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Materials Science in Additive Manufacturing Quality of a 3D-printed steel part

The microstructural characteristics of LPBF the need for comprehensive global standards has become
components play a crucial role in determining their increasingly critical. Since 2011, the ISO TC/261 and ASTM
performance. AM steel grades, which typically exhibit F42 committees have collaborated to establish unified AM
martensitic microstructures in conventional processing, standards, with over 30 joint ISO/ASTM groups working
may contain small amounts of retained austenite due to avoid duplication and streamline resources. In 2016,
to the rapid cooling rates associated with AM. This America Makes and American National Standards Institute
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behavior has been observed in various steels, including launched the Additive Manufacturing Standardization
precipitation hardening steels like 17-4 PH, 21-23 maraging Collaborative to accelerate the creation of industry-wide
steels such as 18-Ni300, 24,25 and martensitic stainless steels standards, identifying 93 gaps, including 18 high-priority
like AISI420. These rapid cooling rates often lead to areas requiring further research. Despite the challenges,
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fine-grained microstructures, significantly influencing collaboration between ISO, CEN, and ASTM ensures the
the mechanical properties of the final component. 24,25 global adoption of these standards, with CEN integrating
Furthermore, the cooling rate, laser parameters, and them into European norms, and regular stakeholder
melt pool size significantly affect the microstructure and meetings helping to accelerate AM standardization.
texture of AM components, often leading to anisotropy Specifically addressing LPBF, recent advancements
and specific grain orientations that depend on the have enabled the production of complex geometries with
process parameters. 27-29 It has been demonstrated that high precision. Studies on maraging steels, 36-38 particularly
components fabricated from AM steel grades frequently 1.2709, have demonstrated superior mechanical properties,
exhibit a fine-grained microstructure due to these rapid including enhanced strength and toughness when
cooling rates. The boundaries of melt pools can be visible processed through LPBF. 39,40 Furthermore, recent studies
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as a superstructure, 28,29 and elongated, oriented grains have provided new insights into process optimization
are commonly observed, depending on the processing and microstructural control in LPBF maraging steel, 41,42
parameters. 22,30,31 reinforcing the relevance of our integrated approach.
The mechanical properties of AM-fabricated steel Although maraging steel fabricated by LPBF has been
grades frequently meet or exceed conventional standards studied, few works have systematically linked feedstock
for technical applications. Grain refinement leads to uniformity, microstructure, and non-destructive
significant improvements in yield and ultimate tensile mechanical evaluation in a single integrated approach.
strength. For instance, a low remaining porosity (0.1%) This gap complicates consistent quality assurance and
results in ductile failure modes with elongation values impedes broader industrial adoption for high-performance
comparable to wrought metal. However, a high porosity applications. Therefore, the present study investigates a
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(2.4%) leads to brittle failure modes and drastically 3D-printed maraging steel demonstration part with the
reduced elongation. As such, the static strength of AM following objectives: (1) To characterize powder feedstock
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components is highly dependent on both the density and morphology and composition to assess uniformity, (2) to
microstructure produced during the AM process. AM analyze the resulting geometry, surface roughness, density,
parts often have finer microstructures than conventionally and microstructure of the LPBF-built part, (3) to evaluate
manufactured components, resulting in higher static mechanical behavior through non-destructive hardness-
strength. The yield strength of AM specimens generally based methods, and (4) to benchmark our results against
follows the Hall–Petch relationship, as demonstrated established data from the feedstock supplier and existing
in various AM methods, using Ti-6Al-4V. The maraging steel literature. By correlating these findings, we
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microstructure of AM-fabricated parts is also anisotropic demonstrate a streamlined path for quality assessment in
with respect to the building direction, influencing tensile metal AM, bridging feedstock considerations and final part
properties and elongation. 27,34,35 Typically, strength and performance. Our integrated analysis thus reinforces the
strain to failure are lower along the build direction than potential of LPBF maraging steel to meet critical mechanical
orthogonal to it. demands, contributing new insights into standardized
evaluation procedures for advanced AM applications.
Due to the subtle differences between each AM
technique and the hundreds of systems currently available, 2. Integrated AM: Process, materials, and
keeping up with this rapidly evolving technology is part fabrication
challenging. New entrants and quickly developing
innovations further complicate purchasing decisions, 2.1. LPBF of metals and 3D-printing workflow
making it difficult for standards to keep pace. As the metal Often referred to by different names, powder bed fusion
AM sector progresses toward industrial-scale production, (or melting) is an AM process where thermal energy is

Volume 4 Issue 2 (2025) 3 doi: 10.36922/MSAM025040002