High yield, nonaxisymmetric atomization of nickel base superalloys

A preliminary study has shown that certain nonaxisymmetric close-coupled atomization geometries demonstrate superior efficiency in the production of fine nickel base superalloy powder compared to conventional close-coupled atomization utilizing an axisymmetric annular gas orifice and melt nozzle. Test conditions range from creating minor disturbances in the gas flow to substantial changes to both the gas flow and geometry of the melt nozzle. Various tests assess the mechanisms by which this performance is achieved; these include local static and dynamic pressure measurements, flow visualization and water atomization tests. The principal physical mechanisms leading to yield improvement are thought to be atomization plume spreading, and improved melt film formation at the nozzle tip. The film formation and stabilization effects have a basis in a flow model developed previously for symmetric geometries. The highest improvement in powder yield occurs when the nonaxisymmetric atomization plumes. Recognition of these plume characteristics provides a basis for process control and improved yields of fine powder.