Date of Award

Winter 2018

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Metallurgical Engineering

Committee Chair

R. Bruce Madigan

First Advisor

Dan Trudnowski

Second Advisor

Denis Clark

Third Advisor

Josh Wold

Fourth Advisor

Scott Coguill

Abstract

The goal of the present research was to bridge the gap between powder-based and wire-based additive manufacturing (AM) processes using gas metal arc welding (GMAW). Powder-based AM processes typically can produce components with high geometric resolution (small features), but at low deposition rates. Wire-based AM processes typically can produce components with low geometric resolution, but at high deposition rates. AM with GMAW is a wire-based AM process in the wire arc additive manufacturing (WAAM) category of AM. To bridge the gap between powder-based and wire-based AM processes, GMAW’s deposition rate has to be reduced, allowing small features to be built.

The method proposed to build small features with GMAW was to develop a system, called GLADiS (GMAW laser assisted deposition integrated system), to perform an improved metal deposition strategy. The improved metal deposition strategy was composed of four components: single droplet deposition (SiDD), noncontact arc starting, electrode extension minimization, and laser arc stabilization. SiDD would allow single molten metal droplets to be deposited anywhere on a build plane rather than running continuous weld beads. SiDD would only be possible using an alternative, noncontact arc starting technique. Minimizing the electrode extension would allow the deposition rate to be reduced, while still maintaining sufficient current for droplet/substrate coalescence. Using a laser to stabilize the arc would ensure that individual droplets would be transferred to the correct location on the substrate.

Results showed that GLADiS was capable of building extremely thin walls using SiDD. In addition, minimizing the electrode extension was found to improve droplet/substrate coalescence. The final system used a 532nm laser to assist in arc starting and to stabilize the arc. Linear wall specimens made of steel could be produced at a 0.1lb/hr deposition rate and with a wall thickness of 0.1in or less.

Weld metal deposits produced by the SiDD process were found to have a microstructure composed of extremely small grains, indicating that it would have excellent strength and toughness. In addition, only a small number of voids were found in the deposits.

Comments

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering

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