Elevated temperature crack growth in inertially welded nickel-based superalloys and gamma based titanium aluminides

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2030-07-01 accepted http://eprints.org/relation/hasVolatileVersion http://etheses.bham.ac.uk/id/document/43569 http://eprints.org/relation/hasVersion http://etheses.bham.ac.uk/id/document/43569 http://eprints.org/relation/hassmallThumbnailVersion http://etheses.bham.ac.uk/id/document/43569 http://eprints.org/relation/hasVolatileVersion http://etheses.bham.ac.uk/id/document/43570 http://eprints.org/relation/hasVersion http://etheses.bham.ac.uk/id/document/43570 http://eprints.org/relation/haspreviewThumbnailVersion http://etheses.bham.ac.uk/id/document/43570 http://eprints.org/relation/hasVolatileVersion http://etheses.bham.ac.uk/id/document/43571 http://eprints.org/relation/hasVersion http://etheses.bham.ac.uk/id/document/43571 http://eprints.org/relation/hasIndexCodesVersion http://etheses.bham.ac.uk/id/document/43571 43569 2 105108 document 43569 small.png image/png 73d8be44ff500039a524b35039a0ab3d MD5 4468 2015-08-06 16:13:12 http://etheses.bham.ac.uk//id/eprint/1432/2/small.png 1432 2 2 image/png thumbnail_small Thumbnail Documents conversion from application/pdf to thumbnail_small en staffonly

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http://eprints.org/relation/isVersionOf http://etheses.bham.ac.uk/id/document/43511 http://eprints.org/relation/isVolatileVersionOf http://etheses.bham.ac.uk/id/document/43511 http://eprints.org/relation/isIndexCodesVersionOf http://etheses.bham.ac.uk/id/document/43511 archive 4031 disk0/00/00/14/32 2015-09-01 16:23:14 2019-01-23 09:54:10 2015-09-01 16:23:14 thesis show 0 Po-Sri Chatuporn Bowen Paul Li Hang Yue University of Birmingham Elevated temperature crack growth in inertially welded nickel-based superalloys and gamma based titanium aluminides unpub TN 10col_ephy Was embargoed until July 2015. Author did not respond to enquiry about access to e-version so standard Rolls-Royce restriction of 15 further years of option C was applied. Full abstract An evaluation of inertia friction welds in RR1000 has been conducted through microtensile and sustained load crack growth tests on pre-cracked testpieces. As-welded and two post weld heat treatment conditions have been considered. The fatigue crack growth behaviour of γ TiAl has also been considered, with a focus on establishing fatigue crack growth thresholds. Tensile tests on thin film testpieces were used to deliver tensile properties of parent material and the weld line in the as-welded condition only. Comparing tensile properties of micro thin-film samples to standard specimens revealed that micro tensile samples in parent material give comparable tensile properties at room temperature whilst those at 600 and 650oC revealed slightly lower fracture stress and percentage elongation to failure. The reduction in fracture stress and percentage elongation was deduced to be due to the increased susceptibility of grain boundaries to oxidation in weld material. Two types of sustained load tests were performed. In one case the load (initial stress intensity factor, K) was held constant and the test temperature is increased. This method was used for the as-welded condition only. For the second method, the test temperature (600, 650 and 700oC) was kept constant and the load was periodically increased. This was used for the as welded and both post weld heat treatment (PWHT) conditions. Under a constant heating rate of 10oC/min a slightly higher temperature was needed for a sample under a lower initial stress intensity factor (K) to activate crack growth under the constant load testing. Whereas under the constant temperature testing, a strong dependence of Kth and crack growth rate on test temperature was observed. Intergranular crack paths were observed in every case. Any influence of PWHT on Kth can be observed only at a temperature of 600oC. The effects of specimen geometry (single edge bend and corner crack tension) and morphology of pre-crack on Kth were also studied at 650oC. Kth was shown to be up to 5 MPa.m1/2 lower in corner crack specimens. For a given testpiece geometry, an intergranular pre-crack front was observed to reduce Kth by approximately 2 MPa.m1/2 compared to a transgranular pre-crack front (produced at room temperature). At 650oC the crack was unable to grow along the weld under a pure mode II stress intensity factor conditions. Instead, the crack deviated out of the weld from the precrack tip, growing at an angle to the direction of maximum mode II loading and where a significant proportion of mode I opening is imposed. Fatigue threshold (ΔKth) and fatigue crack growth resistance curves in near fully lamellar γ TiAl at R ratios of 0.1 and 0.5 were studied at room temperature, 400 and 650oC. An increasing ΔK procedure was selected to determine ΔKth, because it was found to give a lower ΔKth value compared to a conventional load shedding procedure. ΔKth values were also not significantly affected by the nature of the initial defect (notch and fatigue pre-crack). The effects of test temperature and R ratio on ΔKth were observed to be small. However an increase in fatigue crack growth rates were observed in general at 400 and 650oC compared with those observed at room temperature. This was mainly attributed to an increase in plasticity at 400 and 650oC. Notably, fatigue crack growth resistance curves indicate that Kmax is the dominant factor which controls fatigue crack growth at room temperature, whereas crack growth at 400 and 650oC appear to be controlled primarily by the stress intensity factor range, ΔK. An evaluation of inertia friction welds in RR1000 has been conducted through microtensile and sustained load crack growth tests on pre-cracked testpieces. As-welded and two post weld heat treatment conditions have been considered. The fatigue crack growth behaviour of γ TiAl has also been considered, with a focus on establishing fatigue crack growth thresholds. 2011-07 2011-03 graduation eng author unchecked 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. Rolls-Royce restricted 285 University of Birmingham School of Metallurgy and Materials d_ph na 2011-07 graduation