| High spherical metal or alloy powders with less oxygen content and excellent performance can be made by gas atomization. However, the process of gas atomization is a complex process with mutual coupling multiphase flows. Now there are less research on the preparation of the powder with different atomizing gases. In this paper, CFD with FLUENT software were used to simulate the flow field with single-phase and the flow field with gas-melt phases in supersonic gas atomization including four kinds of atomizing gases. They were Ar, Air, N2and He. And the structures of their flow fields were analyzed. Al3Ni alloy powders have been made by gas atomization method with the Ar, Air, N2and He. The system on the effect of different atomizing gas on gas flow field for supersonic gas atomization was established.The main"conclusions are as follows:The maximum speed of atomizing gas in the four kinds of flow fields were535.19m/s(Ar),705.74m/s(Air),711.92m/s(N2),1704.22m/s(He). The minimum temperature of flow fields were24.96K(Ar),52.59K(Air),60.75K(N2),20.43K(He). The suction pressure△P were-90.26KPa(Ar),-75.49KPa(Air),-71.25KPa(N2),-50.85KPa(He). The distribution of temperature in the flow filed was same with the velocity field. There was a pressure gradient on the top of melt delivery tube on the gas flow field.The acreage of effectively atomization zone became small when the melt was injected in the gas-melt flow field. The maximum speed of the four kinds of flow fields were459.13m/s(Ar),624.07m/s(Air),632.78m/s(N2),1563.63m/s(He). The distance were2mm(Ar),22mm(Air),25mm(N2),10mm(He) between the top of melt delivery tube and the top of melt interacting with gas. The surface of melt shifted from convex to concave when the metallic melt came out from the melt delivery tube. The3D simulation results of gas-melt made the process of gas atomization visible.The results of atomizing Al3Ni alloy showed that the D50size of powders by preparation with gas atomization were19.13μm(He),38.25μm(Ar),36.42μm(N2),40.32μm(Air). The distribution of particle size of powders by preparation with He atomization became single-peak. And three others showed two-peak distribution. The metallographic structures of powders combined with Al2Ni, Al3Ni2and Al. The sphere shape of powders became better with Air-N2-Ar-He changing. The distance of crystal surface became smaller along with the value of20in XRD increasing with Air-N2-Ar-He changing. |
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