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
On Thermomechanical Fatigue of Single-Crystal Superalloys
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Thanks to their excellent mechanical and chemical properties at temperatures up to 1000 °C, nickel-based superalloys are used in critical components in high-temperature applications such as gas turbines and aero engines. One of the most critical components in a gas turbine is the turbine blade, and to improve the creep and fatigue properties of this component, it is sometimes cast in single-crystal form rather than in the more conventional poly-crystalline form. Gas turbines are most commonly used for power generation and the turbine efficiency is highly dependent on the performance of the superalloys.

Today, many gas turbines are used as a complement for renewable energy sources, for example when the wind is not blowing or when the sun is not shining. This means that the turbine runs differently compared to earlier, when it ran for longer time periods with a lower number of start-ups and shut-downs. This new way of running the turbine, with an increased number of start-ups and shut-downs, results in new conditions for critical components, and one way to simulate these conditions is to perform thermomechanical fatigue (TMF) testing in the laboratory. During TMF, both mechanical strain and temperature are cycled at the same time, and one fatigue cycle corresponds to the conditions experienced by the turbine blade during one start-up and shutdown of the turbine engine.

In the work leading to this PhD thesis, TMF testing of single-crystal superalloys was first performed in the laboratory and this was then followed microstructure investigations to study the occurring deformation and damage mechanisms. Specimens with different crystallographic directions have been tested in order to investigate the anisotropic behaviour shown by these materials. Results show a significant orientation dependence during TMF, in which specimens with a low elastic stiffness perform better. However, it is also shown that specimens with a higher number of active slip planes perform better during TMF compared to specimens with less active slip systems. This is because a higher number of active slip systems results in a more widespread deformation and seems to be beneficial for the TMF life. Further, microscopy shows that the deformation during TMF is localised to several deformation bands and that different deformation and damage mechanisms prevail according to in which crystal orientation the material is loaded. Deformation twinning is shown to be a major deformation mechanism during TMF, and the interception of twins seems to trigger recrystallization. This work also studies the effects of alloying a single-crystal superalloy with Si or Re, and results show a significant Si-effect where the TMF life increases by a factor of 2 when Si is added to the alloy.

Finally, this research results in an increased knowledge of the mechanical response as well as a deeper understanding of the deformation and damage mechanisms that occur in single-crystal superalloys during TMF. It is believed that in the long-term, this can contribute to a more efficient and reliable power generation by gas turbines.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. , 83 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1626
National Category
Materials Engineering Materials Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-111643DOI: 10.3384/diss.diva-111643ISBN: 978-91-7519-211-6 (print)OAI: oai:DiVA.org:liu-111643DiVA: diva2:758516
Public defence
2014-11-28, ACAS, Hus A, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2014-10-27 Created: 2014-10-27 Last updated: 2014-10-27Bibliographically approved
List of papers
1. Crystallographic Orientation Influence on the Serrated Yielding Behavior of a Single-Crystal Superalloy
Open this publication in new window or tab >>Crystallographic Orientation Influence on the Serrated Yielding Behavior of a Single-Crystal Superalloy
2013 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 6, no 2, 437-444 p.Article in journal (Refereed) Published
Abstract [en]

Since Ni-based single-crystal superalloys are anisotropic materials, their behavior in different crystal orientations is of great interest. In this study, the yielding behavior in both tension and compression for 〈001〉, 〈011〉 and 〈111〉 oriented materials at 500 °C has been investigated. The 〈011〉 direction showed a serrated yielding behavior, a great tension/compression asymmetry in yield strength and visible deformation bands. However, the 〈001〉 and 〈111〉 directions showed a more homogeneous yielding, less tension/compression asymmetry in yield strength and no deformation bands. Microstructure investigations showed that the serrated yielding behavior of the 〈011〉 direction can be attributed to the appearance of dynamic strain aging (DSA) and that only one slip system is active in this direction during plastic deformation.

Place, publisher, year, edition, pages
Basel: MDPI AG, 2013
Keyword
single.crystals; superalloy; yield phenomena; tension/compression asymmetry; dynamic strain aging
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-88406 (URN)10.3390/ma6020437 (DOI)000315398600004 ()
Available from: 2013-03-26 Created: 2013-02-05 Last updated: 2017-12-06Bibliographically approved
2. Low-Cycle Fatigue Behaviour of a Ni-Based Single-Crystal Superalloy
Open this publication in new window or tab >>Low-Cycle Fatigue Behaviour of a Ni-Based Single-Crystal Superalloy
2014 (English)In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 891-892, 416-421 p.Article in journal (Refereed) Published
Abstract [en]

In this study, low-cycle fatigue (LCF) tests at 500 degrees C in the < 001 >, < 011 > and < 111 > directions have been performed for the Ni-based single-crystal superalloy MD2. All tests were carried out in strain control with R-is an element of = -1. The < 001 > direction has the lowest stiffness of the three directions and also shows the best fatigue properties in this study followed by the < 011 > and < 111 > directions, respectively. It is well recognised that Ni-based single-crystal superalloys show a tension/compression asymmetry in yield strength and this study shows that a tension/compression asymmetry is also present during LCF conditions. At mid-life, the < 001 > direction generally has a higher stress in tension than in compression, while the opposite is true for the < 011 > direction. For the < 111 > direction the asymmetry is found to be strain range dependent. The < 011 > and < 111 > directions show a cyclic hardening behaviour when comparing cyclic stress-strain curves with monotonic stress-strain curves. In addition, the < 011 > and < 111 > directions show a serrated yielding behaviour for a number of cycles while the yielding of the < 001 > direction is more stable.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2014
Keyword
Ni-based single-crystal superalloy, LCF, tension/compression asymmetry, serrated yielding
National Category
Engineering and Technology Materials Engineering
Identifiers
urn:nbn:se:liu:diva-104750 (URN)10.4028/www.scientific.net/AMR.891-892.416 (DOI)000337767700064 ()
Conference
Fatigue 2014, 11th International Fatigue Congress, Melbourne Cricket Ground, Melbourne, Australia, 2-7 March 2014.
Available from: 2014-02-25 Created: 2014-02-25 Last updated: 2017-12-05
3. In- and Out-of Phase Thermomechanical Fatigue of a Ni-Based Single-Crystal Superalloy
Open this publication in new window or tab >>In- and Out-of Phase Thermomechanical Fatigue of a Ni-Based Single-Crystal Superalloy
2014 (English)In: 2014 EUROSUPERALLOYS 2014 – 2nd European Symposium on Superalloys and their Applications / [ed] J. Y. Guédou and J. Choné, EDP Sciences, 2014, Vol. 14, Article no. 19003- p.Conference paper, Published paper (Refereed)
Abstract [en]

In this study, the difference between in-phase (IP) and out-of-phase (OP) thermomechanical fatigue (TMF) cycling from 100 to 750 °C has been investigated for the Ni-based single-crystal superalloy MD2. In addition, two different crystal orientations were studied, the ⟨001⟩ and ⟨011⟩ orientations respectively. When comparing IP and OP TMF lives, a strain range dependency is found for the ⟨001⟩ direction. For high strain ranges, IP cycling leads to a higher number of cycles to failure compared to OP. However at lower strain ranges, OP cycling leads to a higher number of cycles to failure compared to IP. Microstructure investigation shows that for the ⟨001⟩ direction, deformation twinning within the γ/γ′-microstructure is much more pronounced during OP conditions compared to IP. However for the ⟨011⟩ direction, the opposite is observed; twinning is more pronounced during IP TMF. From the microstructure investigation it is also visible that intersections between twins seems to trigger formation of TCP phases and recrystallization. These intersections also work as initiation points for TMF damage.

Place, publisher, year, edition, pages
EDP Sciences, 2014
Series
MATEC Web of Conferences, ISSN 2261-236X ; 14
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-111066 (URN)10.1051/matecconf/20141419003 (DOI)000351930400073 ()
Conference
EUROSUPERALLOYS 2014 – 2nd European Symposium on Superalloys and their Applications, 12-16 May 2014, Giens, France
Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2016-05-26Bibliographically approved
4. Deformation and Damage Mechanisms During Thermomechanical Fatigue of a Single-crystal Superalloy in the <001> and <011> Directions
Open this publication in new window or tab >>Deformation and Damage Mechanisms During Thermomechanical Fatigue of a Single-crystal Superalloy in the <001> and <011> Directions
2012 (English)In: Superalloy 2012: 12th International Symposium on Superalloys / [ed] Eric S. Huron, Roger C. Reed, Mark C. Hardy, Michael J. Mills, Rick E. Montero, Pedro D. Portella and Jack Telesman, The Minerals, Metals, and Materials Society, 2012, 215-223 p.Conference paper, Oral presentation only (Refereed)
Abstract [en]

The purpose of this paper is to investigate the differences in mechanical response and microstructural behavior when the single-crystal Ni-based superalloy CMSX-4 is subjected to thermomechanical fatigue (TMF) in two different crystallographic directions, <001> and <011>. An out-of-phase (OP) straincontrolled TMF cycle with R=-∞ in the temperature range 100 to 850 °C was used. As expected, the material exhibited, when loaded in the <001> direction, a higher number of cycles to failure compared to the <011> direction, when equivalent strain ranges were compared. High strain ranges led to crystallographic fractures along one of the {111} planes while low strain ranges led to non-crystallographic fractures. This result was valid for both <001> and <011> directions. Specimens with random fractures also showed recrystallization close to the fracture surface. Twinning was found to be a major deformation mechanism for most specimens. A change in deformation mechanism from twinning to shearing was found in specimens subjected to loading in the <011> direction when going from low to high strain ranges. This investigation also indicated that crack propagation is a consequence of recrystallization and not the other way around.

Place, publisher, year, edition, pages
The Minerals, Metals, and Materials Society, 2012
Keyword
singel-crystal supearlloy, thermomechanical fatigue, deformation mechanisms, twinning, shearing
National Category
Engineering and Technology Materials Engineering
Identifiers
urn:nbn:se:liu:diva-81528 (URN)978-0-470-94320-5 (ISBN)
Conference
Superalloy 2012: 12th International Symposium on Superalloys, September 9-13 2012, Seven Springs, USA
Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2014-10-27Bibliographically approved
5. Creep and Stress Relaxation Anisotropy of a Single-Crystal Superalloy
Open this publication in new window or tab >>Creep and Stress Relaxation Anisotropy of a Single-Crystal Superalloy
2014 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 45, no 5, 2532-2544 p.Article in journal (Refereed) Published
Abstract [en]

In this study, the TMF stress relaxation and creep behavior at 1023 K and 1223 K (750 °C and 950 °C) have been investigated for a Ni-based single-crystal superalloy. Specimens with three different crystal orientations along their axes were tested; 〈001〉, 〈011〉, and 〈111〉, respectively. A highly anisotropic behavior during TMF stress relaxation was found where the 〈111〉 direction significantly shows the worst properties of all directions. The TMF stress relaxation tests were performed in both tension and compression and the results indicate a clear tension/compression asymmetry for all directions where the greatest asymmetry was observed for the 〈001〉 direction at 1023 K (750 °C); here the creep rate was ten times higher in compression than tension. This study also shows that TMF cycling seems to influence the creep rate during stress relaxation temporarily, but after some time it decreases again and adapts to the pre-unloading creep rate. Creep rates from the TMF stress relaxation tests are also compared to conventional constant load creep rates and a good agreement is found.

Place, publisher, year, edition, pages
Springer, 2014
Keyword
Single-crystal superalloy, thermomechanical fatigue, creep, stress relaxation, deformation mechanism
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:liu:diva-89949 (URN)10.1007/s11661-014-2198-0 (DOI)000334428000026 ()
Note

On the day of the defense data of the Licentiate Thesis the status of this article was Manuscript.

Available from: 2013-03-12 Created: 2013-03-12 Last updated: 2017-12-06Bibliographically approved
6. Modelling of Thermomechanical Fatigue Stress Relaxation in a Single-Crystal Nickel-Base Superalloy
Open this publication in new window or tab >>Modelling of Thermomechanical Fatigue Stress Relaxation in a Single-Crystal Nickel-Base Superalloy
2014 (English)In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 90, 61-70 p.Article in journal (Refereed) Published
Abstract [en]

The thermomechanical fatigue (TMF) stress relaxation of the single-crystal nickel-base superalloy MD2 has been analysed and modelled in this paper. In-phase and out-of-phase TMF experiments in the nominal [001],[011] and [111] crystal orientations have been performed. The TMF cycle consists of two loadings each with a 100 h long hold-time. A simple crystallographic creep model, based on Norton’s creep law, has been developed and used in conjunction with a crystal plasticity model. The model takes anisotropy and tension/compression asymmetry into account, where the anisotropic behaviour is based on the crystallographic stress state. The values of the creep parameters in the anisotropic expression were determined by inverse modelling of the conducted TMF experiments, a parameter optimisation were performed. The developed model predicts the stress relaxation seen in the TMF experiments with good correlation.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
single-crystal superalloy, thermomechanical fatigue, creep, stress relaxation, anisotropy, parameter optimisation
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-107983 (URN)10.1016/j.commatsci.2014.04.009 (DOI)000336656200009 ()
Available from: 2014-06-24 Created: 2014-06-24 Last updated: 2017-12-05Bibliographically approved
7. Influence of crystal orientation on the thermomechanical fatigue behaviour in a single-crystal superalloy
Open this publication in new window or tab >>Influence of crystal orientation on the thermomechanical fatigue behaviour in a single-crystal superalloy
2015 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 623, no 19, 68-77 p.Article in journal (Refereed) Published
Abstract [en]

In this study, the influuence from crystal orientation on the thermomehanical fatigue (TMF) behaviour of the recently developed single-rystal superalloy STAL-15 is considered, both from an experimental and a nite element (FE) perspective. Experimental results show that there is a strong inuence from the elastic stiffness, with respect to the loading direction, on the TMF life. However, the results also indicate that the number of active slip planes duringdeformation inuence the TMF life, where specimens with a higher number of active slip planes are favoured compared to specimens with fewer active slip planes. The higher number of active slip planes results in a more widespread deformation compared to a more conentrated deformation when only one slip plane is active. Deformation bands with smeared and elongated  γ-precipitates together with deformation twinning were found to be major deformation mechanisms, where the twins primarily were observed in specimens with several active slip planes. From an FE-perspective, therystal orientation with respect to the loading direction is quantied and adopted into a framework which makes it possible to describe the internal crystallographic arrangement and its entities in a material model. Further, a material model which incorporates the crystalorientation is able to predict the number of slip planes observed from microstructural observations, as well as the elasticstiness of the material with respect to the loading direction.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Single-crystal superalloy, Crystal orientation dependence, Thermome hanical fatigue, Deformation mechanisms, Finite element
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-111639 (URN)10.1016/j.msea.2014.11.026 (DOI)000349063100009 ()
Note

On the day of the defence day the status of this article was Manuscript.

The work has been financially supported by Siemens Industrial Turbomachinery AB in Finspang, Sweden, and the Swedish Energy Agency, via the Research Consortium of Materials Technology for Thermal Energy Processes, Grant no. KME-702. In addition, the support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU #2009-00971) is also acknowledged.

Available from: 2014-10-27 Created: 2014-10-27 Last updated: 2017-12-05Bibliographically approved
8. Thermal-­Mechanical Fatigue Behaviour of a New Single Crystal Superalloy: Effects of Si and Re Alloying
Open this publication in new window or tab >>Thermal-­Mechanical Fatigue Behaviour of a New Single Crystal Superalloy: Effects of Si and Re Alloying
Show others...
2015 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 95, 456-467 p.Article in journal (Refereed) Published
Abstract [en]

The mechanical behaviour of a new single crystal superalloy suitable for power generation applications is considered. Effects of alloying with either Si or Re are elucidated. Out-of-phase thermal-mechanical fatigue is emphasised, although to clarify the effects arising some static creep deformation tests are also carried out. A significant Si-effect is found: a modest addition of 0.25 wt. % Si increases the TMF life by a factor of 2. Thinner deformation bands which traverse the γ'-phase are promoted by Si alloying, with a concomitant greater resistance to recrystallization and cracking along them. Alloying with Re, whilst improving the creep behaviour more markedly than Si, does not have such a strong effect on TMF life. The results provide insights into the composition/performance relationships relevant to the TMF performance of single crystal superalloys.

Place, publisher, year, edition, pages
Elsevier, 2015
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-111640 (URN)10.1016/j.actamat.2015.03.060 (DOI)000358626200046 ()
Note

On the day of the defence date the status of this article was Manuscript.

The work has been supported financially by Siemens Industrial Turbomachinery AB in Finspang, Sweden and the Swedish Energy Agency, via the Research Consortium of Materials Technology for Thermal Energy Processes, Grant No. KME-702. In addition, the support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU #2009-00971) is also acknowledged. Funding from the Engineering and Physical Sciences Research Council (EPSRC) of the UK is acknowledged under Grant EP/J013501/1 'Multifunctional High Performance Alloys for Extreme Environments'.

Available from: 2014-10-27 Created: 2014-10-27 Last updated: 2017-12-05Bibliographically approved

Open Access in DiVA

On Thermomechanical Fatigue of Single-Crystal Superalloys(6543 kB)1700 downloads
File information
File name FULLTEXT01.pdfFile size 6543 kBChecksum SHA-512
b8b0afc66389c270cdcf570e1ba012b014fbd38f062c99779e5d71603432224888e89bcd7a1b2f7130b524c5b41f6a3ced9bc9c0a477c2618f03092cb8537dda
Type fulltextMimetype application/pdf
omslag(2300 kB)43 downloads
File information
File name COVER01.pdfFile size 2300 kBChecksum SHA-512
d8f0d78f88c24f802cf04935c0ca8876550cc57f2386304c0f2752d1f1beb9a05cbd06c5899a00d764200b7dbc3bc6a2fafd50975e5c25bc0051ed95bf5ef37e
Type coverMimetype application/pdf

Other links

Publisher's full text

Search in DiVA

By author/editor
Segersäll, Mikael
By organisation
Engineering MaterialsThe Institute of Technology
Materials EngineeringMaterials Chemistry

Search outside of DiVA

GoogleGoogle Scholar
Total: 1700 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
isbn
urn-nbn

Altmetric score

doi
isbn
urn-nbn
Total: 2080 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