Abstract:Ultrafine 98W-1Ni-1Fe powder injection molding was studied. The influence of ball milling and stearic acid (SA) addition on ultrafine powder characteristics and feedstock rheological behavior was investigated systematically. Results show that ball milling and SA addition can effectively increase powder loading of feedstock. SA addition can also avoid surface interactions between powder and binder during feedstock preparation, thus shortening the mixing time. SA addition is effective in reducing feedstock viscosity, but this effect decreases with increasing temperature and becomes disadvantageous when temperature is higher than 125 °C. SA addition can also reduce the temperature required for injection molding. The feedstock of powder with SA addition gets its best shear stability and lowest viscosity at 115 °C, while the feedstock of powder without SA addition obtains its best shear stability and lowest viscosity at 135 °C. Meanwhile, the former has lower temperature sensitivity and better comprehensive rheology than the latter, so the former is more suitable for ultrafine 98W-1Ni-1Fe injection molding.

Key words: ultrafine 98W-1Ni-1Fe powder; ball milling; stearic acid addition; powder injection molding; rheological behavior