Particle size distribution of tin powder produced by centrifugal atomisation using rotating cups

- The particle sizes of centrifugally atomised powders follow lognormal distribution.
- The median particle size correlated with the melt film thickness before disintegration.
- The cup atomiser with an optimum wall angle produced the finest powders.
- The geometric standard deviations of the particle size distributions fall in 1.6-2.5.

Centrifugal atomisation is a low-cost technology for producing metal powders, but its wide applications are hampered by its limited capability of producing fine powders and there is insufficient research on the particle size distributions of centrifugally produced powders. This paper studies the effects of the atomiser geometry and the key process parameters on the particle size distribution of tin powders produced by centrifugal atomisation. The results showed that the particle sizes of the as-produced powders follow lognormal distribution. The median particle size for all atomisers decreases with increasing atomiser rotation speed and with decreasing melt flow rate, due to reduced film thickness of the melt before disintegration. The cup atomiser with a wall angle of 67.5° produced the finest powders, because of a significant improvement of dynamic wetting between the melt and the atomiser. The particle size distributions of all the powder samples have a similar lognormal bell shape with the geometric standard deviations between 1.6 and 2.5. Narrow particle size distributions can be achieved by reducing the variability of any of the processing parameters affecting the particle size.

54