Comparison of Flowability and Sinterability Among Different Binder Jetting Feedstock Powders: Nanopowder, Micropowder, and Granulated Powder

Abstract

Feedstock powders used in binder jetting additive manufacturing include nanopowder, micropowder, and granulated powder. Two important characteristics of the feedstock powders are flowability and sinterability. This paper aims to compare the flowability and sinterability of different feedstock powders. Three powders were compared: nanopowder (with a particle size of ~100 nm), micropowder (with a particle size of 70 µm), and granulated powder (with a granule size of ~70 µm) made from the nanopowder by spray freeze drying. Flowability metrics measured included apparent density, tap density, volumetric flow rate, mass flow rate, Hausner ratio, Carr index, and repose angle. Sinterability metrics employed included sintered bulk density, volumetric shrinkage, and densification ratio. Results show that the granulated powder has a higher flowability than the nanopowder and a higher sinterability than the micropowder. Moreover, different flowability metric values of the granulated powder are either higher or lower than those of the micropowder, indicating these two powers have a comparably high flowability. Similarly, different sinterability metric values of the granulated powder are either higher or lower than those of the nanopowder, indicating these two powders have a comparably high sinterability.