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Engineering Science in
Additive Manufacturing Additive manufacturing of EH36 steels

facilitating microcrack nucleation along grain boundaries. contributes to increased wear resistance but also escalates
In addition, the localized stress concentration around tool wear under high-temperature machining conditions.
the slip marking was intensified by an adjacent unmelted The chip morphology further reflects the distinct
particle, accelerating crack initiation. Approximately machinability characteristics of AMed EH36 steel.
120 µm to the right of this slip marking, another prominent Chips from AMed EH36 steel exhibit finer serrations,
nucleation site was identified, featuring a tearing ridge fewer burrs with easier removal, and lower stress
extending outward from a narrow tail-like feature toward concentrations compared to those from HR EH36 steel,
the sample center. 34 which display coarse serrations and more rigid burrs. In

6. Machinability of AMed EH36 steel addition, the significantly reduced chip radius observed
in AMed EH36 steel reflects the influence of refined
The machinability of AMed EH36 steel is an important factor microstructures resulting from rapid cooling during the AM
influencing its applicability in industrial environments, process. This smaller chip radius, combined with smoother
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particularly in marine and offshore applications. Bai et al. chip morphology, is attributed to lower ductility in the
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provided a comprehensive analysis of the machinability AMed EH36 steel. In addition, the chip compression ratio
of EH36 steel fabricated using DED-LB, highlighting for AMed EH36 steel is approximately 2.5, which is higher
the influence of microstructural anisotropy, cutting than the 2.2 observed for its HR counterpart, indicating
parameters, and the thermal-mechanical history of the greater chip shrinkage during milling. These differences,
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material. The microstructure of EH36 steel fabricated by observed at cutting speeds of 150 m/min and 250 m/min,
DED-LB primarily consists of acicular martensite, with suggest that the AM process improves surface finish quality
smaller grain sizes resulting from rapid cooling rates while necessitating optimized machining parameters to
during the deposition process. This contrasts sharply with manage higher stress concentrations and reduced material
the ferrite-pearlite structure observed in conventionally flow. In conclusion, the machinability of AMed EH36
hot-rolled (HR) counterparts. Such microstructural steel is influenced by its unique microstructure, cutting
differences translate to higher hardness in the as-print parameters, and the anisotropic nature of the material.
samples, with the top face showing approximately 31%
higher microhardness than HR samples. Despite these 7. Research gaps and future directions
advantages, the anisotropic nature of samples introduces Despite significant advancements in the AM of EH36 steel,
challenges in machining. For instance, the top surface, several critical research gaps remain. These gaps span
oriented perpendicular to the build direction, shows across scanning strategy optimization, unexplored AM
lower cutting forces compared to the side surface, which techniques, enhanced applications, corrosion performance,
is aligned with the build direction. This variation arises standardization, and advanced technologies, which
due to the differing melt pool boundaries intersected by collectively present opportunities for future investigation.
the cutting tool during machining. The machinability of
AMed EH36 steel also depends on the milling conditions. 7.1. Optimizing scanning strategies
Increasing the cutting speed leads to thermal softening Optimizing scanning strategies can effectively tailor grain
of the material, thereby reducing cutting forces across all orientation, thereby exerting a significant influence on the
samples, including HR EH36 steel. mechanical properties of fabricated alloys. Therefore,
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Surface roughness significantly improves with post- AMed EH36 steel should incorporate texture optimization
processing, particularly milling. The roughness of AMed within computer-aided design workflows, enabling the
EH36 steel, initially greater than 20 µm due to the concurrent optimization of both external geometries and
spheroidization effect and layer tracks, reduces to below internal mechanical properties through precise scanning
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1 µm after milling. The side surface achieves a smoother strategy modulation. It is also crucial to investigate
finish, with a minimum roughness value of 0.41 µm, and the how variations in scanning strategies impact localized
top surface with a roughness value of 0.51 µm at a cutting mechanical behavior, facilitating the targeted enhancement
speed of 250 m/min. This improvement underscores of critical attributes such as fatigue resistance, corrosion
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the importance of secondary machining operations for resistance, and overall structural integrity. 83
achieving industrial-grade surface quality. Tool wear is
another critical consideration when machining AMed 7.2. Emerging AM techniques and hybrid
EH36 steel. It exhibits higher tool wear rates compared approaches for EH36 steel
to HR EH36 steel, particularly at higher cutting speeds. While PBF-LB, DED-LB, and DED-Arc have been
The martensitic microstructure of the AMed EH36 steel extensively studied, other promising AM technologies,

Volume 1 Issue 1 (2025) 9 doi: 10.36922/ESAM025060005