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Materials Science in Additive Manufacturing Y O influence in heat-treated LPBF IN718 composite
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metals with the wear resistance, stiffness, and rigidness of despite the advantages of using AM for IN718 MMCs, the
ceramic materials. One of the prime material candidates development of printed IN718 MMCs is quite recent and
to be used as the base metal is Inconel 718 (IN718) due only limited to a few groups of researchers [12-15] .
to its excellent strength, ductility, and creep resistance at One of the most commonly used types of reinforcements
high temperatures . Thus, the material is in high demand is oxides due to several of their outstanding properties .
[3]
[16]
in the aerospace industry, presenting the need to further This paper presents a comprehensive microstructural and
enhance its mechanical properties to widen its industry mechanical property study of the IN718 MMC reinforced
applications.
with yttrium oxide (Y O ). The study was done in heat-
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The traditional manufacturing methods for MMCs treated MMC because IN718 must be heat treated to
can be categorized into either solid-state or liquid- make use of its precipitation hardening characteristic.
state methods . For solid-state methods, the alloying Thus, it is of utmost importance to understand the effect
[4]
of individual components takes place by repeatedly of the reinforcement particles on the different phases in
welding and fracturing the raw powder, which takes a IN718. Unfortunately, studies regarding the heat-treated
very long time to complete. Friction stir processing (FSP) IN718/Y O material system have not been presented.
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is another promising solid-state method that is able to There are only a handful of studies related to the heat
produce MMCs. However, this method is primarily used treatment of oxide-reinforced Ni-based alloys [17,18] while
to produce surface composites [5,6] and requires extensive most of the studies are for Fe-based alloys [19–21] . As such,
process optimization and simulation to understand this study will provide a comprehensive comparison of the
the effects of those parameters on the homogeneity of microstructures and mechanical properties between the
the composite . Liquid-state methods usually involve Y O -reinforced IN718 Ni-based alloys and the monolithic
[7]
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different ways of introducing the reinforcement particles IN718 in the as-printed state as well as after each stage of
into the liquid melt . This can be done by simply adding the heat treatment. This study also showed the importance
[8]
the reinforcement particles into a molten metal followed of heat treatment to the Y O -reinforced IN718 as the value
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by mechanical agitation such as stirring. The primary added of the Y O nanoparticles could not be showcased in
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problems are to ensure the homogeneous dispersion of the as-printed state.
the particles within the liquid melt as well as to ensure
good wettability between the reinforcement and the 2. Methods and materials
matrix, which can be challenging . On the other hand, the 2.1. Powder preparation and LPBF process
[9]
liquid melt can also be infiltrated into a ceramic preform
to manufacture MMCs . However, the properties of Commercially available IN718 powder (20 – 63 µm) was
[10]
the MMCs manufactured by this method depend on the purchased from Höganäs. The chemical compositions of
characteristics of the preform, which requires monitoring the powder are listed in Table 1. The scanning electron
the size, shape, and interconnectedness of the pores or cells. microscopy (SEM) images of the IN718 and nano-
As such, it is often substantially complex and expensive to Y O 30 – 100 nm) powder are shown in Figure 1A and B,
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design and manufacture the preform . respectively.
[11]
It should also be noted that the final product from the The reinforcement particles were mixed with the IN718
traditional manufacturing methods usually has simple powder using the Inversina 20L tumbler mixer for 8 h.
forms such as tube, sheet, or ingot. Due to the high strength The amount of reinforcement particles was 1 wt.%. Steel
of IN718, it is difficult and costly to produce complex parts balls were added with a 1 – 3, ball-to-powder, ratio during
from those simple forms. Fortunately, due to the excellent mixing to enhance the dispersion homogeneity. A uniform
weldability of IN718, the material and its composites mixture of powder was obtained as shown in Figure 1C.
are suitable to be fabricated by additive manufacturing It can be seen that the Y O particles were able to attach
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(AM), a method that has revolutionized the traditional themselves to the surface of the IN718 powder particles.
manufacturing industry. In this study, laser powder bed The time needed for a homogeneous powder mixture
fusion (LPBF) is utilized to fabricate IN718 MMCs to was first determined visually using a camera by observing
overcome the drawbacks of traditional manufacturing the mixture after 2, 4, 6, and 8 h of mixing as shown
methods. For instance, the technology is well known for its in Figure 2A-D. It was observed that the white Y O 3
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ability to produce near-net shape products. Furthermore, nanoparticles were still agglomerated after 2 h of mixing.
homogeneously dispersed reinforcement particles could As the mixing time increased, the nanoparticles were
be achieved using the technology by making use of its distributed more homogeneously in the mixture, and they
short melt-pool lifetime and high cooling rate. However, were no longer in large clusters after 6 h and were fully

Volume 1 Issue 4 (2022) 2 https://doi.org/10.18063/msam.v1i4.25