Particle morphology of water atomised iron‑carbon powders

Water atomisation can produce metal powders faster and at lower cost than gas atomisation, but it is well known that the powder particles are irregular and may contain a large number of pores. The current study analyses three iron‑carbon alloys with different superheats, produced as powder by water atomisation and compares the particle shapes and porosity in each. The alloy with the most carbon (4.2 wt%) showed the highest circularity (0.72) for 20–45 μm particles, but the lowest (0.59) for 180-212 μm particles. This is consistent with collisions between droplets affecting particle shape. The lowest-carbon melt (0.22 wt%) solidified fastest, so underwent fewest collisions and showed similar circularity for all particle sizes. The breakdown of water to form hydrogen and the formation of hydrogen bubbles was the most likely cause of porosity. The findings of this study may be used to inform future water atomisation process design to control particle shape and minimise porosity.