Abstract
The Laser Powder Bed Fusion process involves complex thermodynamic and heat transfer mechanisms which results in a complicated understanding of the material's microstructure and phase transformation processes. In the case of additive manufacturing maraging steels, these present heterogeneous structures which mainly consist of Body-Centred Tetragonal (BCT) martensite and retained austenite (Face-Centred Cubic (FCC) phase structure), unlike conventionally processed material. Research has already been done on the competitive or collaborative nature of austenite growth/reversion and precipitation in these materials. However, for Laser Powder Bed Fusion maraging steels, studies have focused on either the effect of the heterogeneous structures on austenite reversion kinetics or the formation, evolution and behaviour of precipitation. Still, no comprehensive research exists that covers in detail the relation between solute heterogeneity from the meso- to the nanoscale and its influence on both phase distribution and ageing physical phenomena. To do so, multiscale chemical analyses and microstructural characterisation techniques were used to investigate a maraging steel M300 in different transformed conditions: as-built, aged at 480 and 540 °C. The results showed that competing mechanisms during printing caused segregation at the mesoscale, which remains in aged samples. Vaporisation led to Cr segregation, while melt convections caused Ni and Ti depletion at melt pool boundaries. Retained austenite location was found at melt pool boundaries and away from them on the as-built structure. Its preferential location remains unclear. Dissimilarities from conventional material were identified in nanosized clustering and precipitates on aged samples.
| Original language | English |
|---|---|
| Article number | 104494 |
| Journal | Additive Manufacturing |
| Volume | 94 |
| DOIs | |
| State | Published - Aug 25 2024 |
Funding
The authors greatly acknowledge the support provided to this work by the European Commission, Research Fund for Coal and Steel Programme under the contract RFCS-2022\u2013101112371. The authors want to thank ArcelorMittal Global R&D Slab (Avil\u00E9s, Spain) for providing us with the material. The authors very much appreciate the support of the National Electron Microscopy Centre (Complutense University of Madrid), the Electron Microscopy Service facility (Polytechnic University of Valencia), the Advanced Microscopy Laboratory (Zaragoza University), the metallography and microscopy laboratories from CENIM-CSIC. The authors would also like to acknowledge Isaac Toda-Caraballo and Roger Castellote-\u00C1lvarez for their support with EPMA data post processing. APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory (Ref. CNMS2022-B-01449). The authors would like to thank James Burns for assistance in performing APT sample preparation and running the APT experiments. The authors greatly acknowledge the support provided to this work by the European Commission, Research Fund for Coal and Steel Programme under the contract RFCS-2022-101112371. The authors want to thank ArcelorMittal Global R&D Slab (Avil\u00E9s, Spain) for providing us with the material. The authors very much appreciate the support of the National Electron Microscopy Centre (Complutense University of Madrid), the Electron Microscopy Service facility (Polytechnic University of Valencia), the Advanced Microscopy Laboratory (Zaragoza University), the metallography and microscopy laboratories from CENIM-CSIC. The authors would also like to acknowledge Isaac Toda-Caraballo and Roger Castellote-\u00C1lvarez for their support with EPMA data post processing. APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory (Ref. CNMS2022-B-01449). The authors would like to thank James Burns for assistance in performing APT sample preparation and running the APT experiments. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).
Keywords
- Atom probe tomography
- Laser powder bed fusion
- Maraging steels
- Precipitation
- Retained/reverted austenite
