Suspension plasma spraying of nanostructured WC-12Co coatings |
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Authors: | J Oberste Berghaus B Marple C Moreau |
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Affiliation: | (1) Industrial Materials Institute, NRC, Boucherville, Québec, Canada |
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Abstract: | Nanostructured WC-12% Co coatings were deposited by suspension plasma spraying of submicron feedstock powders, using an internal
injection plasma torch. The liquid carrier used in this approach allows for controlled injection of much finer particles than
in conventional thermal spraying, leading to thin coatings with a fine surface finish. A polyethylene-imine (PEI) dispersant
was used to stabilize the colloidal suspension in an ethanol carrier. In-flight particle states were measured for a number
of operating conditions of varying plasma gas flow rates, feed rates, and standoff distances and were related to the resulting
microstructure, phase composition (EDS, SEM, XRD), and Vickers hardness. High in-flight particle velocities (>800 m/s) were
generated, leading to dense coatings. It was observed that the coating quality was generally compromised by the high temperature
and reactivity of the small particles. To compensate for this shortcoming, the suspension feed rate was adjusted, thereby
varying the thermal load on the plasma. Results showed that a slightly larger agglomerate size, in conjunction with low particle
jet temperatures, could somewhat limit the decomposition of WC into brittle W2C/W3C and amorphous cobalt containing binder phases.
This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, OH, 2006. |
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Keywords: | nanostructured coatings suspension plasma spraying tungsten-carbide cobalt |
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