Evaluation and Suppression of Porosity in Gas-atomized Powders

Recently, the demand for high-quality gas-atomized powders has increased. Some particles in gas-atomized powders contain internal pores, and the presence of these pores may result in the degradation of various properties of the final product manufactured through a specific process. However, the mechanism of the internal pore formation has not yet been elucidated. In this study, various alloy powders were prepared using the gas atomization method, and their internal pores were observed using synchrotron X-ray CT. The results showed that alloys with a wider solid–liquid coexistence temperature range exhibited a higher porosity–volume ratio. This suggests that gas bubbles are more likely to be entrained during secondary droplet breakup. It was also found that introducing a small amount of hydrogen as a reducing agent into the spray gas reduced these quantities.