Study of free fall gas atomisation of liquid metals to produce powder

A free fall gas atomising unit was designed and constructed to produce meta l powder. The effect of focal length, number, and diameter of nozzles and a pex angle of atomisers is studied on size and size distribution of the powd er, atomisation efficiency, and particle shape by disintegrating the molten stream at various plenum pressures, superheats, and free fall distances. D roplets were found to be solidified and built up around the nozzles and the liquid delivery tube whenever the atomiser was used beyond a particular va lue of the plenum pressure; this pressure is termed limiting plenum pressur e. All the powder collectives produced under a wide range of conditions wer e found to obey log normal distribution function. The geometric standard de viation was shown to bear a constant value. The mass median size was correl ated with the dynamic parameters characterising the atomising field and a c orrelation is proposed. The atomisation efficiency was correlated with the mass flowrate and velocity of gas.