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Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-8304-0221
Siemens Ind Turbomachinery AB, Sweden.
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2016 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 47A, no 7, 3664-3676 p.Article in journal (Refereed) PublishedText
Abstract [en]

The current study focused on the surface integrity issues associated with broaching of Inconel 718 and the structural stability of the broached specimen at high temperatures, mainly involving the microstructural changes and residual stress relaxation. The broaching operation was performed using similar cutting conditions as that used in turbo machinery industries for machining fir-tree root fixings on turbine disks. Thermal exposure was conducted at 723 K, 823 K, and 923 K (450 A degrees C, 550 A degrees C, and 650 A degrees C) for 30, 300, and 3000 hours, respectively. Surface cavities and debris dragging, sub-surface cracks, high intensity of plastic deformation, as well as the generation of tensile residual stresses were identified to be the main issues in surface integrity for the broached Inconel 718. When a subsequent heating was applied, surface recrystallization and alpha-Cr precipitation occurred beneath the broached surface depending on the applied temperature and exposure time. The plastic deformation induced by the broaching is responsible for these microstructural changes. The surface tension was completely relaxed in a short time at the temperature where surface recrystallization occurred. The tensile layer on the sub-surface, however, exhibited a much higher resistance to the stress relief annealing. Oxidation is inevitable at high temperatures. The study found that the surface recrystallization could promote the local Cr diffusion on the broached surface.

Place, publisher, year, edition, pages
SPRINGER , 2016. Vol. 47A, no 7, 3664-3676 p.
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:liu:diva-130060DOI: 10.1007/s11661-016-3515-6ISI: 000377434700041OAI: oai:DiVA.org:liu-130060DiVA: diva2:947021
Note

Funding Agencies|Linkoping University [2009-00971]

Available from: 2016-07-06 Created: 2016-07-06 Last updated: 2016-08-20

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The full text will be freely available from 2017-04-22 16:04
Available from 2017-04-22 16:04

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Chen, ZhePeng, RuMoverare, JohanJohansson, Sten
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