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

The appeal of AM lies in its nearly limitless design processes follow a broadly similar workflow. The process
possibilities, enabling the fabrication of parts with begins with a 3D computer-aided design (CAD) model,
functionalities that are often unattainable through conventional which can be developed from scratch, reverse-engineered,
manufacturing methods. Entire assemblies can be constructed or generated through imaging. This model is then sliced into
at one go, reducing the need for multiple components and thin layers, each with a thickness ranging from 20 to several
simplifying supply chains. AM constructs components with hundred microns, depending on the specific AM technique.
precision, using only the material required for each layer, The part is constructed by depositing material layer by
making it an ideal solution for creating customized, unique layer and selectively melting it using a heat source, such as
products – even in high-volume production environments. a laser or electron beam. Despite the general similarity in
The lack of tooling further streamlines workflows, minimizing process, significant differences exist between methods such
setup times and wear, while lightweight designs can be achieved as laser beam melting (LBM), electron beam melting, and
due to the high structural integrity and reduced weight of laser metal deposition, particularly regarding their material
AM parts. These advantages make AM an attractive option deposition strategies, precision, speed, and associated
across various industries, offering unprecedented innovation mechanical properties. Understanding these differences
potential and efficiency. 2 is essential for optimizing the production process and
However, despite its tremendous advantages, the path ensuring high-quality outcomes, and a thorough discussion
to fully realizing the potential of AM, particularly in metal on metal AM can be found in the literature. 12
manufacturing, is fraught with challenges. While laser- The quality of AM-produced components is influenced
based methods, such as LPBF and laser-directed energy by numerous factors, including powder characteristics, laser
deposition, have achieved industrial maturity over the past energy input, scan speed, and environmental conditions
two decades, several uncertainties and limitations persist. during the build. For instance, the particle size and
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Chief among these concerns is the consistency of feedstock distribution of the powder directly affect the mechanical
material quality and the mechanical properties of the printed properties, surface roughness, and dimensional accuracy
parts, both of which play critical roles in determining of the printed parts. 14-17 One of the most significant
the reliability and performance of the final components. challenges is achieving acceptable surface roughness. Due
Variations in powder quality can lead to inconsistencies in to the nature of the layer-by-layer manufacturing process,
microstructure and mechanical performance, thus affecting LPBF parts typically exhibit high surface roughness
the overall reliability of AM-produced parts. 3 values, often exceeding the requirements for high-
Another major challenge involves testing methodologies precision applications. The surface roughness of LPBF
and evaluation strategies. In many cases, existing techniques parts is influenced by factors such as laser power, scanning
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must be refined or completely redesigned to suit the unique strategy, part orientation, and inert gas flow direction.
characteristics of AM parts. This can be particularly Typically, LPBF parts exhibit arithmetic mean roughness
problematic for less experienced users, who may find that (Ra) values ranging from 5 to 50 μm, depending on the
traditional designs are incompatible with AM processes. As specific process parameters and materials used. Without
a result, significant design adaptations are often required to post-processing, LPBF parts cannot meet strict surface
fully exploit AM’s capabilities, with multiple iterative tests roughness standards, such as Ra below 0.8 μm for machine
and validation steps needed to ensure component quality. components or below 1 μm for dental implants. Achieving
Addressing these uncertainties is critical to ensuring the the desired surface finish often necessitates post-processing
long-term success and reliability of metal AM in industrial methods such as traditional CNC machining.
applications, particularly for high-stakes sectors such as The LPBF process is highly sensitive to various
aerospace, automotive, and medical devices. 4 parameters, such as laser power, scan speed, and powder

In recent years, research and development in AM, material properties such as size and morphology. Improper
particularly in the realm of metal 3D printing, have control of these parameters can lead to defects, such as
accelerated rapidly. There have been substantial efforts unmolten powder particles, porosity, and cracks, which
to standardize metal AM techniques and terminology, compromise the mechanical integrity of the final part. 19,20
such as those outlined in International Organization for These defects are typically categorized into three main
Standardization (ISO)/American Society for Testing and types: porosities, incomplete fusion holes, and cracks,
Materials (ASTM) 52900:2021. However, practical usage in each requiring careful management through process
5
commercial and industrial settings often deviates from these optimization. Increasing energy density generally helps
standards. This has led to a variety of similar designations. 6-11 reduce defects such as balling, thereby improving surface
Although the designations vary, the underlying AM quality, and reducing roughness.

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