Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Effect of thermal exposure on microstructure and nano-hardness of broached Inconel 718
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Siemens Industrial Turbomachinery AB, Finspång, Sweden.
Division of Production and Materials Engineering, Lund university, Sweden.
Show others and affiliations
2014 (English)In: MATEC Web of Conferences Vol. 14 (2014) EUROSUPERALLOYS 2014 – 2nd European Symposium on Superalloys and their Applications: Session 8: Recrystallization and Grain Growth / [ed] J.Y. Guédou and J. Choné, Les Ulis, France: E D P Sciences , 2014, 08002-p.1-08002-p.6 p.Conference paper, Published paper (Refereed)
Abstract [en]

Inconel 718 is a high strength, heat resistant superalloy that is used extensively for components in hot sections of gas turbine engines. This paper presents an experimental study on the thermal stability of broached Inconel 718 in terms of microstructure and nano-hardness. The broaching process used in this study is similar to that used in gas turbine industries for machining fir-tree root fixings on turbine discs. Severe plastic deformation was found under the broached surface. The plastic deformation induces a work-hardened layer in the subsurface region with a thickness of ∼50 μm. Thermal exposure was conducted at two temperatures, 550 C and 650 C respectively, for 300 h. Recrystallization occurs in the surface layer during thermal exposure at 550 C and α-Cr precipitates as a consequence of the growth of recrystallized δ phases. More recrystallized grains with a larger size form in the surface layer and the α-Cr not only precipitates in the surface layer, but also in the sub-surface region when the thermal exposure temperature goes up to 650 C. The thermal exposure leads to an increase in nano-hardness both in the work-hardened layer and in the bulk material due to the coarsening of the main strengthening phase γ′′.

Place, publisher, year, edition, pages
Les Ulis, France: E D P Sciences , 2014. 08002-p.1-08002-p.6 p.
Series
MATEC Web of Conferences, ISSN 2261-236X ; Volume 14
Keyword [en]
Structural integrity, Broaching, Inconel 718, Plastic deformation, Residual stresses, Thermal exposure, Superalloy
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:liu:diva-111058DOI: 10.1051/matecconf/20141408002ISI: 000351930400024Scopus ID: 2-s2.0-84906910411OAI: oai:DiVA.org:liu-111058DiVA: diva2:752936
Conference
2nd European Symposium on Superalloys and Their Applications, May 12-16, 2014, French Riviera, Giens, France
Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2016-09-07Bibliographically approved
In thesis
1. Surface Integrity of Broached Inconel 718 and Influence of Thermal Exposure
Open this publication in new window or tab >>Surface Integrity of Broached Inconel 718 and Influence of Thermal Exposure
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Inconel 718 is a nickel-based superalloy that is extensively used as a disc material in gas turbine engines. The service life of gas turbine discs is normally governed by the modes of material degradation and fatigue failure since they work mostly at high temperatures and are subjected to cyclic mechanical loadings. Fatigue failures often start with the initiation of cracks at the surface and the precise details of the failure process significantly depend on the surface conditions. In turbine disc production, one of the last manufacturing steps is to broach root fixings, commonly of fir-tree design, for blade mounting. It has always been a challenge when machining Inconel 718 due to its high strength retention at elevated temperatures, rapid work hardening, as well as low thermal conductivity. This usually leads to rapid tool wear, and consequently shorter tool life, and at the end to the deterioration of the surface integrity of the machined components.

The aim of this licentiate thesis is to increase our knowledge about the surface integrity, especially microstructure and residual stresses, of broached Inconel 718 and its stability under thermal exposure. This knowledge can later be used for analyzing the initiation and propagation of fatigue cracks in broached Inconel 718, particularly in the case of high temperature fatigue, thereby giving a better understanding of the failure mechanism of gas turbine discs from a fatigue point of view.

A broaching operation has been performed using similar cutting conditions as that used in turbo machinery industries for producing fir-tree root fixings. In addition, service damages were analyzed in a retired dis of Inconel 718. Surface defects, severe plastic deformation and generation of high tensile residual stresses have been found to be the main damages to the surface integrity caused by the broaching operation. The machining induced plastic deformation was found to accelerate the microstructural degradation beneath the broached surface when subjected to thermal exposure. The surface tensile residual stresses can be completely removed after short thermal exposure, the tensile layer in the sub-surface region, however, exhibited a high resistance to stress relief at high temperatures. The damage analysis on the retired disc indicated that presence of the highly deformed layer on the machined surface is negative for preventing the occurrence of fretting fatigue in turbine discs.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 44 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1676
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-111062 (URN)10.3384/lic.diva-111062 (DOI)LIU-TEK-LIC-2014:108 (Local ID)978-91-7519-249-9 (ISBN)LIU-TEK-LIC-2014:108 (Archive number)LIU-TEK-LIC-2014:108 (OAI)
Presentation
2014-10-10, ACAS, A-building, Campus Valla, Linköpings universitet, 10:15 (English)
Opponent
Supervisors
Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2014-10-06Bibliographically approved

Open Access in DiVA

fulltext(1190 kB)96 downloads
File information
File name FULLTEXT01.pdfFile size 1190 kBChecksum SHA-512
a2a46b86dc010d0932b5215bfc65b121e04b83c045b418c4b001e642f1fa45e27b919833e9add081e80b36f58f9f65334ee5689a987f387bd0986a03741e4673
Type fulltextMimetype application/pdf

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Chen, ZhePeng, RuJohansson, Sten
By organisation
Engineering MaterialsThe Institute of Technology
Materials Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 96 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 207 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf