Date of Award
2024-08-01
Degree Name
Doctor of Philosophy
Department
Mechanical Engineering
Advisor(s)
Francisco Medina
Abstract
The maturation and adoption of Additive Manufacturing (AM) has enabled increasingly complex designs to be successfully manufactured. Coupled with developments in materials for high temperature applications, AM has reduced lead times and increased performance of aerospace propulsion components such as propellant tanks, injectors, combustion chambers, and nozzles. While many designs have leveraged the use of Laser Powder Bed Fusion (L – PBF), a variety of these components are simply too large for existing L – PBF platforms. Laser Powder Directed Energy Deposition (LP – DED) can overcome the size constraint, with commercial platforms offering build volumes from 0.6 m x 0.6 m x 0.6 m up to custom platforms of 7 m x 7 m x 36 m. Most material development for LP – DED has focused on steel, aluminum, copper, titanium, and nickel based super alloys to name a few. While each of these have their unique set of advantages, many propulsion applications operate at temperatures in which these materials exhibit a significant drop in strength. Refractory metal alloys offer attractive properties to address the problem of elevated temperature operations due to their ability to retain strength at elevated temperatures and have relatively high melting temperatures (> 2000°C). Niobium based alloy C103 is one of the early refractory metals used in the aerospace community, implemented in the nozzle extension of the Apollo Lunar Module. The high costs, buy-to-fly ratios and machining difficulty led to a decline in its use. Interest in this alloy has been renewed with the popularization of AM. The work in this dissertation addresses a gap in the literature pertaining to the parameter development and in-depth characterization of LP - DED C103. Relative densities above 99% and mechanical properties superior to wrought and other powder bed fusion (PBF) results indicate that LP - DED of C103 is both viable and scalable. A statistical approach is used for the development of optimal parameters. We show that the use of relative density as the only metric of performance is insufficient. The use of geometrical accuracy of the printed component as a metric of performance is proven to result in optimal process parameters. Unique microstructural features are identified in AM C103 for the first time, such as the spatial variation of grain size and the segregation of Hf into cellular structures. A detailed comparison of the effects of commercially available powder manufacturing methods is presented. The results reveal that changes in powder size distribution (PSD), morphology, and chemistry lead to changes in the microstructure that affect fatigue life performance. Finally, we explore the interplay between interlayer dwell time and thermo-physical properties of the build plate on residual stress induced distortion and burn-out failures. Attempts to model the failure mechanism highlight the need for the development of advanced computational models to capture the intricate heat transfer mechanisms during the print process.
Language
en
Provenance
Received from ProQuest
Copyright Date
2024-08-01
File Size
368 p.
File Format
application/pdf
Rights Holder
Brandon Colon
Recommended Citation
Colon, Brandon, "Development & Characterization Of Additively Manufactured Laser Powder - Directed Energy Deposition C103 For Propulsion Applications" (2024). Open Access Theses & Dissertations. 4172.
https://scholarworks.utep.edu/open_etd/4172