Influence of Material Properties on the Spheroidisation Process in Gas Atomisation

For many contemporary powder metallurgical 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 atomisation 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.