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Investigations on Binder Jetting Additive Manufacturing: Process Physics and Innovative Approaches
Abstract
This study investigated several aspects of binder jetting additive manufacturing,
including the effects of particle size, printing orientation, powder bed compaction, and
texturing on the density, microstructure, and mechanical behavior of the fabricated parts.
The effects of particle size on flowability and sinterability of the feedstock powder
and resultant properties of fabricated parts were studied. The results showed that
flowability increased, but sinterability decreased as particle size increased. The highest
density was achieved by the medium powder due to the balance between flowability and
sinterability. The results demonstrated that the compressive strength was dominated by
sinterability, as the highest strength was achieved by the fine powder. Additionally, the
effect of printing orientation on the flexural strength of the parts from binder jetting was
investigated. Despite no noticeable difference in density among various printing
orientations, significant change in flexural strength was observed. Analysis of the
microstructure revealed that printing orientation played a crucial role in determining the
defect distributions, which was attributed to the difference observed in the flexural
strength.
In addition, a novel approach of combining powder bed compaction and
nanopowders was introduced to improve the density of parts fabricated through binder
jetting. The study revealed that at the same layer thickness, higher compaction thickness
resulted in higher powder bed density, higher sintered density, and smaller number and
size of pores in sintered samples. Finally, this work demonstrated, for the first time, the successful fabrication of textured ceramics using binder jetting. This was achieved using
two different binder jetting machines: a lab-designed press-compaction-assisted binder
jetting machine, and a commercially available roller-compaction-assisted binder jetting
machine. A mixture of alumina nanoplatelets and nanoparticles was used as the feedstock
powder (the nanoplatelets served as templates for epitaxial grain growth during sintering,
while the nanoparticles were consumed by the grain growth). Varying the nanoplatelet
fraction in the feedstock powder revealed that the sintered density decreased as the
nanoplatelet fraction increased, while the degree of texture increased. Texture evaluation
indicated that the development of texture mostly occurred during sintering. Interestingly,
the flexural strength of the sintered samples with nanoplatelets was higher than those
without nanoplatelets, suggesting the increased degree of texture has a stronger effect on the flexural strength than the reduced sintered density under these conditions.
Citation
Moghadasi, Mohammadamin (2023). Investigations on Binder Jetting Additive Manufacturing: Process Physics and Innovative Approaches. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /199886.