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  • 1.
    Bacos, M P
    et al.
    Office National d'Etudes et de Recherches Aérospatiales, France.
    Josso, P
    Office National d'Etudes et de Recherches Aérospatiales, France.
    Vialas, N
    CIRIMAT––ENSIACET-INPT, Toulouse, France.
    Poquillon, D
    CIRIMAT––ENSIACET-INPT, Toulouse, France.
    Pieraagi, B
    CIRIMAT––ENSIACET-INPT, Toulouse, France.
    Monceau, D
    CIRIMAT––ENSIACET-INPT, Toulouse, France.
    Nicholls, J R
    Cranfield University, United Kingdom.
    Simms, N
    Cranfield University, United Kingdom.
    Encinas-Oropesa, A
    Cranfield University, United Kingdom.
    Ericsson, Torsten
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Stekovic, Svjetlana
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    ALLBATROS advanced long life blade turbine coating systems2004In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 24, no 11-12, p. 1745-1753Article in journal (Refereed)
    Abstract [en]

    The scientific and technological objectives of this program are to increase the efficiency, reliability and maintainability of industrial gas turbine blades and vanes by

    • developing coatings that can warrant a 50 000 h life, i.e. twice that of the usual life, of the hot components (800–1100 °C) even with the use of renewable fuels such as biomass gas or recovery incinerator gas i.e. low-grade fuels with high pollutant levels,

    • characterising advanced existing coatings to assess lifetime and performance of coatings and coated materials,

    • providing material coating data and design criteria to use coating as a design element,

    • increasing the fundamental understanding of the behaviour of coated materials, their degradation, fracture mechanisms and engineering because of the strong need for a mechanism-based modelling of durability.

    These programmes permitted the selection of two reference coatings and the development of two innovative coatings. Concurrently work has been done in order to develop corrosion, oxidation and thermo-mechanical property models. Correlations between coatings development, experimental results and calculations will be discussed.

  • 2.
    Bacos, M-P
    et al.
    Office National DÉtude et de Recherces Aerospatiales Chatillon Cedex France.
    Josso, P
    Office National DÉtude et de Recherces Aerospatiales Chatillon Cedex France.
    Vialas, N
    CIIRMAT Toulouse, France.
    Poquillon, D
    CIRIMAT Toulouse.
    Pierraggi, B
    CIRIMAT Toulouse. France.
    Monceau, D
    CIRIMAT Toulouse, France.
    Nicholls, J R
    Cranfield University Bedford, UK.
    Simms, N
    Cranfield University Bedford.
    Encinas-Oropesa, A
    Cranfiled University Bedford, UK.
    Ericsson, Torsten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Stekovic, Svjetlana
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    ALLBATROS Advanced Long Life BlAde TuRbine COating Systems2003In: The First International Conference on Gas Turbine Technologies,2003, 2003Conference paper (Refereed)
  • 3.
    Cruchley, S
    et al.
    University of Birmingham, England .
    Evans, H E.
    University of Birmingham, England .
    Taylor, M P.
    University of Birmingham, England .
    Hardy, M C.
    Rolls Royce Plc, England .
    Stekovic, Svjetlana
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chromia layer growth on a Ni-based superalloy: Sub-parabolic kinetics and the role of titanium2013In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 75, p. 58-66Article in journal (Refereed)
    Abstract [en]

    Oxidation of the Ni-based superalloy RR1000 has been undertaken in air over the temperature range 600-900 degrees C for times up to 5000 h. The surface oxide consisted of a protective Ti-doped chromia layer but with rutile forming on its outer surface. Sub-surface oxidation of Al and Ti also occurred. The thickening kinetics of the chromia layer were sub-parabolic with initial rates around two orders of magnitude higher than expected for Ti-free chromia. This enhancement and the sub-parabolic kinetics are accounted for by Ti-doping of the chromia layer. Over time the enhancement reduced because of Ti-depletion in the alloy.

  • 4.
    Cruchley, S.
    et al.
    University of Birmingham, England .
    Sun, J.F.
    University of Birmingham, England .
    Taylor, M.P.
    University of Birmingham, England .
    Evans, H.E.
    University of Birmingham, England .
    Bowen, P.
    University of Birmingham, England .
    Sumner, J.
    Cranfield University, England .
    Nicholls, J.R.
    Cranfield University, England .
    Simms, N.J.
    Cranfield University, England .
    Shollock, B.A.
    University of London Imperial Coll Science Technology and Med, England .
    Chater, R.J.
    University of London Imperial Coll Science Technology and Med, England .
    Foss, B.J.
    University of London Imperial Coll Science Technology and Med, England .
    Hardy, M.C.
    Rolls Royce PLC, England .
    Stekovic, Svjetlana
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Cautionary note on use of focused ion beam sectioning as technique for characterising oxidation damage in Ni based superalloys2014In: Materials at High Temperature, ISSN 0960-3409, E-ISSN 1878-6413, Vol. 31, no 1, p. 27-33Article in journal (Refereed)
    Abstract [en]

    Previous observations on Ni based superalloys, obtained through the use of focused ion beam (FIB) sample preparation and imaging, have reported the presence of subsurface voids after oxidation. In this present study, oxidised specimens of the Ni based superalloy, RR1000, were subjected to conventional sample preparation as well as both dual and single beam FIB preparation, with the aim of re-examining the previous observations of subsurface void formation. It is clear from FIB preparations that features previously interpreted as networks of voids have been demonstrated to be internal oxides by varying the sample tilt angles and imaging signal using either secondary electrons (SEs) or secondary ions (SIs). Conventional preparation methods illustrate the presence of subsurface alumina intrusions and the absence of voids, supporting previous evidence. The positive identification of voids and oxides by FIB can be complex and prone to misinterpretation and thus, the use of several imaging conditions and tilt angles must be used, along with conventional preparation methods, to confirm or refute the presence of voids underneath oxides.

  • 5.
    Messe, O. M. D. M.
    et al.
    University of Cambridge, England.
    Stekovic, Svjetlana
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Hardy, M. C.
    Rolls Royce PLC, England.
    Rae, C. M. F.
    University of Cambridge, England.
    Characterization of Plastic Deformation Induced by Shot-Peening in a Ni-Base Superalloy2014In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 66, no 12, p. 2502-2515Article in journal (Refereed)
    Abstract [en]

    The shot-peening process is currently employed in most industries to improve the longevity of components by inhibiting crack initiation as well as crack growth at the surface. The protective effect of shot peening has been mainly attributed to compressive stresses within the deformed layer. Intensive research has been carried out to quantify the near-surface residual stresses on entry into service and evolution throughout life. In nickel-base superalloys, the focus of research on the effects of shot-peening has performed using x-rays from either laboratory or synchrotron-based sources. However, this approach cannot evaluate in detail the deformation mechanisms nor the role of the gamma precipitates in a nickel-base superalloy; the latter is responsible for its unique properties. Our study uses a complementary range of techniques to investigate in detail the microstructure and deformation mechanisms associated with shot-peening in a coarse-grained nickel-based superalloy strengthened with coherent gamma precipitates. These include scanning electron microscopy and transmission electron microscopy, nanoindentation and micropillar compression. Accurate mapping of the dislocation structure produced throughout the deformed layers have been performed. Using an unconventional specimen preparation technique, it provides the basis for a more complete interpretation of how shot-peening inhibits fatigue cracking.

  • 6.
    Stekovic, Svjetlana
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Comparison of low cycle fatigue properties of two uncoated and coated single crystal nickel-base superalloys2005In: 9th International Fatigue Congress,2006, 2005Conference paper (Other academic)
  • 7.
    Stekovic, Svjetlana
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Damage Occurring During Low Cycle Fatigue of a Coated Single Crystal Nickel-Base Superalloy SCB2005In: 2005 ASME International Mechanical Engineering Congress and Exposition,2005, 2005Conference paper (Other academic)
  • 8.
    Stekovic, Svjetlana
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of long term aging on microstructure, LCF properties and deformation behaviour of coated nickel-base superalloys at elevated temperaturesManuscript (preprint) (Other academic)
    Abstract [en]

    The objective of this study is to examine and establish the influence of long-term aging on microstructure, low-cycle fatigue life properties and the fracture behaviour of coated polycrystalline and single-crystal nickel-base superalloys. Long-term aging in metallic coating results in the changes of mechanical properties due to the significant interdiffusion of the main alloying elements between substrate and coatings. For this purpose, a polycrystalline nickel-base superalloy IN792 and two single crystal nickel-base superalloys CMSX-4 and SCB coated with three different coatings were used. The coatings were an overlay coating AMDRY997, a platinum-aluminide diffusion coating RT22 and an innovative coating with interdiffusion barrier of NiW called IC1. Cylindrical solid specimens were first aged at 1050oC under 2000 h to simulate long-term exposure of aircraft engine service environment and then cyclically deformed with fully reversed tension-compression loading total strain amplitude control at two elevated temperatures of 500oC and 900oC and a constant strain rate of 10-4s-1 (6%/ min) in air atmosphere without any dwell time. This tests indicate that long-term aging influences the fatigue behaviour and fracture of coated superalloys by oxidation and diffusion mechanisms when compared to non-aged and uncoated samples. Fatigue life of aged samples exhibit longer life in some cases and shorter life during other test conditions. Fatigue cracks in most cases were initiated at the surface of the coating, growing intergranularly perpendicular to the load axis. Major degradation mechanism in AMDRY997 coating deposited on CMSX-4 tested at 900oC is surface oxidation and interdiffusion with the substrate. Cracks in this aged coated system propagated transgranularly through the coating changing the path behaviour when passing the interdiffusion zone.

  • 9.
    Stekovic, Svjetlana
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Isothermal low cycle fatigue of uncoated and coated nickel-base superalloys2004Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    High strength nickel-base superalloys have been used in turbine blades for many years because of their superior performance at high temperatures. However, the superalloys have limited oxidation and corrosion resistance and to solve this problem, protective coatings are deposited on the surface of the superalloys.

    The positive effect of coatings is based on protecting the surface zone in contact with hot gas atmosphere with elements like aluminium, chromium, which form a thermodynamically stable oxide layer that acts as a diffusion barrier to slow down the react ion between the substrate material and the aggressive environment. There are also other degradation mechanisms that affect nickel-base superalloys such as aging of microstructure, fatigue and creep. Long-term aging in metallic coating results in the changes of mechanical properties due to the significant interdiffusion of the main alloying elements between substrate and coatings. However, application of the coatings has mechanical side effects, the significance of which is not yet fully investigated.

    This work covers a study on the fatigue behaviour of a polycrystalline, IN792, and two single crystal nickel-base superalloys, CMSX-4 and SCB, coated with three different coatings, an overlay coating AMDRY997, a platinum aluminide modified diffusion coating RT22 and an innovative coating with an interdiffusion barrier of NiW called ICl , under low cycle fatigue loading conditions. Both low cycle fatigue properties, cyclic strain and stress response and fracture behaviour of the uncoated, coated and long-term aged coated specimens are presented.

    The main conclusions are that at 500oC the presence of the coatings have, in most cases, reduced the fatigue lives of the nickel-base substrates while at 900oC the coatings do improve the fatigue lives of the superalloys except RT22 coated on some superalloys and under certain test conditions. The reduction of the fatigue life at 500oC can be related to early cracking of the coatings below their ductile to brittle transition temperature (DBTT), where their surface roughness can act as notches affecting fatigue crack initiation. The beneficial effect of the coating at 900oC may be due to slower crack propagation caused by oxidation at the front of the crack tip. The tests also indicate that long-term aging influences the fatigue and fracture behaviour of coated superalloys by oxidation and diffusion mechanisms when compared to non-aged and uncoated samples. The aged samples exhibit longer life in some cases and shorter life during other test conditions. Fatigue cracks were in most cases initiated at the surface of the coatings, growing intergranularly perpendicular to the load axis.

    List of papers
    1. Strain controlled fatigue and fracture behaviour of uncoated and coated polycrystalline and single crystal nickel-base superalloys at elevated temperature
    Open this publication in new window or tab >>Strain controlled fatigue and fracture behaviour of uncoated and coated polycrystalline and single crystal nickel-base superalloys at elevated temperature
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    In this paper, the low-cycle fatigue life and mechanisms governing the fracture behaviour of coated nickel-base superalloys are presented and discussed. Cylindrical solid specimens were cyclically deformed with fully reversed tension-compression loading total strain amplitude control at two elevated temperatures and a constant strain rate of 10-4 s-1 (6%/ min) in air atmosphere without any dwell time. Three nickel-base superalloys, IN792, CMSX-4 and SCB, were coated with three different coatings: an overlay coating AMDRY997, a diffusion coating RT22 and an innovative coating ICl. The cyclic stress response, low-cycle fatigue (LCF) life and final fracture behaviour at the two temperatures are observed and compared.

    At 500oC the coatings reduced fatigue life relative to the uncoated specimens while at 900oC the coated specimens showed longer life at all strain ranges than the uncoated specimens except RT22 under certain test conditions. The decrease in the fatigue life was caused by brittle coating cracking under their ductile to brittle transition temperature (DBTT). Over DBTT, lower yield strength of the coated superalloys with subsequent increase in ductility could cause the improvement of the fatigue life. These cracks could be also slowed by oxidation on front of the crack tip.

    All uncoated and coated superalloys exhibit hardening and higher stress levels at higher applied strain amplitudes and at 500°C. At 900oC softening occurred together with lower stress response level. The coatings lowered the stress level response of the superalloys from about 12% to 31 %. Higher hardening was observed for polycrystalline IN792 caused by dislocation pileups at the the grain boundaries.

    Most of the observed cracks initiated at the coating surface and majority was arrested in the transition zone except for IN792 where internal pores served as initiation sites for most cracks. Some improvement in the fatigue life have also been seen in coated IN792. No cracks found initiated from TCP phases were found. Cracks initially grew more or less perpendicular to the load axis in Stage II manner. Crack propagation path in IN792 is governed by grain or dendrite boundaries while in single crystals crack growth path is determined by concentration of deformation and damage in γ and γ' phases. Surface roughness or rumpling was found in the overlay coating AMDRY997 with some cracks initiated from the rumples maybe due to cyclic straining and not thermal cycling.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-100230 (URN)
    Available from: 2013-10-31 Created: 2013-10-31 Last updated: 2013-10-31
    2. Influence of long term aging on microstructure, LCF properties and deformation behaviour of coated nickel-base superalloys at elevated temperatures
    Open this publication in new window or tab >>Influence of long term aging on microstructure, LCF properties and deformation behaviour of coated nickel-base superalloys at elevated temperatures
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The objective of this study is to examine and establish the influence of long-term aging on microstructure, low-cycle fatigue life properties and the fracture behaviour of coated polycrystalline and single-crystal nickel-base superalloys. Long-term aging in metallic coating results in the changes of mechanical properties due to the significant interdiffusion of the main alloying elements between substrate and coatings. For this purpose, a polycrystalline nickel-base superalloy IN792 and two single crystal nickel-base superalloys CMSX-4 and SCB coated with three different coatings were used. The coatings were an overlay coating AMDRY997, a platinum-aluminide diffusion coating RT22 and an innovative coating with interdiffusion barrier of NiW called IC1. Cylindrical solid specimens were first aged at 1050oC under 2000 h to simulate long-term exposure of aircraft engine service environment and then cyclically deformed with fully reversed tension-compression loading total strain amplitude control at two elevated temperatures of 500oC and 900oC and a constant strain rate of 10-4s-1 (6%/ min) in air atmosphere without any dwell time. This tests indicate that long-term aging influences the fatigue behaviour and fracture of coated superalloys by oxidation and diffusion mechanisms when compared to non-aged and uncoated samples. Fatigue life of aged samples exhibit longer life in some cases and shorter life during other test conditions. Fatigue cracks in most cases were initiated at the surface of the coating, growing intergranularly perpendicular to the load axis. Major degradation mechanism in AMDRY997 coating deposited on CMSX-4 tested at 900oC is surface oxidation and interdiffusion with the substrate. Cracks in this aged coated system propagated transgranularly through the coating changing the path behaviour when passing the interdiffusion zone.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-100231 (URN)
    Available from: 2013-10-31 Created: 2013-10-31 Last updated: 2013-10-31
    3. ALLBATROS advanced long life blade turbine coating systems
    Open this publication in new window or tab >>ALLBATROS advanced long life blade turbine coating systems
    Show others...
    2004 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 24, no 11-12, p. 1745-1753Article in journal (Refereed) Published
    Abstract [en]

    The scientific and technological objectives of this program are to increase the efficiency, reliability and maintainability of industrial gas turbine blades and vanes by

    • developing coatings that can warrant a 50 000 h life, i.e. twice that of the usual life, of the hot components (800–1100 °C) even with the use of renewable fuels such as biomass gas or recovery incinerator gas i.e. low-grade fuels with high pollutant levels,

    • characterising advanced existing coatings to assess lifetime and performance of coatings and coated materials,

    • providing material coating data and design criteria to use coating as a design element,

    • increasing the fundamental understanding of the behaviour of coated materials, their degradation, fracture mechanisms and engineering because of the strong need for a mechanism-based modelling of durability.

    These programmes permitted the selection of two reference coatings and the development of two innovative coatings. Concurrently work has been done in order to develop corrosion, oxidation and thermo-mechanical property models. Correlations between coatings development, experimental results and calculations will be discussed.

    Keywords
    MCrAlY, Aluminium, Oxidation, Corrosion, Thermo-mechanics, Turbine
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-22775 (URN)10.1016/j.applthermaleng.2003.11.018 (DOI)000222717900018 ()2106 (Local ID)2106 (Archive number)2106 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
  • 10.
    Stekovic, Svjetlana
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Low Cycle Fatigue and Fracture of a Coated Superalloy CMSX-42006In: 16th European Conference of Fracture, ECF16, Greece, 2006Conference paper (Other academic)
  • 11.
    Stekovic, Svjetlana
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Low Cycle Fatigue and Thermo-Mechanical Fatigue of Uncoated and Coated Nickel-Base Superalloys2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    High strength nickel-base superalloys have been used in turbine blades for many years because of their superior performance at high temperatures. In such environments superalloys have limited oxidation and corrosion resistance and to solve this problem, protective coatings are deposited on the surface. The positive effect of coatings is based on protecting the surface zone in contact with hot gas atmosphere with a thermodynamically stable oxide layer that acts as a diffusion barrier. During service life, mechanical properties of metallic coatings can be changed due to the significant interdiffusion between substrate and coating. There are also other degradation mechanisms that affect nickel-base superalloys such as low cycle fatigue, thermo-mechanical fatigue and creep.

    The focus of this work is on a study of low cycle fatigue and out-of-phase thermo-mechanical fatigue behaviour of three uncoated and coated nickel-base superalloys. Polycrystalline IN792 and two single crystals CMSX-4 and SCB were coated with four different coatings; an overlay coating AMDRY997 (NiCoCrAlYTa), a platinum aluminide modified diffusion coating RT22 and two innovative coatings with a NiW interdiffusion barrier in the interface called IC1 and IC3. A low cycle fatigue and thermo-mechanical fatigue device was designed and set-up to simulate service loading of turbine blades and vanes. The low cycle fatigue tests were run at 500oC and 900oC while the thermo-mechanical fatigue tests were run between 250oC and 900oC.To simulate long service life, some coated specimens were exposed at 1050oC for 2000 h before the tests.

    The main conclusions are that the presence of the coatings is, in most cases, detrimental to LCF lives of the superalloys at 500oC while the coatings do improve the LCF lives of the superalloys at 900oC. Under TMF loading conditions, the coatings have negative effect on the lifetime of IN792. On single crystals, they are found to improve TMF life of the superalloys, especially at lower strains. The tests also indicate that long-term aging influences the fatigue and fracture behaviour of coated superalloys by oxidation and diffusion mechanisms when compared to non-aged specimens. The aged specimens exhibit longer life in some cases and shorter life during other test conditions. Fatigue cracks were in most cases initiated at the surface of the coatings, growing transgranularly perpendicular to the load axis.

    List of papers
    1. Low Cycle Fatigue and Fracture of a Coated Superalloy CMSX-4
    Open this publication in new window or tab >>Low Cycle Fatigue and Fracture of a Coated Superalloy CMSX-4
    2006 (English)In: 16th European Conference of Fracture, ECF16, Greece, 2006Conference paper, Published paper (Other academic)
    Series
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14663 (URN)10.1007/1-4020-4972-2_135 (DOI)978-1-4020-4971-2 (Print) 978-1-4020-4972-9 (Online) (ISBN)
    Available from: 2007-10-12 Created: 2007-10-12 Last updated: 2009-06-04
    2. Low-Cycle Fatigue and Damage of an Uncoated and Coated Single Crystal Nickel-Bse Superalloy SCB
    Open this publication in new window or tab >>Low-Cycle Fatigue and Damage of an Uncoated and Coated Single Crystal Nickel-Bse Superalloy SCB
    2007 (English)In: International Journal of Materials Research, ISSN 1862-5282, Vol. 98, no 1, p. 26-32Article in journal (Refereed) Published
    Abstract [en]

    This paper presents low-cycle fatigue (LCF) behaviour and damage mechanisms of uncoated and coated specimens of a single crystal nickel-base superalloy SCB tested at 500°C and 900°C. Four coatings were deposited on the base material, an overlay coating AMDRY997, a platinum-modified aluminide diffusion coating RT22 and two innovative coatings called IC1 and IC3 with a NiWdiffusion barrier in the interface. AMDRY997 and RT22 were used as reference coatings. The LCF tests were performed at three strain amplitudes, 1.0, 1.2 and 1.4%, with R ¼ % 1, in laboratory air and without any dwell time. The LCF life of the specimens is determined by crack initiation and propagation. Crack data are presented for different classes of crack size in the form of crack density, that is, the number of cracks normalised to the investigated interface length. Micrographs of damage of the coatings are also shown.

    The effect of the coatings on the LCF life of the superalloy was dependent on the test temperature and deposited coating. At 500°C all coatings had a detrimental effect on the LCF life of the superalloy. At 900°C both AMDRY997 and IC1 prolonged the fatigue life of the superalloy by factors ranging between 1.5 and 4 while RT22 and IC3 shortened the life of the coating–substrate system. Specimens coated with RT22 exhibited generally more damage than other tested coatings at 9008 C. Most of the cracks observed initiated at the coating surface and a majority were arrested in the interdiffusion zone between the base material and the coating. No topologically close-packed phases were found. Delamination was only found in AMDRY997 at higher strains. Surface roughness or rumpling was found in the overlay coating AMDRY997 with some cracks initiating from the rumples. The failure morphology at 900°C reflected the role of oxidation in the fatigue life, the crack initiation and propagation of the coated specimens. The wake of the cracks grown into the substrate was severely oxidised leading to the loss of Al and Ti to the oxide and resulting in the formation of a ϒ’ depleted zone. The cracks grew more or less perpendicular to the load axis in a Stage II manner.

     

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14664 (URN)
    Available from: 2007-10-12 Created: 2007-10-12 Last updated: 2009-05-14
    3. Comparison of Low-Cycle Fatigue Properties of Two Coated Single Crystal Nickel-Base Superalloys, CMSX-4 and SCB
    Open this publication in new window or tab >>Comparison of Low-Cycle Fatigue Properties of Two Coated Single Crystal Nickel-Base Superalloys, CMSX-4 and SCB
    2006 (English)In: 9th International Fatigue Congress, 2006Conference paper, Published paper (Refereed)
    Series
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14665 (URN)
    Available from: 2007-10-12 Created: 2007-10-12 Last updated: 2009-06-04
    4. Low Cycle Fatigue, Thermo-Mechanical Fatigue and Failure of an Uncoated and Coated Polycrystalline Nickel-Base Superalloy IN792
    Open this publication in new window or tab >>Low Cycle Fatigue, Thermo-Mechanical Fatigue and Failure of an Uncoated and Coated Polycrystalline Nickel-Base Superalloy IN792
    2007 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940Article in journal (Refereed) Submitted
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14666 (URN)
    Available from: 2007-10-12 Created: 2007-10-12 Last updated: 2017-12-13
    5. Influence of Long Term Aging on Microstructure and Low Cycle Fatigue Behaviour of Two Coated Nickel-Base Superalloys
    Open this publication in new window or tab >>Influence of Long Term Aging on Microstructure and Low Cycle Fatigue Behaviour of Two Coated Nickel-Base Superalloys
    2007 (English)Manuscript (preprint) (Other academic)
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14667 (URN)
    Available from: 2007-10-12 Created: 2007-10-12 Last updated: 2013-10-31
  • 12.
    Stekovic, Svjetlana
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Low Cycle Fatigue of an Uncoated and Coated Single Crystal Nickel-Base Superalloy SCB2005In: AeroMat 2005,2005, 2005Conference paper (Other academic)
  • 13.
    Stekovic, Svjetlana
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Low Cycle Fatigue of Single Crystal Nickel-Base Superalloy CMSX-4 Coated with a New Coating IC12005In: AeroMat 2005,2005, 2005Conference paper (Other academic)
  • 14.
    Stekovic, Svjetlana
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Low cycle fatigue of single crystal nickel-base superalloy cmsx-4 coated wsith a new coating IC12005In: IMECE 2005 ASME Intgernational Mechanical Engineering Congress and Exposition,2005, Orlando: American Society of Mechanical Engineers , 2005, p. 235-Conference paper (Refereed)
  • 15.
    Stekovic, Svjetlana
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Strain controlled fatigue and fracture behaviour of uncoated and coated polycrystalline and single crystal nickel-base superalloys at elevated temperatureManuscript (preprint) (Other academic)
    Abstract [en]

    In this paper, the low-cycle fatigue life and mechanisms governing the fracture behaviour of coated nickel-base superalloys are presented and discussed. Cylindrical solid specimens were cyclically deformed with fully reversed tension-compression loading total strain amplitude control at two elevated temperatures and a constant strain rate of 10-4 s-1 (6%/ min) in air atmosphere without any dwell time. Three nickel-base superalloys, IN792, CMSX-4 and SCB, were coated with three different coatings: an overlay coating AMDRY997, a diffusion coating RT22 and an innovative coating ICl. The cyclic stress response, low-cycle fatigue (LCF) life and final fracture behaviour at the two temperatures are observed and compared.

    At 500oC the coatings reduced fatigue life relative to the uncoated specimens while at 900oC the coated specimens showed longer life at all strain ranges than the uncoated specimens except RT22 under certain test conditions. The decrease in the fatigue life was caused by brittle coating cracking under their ductile to brittle transition temperature (DBTT). Over DBTT, lower yield strength of the coated superalloys with subsequent increase in ductility could cause the improvement of the fatigue life. These cracks could be also slowed by oxidation on front of the crack tip.

    All uncoated and coated superalloys exhibit hardening and higher stress levels at higher applied strain amplitudes and at 500°C. At 900oC softening occurred together with lower stress response level. The coatings lowered the stress level response of the superalloys from about 12% to 31 %. Higher hardening was observed for polycrystalline IN792 caused by dislocation pileups at the the grain boundaries.

    Most of the observed cracks initiated at the coating surface and majority was arrested in the transition zone except for IN792 where internal pores served as initiation sites for most cracks. Some improvement in the fatigue life have also been seen in coated IN792. No cracks found initiated from TCP phases were found. Cracks initially grew more or less perpendicular to the load axis in Stage II manner. Crack propagation path in IN792 is governed by grain or dendrite boundaries while in single crystals crack growth path is determined by concentration of deformation and damage in γ and γ' phases. Surface roughness or rumpling was found in the overlay coating AMDRY997 with some cracks initiated from the rumples maybe due to cyclic straining and not thermal cycling.

  • 16.
    Stekovic, Svjetlana
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Ericsson, Torsten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of Long Term Aging on Microstructure and Low Cycle Fatigue Behaviour of Two Coated Nickel-Base Superalloys2007Manuscript (preprint) (Other academic)
  • 17.
    Stekovic, Svjetlana
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Ericsson, Torsten
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Low-Cycle Fatigue and Damage of an Uncoated and Coated Single Crystal Nickel-Bse Superalloy SCB2007In: International Journal of Materials Research, ISSN 1862-5282, Vol. 98, no 1, p. 26-32Article in journal (Refereed)
    Abstract [en]

    This paper presents low-cycle fatigue (LCF) behaviour and damage mechanisms of uncoated and coated specimens of a single crystal nickel-base superalloy SCB tested at 500°C and 900°C. Four coatings were deposited on the base material, an overlay coating AMDRY997, a platinum-modified aluminide diffusion coating RT22 and two innovative coatings called IC1 and IC3 with a NiWdiffusion barrier in the interface. AMDRY997 and RT22 were used as reference coatings. The LCF tests were performed at three strain amplitudes, 1.0, 1.2 and 1.4%, with R ¼ % 1, in laboratory air and without any dwell time. The LCF life of the specimens is determined by crack initiation and propagation. Crack data are presented for different classes of crack size in the form of crack density, that is, the number of cracks normalised to the investigated interface length. Micrographs of damage of the coatings are also shown.

    The effect of the coatings on the LCF life of the superalloy was dependent on the test temperature and deposited coating. At 500°C all coatings had a detrimental effect on the LCF life of the superalloy. At 900°C both AMDRY997 and IC1 prolonged the fatigue life of the superalloy by factors ranging between 1.5 and 4 while RT22 and IC3 shortened the life of the coating–substrate system. Specimens coated with RT22 exhibited generally more damage than other tested coatings at 9008 C. Most of the cracks observed initiated at the coating surface and a majority were arrested in the interdiffusion zone between the base material and the coating. No topologically close-packed phases were found. Delamination was only found in AMDRY997 at higher strains. Surface roughness or rumpling was found in the overlay coating AMDRY997 with some cracks initiating from the rumples. The failure morphology at 900°C reflected the role of oxidation in the fatigue life, the crack initiation and propagation of the coated specimens. The wake of the cracks grown into the substrate was severely oxidised leading to the loss of Al and Ti to the oxide and resulting in the formation of a ϒ’ depleted zone. The cracks grew more or less perpendicular to the load axis in a Stage II manner.

     

  • 18.
    Stekovic, Svjetlana
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Ericsson, Torsten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Thermo-Mechanical and Low Cycle Fatigue of Two Uncoated and Coated Single Crystal Nickel-Base Superalloys, CMSX-4 and SCB2007In: Fatigue 2007 - The 6th Engineering Integrity Society International Conference on Durability and Fatigue,2007, 2007Conference paper (Other academic)
  • 19.
    Stekovic, Svjetlana
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Ericsson, Torsten
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Comparison of Low-Cycle Fatigue Properties of Two Coated Single Crystal Nickel-Base Superalloys, CMSX-4 and SCB2006In: 9th International Fatigue Congress, 2006Conference paper (Refereed)
  • 20.
    Stekovic, Svjetlana
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Ericsson, Torsten
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Low Cycle Fatigue, Thermo-Mechanical Fatigue and Failure of an Uncoated and Coated Polycrystalline Nickel-Base Superalloy IN7922007In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940Article in journal (Refereed)
1 - 20 of 20
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