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Objective of this study is to prepare the binder jetting feedstock powder by spray freeze drying and study the effects of its parameters on the powder properties. Binder jetting additive manufacturing is a promising technology for fabricating ceramic parts with complex or customized geometries. However, this process is limited by the relatively low density of the fabricated parts even after sintering. The main cause comes from the contradicting requirements of the particle size of the feedstock powder: a large particle size (>5 μm) is required for a high flowability while a small particle size (<1 μm) for a high sinterability. For the first time, a novel technology for the feedstock material preparation, called spray freeze drying, is investigated to address this contradiction. Using raw alumina nanopowder (100 nm), a full factorial design at two levels for two factors (spraying pressure and slurry feed rate) was formed to study their effects on the properties (i.e., granule size, flowability, and sinterability) of the obtained granulated powder. Results show that high pressure and small feed rate lead to small granule size. Compared with the raw powder, the flowability of the granulated powders was significantly increased, and the high sinterability was also maintained. This study proves that spray freeze granulation is a promising technology for the feedstock powder preparation of binder jetting additive manufacturing.
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This content will become publicly available on October 30, 2027
Powder Engineering via Ultrasonic Atomization of 17-4 PH Stainless Steel: Process-Structure Relationships for Cold Spray Feedstock Design
Cold spray additive manufacturing (CSAM) is a solid-state deposition process that largely preserves feedstock microstructural features in the bulk deposit, making tuning of powder properties a direct lever for engineering deposit performance. This characteristic is particularly attractive for the fabrication of components subjected to extreme, directionally biased thermomechanical environments, such as the walls of rotating detonation engines (RDEs), where GRCop-42 (Cu-4Cr-2Nb at.%) is a leading candidate material. Realizing feedstock-driven microstructural design in CSAM requires upstream control of the powder itself. Ultrasonic atomization (UA) offers systematic control over droplet solidification conditions, and therefore over powder microstructure, prior to deposition. In this work, 17-4 precipitation-hardening (PH) stainless steel is used as a model system to establish process-structure linkages across the UA parameter space. A two-factor full-factorial study varied torch current and gas recirculation rate, and the resulting powders were characterized by particle size distribution (PSD) analysis, scanning electron microscopy (SEM), backscattered-electron imaging, inert gas fusion, and instrumented microhardness. A single-particle micropillar compression test within a SEM was also performed. The results demonstrate that UA processing parameters systematically influence powder impurities concentration and internal porosity, with dissolved oxygen and nitrogen content tracking together in a manner consistent with a cavitation-driven gas-entrainment mechanism. Single-particle testing further revealed ductile deformation without fracture, indicating feedstock deformability relevant to cold spray consolidation. Together, these findings lay the groundwork for feedstock-informed materials design in CSAM.
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- Award ID(s):
- 2522673
- PAR ID:
- 10703311
- Publisher / Repository:
- World Powder Metallurgy Congress & Exhibition
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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