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. 2023 Mar 16;16(6):2397.
doi: 10.3390/ma16062397.

Assessment of Ferritic ODS Steels Obtained by Laser Additive Manufacturing

Lucas Autones  1 , Pascal Aubry  2 , Joel Ribis  1 , Hadrien Leguy  1 , Alexandre Legris  3 , Yann de Carlan  1
Affiliations

Assessment of Ferritic ODS Steels Obtained by Laser Additive Manufacturing

Lucas Autones et al. Materials (Basel). .

Abstract

This study aims to assess the potential of Laser Additive Manufacturing (LAM) for the elaboration of Ferritic/Martensitic ODS steels. These materials are usually manufactured by mechanical alloying of powders followed by hot consolidation in a solid state. Two Fe-14Cr-1W ODS powders are considered for this study. The first powder was obtained by mechanical alloying, and the second was through soft mixing of an atomized Fe-14Cr steel powder with yttria nanoparticles. They are representative of the different types of powders that can be used for LAM. The results obtained with the Laser Powder Bed Fusion (LPBF) process are compared to a non-ODS powder and to a conventional ODS material obtained by Hot Isostatic Pressing (HIP). The microstructural and mechanical characterizations show that it is possible to obtain nano-oxides in the material, but their density remains low compared to HIP ODS steels, regardless of the initial powders considered. The ODS obtained by LAM have mechanical properties which remain modest compared to conventional ODS. The current study demonstrated that it is very difficult to obtain F/M ODS grades with the expected characteristics by using LAM processes. Indeed, even if significant progress has been made, the powder melting stage strongly limits, for the moment, the possibility of obtaining fine and dense precipitation of nano-oxides in these steels.

Keywords: Oxide Dispersion Strengthened (ODS) steels; Powder Bed Fusion (PBF); Small Angle X-ray Scattering (SAXS); additive manufacturing; ferritic steels; transmission electron microscopy (TEM).

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
SEM images of the matrix Fe-14Cr-1W-0.22Ti powder A-Ti (a), of the «composite» ODS powder SM-R0.5 (b), and the mechanically alloyed ODS powder MA-R0.2 (c).
Figure 2
Figure 2
Picture of samples built on the 316L substrate plate using the ODS powder SM-R0.5.
Figure 3
Figure 3
Relative density of the SLM consolidated samples, measured by Archimedes method, in relation to the volume energy density applied with powders A-Ti, SM-R0.5, and MA-R0.5.
Figure 4
Figure 4
Optical images after etching showing the melt pool geometry and the microstructure along the build direction (BD) of SLM samples consolidated with powder A (a,d), ODS powder SM-R0.5 (b,e), ODS powder MA-R0.2 (c,f).
Figure 5
Figure 5
IPF maps obtained by EBSD of the microstructure along the build direction (BD) of SLM samples consolidated with powder A (a), ODS powder SM-R0.5 (b), and ODS powder MA-R0.2 (c).
Figure 6
Figure 6
SEM-BSE images of SLM samples built with the ODS powder SM-R0.5 (a) and ODS powder MA-R0.2 (b). Red circles highlight the Y-rich coarse phases inside the parts, and red numbers identify particles on which EDX analysis is performed.
Figure 7
Figure 7
SEM-BSE images (×10 k) showing the nanoparticles distribution inside the microstructure of the SLM samples consolidated with powder A (a), ODS powder SM-R0.5 (b), and ODS powder MA-R0.2 (c).
Figure 8
Figure 8
Particle size distribution measured with SEM images of SLM ODS samples built with powder SM-R0.5 (a) and powder MA-R0.2 (b).
Figure 9
Figure 9
STEM images of the precipitation inside the SLM part consolidated with the ODS powder SM-R0.5 at magnifications (a) ×20 k, (b) ×30 k, and (c) ×150 k.
Figure 10
Figure 10
Particle size distribution measured with TEM images of SLM ODS samples built with powder SM-R0.5.
Figure 11
Figure 11
HR-TEM image of a 2 nm particle in the SLM sample built with composite ODS powder SM-R0.5.
Figure 12
Figure 12
STEM EDX maps of the SLM sample built with composite ODS powder SM-R0.5. Each color map corresponds to an element and its characteristic spectral line.
Figure 13
Figure 13
Experimental SAXS data and fits of the conventional HIPed ODS and the SLM materials.
Figure 14
Figure 14
Tensile stress-strain curves at 20 °C, 650 °C and 700 °C of the (a) HIP ODS and the SLM samples built with powders (b) A, (c) MA-R0.2, and (d) SM-R0.5.
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