Doctoral Dissertations

Keywords and Phrases

Carbides; Fibrous monolith; Friction stir welding; High entropy carbides; Thermal conductivity; Vickers hardness

Abstract

"This research focuses on the development of hard materials and fibrous monolith composites for the purpose of adding to current friction stir welding tool technology. Well studied hard material systems, such as WC-Co, were incorporated and evaluated as cell materials for fibrous monolith composites with ductile cell boundaries of Co, W, and Mo. The indentation behavior of the WC-Co and WC-Co-cBN composites indicated possible crack deflection at the cell/cell boundary interface. Cylindrical pin friction stir welding tools were developed for each of the three fibrous monolith material systems. Welding was achieved on AA1100 aluminum, 260 brass, and AISI 1018 steel with WC-Co/Co fibrous monolith tools. It was determined that further refinement of process control and tool geometries could enable further success in welding higher hardness materials.

The development of hard material systems was then focused on the synthesis and property measurement of novel high entropy carbide (HEC) ceramics. Five high purity and density HEC ceramics consisting of group 4-6 transition metals were synthesized and the hardness, thermal, and electrical properties were measured. The maximum Vickers hardness of the HECs was 43.5 ± 0.4 GPa for (Hf0.2,Mo0.2,Ti0.2,W0.2,Zr0.2)C at a load of 0.05 kgf. The room temperature thermal conductivity ranged from 5.1 W/mK for (Hf0.2Mo0.2Ti0.2W0.2Zr0.2 )C to 9.0 W/mK for (Cr0.2Hf0.2Ta0.2Ti0.2Zr0.2)C. The electron contribution to thermal conductivity calculated from measured electrical resistivity varied from 41% to 52% of the total thermal conductivity" -- Abstract, p. iv

Advisor(s)

Watts, Jeremy Lee, 1980-

Committee Member(s)

Hilmas, Greg
Fahrenholtz, William
O'Malley, Ronald J.
Liou, Frank W.

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Ceramic Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2024

Pagination

xiv, 150 pages

Note about bibliography

Includes_bibliographical_references_(pages 54, 71, 96, 124 & 135-148)

Rights

©2024 Paul Michael Brune , All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12374

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