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Effects of creep and oxidation interaction on high temperature crack growth behaviour of nickel based superalloys

Fisk, Joseph Charles (2013)
Ph.D. thesis, University of Birmingham.

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A complete and comprehensive understanding of dwell crack growth behaviour is required for two compressor and turbine disc alloys, Udimet 720Li and RR1000, both having a fine grain microstructure. The effect of temperature, dwell time and dwell load has been studied in air and vacuum along with detailed fractographic and microstructural analysis to understand the relevant contributions of oxidation, creep and microstructure. The study has been extended to determine the effect of an overload segment in the load waveform, the rationale being that this type of waveform better models real loading cycles on engines in service. In support with extensive modelling carried out within Rolls-Royce plc in order to understand the stress state ahead of the crack tip and its relaxation over dwell time, the effect of overload factor, test temperature and dwell time has also been examined empirically. In good agreement with the findings of others, crack growth rates according to overload cycling are shown to propagate significantly slower than crack growth rates according to (otherwise similar) dwell-only loading, or static loads; even at high temperature and in an oxidising environment. A good agreement between modelled predictions and experimental results has been achieved, indicating that the retardation of crack growth rates is mainly affected by mechanical factors.

Type of Work:Ph.D. thesis.
Supervisor(s):Bowen, Paul and Li, Hang Yue
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:Department of Metallurgy and Materials
Subjects:T Technology (General)
TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:4572
This unpublished thesis/dissertation is copyright of the author and/or third parties.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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