Electrophoretic deposition of primary coat onto investment casting wax patterns


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Roach, Peter J (2013). Electrophoretic deposition of primary coat onto investment casting wax patterns. University of Birmingham. Ph.D.

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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: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Metallurgy and Materials
Funders: Engineering and Physical Sciences Research Council, Other
Other Funders: European Investment Casters Federation
Subjects: T Technology > TN Mining engineering. Metallurgy
URI: http://etheses.bham.ac.uk/id/eprint/3859


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