Research Summaries

Back Development Of Nanoparticle Formulations For Alternative Metal Additive Manufacturing Routes

Fiscal Year 2018
Division Research & Sponsored Programs
Department Naval Research Program
Investigator(s) Luhrs, Claudia C.
Sponsor NPS Naval Research Program (Navy)
Summary Additive Manufacturing (AM) techniques to fabricate metal parts require lasers or electron beams to produce localized melt or sintering of the raw powder, allowing the layer by layer fabrication of complex components. The resulting build is usually heat treated after to imprint the final microstructural features. Powder metallurgy (PM) in the other hand refers to techniques that allow the fabrication of consolidated parts from metal powders. During PM the raw powders are compressed into the desired shape and sintered. The result is a ‘green’ specimen that requires annealing in controlled atmospheres. AM and PM techniques share some characteristics: a) micron size particles, produced by atomization techniques, are employed as the raw material, b) since no tooling or material removal is required, costs can be drastically reduced and c) builds generated require post-processing (annealing or hot isostatic pressing) to achieve the desired microstructure, reduce porosity and gain the targeted mechanical properties. The proposed work attempts to generate metal parts using, instead of expensive direct sintering equipment (metal 3D printer), a conventional 3D printer (like the ones used for polymeric filaments) equipped with a syringe pump to extrude a paste composed of metal nanoparticles. That is, we will employ the layer by layer approach of AM to form a green body that will resemble the ones generated by PM. There will be no compression/sintering steps during the printing stage. The key for success will be the development of nanoparticle paste formulations, which, due to their higher surface areas/surface energy will tend to sinter at lower temperatures in a post-processing annealing step. Apart of nanoparticles, the paste will contain additives to impart the right viscosity to the mixture, so it could flow through the nozzle but also stay together during the printing operation to form a mechanically robust object that can endure the degassing of volatiles and annealing.
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