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Microstructure evolution along build direction for thin-wall components fabricated with wire-direct energy deposition

Janmejay Dattatraya Kulkarni (Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, Hyderabad, India)
Suresh Babu Goka (Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, Hyderabad, India)
Pradeep Kumar Parchuri (Joining and Welding Research Institute, Osaka University, Ibaraki, Japan)
Hajime Yamamoto (Joining and Welding Research Institute, Osaka University, Ibaraki, Japan)
Kazuhiro Ito (Joining and Welding Research Institute, Osaka University, Ibaraki, Japan)
Suryakumar Simhambhatla (Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, Hyderabad, India)

Rapid Prototyping Journal

ISSN: 1355-2546

Article publication date: 12 July 2021

Issue publication date: 3 August 2021

378

Abstract

Purpose

The use of a gas metal arc welding-based weld-deposition, referred to as wire-direct energy deposition or wire-arc additive manufacturing, is one of the notable additive manufacturing methods for producing metallic components at high deposition rates. In this method, the near-net shape is manufactured through layer-by-layer weld-deposition on a substrate. However, as a result of this sequential weld-deposition, different layers are subjected to different types of thermal cycles and partial re-melting. The resulting microstructural evolution of the material may not be uniform. Hence, the purpose of this study is to assess microstructure variation along with the lamination direction (or build direction).

Design/methodology/approach

The study was carried out for two different boundary conditions, namely, isolated condition and cooled condition. The microstructural evolution across the layers is hypothesized based on experimental assessment; this included microhardness, scanning electron microscopy imaging and electron backscatter diffraction analysis. These conditions subsequently collaborated with the help of thermal modeling of the process.

Findings

During a new layer deposition, the previous layer also is subject to re-melt. While the newly added layer undergoes rapid cooling through a combination of convection, conduction and radiation losses, the penultimate layer, sees a slower cooling curve due to its smaller exposure area. This behavior of rapid-solidification and subsequent re-melting and re-solidification is a progressing phenomenon across the layers and the bulk of the layers have uniform grains due to this remelt-re-solidification phenomenon.

Research limitations/implications

This paper studies the microstructure variation along with the build direction for thin-walled components fabricated through weld-deposition. This study would be helpful in addressing the issue of anisotropy resulting from the distinctive thermal history of each layer in the overall theme of metal additive manufacturing.

Originality/value

The unique aspect of this paper is the postulation of a generic hypothesis, based on experimental findings and supported by thermal modeling of the process, for remelt-re-solidification phenomenon followed by temperature raising/lowering repetitively in every layer deposition across the layers. This is implemented for different types of base plate conditions, revealing the role of boundary conditions on the microstructure evolution.

Keywords

Acknowledgements

The authors acknowledge JWRI, Osaka University for providing facilities for a part of this work under the Sakura Science Program of Japan Science and Technology Agency (JST) and JWRI International Joint Research Collaborators (JIJReC) program 2017.

Citation

Kulkarni, J.D., Goka, S.B., Parchuri, P.K., Yamamoto, H., Ito, K. and Simhambhatla, S. (2021), "Microstructure evolution along build direction for thin-wall components fabricated with wire-direct energy deposition", Rapid Prototyping Journal, Vol. 27 No. 7, pp. 1289-1301. https://doi.org/10.1108/RPJ-04-2020-0085

Publisher

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Emerald Publishing Limited

Copyright © 2021, Emerald Publishing Limited

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