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Raza, T., Hurtig, K., Asala, G., Andersson, J., Svensson, L.-E. & Ojo, O. A. (2019). Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718. Metals, 9(8), Article ID 881.
Open this publication in new window or tab >>Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718
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2019 (English)In: Metals, E-ISSN 2075-4701, Vol. 9, no 8, article id 881Article in journal (Refereed) Published
Abstract [en]

The weldability of additive manufactured Alloy 718 was investigated in various heat-treated conditions. The microstructure of the base metal was examined in detail in order to understand the effect of different pre-weld heat treatments; i.e., solution, solution and aging, and hot isostatic pressing. After welding, the variation in total crack lengths, maximum crack length and the total number of cracks in the heat affected zone (HAZ) were used as criteria for the cracking susceptibility of each material condition where wrought Alloy 718 was used as the reference material. Selective laser melting (SLM) manufactured Alloy 718 was susceptible to HAZ cracking in all material conditions. Total crack lengths in HAZ were highest in the SLM as-built condition and lowest in the SLM hot isostatic pressed condition. The cracks that were found in the HAZ of the welded materials consisted of liquation cracks, with eutectic product surrounding the cracks, as well as cracks from which liquation products were absent.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
selective laser melting; Alloy 718; heat treatments; gas tungsten arc welding; heat affected zone cracking
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14595 (URN)10.3390/met9080881 (DOI)000484510000071 ()2-s2.0-85073280907 (Scopus ID)
Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2020-01-14
Raza, T., Andersson, J. & Svensson, L.-E. (2019). Varestraint testing of selective laser additive manufactured alloy 718: influence of grain orientation. Metals, 9(10), Article ID 1113.
Open this publication in new window or tab >>Varestraint testing of selective laser additive manufactured alloy 718: influence of grain orientation
2019 (English)In: Metals, ISSN 2075-4701, Vol. 9, no 10, article id 1113Article in journal (Refereed) Published
Abstract [en]

The effect of grain orientation on hot cracking susceptibility of selective laser additive manufactured Alloy 718 was investigated by Varestraint testing. Electron backscattered diffraction showed that cracks in heat affected zone (HAZ) of the welded samples occurred in high angle grain boundaries. The extent of HAZ cracking was smaller in samples tested parallel to the elongated grain orientation and larger in samples transverse to the elongated grain orientation. However, for solidification cracking in the weld metal, no significant difference with respect to grain orientation in the base metal was found. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

Place, publisher, year, edition, pages
MDPI AG, 2019
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14708 (URN)10.3390/met9101113 (DOI)2-s2.0-85074226227 (Scopus ID)
Funder
Vinnova
Available from: 2019-11-14 Created: 2019-11-14 Last updated: 2020-01-10
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
Raza, T., Andersson, J. & Svensson, L.-E. (2018). Microstructure of Selective Laser Melted Alloy 718 in As-Manufactured and Post Heat Treated Condition. Paper presented at 8th Swedish Production Symposium, SPS 2018; Waterfront Convention CentreStockholm; Sweden; 16 May 2018 through 18 May 2018; Code 147722. Procedia Manufacturing, 25, 450-458
Open this publication in new window or tab >>Microstructure of Selective Laser Melted Alloy 718 in As-Manufactured and Post Heat Treated Condition
2018 (English)In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, p. 450-458Article in journal (Refereed) Published
Abstract [en]

Manufacturing of Alloy 718 with selective laser melting (SLM) process faces several challenges. One of the challenges is the process-induced porosities in as-manufactured SLM parts. Another challenge is the microstructure of Alloy 718 that contains a high amount of segregating elements, such as MC-type carbides and γ/Laves phase eutectics in interdendritic regions. The microstructural heterogeneity in the as-manufactured SLM part unavoidably leads to mechanical heterogeneity and hence, post-processing heat treatments become necessary to achieve a homogeneous microstructure. Therefore, by investigating various post heat treatment options the knowledge on how to decrease/eliminate these segregations will be developed. © 2018 Elsevier B.V. All rights reserved.

Keywords
Selective laser melting, Alloy 718, Process parameters, Post heat treatments
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13921 (URN)10.1016/j.promfg.2018.06.100 (DOI)2-s2.0-85065659917 (Scopus ID)
Conference
8th Swedish Production Symposium, SPS 2018; Waterfront Convention CentreStockholm; Sweden; 16 May 2018 through 18 May 2018; Code 147722
Funder
VinnovaSwedish National Space Board
Available from: 2019-06-05 Created: 2019-06-05 Last updated: 2019-07-26Bibliographically approved
Raza, T., Andersson, J. & Svensson, L.-E. (2018). Varestraint weldability testing of additive manufactured alloy 718. Science and technology of welding and joining, 23(7), 606-611
Open this publication in new window or tab >>Varestraint weldability testing of additive manufactured alloy 718
2018 (English)In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 23, no 7, p. 606-611Article in journal (Refereed) Published
Abstract [en]

The weldability in terms of susceptibility towards hot cracking of selective laser melted (SLM) Alloy 718 was investigated and wrought Alloy 718 was used as reference material. Varestraint testing was carried out by means of investigating the weldability in three conditions; (1) SLM as-built, (2) hot isostatic pressing at 1160°C at 105MPa for 3h and (3) wrought Alloy 718 in the mill-annealed condition. The material exhibited intergranular cracking in all three conditions; however,theSLMHIPedconditionhadanincreasedmagnitudeofcracksusceptibilityatallstrain levels.TheincreasedsensitivityoftheHIPedmaterialwasduetothesignificantlylargergrainsize incomparison.TheSLMas-builtconditionshowedthesamedegreeofcrackingasthewrought material.

Keywords
Weldability; Selective laser melting; Alloy718
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-12077 (URN)10.1080/13621718.2018.1437338 (DOI)000440719100008 ()2-s2.0-85041916665 (Scopus ID)
Funder
VINNOVASwedish National Space Board
Note

Published online: 12 Feb 2018

Available from: 2018-02-13 Created: 2018-02-13 Last updated: 2019-01-28Bibliographically approved
Raza, T. (2016). A review of selective laser melting: Process parameters and its influence on microstructure, defects and strength in superalloy Alloy 718.. In: : . Paper presented at Aerospace Technology Congress 2016, Stockholm, Sweden, October 11-12, 2016.
Open this publication in new window or tab >>A review of selective laser melting: Process parameters and its influence on microstructure, defects and strength in superalloy Alloy 718.
2016 (English)Conference paper, Oral presentation only (Other academic)
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-10582 (URN)
Conference
Aerospace Technology Congress 2016, Stockholm, Sweden, October 11-12, 2016
Available from: 2017-01-13 Created: 2017-01-13 Last updated: 2018-08-12Bibliographically approved
Raza, T., Andersson, J. & Svensson, L. E. (2016). A review of the effect of selective laser melting process parameters and its influence on microstructure, defects and strength in the iron-nickel based superalloy Alloy 718. In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016. Paper presented at 7th International Swedish Production Symposium, SPS16, Lund, Sweden, October 25–27, 2016 (pp. 1-8). Lund: Swedish Production Academy
Open this publication in new window or tab >>A review of the effect of selective laser melting process parameters and its influence on microstructure, defects and strength in the iron-nickel based superalloy Alloy 718
2016 (English)In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, p. 1-8Conference paper, Published paper (Refereed)
Abstract [en]

This review presents a basic insight into the powder-bed fusion process selective laser melting (SLM), with focus on the microstructure and mechanical properties of the iron-nickel based superalloy Alloy 718. The microstructures and mechanical properties of SLM components are highly affected by the process parameters. Laser power, scanning speed, powder layer thickness and hatch distance, are the primary process parameters which can be adjusted in order to influence the microstructure and minimize potential defects. SLM-manufactured Alloy 718 generally produce a columnar microstructure which is a result of epitaxial formation and dendritic grain growth in the build direction (perpendicular to the substrate). Gas porosity, lack of fusion and residual stresses are process induced problems observed in SLM-manufactured Alloy 718. The microstructure of the as-manufactured Alloy 718 is susceptible to microsegregation of Nb and Mo as well as to subsequent non-equilibrium phase transformation. A post-process heat treatment of as-manufactured Alloy 718 is required in order to improve general mechanical properties and to relieve the residual stresses. The tensile strength, yield strength and hardness of heat treated SLM-manufactured Alloy 718 are comparable to that of wrought material.

Place, publisher, year, edition, pages
Lund: Swedish Production Academy, 2016
Keywords
Selective laser melting, process parameters, Alloy 718, microstructure, defects, strength
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-10142 (URN)
Conference
7th International Swedish Production Symposium, SPS16, Lund, Sweden, October 25–27, 2016
Available from: 2016-12-07 Created: 2016-11-16 Last updated: 2018-08-12Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-4598-4790

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