Formulation of zircon-free slurries and the development of ceramic shell moulds for investment casting

Solanki, Riten (2018). Formulation of zircon-free slurries and the development of ceramic shell moulds for investment casting. University of Birmingham. Eng.D.

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Abstract

Ceramic slurries for investment casting with the potential to replace the use of zirconium silicate have been investigated. Alumina, aluminoslicates, mullite, zirconia-mullite and zircon refractory materials were characterised and paired with colloidal silica to evaluate their slurry properties. It was found that the particle size distribution of the filler affected the viscosity of the slurries under a shear rate of drainage. A larger proportion of fines in the filler were shown to form slurries with a longer draining time. This was found to impact the shell thermo-mechanical properties by influencing the type of siloxane network formed and the rate of sintering. A combination of synthetic fused mullite and alumina fillers with different ratios was evaluated. It was shown that the shell mechanical properties at cast temperatures could be altered by adjusting the proportion of alumina present, which influenced the extent of reaction sintering occurring. The compatibility of colloidal silica types with mullite and alumina fillers were assessed to determine the stability of slurries. An optimised slurry formulation that substitutes zirconium silicate with synthetic refractories was developed; with long slurry stability and the ability to tailor the shell strength at cast temperatures, through changing the filler ratio. Casting of turbine blades was performed with the optimised shell system and found to give satisfactory casting performance for the number of trials undertaken.

Type of Work:

Thesis (Doctorates > Eng.D.)

Award Type:

Doctorates > Eng.D.

Supervisor(s):