The computational modelling of centrifugal casting, as a process to manufacture titanium aluminide aero engine components

Humphreys, Nicholas James (2013). The computational modelling of centrifugal casting, as a process to manufacture titanium aluminide aero engine components. University of Birmingham. Ph.D.

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Abstract

Significant research has been undertaken into the use of intermetallic gamma titanium aluminide alloys (γ- TiAl). The first-rate high temperature properties of the alloys, coupled with an inherent low density, make them an attractive prospect for the aerospace and automotive industries. In this work, the utilisation of γ-TiAl as a structural material, specifically as low pressure (LP) turbine blades for aerospace engines, was considered as a replacement for conventional nickel-based superalloys.

These alloys however are difficult to work with, being highly reactive in a molten state, dictating a low superheat during processing. Centrifugal casting is therefore utilised as a production method, as under the centrifugal force, metal can fill cross sections substantially less than a millimetre. However, due to the high liquid metal velocity developed there is a high risk of turbulent flow and the trapping of any gas present within the liquid metal.

The objective is to develop a comprehensive computational model of centrifugal casting that can reliably predict the macro defects that arise from the process. This challenging application involves a combination of complex rotating geometries, significant centrifugal force, and high velocity, transient free surface flows, coupled with heat transfer and solidification. Capturing these interacting physical phenomena and associated defects is a complex modelling task.

This contribution will describe the development and enhancements required to enable conventional free surface algorithms to capture the details of the flow: by maintaining a sharp metal-gas interface and reducing numerical diffusion whilst maintaining solution stability, on what are inevitably complex three dimensional geometries.
Validation of the model has been done using a series of water experiments and castings to capture the flow dynamics.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):