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Evaluation of laser shock peen additive manufacture inconel 718 for high temperature applications
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Yong, Ching Kiat (2022) Evaluation of laser shock peen additive manufacture inconel 718 for high temperature applications. EngD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3896058
Abstract
Nickel superalloys find several applications in the aerospace and automotive industry, notably as safety-critical components such as turbine blades and turbine discs. A new kind of manufacturing technique termed Additive Manufacturing (AM) has gained significant interest due to its capabilities of fabricating components that could minimise material wastage and/or components that possess complex geometries, possibly unmanufacturable using conventional technologies. Among the various AM processes for metallic components, powder bed fusion (PBF) has shown great potential for manufacturing Inconel 718 (IN718) components. The future of PBF is undoubtedly promising but there are still some gaps to fill before AM components materials are ready for widespread industrial application.
Laser shock peening (LSP) is an effective surface enhancement process that is used in an aeroengine manufacturing line to strengthen components resistance to surface-related failures. Pioneering work in the late 1990s employed synchrotron radiation for residual stress assessment to enable the adoption of LSP in aeroengine components. The technology is now used in engines worth tens of billions of pounds. Back to the present time, there is a push to adopt AM technology as a step-change in production and integrating LSP into AM IN718 seems to be an obvious way forward.
The work presented in this thesis aims to better understand the effects that LSP has brought to AM IN718, which have not been systematically investigated. Microstructures of AM IN718 have been characterised with scanning electron microscopy (SEM) using the electron backscattered diffraction (EBSD) technique and transmission electron microscopy (TEM) to correlate microstructural changes with the process conditions. Mechanical properties (e.g. microhardness and tensile properties) have also been measured and rationalised with regards to the LSP treatments. Specimens were put under various thermal and mechanical loading to simulate the aeroengine setting. Synchrotron X-ray diffraction (SXRD) was utilised to assess the residual stress relaxation of these specimens and the phases present in AM IN718. Full width half maximum (FWHM) data from the SXRD experiment were used to characterise the cold work present in the specimens that were LSP-ed. Three point flexure test was selected as the appropriate test scenario to evaluate the mechanical performance of the LSP AM IN718 at a structural level.
Comparison of the observed mechanical performance indicates that there is potential for LSP to be integrated with the AM process of IN718. Within a 550°C environment, the LSP-ed specimens hold up to 50% of its initial residual stress after going through about a million flexural cycles. Surface roughness and cold work were found to be key factors controlling the fatigue performance. Microstructure analysis suggests that LSP bring minimal cold work to AM IN718 which is the contributing factor to it’s excellent containment of residual stress. Results from this licentiate thesis provide the basis for the further industrial research on the cyclic mechanical properties of AM IN718.
Item Type: | Thesis (EngD) | ||||
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Subjects: | T Technology > TA Engineering (General). Civil engineering (General) T Technology > TN Mining engineering. Metallurgy T Technology > TS Manufactures |
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Library of Congress Subject Headings (LCSH): | Heat resistant alloys, Heat resistant alloys -- Microstructure, Heat resistant alloys -- Thermal properties, Laser peening, Additive manufacturing | ||||
Official Date: | January 2022 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Engineering | ||||
Thesis Type: | EngD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Gibbons, Gregory John, 1970- ; West, Geoff, 1977- ; Wong, Chow Cher | ||||
Sponsors: | Singapore. Agency for Science, Technology and Research | ||||
Format of File: | |||||
Extent: | multiple pagings : illustrations, charts | ||||
Language: | eng |
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