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Time-dependent crack growth in a coarse-grained Ni-based superalloy RR1000

Sun, Jifeng (2013)
Ph.D. thesis, University of Birmingham.

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Abstract

The dwell fatigue crack growth behaviour of coarse grained RR1000 has been studied using advanced mechanical testing and characterization techniques. Crack growth under sustained loading has also been considered.
Environmentally enhanced crack growth at high temperatures in air follows a stress assisted grain boundary oxidation (SAGBO) mechanism, with a 100-300 nm long Al2O3 intrusion ahead of the crack tip. When its thickness of reaches a critical value, this intrusion fails and crack advance ensues. The crack growth process is discontinuous and highly uneven. The dwell fatigue/sustained loading crack growth rates are affected by the stress relaxation ability of the materials, which is related to the size and distribution of tertiary γ' precipitates, testing temperature and stress state.
Oxidation damage is deduced to be a dominant factor affecting crack growth over a range of temperature from 600 to 700 °C. At 700 °C oxidation damage begins to have an effect on fatigue crack growth at a dwell time of 30 s. Creep damage is suggested to make the dominant contribution to crack growth at 750 and 775 °C both in air and in vacuum.

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:School of Metallurgy and Materials
Subjects:TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:4082
This unpublished thesis/dissertation is copyright of the author and/or third parties.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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