Alghamdi, Mazen
(2022)
Understanding Kinetics of Carbon Transport across Length-Scales at Diamond-Transition Metal Interfaces.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Fundamental insights into the interplay of chemical potential, microstructure, thermomechanical conditions, and composition gradients enable new approaches for controlling tool-material interactions and resulting tool-wear in machining processes. The diamond turning process, which involves material removal at micrometer length-scales will be shown to involve the formation of an inseparably connected known as built-up edge (BUE). Here, tribochemical interactions occur between single-crystal diamond and the deformed chip to first generate inter-diffusion and contact. This initiates rapid degradation of the cutting edge when the built-up edge fractures. These interactions were explored between diamond and a range of transition metals: titanium (Ti), Niobium (Nb), and zirconium (Zr). Tribochemical effects are revealed even at low deformation speeds (quasistatic; <mm/s), where thermal effects are negligible. These effects accelerate at higher deformation speeds and contribute to industrially observed rapid wear on faces of diamond cutting tools during machining of d-shell rich metals. This phenomena imposes a constraint on the accuracy of diamond turning techniques.
We present a characterization of C transport under mechanical load that occurs at contact area between the tool and chip interface during plane strain machining (PSM). The microstructural features of the BUE and structure of the diamond-transition metal interaction zone were characterized using electron microscopy. In partially detached chips built on single-crystal diamond, microstructural transformation from bulk to highly deformed chips were studied under conditions that mimic the industrially relevant diamond turning. Phase transformations that accompany such deformation, in the presence of inter-diffusion will be presented as a function of deformation load, speed, and temperature. Corresponding inter-diffusion is examined by revealing the phase evolution, element concentration profiles, and microstructure evolution. The current and ongoing research works to expand the implementations in this study such as exploring a range of mechanical stress states and its effect on enhanced diffusion at the interface and implications for the design of wear-resistant diamond tooling.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
10 June 2022 |
| Date Type: |
Publication |
| Defense Date: |
25 March 2022 |
| Approval Date: |
10 June 2022 |
| Submission Date: |
13 April 2022 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
126 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Industrial Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Keywords: Plane strain machine (PSM), Built up edge (BUE), Inter-diffusion, Niobium carbide (NbC), Electron diffraction (ED). |
| Date Deposited: |
10 Jun 2022 19:34 |
| Last Modified: |
10 Jun 2022 19:34 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/42607 |
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