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Inert refractory systems for casting of titanium alloys

Cheng, Xu (2012)
Ph.D. thesis, University of Birmingham.

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Research has been undertaken to develop new yttria slurry systems for use in mould face coats for investment casting TiAl alloy, solving the pre-gelation problems of commercial yttria slurry systems to increase slurry life. Meanwhile, the new face coats should also have excellent sintering properties, chemical inertness, surface finish and be easy to prepare.

The processes of developing the new slurry started with the filler powder investigation by adding different sintering additives into the yttria powder to achieve good sintering properties. Then the best filler powder candidates were selected to make the slurry. Finally, the new face coat slurries were used to make the shell face coat and the chemical inertness of those shells were investigated through the sessile drop and investment casting. In the research, the filler powder and face coat sintering properties were quantified through density, dilatometer testing, X-ray diffraction (XRD) and microstructural change at different testing temperatures. The interaction of different face coat systems and the metal were identified using hardness tests, sessile drop contact angle and the microstructural change at the metal/shell interface.

In this research, three water-based binder face coat systems containing YF\(_3\), Y\(_2\)O\(_3\)+0.5wt% Al\(_2\)O\(_3\)+ 0.5 wt% ZrO\(_2\) (YAZ), and B\(_2\)O\(_3\) additives were found to have similar or even better sintering properties compared to a commercial face coat. Meanwhile, they had long life.

Type of Work:Ph.D. thesis.
Supervisor(s):Green, Nick and Yuan, Chen
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Subjects:T Technology (General)
TD Environmental technology. Sanitary engineering
TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:3838
This unpublished thesis/dissertation is copyright of the author and/or third parties.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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