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dc.contributor.supervisor Richards, Norman(Mechanical and Manufacturing Engineering) en_US
dc.contributor.author Abrokwah, Emmanuel
dc.date.accessioned 2012-03-16T19:45:20Z
dc.date.available 2012-03-16T19:45:20Z
dc.date.issued 2012-03-16
dc.identifier.uri http://hdl.handle.net/1993/5195
dc.description.abstract Directionally solidified Rene 80 (DS R80) and polycrystalline Inconel 738(IN 738) Superalloys were tested in thermo-mechanical fatigue (TMF) over the temperature range of 500-900°C and plastic strain range from 0.1 to 0.8% using a DSI Gleeble thermal simulator. Thermo-mechanical testing was carried out on the parent material (baseline) in the conventional solution treated and aged condition (STA), as well as gas tungsten arc welded (GTAW) with an IN-738 filler, followed by solution treatment and ageing. Comparison of the baseline alloy microstructure with that of the welded and heat treated alloy showed that varying crack initiation mechanisms, notably oxidation by stress assisted grain boundary oxidation, grain boundary MC carbides fatigue crack initiation, fatigue crack initiation from sample surfaces, crack initiation from weld defects and creep deformation were operating, leading to different “weakest link” and failure initiation points. The observations from this study show that the repaired samples had extra crack initiation sites not present in the baseline, which accounted for their occasional poor fatigue life. These defects include lack of fusion between the weld and the base metal, fusion zone cracking, and heat affected zone microfissures. en_US
dc.rights info:eu-repo/semantics/openAccess
dc.subject Ni base superalloys en_US
dc.subject Weld repair en_US
dc.subject Thermo-mechanical fatigue en_US
dc.subject Failure analysis en_US
dc.subject Gleeble simulation en_US
dc.title Microstructural studies on failure mechanisms in thermo-mechanical fatigue of repaired DS R80 and IN738 Superalloys en_US
dc.type info:eu-repo/semantics/masterThesis
dc.degree.discipline Mechanical and Manufacturing Engineering en_US
dc.contributor.examiningcommittee Ojo, Olanrewaju (Mechanical and Manufacturing Engineering) Filizadeh, Shaahin (Electrical and Computer Engineering) en_US
dc.degree.level Master of Science (M.Sc.) en_US
dc.description.note May 2012 en_US


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