Abstract
In binder jetting (BJT) additive manufacturing (AM), jetted liquid binder binds powder particles and provides structural integrity to the printed green parts. Following printing, the binder is pyrolyzed before densification to final part. While the effects of binder saturation on the green part quality have been explored, the study of the impact of binder on part densification and subsequent part properties is limited. In this study, the impact of binder on densification is studied through a new approach of binder jetting termed as “shell printing” to vary the amount of binder content in a green part. In this approach, binder is only deposited around the part surface, which effectively traps packed powders inside the bound shell geometry. Post-process sintering consolidates both bound (printed shell) and unbound powders and densifies the part. Manipulation of the shell thickness enables exploration of the effects of binder content on process-structure-property relationships. Using pure copper as an exemplar material, and analyzing parts with varying shell thicknesses, it was found that shell printing significantly affects green part density (3.7% increase), final part density (∼5% increase), grain size (∼290% increase) and tensile strength (8.84% increase) when compared to traditional strategies of homogeneous binder placement. While the traditional binding approach improves green part strength and reduces part slumping during sintering, it also hinders densification, constrains grain growth, and induces porosity at the grain boundaries, as compared to the shell printing approach.
| Original language | English |
|---|---|
| Article number | 103377 |
| Journal | Additive Manufacturing |
| Volume | 62 |
| DOIs | |
| State | Published - Jan 25 2023 |
Funding
This material is based upon work supported by the National Science Foundation under Grant No. 1932213. The authors also acknowledge the Department of the Navy award number N00014–19-1–2736 issued by the Office of Naval Research for financial support. The United States Government has a royalty-free license throughout the world in all copyrightable material contained herein. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation or Office of Naval Research. The authors acknowledge the assistance from Dr. Jonathan Angle of the Nanoscale Characterization and Fabrication Laboratory, Institute for Critical Technology and Applied Science at Virginia Tech in performing the EDS analysis and Dr. Alan Druschitz of Virginia Tech Foundry Institute for Research and Education in performing the OES on the specimens. This material is based upon work supported by the National Science Foundation under Grant No. 1932213 . The authors also acknowledge the Department of the Navy award number N00014–19-1–2736 issued by the Office of Naval Research for financial support. The United States Government has a royalty-free license throughout the world in all copyrightable material contained herein. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation or Office of Naval Research. The authors acknowledge the assistance from Dr. Jonathan Angle of the Nanoscale Characterization and Fabrication Laboratory, Institute for Critical Technology and Applied Science at Virginia Tech in performing the EDS analysis and Dr. Alan Druschitz of Virginia Tech Foundry Institute for Research and Education in performing the OES on the specimens.
Keywords
- Additive Manufacturing
- Binder Jetting
- Binder Saturation
- Copper
- Densification
- Shell Printing