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Materials Science in Additive Manufacturing SLM of ODS steel: Process and properties

Figure 4. Macrostructure of the as-built SLM samples. VED and porosity values of the samples are presented. Magnification: ×100
Abbreviations: SLM: Selective laser melting; VED: Volumetric energy density

as evidenced by the density measurements presented in
Figure 3 and the microstructural observations in Figure 4.
It was demonstrated that when the same SLM process
parameters with pre-heating are employed, the relative
density is increased. This, in turn, facilitates the use of
higher scanning speeds to achieve equal density. This
finding is also consistent with the results obtained by Qin
et al. The range of VED from 80 to 110 J/mm , and pre-
3
32
heating allow for building samples with a density above
33
98%. Numerous studies have shown that the application
of HIP results in decreasing porosity of AM parts, thereby
enhancing their mechanical properties. This process is
34
planned to be studied in future research.
The obtained specimens exhibit no visible defects, such
as cracks or lack-of-fusion. While the highest material
density was obtained at VED values in a range of 90 –
100 J/mm , all samples printed within this energy range Figure 5. X-ray diffraction lines of mixed powder and fabricated
3
exhibited discontinuities between the contours and the specimens
Abbreviations: HT: Heat treatment; SLM: Selective laser melting
bulk material. In addition, their surface quality was inferior
compared to samples fabricated at higher VED values. To characterized by peaks corresponding to the body-
align both density and surface quality, a hybrid approach centered cubic lattice of iron, as shown in Figure 5. No
was implemented wherein the contours were built with the carbide phases were detected on the XRD, likely due to the
higher VED, and for the bulk material fabrication, VED of low volume fraction and nanoscale size (up to 300 nm) of
90 J/mm was applied. This method resulted in improved
3
material density by minimizing internal defects and carbide particles. Apparently, the mass fraction and size
enhanced surface quality. All subsequent analyses were of precipitates are lower than the XRD analysis method
35,36
allows to determine.
Similarly, determining Y O peaks
conducted on samples fabricated using this optimized 2 3
mode. is also challenging.
After heat treatment, a displacement of the peaks
3.3. Microstructural characterization slightly toward higher 2θ angles was observed. This
The X-ray diffraction (XRD) analysis revealed that phenomenon may be explained by the removal of internal
all samples exhibited the same phase composition, stresses. The peak corresponding to the position of the

Volume 4 Issue 1 (2025) 6 doi: 10.36922/MSAM025060004