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Computational simulation of thermally sprayed WC–Co powder

Computational simulation of thermally sprayed WC–Co powder
Computational simulation of thermally sprayed WC–Co powder
WC–Co cemented carbides are a class of hard composite materials of great technological importance. They are widely used as tool materials in a large variety of applications that have high demands on hardness and toughness, including mining, turning, cutting and milling. The HVOF (high velocity oxygen fuel) technology has been very successful in spraying wear resistant WC–Co coatings with higher density, superior bond strengths and less decarburization than many other thermal spray processes, attributed mainly to its high particle impact velocities and relatively low peak particle temperatures. The degree of decomposition and bond strength is directly related to relevant particle parameters such as velocity, temperature and state of melting or solidification. These are consecutively related to process parameters such as powder particle size distribution, carrier gas flow rate, and fuel type employed. To obtain detailed particle data important for thermal spraying, mathematical models are developed in the present paper to predict the particle dynamic behavior in a liquid fuelled HVOF thermal spray gun. The particle transport equations are coupled with the three-dimensional, chemically reacting, turbulent gas flow, and solved in a Lagrangian manner. The melting and solidification within the particles as a result of heat exchange with the surrounding gas flow is solved numerically. The in-flight characteristics of WC–Co particles are studied and the effects of carrier gas parameters on particle behavior are examined. The results demonstrate that WC–Co particles smaller than 5 ?m in diameter undergo melting and solidification prior to impact while most particles never reach liquid state during the HVOF thermal spraying. The flow rate of carrier gas has considerable influence on particle dynamics as well as deposition on substrate. At higher flow rate the powder particles are redirected further away from the substrate center, while smaller flow rate results in better heating, higher impact velocity and deposition closer to the substrate center.
0927-0256
1172-1182
Kamnis, S.
3ca869e0-8c18-4454-94f6-7fb4d2defa23
Gu, S.
a6f7af91-4731-46fe-ac4d-3081890ab704
Lu, T.J.
5a4bb9e5-aa83-40aa-a79e-91a1d3cd22f9
Chen, C.
ebea955a-5c35-4ccb-9431-9aafaa9fda78
Kamnis, S.
3ca869e0-8c18-4454-94f6-7fb4d2defa23
Gu, S.
a6f7af91-4731-46fe-ac4d-3081890ab704
Lu, T.J.
5a4bb9e5-aa83-40aa-a79e-91a1d3cd22f9
Chen, C.
ebea955a-5c35-4ccb-9431-9aafaa9fda78

Kamnis, S., Gu, S., Lu, T.J. and Chen, C. (2008) Computational simulation of thermally sprayed WC–Co powder. Computational Materials Science, 43 (4), 1172-1182. (doi:10.1016/j.commatsci.2008.03.015).

Record type: Article

Abstract

WC–Co cemented carbides are a class of hard composite materials of great technological importance. They are widely used as tool materials in a large variety of applications that have high demands on hardness and toughness, including mining, turning, cutting and milling. The HVOF (high velocity oxygen fuel) technology has been very successful in spraying wear resistant WC–Co coatings with higher density, superior bond strengths and less decarburization than many other thermal spray processes, attributed mainly to its high particle impact velocities and relatively low peak particle temperatures. The degree of decomposition and bond strength is directly related to relevant particle parameters such as velocity, temperature and state of melting or solidification. These are consecutively related to process parameters such as powder particle size distribution, carrier gas flow rate, and fuel type employed. To obtain detailed particle data important for thermal spraying, mathematical models are developed in the present paper to predict the particle dynamic behavior in a liquid fuelled HVOF thermal spray gun. The particle transport equations are coupled with the three-dimensional, chemically reacting, turbulent gas flow, and solved in a Lagrangian manner. The melting and solidification within the particles as a result of heat exchange with the surrounding gas flow is solved numerically. The in-flight characteristics of WC–Co particles are studied and the effects of carrier gas parameters on particle behavior are examined. The results demonstrate that WC–Co particles smaller than 5 ?m in diameter undergo melting and solidification prior to impact while most particles never reach liquid state during the HVOF thermal spraying. The flow rate of carrier gas has considerable influence on particle dynamics as well as deposition on substrate. At higher flow rate the powder particles are redirected further away from the substrate center, while smaller flow rate results in better heating, higher impact velocity and deposition closer to the substrate center.

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Published date: October 2008

Identifiers

Local EPrints ID: 64229
URI: http://eprints.soton.ac.uk/id/eprint/64229
ISSN: 0927-0256
PURE UUID: a76f36f4-1085-43fb-83cb-ce7331dae961

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Date deposited: 17 Dec 2008
Last modified: 15 Mar 2024 11:47

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Contributors

Author: S. Kamnis
Author: S. Gu
Author: T.J. Lu
Author: C. Chen

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