Page 348 - IJB-10-1

International Journal of Bioprinting Corrosion behavior of SLM-prepared 316L steel

1. Introduction directed energy deposition (DED)-based AM methods
on the microstructures and mechanical properties of the
Additive manufacturing (AM), usually referred to 316L steel. Guo et al. , who used the high-power direct
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as three-dimensional (3D) printing, involves several laser deposition (HP DLD) method, reported that the
technologies, such as powder bed fusion (PBF), which microstructures and properties depended significantly on
comprises selective laser melting (SLM) and direct metal the building direction. Regarding the optimized processing
1
laser sintering (DMLS). The technologies are utilized parameters, the therein achieved ultimate tensile strength
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based on a computer-generated model to fabricate a 3D (UTS) reached 900 MPa. Yin et al. documented that
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product. Contrary to the conventional manufacturing the thermal stability of the microstructures as-built by
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methods, such as rolling, forging, extrusion, or drawing, laser powder bed fusion (L-PBF) lasted for up to 400 h
AM technologies create the materials monolithically in between 500°C and 600°C, and decreased significantly
a layer-by-layer fashion. The technologies are suitable to with increasing the temperature to 800°C. As the
fabricate tailored components with complex geometries microstructures and possible presence of printing defects
from various metals, polymers, and also ceramics. also affect the lifetime of the components, several research
7,8
4,5
6
Over the recent years, AM has demonstrated success in groups have examined the fatigue properties of AISI 316
fabrication of intricate components applicable in a variety steel prepared by AM 32-34 and compared the results with
of industrial fields, including aerospace, automotive, or those acquired for conventionally prepared steels 35,36 ; such
biomedicine. For example, AM has already been used comparisons were also performed from the viewpoints of
to fabricate complex bio-applicable structures, such as machinability 37,38 . Interestingly, Vinoth et al. reported that
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scaffolds, and patient-specific implants. 9-11
the wire arc additive manufacturing (WAAM) method can
Despite its indisputable advantage, i.e., the ability to be used to fabricate steel plates that exhibit open pores after
create tailor-made geometries, AM also features several machining, which could be beneficial for a prospective
disadvantages, including residual porosity, surface bio-application.
roughness, inhomogeneous distribution of residual stress, The 316L steel is one of the most commonly used,
and possible distortion of the final components 12,13 . In affordable materials for fabrication of various implants
order to eliminate the printing defects, post-processing via used in human body . Examining the corrosion behavior
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a heat treatment, possibly combined with a high pressure of a bio-applicable material is of high importance because
(such as during the hot isostatic pressing [HIP] method) , corrosion not only decreases the lifetime of the implant,
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or processing via plastic deformation , has been proven but it also triggers release of ions from the implant
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to be advantageous. Besides, optimized deformation materials, which can (negatively) affect the surrounding
(thermomechanical) treatment has been shown to also living tissues and cause inflammatory or anaphylactic
favorably enhance the mechanical properties of AM- responses 27,41 . Shih et al. documented that wrought 316L
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prepared materials (steels) 15-17 . steel components are prone to exhibit localized corrosion
The AISI 316L stainless steel is widely applicable in and would gradually become cytotoxic as a result of the
numerous commercial and industrial fields, from chemical corrosion reactions. Majumdar et al. reported that
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and petrochemical industry , through nuclear energetics , almost 50% of 316L steel implantation failure is related
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18
transportation and marine 20,21 , to food industry and to corrosion. To address this problem, various types of
biomedicine 22,23 . Given its versatility, it has been the focus coatings (e.g., ZnO and TiO films) and surface treatments
2
of numerous researchers working on the optimization of have been introduced to decrease the corrosion rate of the
its production technologies and preparation processes. Its stainless steel 43-45 . As the corrosion behavior is dependent
manufacturability by conventional production methods, as not only on the chemical composition of the material,
well as by modern and unconventional methods, such as but also on the microstructure and intrinsic properties,
hydroforming, electroforming, or severe plastic deformation studies on AM-prepared 316L steel have been performed
(SPD) techniques, has been proven 24-26 . Recently, the 316L as well. Upon comparing the corrosion behaviors of 316L
steel has also been gaining traction among researchers steel samples prepared conventionally and by AM+HIP
and manufacturers dealing with AM technologies 27,28 . As in H SO and HCl solutions, Fredriksson et al. found
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4
2
the selected processing parameters and particular AM that the AM+HIP sample exhibited better resistance to
technology directly influence the acquired microstructures pitting corrosion due to the formation of a thicker passive
and thus the mechanical properties, investigating the layer. The application of HIP has been shown to favorably
correlation of these variables has always been the main enhance the corrosion resistance of AM-prepared steels .
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goal of numerous studies. Saboori et al. reviewed and However, HIP alone is not able to fully eliminate residual
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summarized the effects of processing parameters of porosity, which tends to increase both the corrosion rate
Volume 10 Issue 1 (2024) 340 https://doi.org/10.36922/ijb.1416