POWDER FROM METAL AND CERAMIC MELTS BY LAMINAR GAS STREAMS AT SUPERSONIC SPEEDS

A new atomizing process is presented by which metal or ceramic melt st reams are drawn by parallel gas flows at high velocity, preferably in the sonic and supersonic speed range, and attenuated to a monofil of l ow diameter until it bursts into pieces when passing a Laval nozzle. C ontrary to known processes, the gas flow around the melt monofil is la minar. After cooling, globular particles are formed. The particle size distribution is narrower than in the case of common turbulent desinte gration procedures and energy consumption is lower. A mathematical des cription of the main dependencies is given in simple gas dynamic relat ions. The economical strength of the process applies to powders signif icantly below 100 mum. It was successfully applied to melts at about 2 000-degrees-C. Results have sofar been achieved for metal melts, where as ceramic melts may desintegrate into powders, but fibrous particles are also possible, depending on the relation of viscosity to surface t ension. Uses in the field of MIM and for special metal structures from rapid solidification (RS) are briefly reported. The name of the proce ss, ''Nanoval'' came from atomizing into the nano range by a flow gene rated in a Laval nozzle.