Effect of Electrode Induction Melting Gas Atomization on Powder Quality: Satellite Formation Mechanism and Pressure

Abstract

Electrode induction melting gas atomization (EIGA) is a wildly applied method for preparing ultra-clean and spherical metal powders, which is a completely crucible-free melting and atomization process. Based on several experiments, we found that although the sphericity of metal powders prepared by EIGA was higher than that of other atomization methods, there were still some satellite powders. To understand the formation mechanism of the satellite, a computational fluid dynamics (CFD) approach FLUENT and a discrete particle model (DPM) were developed to simulate the gas atomization process, and several EIGA experiments with different argon pressures (2.5–4.0 MPa) were designed. A numerical simulation of the gas-flow field verified the formation trajectory of satellites, and the Hall flow rate of the powder produced under different pressures was 13.3, 13.8, 15.6, and 16.8, which were consistent with the prediction of the numerical simulation. This study provides theoretical support for understanding the satellite formation mechanism and improving powder sphericity in the EIGA process.

Effects of gas pressure and catheter length on the breakup of discontinuous NiTi droplets in electrode induction melting gas atomization

“…As described in equation (1), higher GMR values are beneficial for finer powder with narrower particle size distributions (figure 3(a)). However, when the gas pressure was 6 MPa, the recirculation zone became larger and the collisions among the powder particles became more frequent, which resulted in aggregations and more satellites (figure 4(d)) [29]. It also resulted in an increase in the D50 value of the powder and a decrease in the yield of the 0-53 μm powder (figure 3(b)).…”

“…This proved that the classification process did not affect the normal distribution of the powder. Furthermore, there was an overlap of the size differentiate distribution curves of the 0-15 μm and 15-53 μm powders, which was caused by Van-der-Waals attractive forces between the particles during the process of classification [29] (figure 7). The particle size distribution range of 15-53 μm was significantly narrower than that of the range of 0-53 μm.…”

“…These factors directly affect the yield and quality of the fine powder, with particle sizes in the range of 15-53 μm used in SLM process. Moreover, the catheter length in the nozzle is a key factor that affects the size of the negative turbulent area and the structure of the flow field [29]. It has also significant effects on the particle size, morphology, and hollow ratio of the NiTi powder prepared by EIGA.…”

An overview of additively manufactured metal matrix composites: preparation, performance, and challenge

“…As reviewed, many metals and alloys can be used as the metal matrix to produce MMCs, such as Al, Ti, Ni Fe, Co, and their alloys. The widely used methods for producing metal matrix powder are gas atomization [180], electrode induction melting gas atomization [181], vacuum induction melting gas atomization [182], plasma atomization [183], water atomization [184], centrifugal atomization [185], and plasma rotating electrode process [186]. Irrespective of the powder production methods, there is a widely acknowledged consensus that the cost of powder employed in the AM process is high [71].…”