Influence of Material Properties on Spheroidisation of Gas Atomization Process

For many contemporary powdermetallurgical applications, spherical powders are preferred. Spherical particles have a lower oxygen content, a better flowability and their behaviour is - compared to irregular particles - better predictable. The powder production process via melt atomization can be divided into the steps a. primary breakup into ligaments, b. ligament breakup and c. secondary breakup and/or spheroidisation, while simultaneously cooling and freezing take place. Apart from thermodynamic conditions during the process, melt properties such as viscosity, density, surface tension, heat capacity and thermal conductivity will influence the processes around spheroidisation. As a first step, a 4-force model (viscosity, surface tension, external dynamic and inertia forces) is applied on the melt droplet to predict the influence of the melt properties on spheroidisation separately. Secondly, the spheroidisation process is calculated for different materials such as Copper, Iron or Titanium for existing atomisation systems. Finally, suggestions are presented which may help to produce more spherical particles.