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

swelling, which is quite necessary for nuclear reactor size of oxides in the materials obtained by SLM is larger (in
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application. the order of 30 – 60 nm), compared to particles obtained by
At present, the most extensively studied and powder metallurgy methods (typically 1 – 10 nm). 18-20 The
widely utilized method of strengthening involves the size of the yttrium-based dispersoids influences coherency,
incorporation of yttrium-based nano-oxides. Numerous and the size above 20 nm results in agglomeration and
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studies have demonstrated the efficacy of yttrium oxide coarsening, which reduces the positive effect of their
(Y O ) additions in enhancing the mechanical strength implementation.
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of steels and various other alloys. This enhancement in A notable challenge associated with the use of powders
strength is accompanied by an improvement in resistance derived from mechanical alloying is their splintered
to radiation-induced swelling under exposure to fission morphology, resulting from the high mechanical stresses
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ions or neutrons. Furthermore, dispersion strengthening applied during the process. This irregular particle shape
through nano-oxides significantly increases the hardness leads to poor flowability, which may be a limitation for
of the matrix material, thereby contributing to an the applications of mechanically alloyed powders in
improvement in wear resistance. The most common AM. Furthermore, studies have demonstrated that the
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addition of oxides is in the order of 0.25 – 1.0 wt.%. In morphology and particle size distribution of the powder
addition to yttrium, other elements may be added to form material significantly influences the final properties of
complex oxides such as Y X O , where X = Ti, Al, Zr, Hf, products fabricated through AM methods. To address
p
m
n
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V, Si, or Ta. The formation enthalpy of this type of oxide these limitations, mechanically alloyed powders require
is lower than that of Y O . spheroidization before use. The plasma spheroidization
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The fabrication of ODS steels remains a significant process involves a melting stage during which oxide
challenge. The most prevalent method of production particles tend to coagulate and migrate to the surface of
involves powder metallurgy, specifically mechanical the molten material due to their relatively lower density
alloying. 7-10 Creating products with complex geometries compared to the metallic matrix. Consequently, the
using powder metallurgy methods is an expensive and resulting spherical powder exhibits non-uniform oxide
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time-consuming process. One of the most common dispersion, which can negatively impact the mechanical
processes used to produce ODS steels is hot isostatic properties of the final product.
pressing (HIP) 2,11,12 and spark plasma sintering. 13-15 For the production of ODS steels by SLM, not only can
However, the use of these techniques is advisable in cases mechanically alloyed powders be used, but also various in
of production of simple and symmetrical shapes.
situ synthesis methods when oxides are forming during the
Another critical limitation is the relatively poor printing process. In Jia et al.’s study, pre-alloyed powders
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weldability of ODS steels, which increases the cost and were used for the in situ synthesis of nanoparticles in ODS
complexity of manufacturing components with intricate steel during SLM by controlling the partial pressure of
geometries. Consequently, there is growing interest in oxygen to prevent the abnormal growth of particles. This
exploring the feasibility of producing ODS steels through approach resulted in the formation of a microstructure
additive manufacturing (AM) techniques. AM has already characterized by finer nanoparticles, a higher volume
shown itself to be a state-of-the-art manufacturing process fraction, and a more uniform spatial distribution and
that allows the production of complex-shaped products size consistency compared to the majority of ODS steels
with high mechanical properties. One of the most manufactured using SLM with mechanically alloyed
commonly used technologies for the production of metal powders. The influence of the properties of in situ formed
products is selective laser melting (SLM). The process nitride and oxide particles in the ODS steel produced by
consists of layer-by-layer laser processing of powder laser powder bed fusion in a nitrogen-rich atmosphere
material according to a CAD model. SLM technology is (with Y O = 0.45 wt.%) was studied by Cakmak et al.
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already widely used in areas such as aerospace, medicine, The incorporation of nanosized Y O reduces the length
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and turbine engineering. An important feature of the SLM of typical for SLM as-built parts columnar grains (from
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process is the high cooling rates (10 – 10 K/s). 16 70 μm to 40 μm). In addition to Y O , Al-O aluminum
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A number of published studies demonstrate the oxides, and Y-Al-O yttrium aluminum oxides were
feasibility of producing ODS steels by SLM. A study observed in the microstructure. A significant challenge
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suggests that optimization of the process parameters in the production of ODS steel through in situ synthesis
could lead to a density of more than 98%. The results during the SLM process lies in the inherent complexity of
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also showed the possibility of obtaining a material with a the technological workflow. This complexity necessitates
uniform distribution of nanosized oxides. However, the precise monitoring and control of all process parameters
Volume 4 Issue 1 (2025) 2 doi: 10.36922/MSAM025060004