by electrode induction gas atomization technology

The structure design of free-fall nozzle directly determines the quality of gas-atomized powders in electrode induction melting gas atomization (EIGA) process, the unreasonable jet angle in free-fall nozzle structure often causes the regurgitation phenomenon, the flake powders, and the low yield of fine powders, which seriously affect the production efficiency and quality of powders. The numerical modeling of free-fall nozzle structure in the self-designed third generation of EIGA superalloy powder preparation device was established using Fluent commercial software for computational fluid dynamics (CFD). The effect of jet angle on the regurgitation phenomenon and the regurgitation mechanism of free-fall nozzle with gas flow recirculation were investigated in the initial atomization of melt. In the results, when the jet angle of free-fall nozzle is too large, there is an obvious regurgitation phenomenon; when the jet angle is too small, the superheat of the melt stream before atomization is insufficient, resulting in the poor sphericity of produced powders. Therefore, to ensure the superheat of melt flow and prevent the regurgitation phenomenon, it is necessary to control the recirculation zone position of gas flow to be lower than the melt inlet position of free-fall nozzle.