Metal Powder Granulation in a Plasma SpoutedFluidized Bed A direct current DC plasma

spouted/fluidized bed was applied to the granulation of spherical alloy grains from metal powder mixtures. From a mixture of iron powder (149 to 210 /'m) and aluminum powder (74 to 88 / m and 125 to 149 /'m). alloy grains from 1 to 5 mm in diameter were obtained. The grains exhibited a dense homogeneous core and a porous nonhomogeneous shell structure. The grains were quite spherical; the average aspect ratio of the grains was >0.85. The mass fraction of iron in the core section of product grains depended on the Al/Fe ratio of initial powder mixtures but was insensitive to the size of product grains and to the size of initial Al particles. Selective growth of seed grains was observed when sufficient seed grains were added to the starting powder mixture (Ref 4).

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