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Materials 2017, 10(1), 8; doi:10.3390/ma10010008

Comparison of Maraging Steel Micro- and Nanostructure Produced Conventionally and by Laser Additive Manufacturing

1
Department Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf, Germany
2
Institut für Eisenhüttenkunde, Rheinisch-Westfälische Technische Hochschule Aachen, Intzestrasse 1, 52072 Aachen, Germany
3
Competence Area Additive Manufacturing and Functional Layers, Fraunhofer Institut für Lasertechnik, Steinbachstrasse 15, 52074 Aachen, Germany
*
Author to whom correspondence should be addressed.
Academic Editor: Guillermo Requena
Received: 1 December 2016 / Revised: 16 December 2016 / Accepted: 20 December 2016 / Published: 24 December 2016
(This article belongs to the Special Issue Metals for Additive Manufacturing)
View Full-Text   |   Download PDF [12056 KB, uploaded 24 December 2016]   |  

Abstract

Maraging steels are used to produce tools by Additive Manufacturing (AM) methods such as Laser Metal Deposition (LMD) and Selective Laser Melting (SLM). Although it is well established that dense parts can be produced by AM, the influence of the AM process on the microstructure—in particular the content of retained and reversed austenite as well as the nanostructure, especially the precipitate density and chemistry, are not yet explored. Here, we study these features using microhardness measurements, Optical Microscopy, Electron Backscatter Diffraction (EBSD), Energy Dispersive Spectroscopy (EDS), and Atom Probe Tomography (APT) in the as-produced state and during ageing heat treatment. We find that due to microsegregation, retained austenite exists in the as-LMD- and as-SLM-produced states but not in the conventionally-produced material. The hardness in the as-LMD-produced state is higher than in the conventionally and SLM-produced materials, however, not in the uppermost layers. By APT, it is confirmed that this is due to early stages of precipitation induced by the cyclic re-heating upon further deposition—i.e., the intrinsic heat treatment associated with LMD. In the peak-aged state, which is reached after a similar time in all materials, the hardness of SLM- and LMD-produced material is slightly lower than in conventionally-produced material due to the presence of retained austenite and reversed austenite formed during ageing. View Full-Text
Keywords: laser metal deposition; additive manufacturing; maraging steel; intrinsic heat treatment; precipitation strengthening; austenite reversion; atom probe tomography laser metal deposition; additive manufacturing; maraging steel; intrinsic heat treatment; precipitation strengthening; austenite reversion; atom probe tomography
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Jägle, E.A.; Sheng, Z.; Kürnsteiner, P.; Ocylok, S.; Weisheit, A.; Raabe, D. Comparison of Maraging Steel Micro- and Nanostructure Produced Conventionally and by Laser Additive Manufacturing. Materials 2017, 10, 8.

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