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  • 1.
    Chen, Zhe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Surface Integrity of Broached Inconel 718 and Influence of Thermal Exposure2014Licentiate 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.

    List of papers
    1. Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures
    Open this publication in new window or tab >>Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures
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    2016 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 47A, no 7, p. 3664-3676Article in journal (Refereed) Published
    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
    Keywords
    Structural integrity, Broaching, Inconel 718, Plastic deformation, Residual stresses, Thermal exposure, Superalloy
    National Category
    Materials Engineering Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-111056 (URN)10.1007/s11661-016-3515-6 (DOI)000377434700041 ()
    Funder
    Linköpings universitet, 2009-00971
    Note

    The original title of this article when published in manuscript form was Structural integrity of broached Inconel 718 subjected to thermal exposure.

    Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2018-02-27Bibliographically approved
    2. Effect of thermal exposure on microstructure and nano-hardness of broached Inconel 718
    Open this publication in new window or tab >>Effect of thermal exposure on microstructure and nano-hardness of broached Inconel 718
    Show others...
    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, p. 08002-p.1-08002-p.6Conference 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
    Series
    MATEC Web of Conferences, ISSN 2261-236X ; Volume 14
    Keywords
    Structural integrity, Broaching, Inconel 718, Plastic deformation, Residual stresses, Thermal exposure, Superalloy
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-111058 (URN)10.1051/matecconf/20141408002 (DOI)000351930400024 ()2-s2.0-84906910411 (Scopus ID)
    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
    3. Analysis of Thermal Effect on Residual Stresses of Broached Inconel 718
    Open this publication in new window or tab >>Analysis of Thermal Effect on Residual Stresses of Broached Inconel 718
    Show others...
    2014 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    Inconel 718 is a nickel based superalloy that is widely used as a turbine disc material in gas turbine industries. This study details the effect of thermal exposure on the residual stresses produced when broaching Inconel 718. The chosen parameters for broaching in this study are similar to those used when manufacturing turbine discs. The broaching operation produced a high level of tensile residual stresses at the broached surface. A layer with tensile residual stresses was formed in the sub-surface region, followed by a layer several times thicker with compressive residual stresses. Thermal exposure was conducted at 550 °C. The depth distributions of residual stresses after thermal exposure are presented and discussed in this paper. Complete relaxation of the surface tensile residual stresses was observed after 30 h thermal exposure, whereas the 3000 h thermal exposure influenced both the surface and sub-surface residual stress states.

    Place, publisher, year, edition, pages
    Trans Tech Publications Inc., 2014
    Series
    Advanced Materials Research, ISSN 1022-6680 ; 996
    Keywords
    Broaching, Incone 718, Residual Stresses, Thermal Exposure, Recrystallization
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-111057 (URN)10.4028/www.scientific.net/AMR.996.574 (DOI)000348282100093 ()
    Conference
    ECRS9 6-10 July, Troyes, Frankrike
    Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2015-02-20Bibliographically approved
    4. Damage analysis of a retired gas turbine disc
    Open this publication in new window or tab >>Damage analysis of a retired gas turbine disc
    2014 (English)In: Proceedings of the 2014 Energy Materials Conference, John Wiley & Sons, 2014, p. 405-410Conference paper, Published paper (Refereed)
    Abstract [en]

    Gas turbine discs operate mostly at high temperature gradients and are subjected to mechanical loads simultaneously. The high thermal and mechanical loads eventually could result in degradation and damages in disc material, thereby increasing the risk of disc failure. In this study, a damage analysis was performed in a retired gas turbine disc made of Inconel 718. Oxidation attack and microstructural degradation as the consequence of the high service temperature have been found to be the main damages that take place in the non-contact area of the retired disc. In the blade/disc contact area, fretting fatigue occurs, with a result that cracks initiate from the oxide/metal interface and propagate in the disc alloy parallel to the sliding direction of fretting, consequently reducing the stability and safety of the disc. Meantime, oxygen diffuses into the fretting fatigue cracks, thereby exacerbating the oxidation attack. A multi-layered scale with periodic formation of the Fe-oxide/spinel layer and the metallic layer is formed on the contact surface. In both contact and non-contact area, recrystallization and α-Cr precipitation take place in the surface layer of the disc alloy. The locations where α-Cr precipitates are commonly considered to be the natural sites for mechanical weakness.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2014
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-111060 (URN)000364592900047 ()978-1-119-02794-2 (ISBN)
    Conference
    Energy Materials 2014 TMS, November 4-6, 2014, Xi’an, China
    Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2015-12-07Bibliographically approved
  • 2.
    Chen, Zhe
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Moverare, Johan
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Peng, Ru Lin
    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.
    Damage analysis of a retired gas turbine disc2014In: Proceedings of the 2014 Energy Materials Conference, John Wiley & Sons, 2014, p. 405-410Conference paper (Refereed)
    Abstract [en]

    Gas turbine discs operate mostly at high temperature gradients and are subjected to mechanical loads simultaneously. The high thermal and mechanical loads eventually could result in degradation and damages in disc material, thereby increasing the risk of disc failure. In this study, a damage analysis was performed in a retired gas turbine disc made of Inconel 718. Oxidation attack and microstructural degradation as the consequence of the high service temperature have been found to be the main damages that take place in the non-contact area of the retired disc. In the blade/disc contact area, fretting fatigue occurs, with a result that cracks initiate from the oxide/metal interface and propagate in the disc alloy parallel to the sliding direction of fretting, consequently reducing the stability and safety of the disc. Meantime, oxygen diffuses into the fretting fatigue cracks, thereby exacerbating the oxidation attack. A multi-layered scale with periodic formation of the Fe-oxide/spinel layer and the metallic layer is formed on the contact surface. In both contact and non-contact area, recrystallization and α-Cr precipitation take place in the surface layer of the disc alloy. The locations where α-Cr precipitates are commonly considered to be the natural sites for mechanical weakness.

  • 3.
    Chen, Zhe
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Avdovic, Pajazit
    Siemens Industrial Turbomachinery, Finspång, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Zhou, Jinming
    Division of Production and Materials Engineering, Lund university.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Analysis of Thermal Effect on Residual Stresses of Broached Inconel 7182014Conference paper (Refereed)
    Abstract [en]

    Inconel 718 is a nickel based superalloy that is widely used as a turbine disc material in gas turbine industries. This study details the effect of thermal exposure on the residual stresses produced when broaching Inconel 718. The chosen parameters for broaching in this study are similar to those used when manufacturing turbine discs. The broaching operation produced a high level of tensile residual stresses at the broached surface. A layer with tensile residual stresses was formed in the sub-surface region, followed by a layer several times thicker with compressive residual stresses. Thermal exposure was conducted at 550 °C. The depth distributions of residual stresses after thermal exposure are presented and discussed in this paper. Complete relaxation of the surface tensile residual stresses was observed after 30 h thermal exposure, whereas the 3000 h thermal exposure influenced both the surface and sub-surface residual stress states.

  • 4.
    Chen, Zhe
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Avdovic, Pajazit
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Zhou, Jinming
    Division of Production and Materials Engineering, Lund university, Sweden.
    Moverare, Johan
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Karlsson, Fredrik
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Effect of thermal exposure on microstructure and nano-hardness of broached Inconel 7182014In: 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, p. 08002-p.1-08002-p.6Conference 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′′.

  • 5.
    Chen, Zhe
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Peng, Ru Lin
    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.
    Avdovic, Pajazit
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Zhou, Jinming
    Division of Production and Materials Engineering, Lund university.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures2016In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 47A, no 7, p. 3664-3676Article in journal (Refereed)
    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.

  • 6.
    Chen, Zhe
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Zhou, Jinming
    Bushlya, Volodymyr
    Saoubi, Rachid M
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Effect of Cutting Conditions on Machinability of AD 730 TM during High Speed Turning with PCBN Tools2017Conference paper (Refereed)
  • 7.
    Chen, Zhe
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Zhou, Jinming
    Division of Production and Materials Engineering, Lund University, Lund, Sweden.
    M'Saoubi, Rachid
    Seco Tools AB, Fagersta, Sweden.
    Gustafsson, David
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Effect of Machining Parameters on Cutting Force and Surface Integrity when High-Speed Turning AD730™ with PCBN Tools2019In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 100, no 9-12, p. 2601-2615Article in journal (Refereed)
    Abstract [en]

    The novel wrought nickel-based superalloy, AD 730™, is a good candidate material for turbine disc applications at high temperatures beyond 650 °C. The present study focuses on the machining performance of this newly developed alloy under high-speed turning conditions with advanced PCBN tools. Meanwhile, the machined surface integrity as influenced by cutting speed and feed rate was also investigated. The surface integrity was thoroughly characterized in terms of surface roughness and morphology, machining-induced plastic deformation, white layer formation, and residual stresses. It has been found that the cutting speed and feed rate had a strong effect on the cutting forces and resultant surface integrity. The cutting forces required when machining the alloy were gradually reduced with increasing cutting speed, while at 250 m/min and above, the flank tool wear became stronger which led to increased thrust force and feed force. A higher feed rate, on the other hand, always resulted in higher cutting forces. Increasing the cutting speed and feed rate in general deteriorated the surface integrity. High cutting speeds within the range of 200–250 m/min and a low feed rate of 0.1 mm/rev are preferable in order to implement more cost-effective machining without largely reducing the surface quality achieved. The formation of tensile residual stresses on the machined AD 730™, however, could be of a concern where good fatigue resistance is critical.

  • 8.
    Chen, Zhe
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Zhou, Jinming
    Division of Production and Materials Engineering, Lund university.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Bushlya, Volodymyr
    Division of Production and Materials Engineering, Lund university.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    ECCI and EBSD Study of Surbsurface Damages in High Speed Turning of Inconel 718 under Different Tools and Machining Parameters2013Conference paper (Refereed)
  • 9.
    Chen, Zhe
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Zhou, Jinming
    Division of Production and Materials Engineering,Lunds University, Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    M'Saoubi, R
    Seco Tools AB, Fagersta, Sweden.
    Gustafsson, David
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Palmert, Frans
    Siemens Industrial Turbomachinery AB, Finspång.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Plastic Deformation and Residual Stress in High Speed Turning of AD730™ Nickel-based Superalloy with PCBN and WC Tools2018In: Procedia CIRP 71 (2018) pp 440-445, Elsevier, 2018, Vol. 71, p. 440-445Conference paper (Refereed)
    Abstract [en]

    A higher gas turbine efficiency can be achieved by increasing the operating temperature in hot sections. AD730™ is a recently-developed wrought/cast nickel-based superalloy which can maintain excellent mechanical properties above 700 ℃. However, machining of AD730™ could be a difficult task like other nickel-based superalloys. Therefore, studies are needed with respect to the machinability of this new alloy.

    In this paper, high-speed turning was performed on AD730™ using polycrystalline cubic boron nitride (PCBN) tools and coated tungsten carbide (WC) tools at varied cutting speeds. The surface integrity was assessed in two important aspects, i.e., surface and sub-surface plastic deformation and residual stresses. The PCBN tools generally showed better performance compared with the WC tools since it led to reduced machining time without largely compromising the surface integrity achieved. The optimal cutting speed was identified in the range of 200-250 m/min when using the PCBN tools, which gives rise to a good combination of machining efficiency and surface integrity. The further increase of the cutting speed to 300 m/min resulted in severe and deep plastic deformation. Meanwhile, a continuous white layer was formed at the machined surface. When turning with the WC tools, the increased cutting speed from 80 m/min to 100 m/min showed very little effect with respect to the plastic deformation on the machined surface. It was found that tensile residual stresses were developed on all machined surfaces no matter when the PCBN or WC tools were used, and the surface tension was generally increased with increasing cutting speed. The tensile layer might need to be modified by e.g., post-machining surface treatments such as shot peening, if taking good fatigue performance into consideration.

  • 10.
    Peng, Ru
    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.
    Avdovic, Pajazit
    Siemens Industrial Turbomachinery, Finspång.
    Billenius, Annethe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chen, Zhe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of Vibration and Heat Treatment on Residual Stress of a Machined 12%Cr-Steeel2014Conference paper (Refereed)
    Abstract [en]

    In this paper we investigated the influence of vibratory stress relieving technique, which is widely used for stress relaxation of weld and casting components/structure, on machining residual stresses in a ring-component of 12% Cr-steel. It was shown that the employed vibratory treatment, without significantly altering the microstructure, turned the surface layer from tension into compression but retained the compressive residual stresses in the subsurface. In comparison, a stress relieving heat treatment, included as a reference in the study, removed completely the surface tensile residual stresses and reduced the subsurface compressive residual stresses to a low level. Significant microstructural changes in the form of recrystallization also occurred in a thin surface layer of the machining affected zone after the heat treatment.

  • 11. Persson, H
    et al.
    Johansson, D
    Chen, Zhe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Lenrich, F
    M'Saoubi, R
    Gustafsson, David
    Bushlya, Volodymyr
    Stahl, JE
    Zhou, Jinming
    Modelling Tool Life in High Speed Machining of AD730™2018In: Procedia Manufacturing 25 (2018) pp 316-321, 2018, Vol. 25, p. 316-321Conference paper (Refereed)
  • 12.
    Zhou, Jinming
    et al.
    Division of Production and Materials Engineering, Lund university.
    Bushlya, Volodymyr
    Division of Production and Materials Engineering, Lund university.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Chen, Zhe
    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.
    Stahl, Jan-Erik
    Division of Production and Materials Engineering, Lund university.
    Analysis of Subsurface Microstructure and Residual Stresses in Machined Inconel 718 with PCBN and Al2O3-SiCw Tools2014In: 2ND CIRP CONFERENCE ON SURFACE INTEGRITY (CSI), Elsevier, 2014, Vol. 13, p. 150-155Conference paper (Refereed)
    Abstract [en]

    Subsurface microstructural alterations and residual stresses caused by machining significantly affect component lifetime and performance by influencing fatigue, creep, and stress corrosion cracking resistance. Assessing the surface quality of a machined part by characterizing subsurface microstructural alterations and residual stresses is essential for ensuring part performance and lifetime in aero-engines and power generators. This comparative study characterizes and analyzes subsurface microstructural alterations and residual stresses in Inconel 718 subjected to high-speed machining with PCBN and whisker-reinforced ceramic cutting tools. Effects of cutting tool materials and microgeometry on subsurface deformation, microstructural alterations, and residual stresses were investigated. Surface and subsurface regions of machined specimens were investigated using X-ray diffraction, electron channeling contrast imaging, and electron back-scatter diffraction to characterize microstructural alterations and measure deformation intensity and depth.

  • 13. Zhou, Jinming
    et al.
    Chen, Zhe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Siemens Industrial Turbomachinery AB, Finspång.
    Persson, Henrik
    Div of Production and Materials Engineering, Lunds University.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    M'Saoubi, Rachid
    Seco Tools AB, Fagersta.
    Gustafsson, David
    Siemens Industrial Turbomachinery AB, Finspång.
    Comparative Assessment of the Surface Integrity of AD730 and IN718 Superalloys in High-Speed Turning with a CBN Tool2019In: Journal of Manufacturing and Materials Processing, ISSN 2504-4494, Vol. 3, no 3, article id 73Article in journal (Refereed)
    Abstract [en]

    Nickel-based superalloys are typical materials used in components of aeroengines and gas turbine machinery. The strength properties of these alloys at high temperatures are crucial not only to the performance (e.g., power generation efficiency, energy consumption, and greenhouse gas emissions) of aeroengines and industrial gas turbines, but also to machinability during component manufacturing. This study comparatively evaluated the surface integrity of two superalloys, AD730® and Inconel 718 (IN718), during high-speed finishing turning using cubic boron nitride (CBN) tools. IN718 is a conventional superalloy used for the hot section components of aeroengines and industrial gas turbines, while AD730® is a novel superalloy with enhanced high-temperature mechanical properties and good potential as a next-generation superalloy for these components. High-speed turning tests of two superalloys were conducted using a CBN cutting tool and jet stream cooling. The achieved surface integrity of the AD730® and IN718 superalloys was characterized and analyzed to assess the comparability of these alloys. 

  • 14. Zhou, Jinming
    et al.
    Persson, H
    Chen, Zhe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    M'Saoubi, R
    Gustafsson, David
    Bushlya, Volodymyr
    Akujärvi, V
    Stahl, JE
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Surface Characterization of AD730™ Part Produced in High Speed Turning with CBN Tool2018In: Procedia CIRP 71 (2018) / [ed] Elsevier, 2018, Vol. 71, p. 215-220Conference paper (Refereed)
1 - 14 of 14
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