Document Type

Thesis - Open Access

Award Date

2022

Degree Name

Master of Science (MS)

Department / School

Mechanical Engineering

First Advisor

Anamika Prasad

Keywords

GRCop, Indentation, Nanomechanical, Porosity, SEM, XRD

Abstract

In an aggressive thermomechanical environment, the superior mechanical as well as thermal properties of materials play an essential role. GRCop which is a copper-based alloy developed by NASA has the potential to fulfill the requirements necessary for hightemperature applications such as the combustion chamber of liquid rocket engines. The first alloy of this family, GRCop-84 (Cu-8 wt.% Cr-4 wt.% Nb) was discovered followed with the development of GRCop-42 (Cu-4 wt.% Cr, 2 wt.% Nb). The reduction in alloying element percentage enhanced thermal conductivity with less built time while maintaining the strength of the material. The conventional fabrication is replaced with a recently developed advanced additive manufacturing (AM) process, laser powder bed fusion (L-PBF) provided effective time and cost-saving and ease to manufacture complex geometric features. However, due to several disadvantages of L-PBF includes volume constraints with high cost associated with powder inventory, the new additive method, blown powder directed energy deposition (DED) was implemented to produce GRCop parts. The mechanical and structural properties of the final part vary due to different working principle of two AM. The present study characterizes and compares the mechanical and structural properties of GRCop alloys manufactured using L-PBF and DED. The materials will be characterized using several techniques including nanoindentation technique for mechanical response whereas surface and structural performance derived using X-ray Diffraction (XRD), Laser Microscopy, Computed Tomography (CT), and Scanning Electron Microscopy (SEM) experimentation techniques. A lower indentation profile was observed for DED samples and was different from the tensile results, which was attributed to the anisotropy effect and differences in Poisson’s ratio between the two samples. Overall, both L-PBF and DED processes demonstrated the capability of producing specimen of comparable strength and surface properties, with LP-DED having the advantage of fast and high-volume reproducibility with reduced feature resolution compared to L-PBF.

Library of Congress Subject Headings

Additive manufacturing.
Copper alloys.
Manufacturing processes.
Nanotechnology.

Number of Pages

49

Publisher

South Dakota State University

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Rights Statement

In Copyright