Shell printing is an advantageous binder jetting technique that prints only a thin shell of the intended object to enclose the loose powder in the core. In this study, powder packing in the shell and core was investigated for the first time. By examining the density and microstructure of the printed samples, powder packing was found to be different between the shell and core. In addition, the powder particle size and layer thickness were found to affect the powder packing in the shell and core differently. At a 200 µm layer thickness, for the 10 µm and 20 µm powders, the core was less dense than the shell and had a layered microstructure. At a 200 µm layer thickness, for the 70 µm powder, the core was denser and had a homogeneous microstructure. For the 20 µm powder, by reducing the layer thickness from 200 µm to 70 µm, the core became denser than the shell, and the microstructure of the core became homogeneous. The different results could be attributed to the different scenarios of particle rearrangement between the shell and core for powders of different particle sizes and at different layer thicknesses. Considering that the core was denser and more homogeneous than the shell when the proper layer thickness and powder particle size were selected, shell printing could be a promising method to tailor density and reduce anisotropy.
Influence of powder type and binder saturation on binder jet 3D–printed and sintered Inconel 625 samples
Binder jet 3D printing combined with post-deposition sintering is a non-beam additive manufacturing (AM) method for the creation of complex metallic structures. Binder saturation and particle morphology are two important factors affecting the quality of printed parts. Here, we investigated the effects of binder saturation on dimension accuracy, porosity, microstructure and microhardness of nickel-based alloy 625 samples made of differently atomized powders. Argon gas atomized (GA) and water atomized (WA) nickel-based alloy 625 powders were used to binder jet samples for a detailed comparative study. The optimal binder saturation for WA system is 60% to 70%, whereas for GA system the optimal is about 80%. Generally, GA samples achieved better overall quality than WA samples in terms of packing density, dimensional accuracy, sintered density, and microhardness. This difference is attributed mainly to the particle morphology including sphericity and roundness. The critical threshold for visible binder bleeding phenomenon in WA and GA systems is determined to be 120% and 140% binder saturation, respectively. Mechanisms for binder bleeding phenomenon at different saturation levels for WA and GA systems are discussed in detail. A pore evolution model is proposed to better understand the printing and sintering processes.
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- Award ID(s):
- 1727676
- NSF-PAR ID:
- 10291360
- Date Published:
- Journal Name:
- The International Journal of Advanced Manufacturing Technology
- ISSN:
- 0268-3768
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s00170-021-07496-3
