PSI - Issue 23

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ScienceDirect

Procedia Structural Integrity 23 (2019) 215–220 Structural Integrity Procedia 00 (2019) 000–000 Structural Integrity Procedia 00 (2019) 000–000

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9th International Conference on Materials Structure and Micromechanics of Fracture E ff ect of additive manufacturing on fatigue crack propagation of a gas turbine superalloy Mattias Calmunger a, ∗ , Robert Eriksson b , Thomas Lindstro¨m b , Daniel Leidermark b 9th International Conference on Materials Structure and Micromechanics of Fracture E ff ect of additive manufacturing on fatigue crack propagation of a gas turbine superalloy Mattias Calmunger a, ∗ , Robert Eriksson b , Thomas Lindstro¨m b , Daniel Leidermark b

a Division of Engineering Materials, Linko¨ping University, 58183 Linko¨ping, Sweden b Division of Solid Mechanics, Linko¨ping University, 58183 Linko¨ping, Sweden a Division of Engineering Materials, Linko¨ping University, 58183 Linko¨ping, Sweden b Division of Solid Mechanics, Linko¨ping University, 58183 Linko¨ping, Sweden

© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the ICMSMF organizers Abstract Additive manufacturing (AM) o ff ers new possibilities in gas turbine technology by, for example, allowing for more complex internal cooling channels. One such application, where AM can improve the function by new designs, is burners. However, the fatigue performance, especially the fatigue crack propagation of AM gas turbine material, is not fully known. In the present study, an AM adopted nickel-based superalloy Hastelloy X was subjected to low-cycle fatigue (LCF) loading at room temperature. The LCF tests were conducted in strain control on additive manufactured smooth bars with two di ff erent build orientations (with an angle of 0 ◦ and 90 ◦ relative to the building platform). During the the manufacturing process, an AM component often solidifies with a dendritic structure. Initial fractography of the ruptured LCF specimens revealed that the dendritic structure was visible on the fracture surface. It was noted that the dendritic structure could easily be mistaken for regular striations although they represent a di ff erent fracture mechanism. The fracture surfaces were therefore cross sectioned and possible correlations between fracture surface characteristics and underlying microstructure were studied using electron backscatter di ff raction and electron channelling contrast imaging. The outcome was used to discuss the e ff ect of AM microstructure on the LCF crack propagation. c 2019 The Authors. Published by Elsevier B.V. his is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) eer-review under responsibility of the scientific committe of the IC MSMF organizers. Keywords: Additive manufacturing; Fatigue; Fractography; EBSD Abstract Additive manufacturing (AM) o ff ers new possibilities in gas turbine technology by, for example, allowing for more complex internal cooling channels. One such application, where AM can improve the function by new designs, is burners. However, the fatigue performance, especially the fatigue crack propagation of AM gas turbine material, is not fully known. In the present study, an AM adopted nickel-based superalloy Hastelloy X was subjected to low-cycle fatigue (LCF) loading at room temperature. The LCF tests were conducted in strain control on additive manufactured smooth bars with two di ff erent build orientations (with an angle of 0 ◦ and 90 ◦ relative to the building platform). During the the manufacturing process, an AM component often solidifies with a dendritic structure. Initial fractography of the ruptured LCF specimens revealed that the dendritic structure was visible on the fracture surface. It was noted that the dendritic structure could easily be mistaken for regular striations although they represent a di ff erent fracture mechanism. The fracture surfaces were therefore cross sectioned and possible correlations between fracture surface characteristics and underlying microstructure were studied using electron backscatter di ff raction and electron channelling contrast imaging. The outcome was used to discuss the e ff ect of AM microstructure on the LCF crack propagation. c 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the scientific committee of the IC MSMF organizers. Keywords: Additive manufacturing; Fatigue; Fractography; EBSD

1. Introduction 1. Introduction

With the use of additive manufacturing (AM), new possibilities arise to optimize components for better perfor mance. Powder bed fusion-laser (PBF-L) is one AM technique where a thin layer of metallic powder is distributed on a substrate, and then melted with a laser beam to achieve one layer of solid material. A new layer of powder is then distributed, and the procedure continues until a complete component has been manufactured. However, due to the rapid solidification and high temperature gradients during AM, the material will receive elongated grains in the building direction (c.f. Saarima¨ki et al. (2018); Wang (2012)), which give rise to the anisotropic material behaviour With the use of additive manufacturing (AM), new possibilities arise to optimize components for better perfor mance. Powder bed fusion-laser (PBF-L) is one AM technique where a thin layer of metallic powder is distributed on a substrate, and then melted with a laser beam to achieve one layer of solid material. A new layer of powder is then distributed, and the procedure continues until a complete component has been manufactured. However, due to the rapid solidification and high temperature gradients during AM, the material will receive elongated grains in the building direction (c.f. Saarima¨ki et al. (2018); Wang (2012)), which give rise to the anisotropic material behaviour

2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the ICMSMF organizers 10.1016/j.prostr.2020.01.089 ∗ Corresponding author. Tel.: + 46-13-281197. E-mail address: mattias.calmunger@liu.se 2210-7843 c 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the scientific committee of the IC MSMF organizers. ∗ Corresponding author. Tel.: + 46-13-281197. E-mail address: mattias.calmunger@liu.se 2210-7843 c 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of the scientific committee of the IC MSMF organizers.