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Electrophoretic deposition of primary coat onto investment casting wax patterns

Roach, Peter J (2013)
Ph.D. thesis, University of Birmingham.

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The objective of the work reported in this thesis was to tailor a colloidal processing technique called electrophoretic deposition (EPD) for use within the investment casting shell formation process, where the EPD coating procedure would be used to form the primary ceramic coating on the melt-out substrate. EPD takes place due to the presence of an electric field within the suspension medium, which attracts charged particles in the suspension towards an electrode of opposite charge, onto which they are deposited.

For the complex structures created using investment casting, the die cast patterns used as the substrate for the ceramic have to be easily removed, and so substrates materials that can either be melted or dissolved out the material to leave the hollow ceramic shell used. To implement EPD into the investment casting process, this substrate needed to be conducting, and so conducting particle-filled investment casting waxes were created and analysed.

Carbon black and graphite filler were incorporated into waxes, and the conductivity and rheology of the resultant composites were studied, to gauge their suitability as an investment casting pattern material.

On the basis of both cost and for environmental reasons, the use of aqueous suspension media for EPD was preferred over the more commonly used organic systems. EPD was carried out using zircon in aqueous suspension, and the low particle concentration suspensions were stabilised through pH modification and anionic dispersant addition. The effect of suspension parameters and EPD set-up parameters on the coatings formed on compressed graphite electrodes and conductive wax electrodes were studied, through yield measurements and cross sectional analysis using scanning electron microscopy.

Type of Work:Ph.D. thesis.
Supervisor(s):Ponton, Clive B and Jones, Samantha
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Keywords:Electrophoresis, Electrophoretic Deposition, Conducting Wax, Investment Casting, Colloidal suspension, Rheology
Subjects:TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:3859
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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