Experimental study of vacuum microplasma spraying
Abstract/Contents
- Abstract
- Vacuum plasma spraying (VPS) is an industrial process for depositing coatings of metal or ceramic in order to impart surface properties to an underlying part, or to build freestanding parts. High-value coatings of high melting point, oxidation-sensitive materials for applications such as aerospace components or biomedical implants are enabled by the vacuum process. Commercially available VPS systems operate at arc power levels of 40--120 kW and with deposition rates of 25¬--50 g/min. In recent years, the plasma spray community has developed interest in scaling down such systems to reduce the cost of small-scale applications and/or for novel applications enabled by lower deposition rates. The work of this dissertation is the first published account of vacuum microplasma spraying (VMPS), operating at arc power levels of 1--2 kW and deposition rates of 0.1--1 g/min. The dissertation documents the design, construction, and testing of the VMPS system, by means of decomposition into subprocesses. For subprocess 0 (powder delivery to the plasma jet), the work entailed development of a novel powder feeder. For subprocess 1 (arc discharge and nozzle flow), a supersonic plasma nozzle with internal powder injection was developed and tested. Flow, calorimetric, and pressure measurements in the nozzle are presented and incorporated into a thermodynamic model for the plasma generated by the arc discharge. For subprocess 2h (plasma--particle heat transfer), a novel "surrogate particle" heat transfer measurement was developed and used to evaluate heat transfer rates to sprayed particles. In conjunction with finite element modeling of convection and radiation to the particle, these experimental data were used to estimate required residence time for sprayed particles of various metals. For subprocess 2m (plasma--particle momentum transfer), a planar laser Mie scattering system was employed for imaging and tuning of particle trajectories, and a particle image velocimetry (PIV) system was used to determine particle velocities and residence times. Final recommendations include the use of smaller particle diameters in order to enhance melting behavior in these low-power plasma jets. The system is capable of depositing challenging, high-value metals and ceramics. With expected improvements from particle size reduction, it is prepared for advanced applications.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2012 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Crawford, William Scott |
|---|---|
| Associated with | Stanford University, Department of Mechanical Engineering |
| Primary advisor | Cappelli, Mark A. (Mark Antony) |
| Thesis advisor | Cappelli, Mark A. (Mark Antony) |
| Thesis advisor | Edwards, Christopher |
| Thesis advisor | Prinz, F. B |
| Advisor | Edwards, Christopher |
| Advisor | Prinz, F. B |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | William Scott Crawford. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2012. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2012 by William Scott Crawford
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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