Rheological properties of gas and water atomized 17-4PH stainless steel MIM feedstocks: Effect of powder shape and size

Abstract

Influence of powder shape resulting from the fabrication route (gas or water atomization) together with the effect of mean particle size and solid loading on rheological properties of highly filled metal powder feedstocks was investigated as a key to processing of Metal Injection Molding (MIM) parts without voids and cracks. Eight 17-4PH gas or water atomized powders varying in the mean particle diameters from 3 to 20 μm were admixed into paraffin wax/high density polyethylene (50/50) binder at powder loadings up to 70 vol.%. The relative viscosity data obtained from capillary rheometer was fitted with rheological models to evaluate maximum loading along with the determination of the same parameter using time dependent torque measurement. It was found out that for coarse particles the processability in terms of rheological behavior is better in case of gas atomized powders in accordance with previous findings, but in case of fine powders, water atomized powders showed higher performance.