Date of Award

3-2022

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Ryan Kemnitz, PhD

Abstract

Additively manufactured tungsten was printed in pure nitrogen, nitrogen-2.5% hydrogen, and nitrogen-5% hydrogen atmospheres as part of a 2^3 full factorial designed experiment and subjected to room temperature and high-temperature three-point-bend testing, chemical analysis, hardness testing, and microstructural imaging techniques. The pure nitrogen specimens exhibited the highest strength and ductility at both high temperature and room temperature. Chemical analysis showed a 2-8x reduction in compositional oxygen relative to unprocessed powder. Hardness values for all samples was between 306.8 and 361.5 HV1. It is proposed that adding hydrogen into the build atmosphere reduced the available energy density for tungsten melting by introducing another competing reaction to that of nitrogen and oxygen, resulting in large cracks and pores in the material. These interruptions in the microstructure resulted in weaker, more brittle metal than that built in a pure nitrogen environment, but the results from the nitrogen environment were comparable in strength range to hot-rolled tungsten.

AFIT Designator

AFIT-ENY-MS-22-M-306

DTIC Accession Number

AD1175625

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