Rheological Behavior of Water-Atomized 316L Stainless Steel Powder Depending on Particle Size

In this study, we investigated the rheological behavior of three water-atomized 316L stainless steel powders mixed in a binder system based on a wax-polymer depending on powder particle size. The critical solids loadings determined via torque rheometer experiments were the same regardless of particle size. Their viscosities were analyzed using a plate-plate rheometer, and the rheological characteristics of the feedstock prepared using them were analyzed through the instability index, flow behavior index, flow activation energy, and moldability index. The smaller particle-sized powder demonstrated higher viscosity and increased instability at the same temperature, however, there was a critical temperature that affected the viscosity variation by improving the instability of feedstock. Regarding the rheological parameters (flow behavior index and flow activation energy), the power law-Arrhenius model was introduced and the results showed that a smaller particle size makes a feedstock more desirable for molding. On the other hand, the moldability index increased as the powder particle size and temperature increased, revealing that viscosity has the greatest effect on moldability. The larger the powder particle size, the greater the effect of temperature on viscosity.