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Karimi Neghlani, PariaORCID iD iconorcid.org/0000-0001-6610-1486
Publications (10 of 12) Show all publications
Karimi Neghlani, P., Schnur, C., Sadeghi, E. & Andersson, J. (2020). Contour design to improve topographical and microstructural characteristics of Alloy 718 manufactured by electron beam-powder bed fusion technique. Additive Manufacturing, 32, Article ID 101014.
Open this publication in new window or tab >>Contour design to improve topographical and microstructural characteristics of Alloy 718 manufactured by electron beam-powder bed fusion technique
2020 (English)In: Additive Manufacturing, ISSN 2214-8604, Vol. 32, article id 101014Article in journal (Refereed) Published
Abstract [en]

Additive manufacturing (AM) processes are being frequently used in industry as they allow the manufacture ofcomplex parts with reduced lead times. Electron beam-powder bed fusion (EB-PBF) as an AM technology isknown for its near-net-shape production capacity with low residual stress. However, the surface quality andgeometrical accuracy of the manufactured parts are major obstacles for the wider industrial adoption of thistechnology, especially when enhanced mechanical performance is taken into consideration. Identifying theorigins of surface features such as satellite particles and sharp valleys on the parts manufactured by EB-PBF isimportant for a better understanding of the process and its capability. Moreover, understanding the influence ofthe contour melting strategy, by altering process parameters, on the surface roughness of the parts and thenumber of near-surface defects is highly critical. In this study, processing parameters of the EB-PBF techniquesuch as scanning speed, beam current, focus offset, and number of contours (one or two) with the linear meltingstrategy were investigated. A sample manufactured using Arcam-recommended process parameters (threecontours with the spot melting strategy) was used as a reference. For the samples with one contour, the scanningspeed had the greatest effect on the arithmetical mean height (Sa), and for the samples with two contours, thebeam current and focus offset had the greatest effect. For the samples with two contours, a lower focus offset andlower scan speed (at a higher beam current) resulted in a lower Sa; however, increasing the scan speed for thesamples with one contour decreased Sa. In general, the samples with two contours provided a lower Sa (∼22 %)but with slightly higher porosity (∼8 %) compared to the samples with one contour. Fewer defects were detected with a lower scanning speed and higher beam current. The number of defects and the Sa value for thesamples with two contours manufactured using the linear melting strategy were ∼85 % and 16 %, respectively,lower than those of the reference samples manufactured using the spot melting strategy.

Keywords
3D printers; Additives; Electron beams; Scanning; Speed; Surface defects; Surface properties; Surface roughness, Alloy 718; Geometrical accuracy; Linear and spot melting strategies; Mechanical performance; Micro-structural characteristics; Near-surface defects; Powder bed; Processing parameters, Melting
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14993 (URN)10.1016/j.addma.2019.101014 (DOI)000522928600020 ()2-s2.0-85078915522 (Scopus ID)
Available from: 2020-02-24 Created: 2020-02-24 Last updated: 2020-05-08Bibliographically approved
Karimi Neghlani, P., Sadeghi, E., Ålgårdh, J., Harlin, P. & Andersson, J. (2020). Effect of build location on microstructural characteristics and corrosion behavior of EB-PBF built Alloy 718. The International Journal of Advanced Manufacturing Technology, 106(7-8), 3597-3607
Open this publication in new window or tab >>Effect of build location on microstructural characteristics and corrosion behavior of EB-PBF built Alloy 718
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2020 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 106, no 7-8, p. 3597-3607Article in journal (Refereed) Published
Abstract [en]

Electron beam-powder bed fusion (EB-PBF), a high-temperature additive manufacturing (AM) technique, shows great promise in the production of high-quality metallic parts in different applications such as the aerospace industry. To achieve a higher build efficiency, it is ideal to build multiple parts together with as low spacing as possible between the respective parts. In the EB-PBF technique, there are many unknown variations in microstructural characteristics and functional performance that could be induced as a result of the location of the parts on the build plate, gaps between the parts and part geometry, etc. In the present study, the variations in the microstructure and corrosion performance as a function of the parts location on the build plate in the EB-PBF process were investigated. The microstructural features were correlated with the thermal history of the samples built in different locations on the build plate, including exterior (the outermost), middle (between the outermost and innermost), and interior (the innermost) regions. The cubic coupons located in the exterior regions showed increased level (~ 20 %) of defects (mainly in the form of shrinkage pores) and lower level (~ 30-35 %) of Nb-rich phase fraction due to their higher cooling rates compared to the interior and middle samples. Electrochemical investigations showed that the location indirectly had a substantial influence on the corrosion behavior, verified by a significant increase in polarization resistance (Rp) from the exterior (2.1 ± 0.3 kΩ.cm2) to interior regions (39.2 ± 4.1 kΩ.cm2). © 2020, The Author(s).

Keywords
3D printers; Additives; Aerospace industry; Corrosion; Corrosive effects; Electron beams; Hardness; High temperature applications, Alloy 718; Electrochemical investigations; Functional performance; Micro-structural characteristics; Micro-structural characterization; Microstructural features; Polarization resistances; Powder bed, Location
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hv:diva-15004 (URN)10.1007/s00170-019-04859-9 (DOI)000511506500069 ()2-s2.0-85077549789 (Scopus ID)
Funder
Knowledge FoundationEuropean Regional Development Fund (ERDF)
Available from: 2020-02-24 Created: 2020-02-24 Last updated: 2020-02-27
Karimi Neghlani, P., Sadeghi, E., Ålgårdh, J. & Andersson, J. (2019). EBM-manufactured single tracks of Alloy 718: Influence of energy input and focus offset on geometrical and microstructural characteristics. Materials Characterization, 148, 88-99
Open this publication in new window or tab >>EBM-manufactured single tracks of Alloy 718: Influence of energy input and focus offset on geometrical and microstructural characteristics
2019 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 148, p. 88-99Article in journal (Refereed) Published
Abstract [en]

Electron beam melting-powder bed fusion (EBM-PBF) is an additive manufacturing process, which is able to produce parts in layer-by-layer fashion from a 3D model data. Currently application of this technology in parts manufacturing with high geometrical complexity has acquired growing interest in industry. To recommend the EBM process into industry for manufacturing parts, improved mechanical properties of final part must be obtained. Such properties highly depend on individual single melted track and single layer. In EBM, interactions between the electron beam, powder, and solid underlying layer affect the geometrical (e.g., re-melt depth, track width, contact angle, and track height) and microstructural (e.g., grain structure, and primary dendrite arm spacing) characteristics of the melted tracks. The core of the present research was to explore the influence of linear energy input parameters in terms of beam scanning speed, beam current as well as focus offset and their interactions on the geometry and microstructure of EBM-manufactured single tracks of Alloy 718. Increased scanning speed led to lower linear energy input values (<0.9 J/mm) in an specific range of the focus offset (0–10 mA) which resulted in instability, and discontinuity of the single tracks as well as balling effect. Decreasing the scanning speed and increasing the beam current resulted in higher melt pool depth and width. By statistical evaluations, the most influencing parameters on the geometrical features were primarily the scanning speed, and secondly the beam current. Primary dendrite arm spacing (PDAS) slightly decreased by increasing the scanning speed using lower beam current values as the linear energy input decreased. By increasing the linear energy input, the chance of more equiaxed grain formation was high, however, at lower linear energy input, mainly columnar grains were observed. The lower focus offset values resulted in more uniform grains along the 〈001〉 crystallographic direction. © 2018 Elsevier Inc. 

Keywords
3D printers; Contact angle; Dendrites (metallography); Design of experiments; Electron beam melting; Electron beams; Scanning; Speed, Alloy 718; Geometrical characteristics; Powder bed; Single-tracks; Solidified microstructures, Geometry
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13365 (URN)10.1016/j.matchar.2018.11.033 (DOI)000458228100011 ()2-s2.0-85058512738 (Scopus ID)
Funder
European Regional Development Fund (ERDF)Knowledge Foundation
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2020-02-04Bibliographically approved
Sadeghi, E., Karimi Neghlani, P., Momeni, S., Seifi, M., Eklund, A. & Andersson, J. (2019). Influence of thermal post treatments on microstructure and oxidation behavior of EB-PBF manufactured Alloy 718. Materials Characterization, 150, 236-251
Open this publication in new window or tab >>Influence of thermal post treatments on microstructure and oxidation behavior of EB-PBF manufactured Alloy 718
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2019 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 150, p. 236-251Article in journal (Refereed) Published
Abstract [en]

The effect of thermal post treatments consisting of heat treatment (HT), hot isostatic pressing (HIP), and combined HIP-HT on microstructure and oxidation behavior of Alloy 718 manufactured by electron beam powder bed fusion (EB-PBF) technique was investigated. Oxidation of the as-built and post-treated specimens was performed in ambient air at 650, 750, and 850 °C for up to 168 h. Directional columnar-grained microstructure, pores and fine Nb-rich carbides were observed in the as-built specimen. The HT specimen presented the columnar microstructure, plate-like δ phase at grain boundaries, and pores. The dominant grain crystallographic orientation was changed from 〈001〉 in the as-built specimen to 〈101〉 after HT. No grain boundary δ phase was observed in the HIPed specimen, but recrystallization occurred in both the HIP and HIP-HT specimens due to a rapid cooling after HIPing motivating the nucleation of fine grains with limited time to grow. After oxidation exposure at 650 and 750 °C for 168 h, no big difference between weight changes of the as-built and post-treated specimens was noted, whereas at 850 °C, the combined HIP-HT specimen showed the most promising corrosion resistance with the least weight change. At 850 °C, a protective scale of Cr 2 O 3 rich in Cr, Ti, and Ni as well as an internal oxide (branched structure of alumina) developed in all the specimens, while, only a protective Cr 2 O 3 scale was found at 650 and 750 °C. The HIP-HT specimen at 850 °C developed an oxide scale, which was denser and more adherent in comparison to the oxide scales formed on the other three specimens, associated with its limited defect distribution and more homogenized microstructure. Moreover, the δ phase formed close to the surface of the exposed specimens during the oxidation exposure at 850 °C most probably led to nucleation and growth of the oxide scale. © 2019 Elsevier Inc.

Keywords
Additive manufacturing, Electron beam powder bed fusion, Alloy 718, Oxidation, Heat treatment, Hot isostatic pressing
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13740 (URN)10.1016/j.matchar.2019.02.016 (DOI)000462420900027 ()2-s2.0-85062014143 (Scopus ID)
Funder
Knowledge Foundation
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2020-02-04Bibliographically approved
Gruber, H., Karimi Neghlani, P., Hryha, E. & Nyborg, L. (2018). Effect of Powder Recycling on the Fracture Behavior of Electron Beam Melted Alloy 718. Powder Metallurgy Progress, 18(1), 40-48
Open this publication in new window or tab >>Effect of Powder Recycling on the Fracture Behavior of Electron Beam Melted Alloy 718
2018 (English)In: Powder Metallurgy Progress, ISSN 1335-8987, Vol. 18, no 1, p. 40-48Article in journal (Other academic) Published
Abstract [en]

Understanding the effect of powder feedstock alterations during multicycle additive manufacturing on the quality of built components is crucial to meet the requirements on critical parts for aerospace engine applications. In this study, powder recycling of Alloy 718 during electron beam melting was studied to understand its influence on fracture behavior of Charpy impact test bars. High resolution scanning electron microscopy was employed for fracture surface analysis on test bars produced from virgin and recycled powder. For all investigated samples, an intergranular type of fracture, initiated by non-metallic phases and bonding defects, was typically observed in the regions close to or within the contour zone. The fracture mode in the bulk of the samples was mainly moderately ductile dimple fracture. The results show a clear correlation between powder degradation during multi-cycle powder reuse and the amount of damage relevant defects observed on the fracture surfaces. In particular, samples produced from recycled powder show a significant amount of aluminum-rich oxide defects, originating from aluminum-rich oxide particulates on the surface of the recycled powder. © 2018 H. Gruber et al., published by Sciendo.

Place, publisher, year, edition, pages
de Gruyter, 2018
Keywords
additive manufacturing of Alloy 718, electron beam melting, powder recycling, powder degradation, fractography of AM components
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-12906 (URN)10.1515/pmp-2018-0005 (DOI)2-s2.0-85051985288 (Scopus ID)
Funder
Vinnova
Note

Funders:  SIP LIGHTer; AoA Production at Chalmers.

Available from: 2018-09-27 Created: 2018-09-27 Last updated: 2019-05-27Bibliographically approved
Karimi Neghlani, P. (2018). Electron beam melting of Alloy 718: Influence of process parameters on the microstructure. (Licentiate dissertation). Trollhättan: University West
Open this publication in new window or tab >>Electron beam melting of Alloy 718: Influence of process parameters on the microstructure
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Additive manufacturing (AM) is the name given to the technology of building 3D parts by adding layer-by-layer of materials, including metals, plastics, concrete, etc. Of the different types of AM techniques, electron beam melting (EBM), as a powder bed fusion technology, has been used in this study. EBM is used to build parts by melting metallic powders by using a highly intense electron beam as the energy source. Compared to a conventional process, EBM offers enhanced efficiency for the production of customized and specific parts in aerospace, space, and medical fields. In addition, the EBM process is used to produce complex parts for which other technologies would be either expensive or difficult to apply. This thesis has been divided into three sections, starting from a wider window and proceeding to a smaller one. The first section reveals how the position-related parameters (distance between samples, height from build plate, and sample location on build plate) can affect the microstructural characteristics. It has been found that the gap between the samples and the height from the build plate can have significant effects on the defect content and niobium-rich phase fraction. In the second section, through a deeper investigation, the behavior of Alloy 718 during the EBM process as a function of different geometry-related parameters is examined by building single tracks adjacent to each other (track-by-track) andsingle-wall samples (single tracks on top of each other). In this section, the main focus is to understand the effect of successive thermal cycling on microstructural evolution. In the final section, the correlations between the main machine-related parameters (scanning speed, beam current, and focus offset) and the geometrical (melt pool width, track height, re-melted depth, and contact angle) and microstructural (grain structure, niobium-rich phase fraction, and primary dendrite arm spacing) characteristics of a single track of Alloy 718 have been investigated. It has been found that the most influential machine-related parameters are scanning speed and beam current, which have significant effects on the geometry and the microstructure of the single-melted tracks.

Place, publisher, year, edition, pages
Trollhättan: University West, 2018. p. 65
Series
Licentiate Thesis: University West ; 22
Keywords
Additive manufacturing; Powder bed fusion; Electron beam melting; Part’s orientation; Microstructure development; Single track; Energy input; Focus offset; Geometrical features, Alloy 718
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13140 (URN)978-91-88847-08-9 (ISBN)978-91-88847-07-2 (ISBN)
Presentation
2018-11-21, C120, Högskolan Väst, Trollhättan, 10:00 (English)
Supervisors
Available from: 2018-11-21 Created: 2018-11-19 Last updated: 2018-11-19
Karimi Neghlani, P., Sadeghimeresht, E., Deng, D., Gruber, H., Andersson, J. & Nylen, P. (2018). Influence of build layout and orientation on microstructural characteristics of electron beam melted Alloy 718. The International Journal of Advanced Manufacturing Technology, 99(S1), 2903-2913
Open this publication in new window or tab >>Influence of build layout and orientation on microstructural characteristics of electron beam melted Alloy 718
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2018 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 99, no S1, p. 2903-2913Article in journal (Refereed) Published
Abstract [en]

Effects of build layout and orientation consisting of (a) height from the build plate (Z-axis), (b) distance between samples, and (c) location in the build plate (X-Y plane) on porosity, NbC fraction, and hardness in electron beam melted (EBM) Alloy 718 were studied. The as-built samples predominantly showed columnar structure with strong ˂001˃ crystallographic orientation parallel to the build direction, as well as NbC and ÎŽ-phase in inter-dendrites and grain boundaries. These microstructural characteristics were correlated with the thermal history, specifically cooling rate, resulted from the build layout and orientation parameters. The hardness and NbC fraction of the samples increased around 6% and 116%, respectively, as the height increased from 2 to 45 mm. Moreover, by increasing the height, formation of ÎŽ-phase was also enhanced associated with lower cooling rate in the samples built with a greater distance from the build plate. However, the porosity fraction was unaffected. Increasing the sample gap from 2 to 10 mm did not change the NbC fraction and hardness; however, the porosity fraction increased by 94%. The sample location in the build chamber influenced the porosity fraction, particularly in interior and exterior areas of the build plate. The hardness and NbC fraction were not dependent on the sample location in the build chamber. © 2018, The Author(s).

Keywords
3D printers, Cooling, Electron beam melting, Electron beams, Grain boundaries, Hardness, Location, Niobium compounds, Porosity, Alloy 718, Build direction, Columnar structures, Crystallographic orientations, Micro-structural characteristics, Micro-structural characterization, Orientation parameter, Sample location, Porous plates
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13043 (URN)10.1007/s00170-018-2621-6 (DOI)000452076900065 ()2-s2.0-85053670925 (Scopus ID)
Funder
European Regional Development Fund (ERDF)Knowledge Foundation
Note

First Online: 17 September 2018

Available from: 2018-10-29 Created: 2018-10-29 Last updated: 2019-05-28Bibliographically approved
Karimi Neghlani, P., Raza, T., Andersson, J. & Svensson, L.-E. (2018). Influence of laser exposure time and point distance on 75-μm-thick layer of selective laser melted Alloy 718. The International Journal of Advanced Manufacturing Technology, 94(5-8), 2199-2207
Open this publication in new window or tab >>Influence of laser exposure time and point distance on 75-μm-thick layer of selective laser melted Alloy 718
2018 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 94, no 5-8, p. 2199-2207Article in journal (Refereed) Published
Abstract [en]

A systematic matrix with 25 samples, using five different point distances and five laser exposure times, depositing 75-μm-thick layers of Alloy 718 has been studied. The work has concentrated on defects formed, hardness of the deposits, and the microstructure. Relatively large amount of defects, both lack of fusion and porosity, was found in several of the specimens in the deposits. The defects were never possible to fully eliminate, but a significant decrease, mainly in the lack of fusion, was seen with increasing laser exposure time. The gas porosity on the other hand was not affected to any larger degree, except for the lowest laser energy input, where a slight increase in porosity was seen. A small increase in hardness was noted with increasing laser energy input. The width of the deposited beads increased with increasing laser energy, while the depth of deposits was more or less constant. However, for the lowest combination of point distance and laser exposure time, quite deep and narrow beads were formed. A comparison was made with deposition of 50-μm-thick layers, with quite similar laser energy input, but with some variation in detailed deposition parameters. It was found that the 75-μm-thick layers contained less lack of fusion, particularly for small point distances. The amount of porosity was also less, but that did not vary with deposition parameters.© 2017 The Author(s)

Keywords
3D printers; Defects; Deposition; Deposits; Hardness; Microstructure, Alloy 718; Deposition Parameters; Large amounts; Laser energies; Laser exposure; Point distances; Selective laser melting; Small points, Porosity
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-11886 (URN)10.1007/s00170-017-1019-1 (DOI)000422886200055 ()2-s2.0-85028818109 (Scopus ID)
Funder
VinnovaSwedish National Space Board
Note

First Online: 06 September 2017

Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2019-05-28Bibliographically approved
Karimi Neghlani, P., Sadeghimeresht, E., Åkerfeldt, P., Ålgårdh, J. & Andersson, J. (2018). Influence of successive thermal cycling on microstructure evolution of EBM-manufactured alloy 718 in track-by-track and layer-by-layer design. Materials & design, 160, 427-441
Open this publication in new window or tab >>Influence of successive thermal cycling on microstructure evolution of EBM-manufactured alloy 718 in track-by-track and layer-by-layer design
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2018 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 160, p. 427-441Article in journal (Refereed) Published
Abstract [en]

Successive thermal cycling (STC) during multi-track and multi-layer manufacturing of Alloy 718 using electron beam melting (EBM) process leads to a microstructure with a high degree of complexity. In the present study, a detailed microstructural study of EBM-manufactured Alloy 718 was conducted by producing samples in shapes from one single track and single wall to 3D samples with maximum 10 longitudinal tracks and 50 vertical layers. The relationship between STC, solidification microstructure, interdendritic segregation, phase precipitation (MC, δ-phase), and hardness was investigated. Cooling rates (liquid-to-solid and solid-to-solid state) was estimated by measuring primary dendrite arm spacing (PDAS) and showed an increased cooling rate at the bottom compared to the top of the multi-layer samples. Thus, microstructure gradient was identified along the build direction. Moreover, extensive formation of solidification micro-constituents including MC-type carbides, induced by micro-segregation, was observed in all the samples. The electron backscatter diffraction (EBSD) technique showed a high textured structure in 〈001〉 direction with a few grains misoriented at the surface of all samples. Finer microstructure and possibility of more γ″ phase precipitation at the bottom of the samples resulted in slightly higher (~11%) hardness values compared to top of the samples. © 2018 Elsevier Ltd

Keywords
3D printers; Carbides; Cooling; Electron beam melting; Electron beams; Hardness; Segregation (metallography); Solidification; Thermal cycling, Alloy 718; Electron backscatter diffraction technique; Interdendritic segregation; Layer by layer; Micro-structure evolutions; Primary dendrite arm spacings; Solidification microstructures; Track by track, Microstructure
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13042 (URN)10.1016/j.matdes.2018.09.038 (DOI)000453008100040 ()2-s2.0-85053828514 (Scopus ID)
Funder
Knowledge Foundation
Note

Funders: Simulation and Control of Material affecting Processes (SiCoMap); "SUMAN-Next"

Available from: 2018-10-29 Created: 2018-10-29 Last updated: 2019-05-28Bibliographically approved
Sadeghimeresht, E., Karimi Neghlani, P., Zhang, P., Peng, R., Andersson, J., Pejryd, L. & Joshi, S. V. (2018). Isothermal Oxidation Behavior of EBM-Additive Manufactured Alloy 718. In: Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C. (Ed.), Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications. Paper presented at 9th International Symposium on Superalloy 718 & Derivatives, Energy, Aerospace, and Industrial Application, Pittsburgh, Pennsylvania, USA, 3-6 June, 2018 (pp. 219-240). Springer
Open this publication in new window or tab >>Isothermal Oxidation Behavior of EBM-Additive Manufactured Alloy 718
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2018 (English)In: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., Springer, 2018, p. 219-240Conference paper, Published paper (Refereed)
Abstract [en]

Oxidation of Alloy 718 manufactured by electron beam melting (EBM) process has been undertaken in ambient air at 650, 700, and 800 °C for up to 168 h. At 800 °C, a continuous external chromia oxide enriched in (Cr, Ti, Mn, Ni) and an internal oxide that was branched structure of alumina formed, whereas at 650 and 700 °C, a continuous, thin and protective chromia layer was detected. The oxidation kinetics of the exposed EBM Alloy 718 followed the parabolic rate law with an effective activation energy of ~248 ± 22 kJ/mol in good agreement with values in the literature for conventionally processed chromia-forming Ni-based superalloys. The oxide scale formed on the surface perpendicular to the build direction was slightly thicker, and more adherent compared to the scale formed on the surface along the build direction, attributed to the varied grain texture in the two directions of the EBM-manufactured specimens. The increased oxygen diffusion and high Cr depletion found on the surface along the build direction were attributed to the fine grains and formation of vacancies/voids along this grain orientation.

Place, publisher, year, edition, pages
Springer, 2018
Series
The Minerals, Metals & Materials Series, ISSN 2367-1181, E-ISSN 2367-1696
Keywords
Additive manufacturing, Electron beam melting, Alloy 718, Oxidation behavior, Grain texture
National Category
Metallurgy and Metallic Materials Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-12347 (URN)10.1007/978-3-319-89480-5_13 (DOI)000445800500013 ()978-3-319-89479-9 (ISBN)978-3-319-89480-5 (ISBN)
Conference
9th International Symposium on Superalloy 718 & Derivatives, Energy, Aerospace, and Industrial Application, Pittsburgh, Pennsylvania, USA, 3-6 June, 2018
Note

First Online: 13 May 2018

Available from: 2018-10-26 Created: 2018-10-26 Last updated: 2020-02-05Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6610-1486

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