Abstract
The influence of nozzle geometry on the particle size of rapidly soldified metal powders was investigated in a pilot plant gas atomiser using a ‘confined design’ nozzle. The tests were made on aluminium alloy AA 2014 using nitrogen as the atomising gas (at 1·56 MPa pressure). Powder particle size was found to be highly responsive to changes in the geometry and the size of the nozzle. Small nozzles with converging diverging gas channels produced finer powders than converging only nozzles or nozzles of larger diameter. Flake formation occurred at relatively low production rates and hence limited the usefulness of nozzles having a small throat area in the gas flow channel. When the throat area was large enough to deliver gas at a mass flowrate of ≥3 times the intended rate of production the nozzles operated well with no interference from flakes. An optimum value of protrusion of the metal flow tube was obtained and at lower or higher positions coarser particles were found to form.
MST/738
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