Tungsten carbide-cobalt by Three Dimensional Printing

Three Dimensional Printing is an additive manufacturing process for rapid prototyping ceramic and metallic parts [Sachs, et al, 1990]. Green (not sintered) tungsten carbide-cobalt parts must have a density greater than 50% of the theoretical density, 14.9 g/cc, for proper sintering and post-processing. Two approaches were assessed for feasibility and robustness: printing slurry into tungsten carbide-cobalt spray dried powder and printing a solvent in spray dried tungsten carbide powder that readily dissolves. For slurry administered to a powder bed of solid, spherical particles, it has been found that the resulting packing primitive packing fraction increases almost linearly with the volume loading of the slurry over a range of powder size. The increase in density is approximately half what would be calculated by assuming that the slurry fills all the porosity in the powder bed. The maximum green density achieved by printing slurry into a spray dried tungsten carbide-cobalt bed was 41%, midway between the lower bound calculated by assuming the vehicle in the slurry infiltrates only the large pores between the spray dried power and the upper bound calculated by assuming that the vehicle of the slurry also infiltrates the find pores within a spray dried granule. A re-dispersible spray dried powder (38-53 micron size range) was fabricated using only the Duramax 3007 dispersant as the binder. This powder redisperses in water. Administering a drop of water to this powder resulted in primitives with 47% packing density, but which had significant quantities of 80 micron voids.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

1998

Author dc:creator

• Kelley, Andrew, III

Advisor dc:contributor.advisor

• Emanuel M. Sachs.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/32316

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/32316