Term of Award

Spring 2022

Degree Name

Master of Science, Mechanical Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Mechanical Engineering

Committee Chair

Bishal Silwal

Committee Member 1

Haijun Gong

Committee Member 2

JingJing Qing

Committee Member 3

Mingzhi Xu

Committee Member 3 Email

mxu@georgiasouthern.edu

Abstract

This study seeks to determine the technical feasibility of fabricating reduced activation ferritic martensitic (RAFM) steel parts, using a wire arc additive manufacturing (WAAM) process. The WAAM process, manufactures a part by depositing layers of metal onto a substrate to build a large scale near net shape part. RAFM alloy steels are next generation steels designed to resist radiation effects in the radiation intense working environments, such as nuclear reactors. To achieve this, process development and testing to design the WAAM production process with the custom RAFM filler wire was carried out. Several welding waveform modes were tested, and it was determined that Pulse waveform mode offers an acceptable weld parameter to successfully fabricate custom made RAFM metal cored wire. After successfully fabricating the first test walls hardness testing and metallography was conducted to categorize the steels microstructure by controlling the interpass temperature. The microstructure present is typical martensitic lath, and the presence of delta ferrite is inevitable. The settings were further tested with the addition of shielding gas experimentation to determine if porosity’s visible in the initial prints could be removed. The shielding gas results did aid in the porosity control, but introduced other issues arose. With a reduction in amperage input from the initial settings and the introduction of wait times to allow the equipment to cool, large scale prints were successfully fabricated. The mechanical properties of the deposited material were tested, such as impact toughness as well as macro and microhardness. These tests resulted in an average impact absorption energy of 6.25J and an average hardness across two-layer deposition interpass test samples of 423.74HV.

Research Data and Supplementary Material

No

Available for download on Saturday, April 22, 2023

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