liu.seSearch for publications in DiVA
Change search
Refine search result
1 - 5 of 5
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • 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
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Order onlineBuy this publication >>
    Deng, Dunyong
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Additively Manufactured Inconel 718: Microstructures and Mechanical Properties2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Additive manufacturing (AM), also known as 3D printing, has gained significant interest in aerospace, energy, automotive and medical industries due to its capabilities of manufacturing components that are either prohibitively costly or impossible to manufacture by conventional processes. Among the various additive manufacturing processes for metallic components, electron beam melting (EBM) and selective laser melting (SLM) are two of the most widely used powder bed based processes, and have shown great potential for manufacturing high-end critical components, such as turbine blades and customized medical implants. The futures of the EBM and SLM are doubtlessly promising, but to fully realize their potentials there are still many challenges to overcome.

    Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties and low cost. Though IN718 is being mostly used as a turbine disk material now, the initial introduction of IN718 was to overcome the poor weldability of superalloys in 1960s, since sluggish precipitation of strengthening phases λ’/λ’’ enables good resistance to strain-age cracking during welding or post weld heat treatment. Given the similarity between AM and welding processes, IN718 has been widely applied to the metallic AM field to facilitate the understandings of process-microstructure-property relationships.

    The work presented in this licentiate thesis aims to better understand microstructures and mechanical properties EBM and SLM IN718, which have not been systematically investigated. Microstructures of EBM and SLM IN718 have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and correlated with the process conditions. Monotonic mechanical properties (e.g., Vickers microhardness and tensile properties) have also been measured and rationalized with regards to the microstructure evolutions before and after heat treatments.

    For EBM IN718, the results show the microstructure is not homogeneous but dependant on the location in the components, and the anisotropic mechanical properties are probably attributed to alignment of porosities rather than texture. Post heat treatment can slightly increase the mechanical strength compared to the as-manufactured condition but does not alter the anisotropy. SLM IN718 shows significantly different microstructure and mechanical properties to EBM IN718. The as-manufactured SLM IN718 has very fine dendritic microstructure and Laves phases in the interdendrites, and is “work-hardened” by the residual strains and dislocations present in the material. Mechanical properties are different between horizontally and vertically built samples, and heat treatment can minimize this difference. Results from this licentiate thesis provide the basis for the further research on the cyclic mechanical properties of EBM and SLM IN718, which would be the focus of following phase of the Ph.D. research.

    List of papers
    1. Microstructure and Anisotropic Mechanical Properties of EBM Manufactued Inconel 718 and Effects of Post Heat Treatment
    Open this publication in new window or tab >>Microstructure and Anisotropic Mechanical Properties of EBM Manufactued Inconel 718 and Effects of Post Heat Treatment
    2017 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 693, p. 151-163Article in journal (Refereed) Published
    Abstract [en]

    Materials manufactured with electron beam melting (EBM) have different microstructures and properties to those manufactured using conventional manufacturing methods. A detailed study of the microstructures and mechanical properties of Inconel 718 manufactured with EBM was performed in both as-manufactured and heat-treated conditions. Different scanning strategies resulted in different microstructures: contour scanning led to heterogeneous grain morphologies and weak texture, while hatch scanning resulted in predominantly columnar grains and strong 〈001〉 building direction texture. Precipitates in the as-manufactured condition included γ′, γ″, δ  , TiN and NbC, among which considerable amounts of γ″ yielded relatively high hardness and strength. Strong texture, directionally aligned pores and columnar grains can lead to anisotropic mechanical properties when loaded in different directions. Heat treatments increased the strength and led to different δ precipitation behaviours depending on the solution temperatures, but did not remove the anisotropy. Ductility seemed to be not significantly affected by heat treatment, but instead by the NbC and defects inherited from manufacturing. The study thereby might provide the potential processing windows to tailor the microstructure and mechanical properties of EBM IN718.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    Electron beam melting; Nickel based superalloy; Microstructure; Anisotropy; Mechanical properties; Heat treatments
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-137289 (URN)10.1016/j.msea.2017.03.085 (DOI)000401384400018 ()2-s2.0-85016252903 (Scopus ID)
    Note

    Funding agencies: Sandvik Machining Solutions AB in Sandviken, Sweden; Faculty Grant SFO-MAT-LiU at Linkoping University [2009-00971]; Chinese Scholarship Council; Agora Materiae

    Available from: 2017-05-10 Created: 2017-05-10 Last updated: 2019-11-07Bibliographically approved
  • 2. Order onlineBuy this publication >>
    Deng, Dunyong
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. 202100-3096.
    On the Microstructures and Anisotropic Mechanical Behaviours of Additively Manufactured IN7182019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Additive manufacturing (AM), also known as 3D printing, offers great design flexibility for manufacturing components with complex geometries, and has attracted significant interest in the aero and energy industries in the past decades. Among the commercial AM processes, selective laser melting (SLM) and electron beam melting (EBM) are the two most widely used ones for metallic materials. Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties, weldability and low cost. Due to its excellent weldability, IN718 has been intensively applied in the AM filed, to gain more understanding of the AM processes and fully realize AM’s potentials.

    The study objects in the present thesis include both EBM and SLM IN718. The solidification conditions in EBM and SLM are very different and are different to that of conventional cast, leading to unique microstructures mechanical properties. Therefore, this thesis aims to gain better understanding of the microstructures and anisotropic mechanical behaviours of both EBM and SLM IN718, by detailed characterizations and by comparisons with the forged counterpart.

    The as-built microstructure of EBM IN718 is spatially dependent: the periphery (contour) region has a mixture of equiaxed and columnar grains, while the bulk (hatch) region has columnar grains elongated along the building direction; the last solidified region close to the top sample surface shows segregation and Laves phases, otherwise the rest of the whole sample is well homogenized. Differently, the as-built microstructure of SLM IN718 is spatially homogeneous: the grains is rather equiaxed and with subgrain cell structures. These microstructures also respond differently to the standard heat treatment routines for the conventional counterparts.

    Anisotropic mechanical properties are evident in the room temperature tensile tests and high temperature dwell-fatigue tests. The anisotropic tensile properties of EBM IN718 at room temperature are more likely due to the directional alignment of porosities along the building direction rather than the strong crysiii tallographic texture of 100 _ building direction. While for SLM IN718, the anisotropy is more likely attributed to the different extents of ‘work-hardening’ or dislocations accumulated between the horizontally and vertically built specimens. The anisotropy mechanisms in dwell-fatigue crack propagations at 550 C for EBM and SLM IN718 are identical: higher effective stress intensity factor when intergranular cracking path is perpendicular to the loading direction, but lower effective stress intensity factor when intergranular cracking path is parallel to or slightly deviated from the loading direction.

    The 2160s dwell-fatigue cracking behaviours at 550 C are of significant interest for AM IN718, of which test condition is similar to that of real service for IN718 disk in turbine engine. Generally, after conventional or short-term heat treatments, EBM IN718 shows better dwell-fatigue cracking resistance than SLM IN718. The damage mechanism is different for EBM and SLM IN718: the intergranular cracking in EBM IN718 is due to environmentally assisted grain boundary attack, while creep damage is active for SLM IN718. The considerably ‘deformed’ microstructure, specifically the subgrain cell structures in SLM IN718 resulted from the manufacturing process, is believed to activate creep damage even at a low temperature of 550 C. And for SLM IN718, heat treatment routine must be carefully established to alter the ‘deformed’ microstructure for better time dependent cracking resistance at elevated temperature.

    List of papers
    1. Microstructure and Anisotropic Mechanical Properties of EBM Manufactued Inconel 718 and Effects of Post Heat Treatment
    Open this publication in new window or tab >>Microstructure and Anisotropic Mechanical Properties of EBM Manufactued Inconel 718 and Effects of Post Heat Treatment
    2017 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 693, p. 151-163Article in journal (Refereed) Published
    Abstract [en]

    Materials manufactured with electron beam melting (EBM) have different microstructures and properties to those manufactured using conventional manufacturing methods. A detailed study of the microstructures and mechanical properties of Inconel 718 manufactured with EBM was performed in both as-manufactured and heat-treated conditions. Different scanning strategies resulted in different microstructures: contour scanning led to heterogeneous grain morphologies and weak texture, while hatch scanning resulted in predominantly columnar grains and strong 〈001〉 building direction texture. Precipitates in the as-manufactured condition included γ′, γ″, δ  , TiN and NbC, among which considerable amounts of γ″ yielded relatively high hardness and strength. Strong texture, directionally aligned pores and columnar grains can lead to anisotropic mechanical properties when loaded in different directions. Heat treatments increased the strength and led to different δ precipitation behaviours depending on the solution temperatures, but did not remove the anisotropy. Ductility seemed to be not significantly affected by heat treatment, but instead by the NbC and defects inherited from manufacturing. The study thereby might provide the potential processing windows to tailor the microstructure and mechanical properties of EBM IN718.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    Electron beam melting; Nickel based superalloy; Microstructure; Anisotropy; Mechanical properties; Heat treatments
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-137289 (URN)10.1016/j.msea.2017.03.085 (DOI)000401384400018 ()2-s2.0-85016252903 (Scopus ID)
    Note

    Funding agencies: Sandvik Machining Solutions AB in Sandviken, Sweden; Faculty Grant SFO-MAT-LiU at Linkoping University [2009-00971]; Chinese Scholarship Council; Agora Materiae

    Available from: 2017-05-10 Created: 2017-05-10 Last updated: 2019-11-07Bibliographically approved
    2. On the formation of microstructural gradients in a nickel-base superalloy during electron beam melting
    Open this publication in new window or tab >>On the formation of microstructural gradients in a nickel-base superalloy during electron beam melting
    2018 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 160, p. 251-261Article in journal (Refereed) Published
    Abstract [en]

    Electron beam melting (EBM) is one of the most widely used additive manufacturing (AM) methods for metallic components and has demonstrated great potential to fabricate high-end components in the aerospace and energy industries. The thermal condition within a melt pool and the complicated thermal cycles during the EBM process are of interest but not yet well-understood, and will significantly affect the microstructural homogeneity of as-manufactured nickel-base superalloy components. To establish the thermal profile evolution during electron beam melting of nickel-base superalloys, Inconel 718 (IN718) is manufactured and characterized in the as-manufactured condition, on account of its representative segregation and precipitation behaviours. The microstructure gradient within a build, specifically the Laves phase volume fraction evolution, is rationalized with the solidification condition and the following in-situ annealing. Precipitations of carbide/nitride/carbonitride, delta and gamma/gamma are also discussed. Hardness is measured and correlated to the Laves phase volume fraction evolution and the precipitation of gamma/gamma . The results of this study will (i) shed light on microstructure evolution during the EBM process with regard to thermal history; and (ii) deepen the current understandings of solidification metallurgy for additive manufacturing of Ni-base superalloys. (C) 2018 Elsevier Ltd. All rights reserved.

    Place, publisher, year, edition, pages
    ELSEVIER SCI LTD, 2018
    Keywords
    Electron beam melting; Inconel 718; Laves; Solidification; In-situ annealing; Thermal history
    National Category
    Manufacturing, Surface and Joining Technology
    Identifiers
    urn:nbn:se:liu:diva-153669 (URN)10.1016/j.matdes.2018.09.006 (DOI)000453008100023 ()
    Note

    Funding Agencies|Sandvik Machining Solutions AB in Sandviken, Sweden; Linkoping University [SFO-MAT-LiU#2009-00971]; Chinese Scholarship Council; Agora Materiae; Swedish Governmental Agency for Innovation Systems (Vinnova) [2016-02675]

    Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-11-07
    3. Microstructure and mechanical properties of Inconel 718 produced by selective laser melting: Sample orientation dependence and effects of post heat treatments
    Open this publication in new window or tab >>Microstructure and mechanical properties of Inconel 718 produced by selective laser melting: Sample orientation dependence and effects of post heat treatments
    2018 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 713, p. 294-306Article in journal (Refereed) Published
    Abstract [en]

    Inconel 718 produced by selective laser melting (SLM) has been characterized with focus on the microstructure, the dependence of sample orientation on the mechanical properties and the effects of post heat treatments. The as-manufactured IN718 has a very fine cellular-dendritic structure with fine Laves phases precipitating in the interdendritic region, and electron backscatter diffraction (EBSD) analysis shows that both the vertically and horizontally built samples have relatively weak texture. The vertically built samples show lower tensile strength but higher ductility than the horizontally built samples, and the mechanism is shown to be partly due to the crystallographic feature but more importantly due to the different amount of residual stress and dislocations accumulated in these two kinds of samples. Applying heat treatments can significantly increase the strength while decrease the ductility correspondingly, and difference in yield strength between the vertically and horizontally built samples decreases with increasing the heat treatment temperatures, mainly due to the removal of residual stress and dislocations.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE SA, 2018
    Keywords
    Selective laser melting; Nickel based superalloy; Microstructure; Mechanical properties; Crystallographic orientation; Residual stress
    National Category
    Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-145799 (URN)10.1016/j.msea.2017.12.043 (DOI)000425557900036 ()
    Note

    Funding Agencies|Siemens AG in Berlin, Germany [IN718]; Linkoping University [2009-00971]; Chinese Scholarship Council; Agora Materiae

    Available from: 2018-03-22 Created: 2018-03-22 Last updated: 2019-12-01
    4. On the dwell-fatigue crack propagation behavior of a high strength superalloy manufactured by electron beam melting
    Open this publication in new window or tab >>On the dwell-fatigue crack propagation behavior of a high strength superalloy manufactured by electron beam melting
    2019 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 760, p. 448-457Article in journal (Refereed) Published
    Abstract [en]

    To demonstrate the reliability of additively manufactured superalloys for critical turbine engine components, dynamic tests simulating in-service condition are required. The present study aims to study the dwell-fatigue crack propagation behaviors of IN718 manufactured via electron beam melting (EBM). The textured and columnar-grained microstructure of EBM IN718 shows anisotropic dwell-fatigue cracking resistance when loading axis is aligned parallel and perpendicular to the columnar grains. High and low angle grain boundaries interact differently with the dwell-fatigue cracking path. The effect of different heat treatments on the cracking behavior is also discussed. The dwell-fatigue crack propagation rate of EBM IN718 is compared with forged IN718 under both dwell-fatigue test condition and pure fatigue test condition. The superiority of dwell-fatigue cracking resistance of EBM IN718 to forged IN718 is shown and discussed.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE SA, 2019
    Keywords
    IN718; Electron beam melting (EBM); Dwell; Fatigue; Crack propagation
    National Category
    Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-159148 (URN)10.1016/j.msea.2019.06.013 (DOI)000474501200044 ()
    Note

    Funding Agencies|Sandvik Machining Solutions AB in Sandviken, Sweden; Chinese Scholarship Council; Swedish Governmental Agency for Innovation Systems (Vinnova) [2016-05175]; Faculty grant SFO-MAT-LiU at Linkoping University [2009-00971]; Agora Materiae

    Available from: 2019-07-30 Created: 2019-07-30 Last updated: 2019-11-07
  • 3.
    Deng, Dunyong
    et al.
    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.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Söderberg, Hans
    Microstructural Heterogeneity Along the Building Direction of Inconel 718 Produced by Electron Beam Melting (EBM)2017Conference paper (Refereed)
  • 4.
    Deng, Dunyong
    et al.
    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.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Söderberg, Hans
    Sandvik Machining Solutions AB, Sandviken, Sweden.
    Microstructure and Anisotropic Mechanical Properties of EBM Manufactued Inconel 718 and Effects of Post Heat Treatment2017In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 693, p. 151-163Article in journal (Refereed)
    Abstract [en]

    Materials manufactured with electron beam melting (EBM) have different microstructures and properties to those manufactured using conventional manufacturing methods. A detailed study of the microstructures and mechanical properties of Inconel 718 manufactured with EBM was performed in both as-manufactured and heat-treated conditions. Different scanning strategies resulted in different microstructures: contour scanning led to heterogeneous grain morphologies and weak texture, while hatch scanning resulted in predominantly columnar grains and strong 〈001〉 building direction texture. Precipitates in the as-manufactured condition included γ′, γ″, δ  , TiN and NbC, among which considerable amounts of γ″ yielded relatively high hardness and strength. Strong texture, directionally aligned pores and columnar grains can lead to anisotropic mechanical properties when loaded in different directions. Heat treatments increased the strength and led to different δ precipitation behaviours depending on the solution temperatures, but did not remove the anisotropy. Ductility seemed to be not significantly affected by heat treatment, but instead by the NbC and defects inherited from manufacturing. The study thereby might provide the potential processing windows to tailor the microstructure and mechanical properties of EBM IN718.

  • 5.
    Xu, Jinghao
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Gruber, Hans
    Chalmers University of Technology, Gothenburg, Sweden.
    Deng, Dunyong
    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.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Short-term Creep Behavior of an Additive Manufactured Non-weldable Nickel-base Superalloy Evaluated by Slow Strain Rate Testing2019In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 179, p. 142-157Article in journal (Refereed)
    Abstract [en]

    Additive manufacturing (AM) of high γ′ strengthened Nickel-base superalloys, such as IN738LC, is of high interest for applications in hot section components for gas turbines. The creep property acts as the critical indicator of component performance under load at elevated temperature. However, it has been widely suggested that the suitable service condition of AM processed IN738LC is not yet fully clear. In order to evaluate the short-term creep behavior, slow strain rate tensile (SSRT) tests were performed. IN738LC bars were built by laser powder-bed-fusion (L-PBF) and then subjected to hot isostatic pressing (HIP) followed by the standard two-step heat treatment. The samples were subjected to SSRT testing at 850 °C under strain rates of 1 × 10−5/s, 1 × 10−6/s, and 1 × 10−7/s. In this research, the underlying creep deformation mechanism of AM processed IN738LC is investigated using the serial sectioning technique, electron backscatter diffraction (EBSD), transmission electron microscopy (TEM). On the creep mechanism of AM polycrystalline IN738LC, grain boundary sliding is predominant. However, due to the interlock feature of grain boundaries in AM processed IN738LC, the grain structure retains its integrity after deformation. The dislocation motion acts as the major accommodation process of grain boundary sliding. Dislocations bypass the γ′ precipitates by Orowan looping and wavy slip. The rearrangement of screw dislocations is responsible for the formation of subgrains within the grain interior. This research elucidates the short-creep behavior of AM processed IN738LC. It also shed new light on the creep deformation mechanism of additive manufactured γ′ strengthened polycrystalline Nickel-base superalloys.

1 - 5 of 5
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • 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