Page 51 - ESAM-1-1

Engineering Science in
Additive Manufacturing Additive manufacturing of EH36 steels

EH36 steel, a high-strength, low-alloy steel, is widely Finally, the review identifies current research gaps, such as
used in marine and offshore industries due to its lightweight the limited use of numerical simulations and the absence of
yet excellent mechanical properties, including high tensile standardized certification procedures, and outlines future
22
strength, toughness, and weldability. These properties research directions aimed at optimizing AM processes and
make it an ideal material for critical structural components accelerating industrial adoption.
such as ship hulls, offshore platforms, and pipelines, which
must withstand extreme mechanical loads and harsh 2. AM techniques for fabrication of EH36
environmental conditions. 23,24 Despite its widespread use, steels
conventional manufacturing techniques such as rolling and Three methods, namely PBF-LB, DED using laser beam
welding impose limitations on the fabrication of complex (DED-LB) and DED using electric arc (DED-Arc), are the
geometries and often lead to inconsistent performance most widely employed for AMed EH36 steels. PBF-LB, also
25
due to residual stresses and material inhomogeneities. known as LPBF, is a powder-based AM process. While both
26
AM offers a promising solution by providing new design terms describe the same process, LPBF is a more commonly
possibilities and enabling the production of near-net-shape used term in research and industry, whereas PBF-LB is the
components with minimal post-processing requirements. 27 formal ASTM designation which will be used throughout
38
Recent studies have begun to explore the application this paper. PBF-LB is one of the most advanced
of AM for EH36 steel, focusing on key aspects such manufacturing methods for the production of components
39
as porosity control, 28,29 microstructural evolution, 30-32 with high performance and complex geometries. It can
mechanical properties, 31-34 fatigue performance, and utilize different laser sources, such as Yb-fiber lasers,
29
machinability. For instance, research has shown that Nd: YAG lasers, and CO₂ lasers, which influence energy
35
adjusting process parameters can significantly improve absorption and thermal gradients within the met pool. 40,41
the densification of additive-manufactured (AMed) Fiber lasers, which operate at 1.06 µm, are widely favored
EH36 steel, reducing porosity and enhancing fatigue due to their higher beam quality, efficiency, and stability.
life. 32,34 Studies on fatigue behavior have revealed that Nd: YAG lasers, operating at 1.06 µm, have historically
the unique microstructures formed during AM, such as been used extensively, providing strong energy absorption
refined ferrite and tempered martensite, can influence in metallic powders though with lower electrical efficiency.
crack initiation and propagation. 29,34 In addition, CO₂ lasers operate at a significantly longer wavelength of
investigations into corrosion resistance have highlighted 10.6 µm, offering high power suitable for various materials.
the potential of AMed EH36 steel to maintain structural However, their lower absorption by metallic powders and
integrity in marine environments, with techniques such reduced beam quality can lead to decreased precision and
as cathodic protection and coating to further enhance process efficiency. The choice of laser type directly impacts
37
36
its performance under cyclic loading conditions. Despite process stability, material properties, and overall build
the promising advancements, there remains a lack of quality. As illustrated in Figure 1A, the process typically
comprehensive reviews that consolidate the current begins by uniformly spreading a fine metallic powder
knowledge on AM techniques for EH36 steel. This gap across the build platform. A high-energy laser beam would
highlights the need for a detailed review to summarize then precisely melt the powder according to the computer-
progress, address existing challenges, and outline future aided design data, fully consolidating each successive layer.
research directions in this field. Subsequent lowering of the build platform enables the layer-
by-layer consolidation of material until the component is
The purpose of this review is to provide a comprehensive fully fabricated. PBF-LB systems typically operate within a
assessment of the application of AM technologies to EH36 sealed build chamber under an inert gas environment, such
steel, addressing the specific challenges and opportunities as argon or nitrogen, to minimize oxidation and ensure
associated with this material. The review begins with an the reproducibility of material properties. Optimized
42
overview of key AM techniques currently applicable to scanning strategies further enhance the process by reducing
EH36 steel, including their process mechanisms, resulting residual stresses and minimizing defects such as porosity
melt pool and microstructural characteristics, and common and cracking, resulting in components with exceptional
defects associated with its processes. It then examines the precision and surface finish. These characteristics make
43
mechanical properties of AMed EH36 steel, such as tensile PBF-LB an effective technique for fabricating EH36 steel
strength, fatigue resistance, and toughness. The effects of components, particularly for applications demanding
post-processing treatments, such as steel heat treatment to stringent mechanical property requirements. DED-LB
enhance mechanical properties or machining to improve process utilizes laser sources similar to those in PBF-LB,
surface roughness on AMed EH36 steel, are also discussed. predominantly fiber lasers and Nd: YAG lasers, due to

Volume 1 Issue 1 (2025) 2 doi: 10.36922/ESAM025060005