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Effects of gas pressure and protrusion length of melt delivery tube on powder size and powder morphology of nitrogen gas atomised tin powders

Abstract Gas atomisation is one of the most commercially used methods for producing metal powders. It is known as the break-up of a liquid metal into fine droplets by gas jets. In the present study, tin powders were produced using a supersonic nozzle in a close coupled gas atomisation system. Atomisation pressure and the protrusion length of the melt delivery tube were varied, and the effects of those variables on powder mean size, powder morphology and gas/melt mass flow ratio were investigated. The powder size decreased with increasing atomisation pressure. The reason of the increase in the gas/melt mass ratio with shorter protrusion length is a decrease in the melt mass flow rate, although the gas mass flow rate is constant at the same pressure. A decrease in the melt mass flow rate is caused by the effect of recirculation zone acting on the tip of the melt delivery tube. The produced tin powders had spherical shapes and clean surfaces.