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Influence of laser powder bed fusion process parameters on voids, cracks, and microhardness of nickel-based superalloy alloy 247LC
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)
University West, Department of Engineering Science, Division of Welding Technology. (PTW)ORCID iD: 0000-0001-9065-0741
Materials Technology Additive Manufacturing Product Development-Industrial Gas Turbines, Siemens Industrial Turbomachinery, Finspång, SE-612 83, Sweden.
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0002-7675-7152
2020 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 13, no 17, article id 3770Article in journal (Refereed) Published
Abstract [en]

The manufacturing of parts from nickel-based superalloy Alloy 247LC by laser powder bed fusion (L-PBF) is challenging, primarily owing to the alloy’s susceptibility to cracks. Apart from the cracks, voids created during the L-PBF process should also be minimized to produce dense parts. In this study, samples of Alloy 247LC were manufactured by L-PBF, several of which could be produced with voids and crack density close to zero. A statistical design of experiments was used to evaluate the influence of the process parameters, namely laser power, scanning speed, and hatch distance (inherent to the volumetric energy density) on void formation, crack density, and microhardness of the samples. The window of process parameters, in which minimum voids and/or cracks were present, was predicted. It was shown that the void content increased steeply at a volumetric energy density threshold below 81 J/mm3. The crack density, on the other hand, increased steeply at a volumetric energy density threshold above 163 J/mm3. The microhardness displayed a relatively low value in three samples which displayed the lowest volumetric energy density and highest void content. It was also observed that two samples, which displayed the highest volumetric energy density and crack density, demonstrated a relatively high microhardness; which could be a vital evidence in future investigations to determine the fundamental mechanism of cracking. The laser power was concluded to be the strongest and statistically most significant process parameter that influenced void formation and microhardness. The interaction of laser power and hatch distance was the strongest and most significant factor that influenced the crack density. © 2020 by the authors.

Place, publisher, year, edition, pages
2020. Vol. 13, no 17, article id 3770
Keywords [en]
Design of experiments; Hatches; Microhardness; Superalloys, Fundamental mechanisms; Fusion process; Nickel- based superalloys; Process parameters; Scanning speed; Statistical design of experiments; Void formation; Volumetric energy densities, Nickel alloys
National Category
Manufacturing, Surface and Joining Technology
Identifiers
URN: urn:nbn:se:hv:diva-15831DOI: 10.3390/MA13173770ISI: 000571624500001Scopus ID: 2-s2.0-85090499027OAI: oai:DiVA.org:hv-15831DiVA, id: diva2:1469021
Funder
Knowledge Foundation, 20160281Available from: 2020-09-19 Created: 2020-09-19 Last updated: 2021-11-18
In thesis
1. Processability of Laser Powder Bed Fusion of Alloy 247LC: Influence of process parameters on microstructure and defects
Open this publication in new window or tab >>Processability of Laser Powder Bed Fusion of Alloy 247LC: Influence of process parameters on microstructure and defects
2020 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is about laser powder bed fusion (L-PBF) of the nickel-based superalloy: Alloy 247LC. Alloy 247LC is used mainly in gas turbine blades and processing the blades with L-PBF confers performance advantage over the blades manufactured with conventional methods. This is mainly because L-PBF is more suitable, than conventional methods, for manufacturing the complex cooling holes in the blades. The research was motivated by the need for academia and industry to gain knowledge about the processability of the alloy using L-PBF. The knowledge is essential in order to eventually solve the problem of cracking which is a major problem when manufacturing the alloy. In addition, dense parts with low void content should be manufactured and the parts should meet the required performance. Thus, the thesis answered some of the important questions related to process parameter-microstructure-defect relationships.

The thesis presented an introduction in chapter 1. A literature review was made in chapter 2 to 4. In chapter 2, the topic of additive manufacturing was introduced followed by an overview of laser powder bed fusion. Chapter 3 focused on superalloys. Here, a review was made from the broader perspective of superalloys but was eventually narrowed down to the characteristics of nickelbased superalloys and finally Alloy 247LC. Chapter 4 reviewed the main research on L-PBF of Alloy 247LC. The methodology applied in the thesis was discussed in chapter 5. The thesis applied statistical design of experiments to show the influence of process parameters on the defects and microstructure, so a detail description of the method was warranted. This was given at the beginning of chapter 5 and followed by the description of the L-PBF manufacturing and the characterization methods. The main results and discussions, in chapter 6, included a preliminary investigation on how the process parameters influenced the amount of discontinuity in single track samples. This was followed by the results and discussions on the investigation of voids, cracks and microhardness in cube samples (detail presentation was given in the attached paper B). Finally, the thesis presented results of the microstructure obtainable in L-PBF manufactured Alloy 247LC. The initial results of the microstructure investigation were presented in paper A.

Place, publisher, year, edition, pages
Trollhättan: University West, 2020. p. 59
Series
Licentiate Thesis: University West ; 31
Keywords
laser powder bed fusion; Alloy 247LC; additive manufacturing; nickel-based superalloys; processability; cracks; voids.
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-16114 (URN)978-91-88847-71-3 (ISBN)978-91-88847-70-6 (ISBN)
Supervisors
Available from: 2020-12-14 Created: 2020-12-14 Last updated: 2021-11-30Bibliographically approved
2. Processability of Laser Powder Bed Fusion of Alloy 247LC-Influence of process parameters on microstructure and defects
Open this publication in new window or tab >>Processability of Laser Powder Bed Fusion of Alloy 247LC-Influence of process parameters on microstructure and defects
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is about laser powder bed fusion (L-PBF) of the nickel-basedsuperalloy Alloy 247LC. Alloy 247LC is mainly used in gas turbine blades and processing the blades with L-PBF may confer performance advantage over the blades manufactured with conventional methods. This is mainly because L-PBFis more suitable, than conventional methods, for manufacturing the complex cooling holes in the blades. The research was motivated by the need for academia and industry to gain knowledge about the processability of the alloy using L-PBF. The knowledge is essential to eventually solve the problem of cracking encountered when processing the alloy. In addition, dense parts with low void content should be processed and the microstructure and properties should meett he required performance. Heat-treatment is usually performed to acquire final properties, so it is also of interest to study this aspect. Thus, the thesis answered some of the important questions related to process parameter-microstructure- property relationships.

Abstract [sv]

Populärvetenskaplig sammanfattning

Denna avhandling handlar om laserpulverbäddsmältning (L-PBF) av legeringen247LC. Legering 247LC används i gasturbinblad och tillverkningen av bladen medL-PBF ger fördelar i förhållande till bladen tillverkade med konventionella metoder. Detta beror huvudsakligen på att L-PBF är mer lämpad än konventionella metoder för att tillverka de komplexa geometrier som krävs förbladen. Forskningen var motiverad utifrån behovet hos akademi och industri att få kunskap om legeringens processbarhet gällande L-PBF. Kunskapen är nödvändig för att kunna lösa problemet med sprickbildning, vilket är ett stort problem vid tillverkningen av legeringen. Avhandlingen besvarade några av de viktiga frågorna relaterade till förhållandet mellan processparametrar och mikrostruktur.

Place, publisher, year, edition, pages
Trollhättan: University West, 2021. p. 134
Series
PhD Thesis: University West ; 45
Keywords
Laser powder bed fusion, Alloy 247LC, additive manufacturing, nickel-based superalloys, processability, cracks, voids, Laserpulverbäddssmältning, legering 247LC, additiv tillverkning, superlegeringar, processbarhet, sprickor, porositet.
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-17799 (URN)978-91-89325-05-0 (ISBN)978-91-89325-06-7 (ISBN)
Public defence
2021-12-16, F131 + zoom, Gustava Melins gata 2, Trollhättan, 13:00 (English)
Opponent
Supervisors
Funder
VinnovaKnowledge Foundation
Note

Till avhandlingen hör en inskickad artikel (paper D) , som inte visas  nu.

Available from: 2021-11-22 Created: 2021-11-18 Last updated: 2022-01-19Bibliographically approved

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Adegoke, OlutayoAndersson, JoelPederson, Robert

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