Page 48 - MSAM-1-2

Materials Science in Additive Manufacturing Process study of DED steel matrix composites

costs and environmental impacts . AM is also able to AlMangour et al. were able to find that for laser powder
[2]
create near net shape parts with complex geometries that bed fusion (L-PBF), which is another type of metal AM
would otherwise be difficult to manufacture [3,4] . technique, 316L with 10 vol.% TiB was optimum to
2
Directed energy deposition (DED) is a popular AM produce finer microstructure and better mechanical
[18]
technique for metals that uses a laser beam to melt metal properties . They attributed the improvement in
powders onto a substrate. There are various names used mechanical properties to Orowan and grain boundary
for DED, including laser metal deposition, laser cladding, strengthening. However, there is currently no known
and laser engineered net shaping. One of the key features research on the process parameter optimization of 316L
of DED is its relatively low energy input, resulting in lower stainless steel reinforced with TiB particles for DED.
2
residual stresses and smaller heat-affected zones . Due to Optimizations of these process parameters are crucial to
[5]
its configuration, DED is ideal for repair and reinforcement produce parts with desired mechanical properties with
cladding applications [6-8] . Furthermore, DED is able to minimal defects, thus, increasing the flexibility and usage
create metal matrix composites (MMC) and functionally of DED for a wider range of applications.
graded materials that can be customized to meet specific In this study, an optimal set of process parameters
requirements [9,10] . for 316L stainless steel with TiB MMC (316L/TiB ) was
2
2
316L stainless steel is one of the most suitable determined. The effects of process parameters on the
materials for DED. It is a low carbon austenitic steel alloy mechanical properties and microstructure of 316L/TiB
2
that has excellent corrosion resistance, ductility, and were evaluated. The Taguchi L9 array was used to design
biocompatibility . It is suitable for marine, biomedical, the experiments and to optimize the process parameters
[11]
chemical, and even nuclear industry [12,13] . However, 316L for optimum mechanical properties. The three process
stainless steel still have relatively low strength, hardness, parameters varied were laser power, scanning speed, and
and wear resistance compared to other alloys such as hopper speed at three different levels. Pre-mixed 316L
Ti6Al4V which limits its applications. These shortcomings stainless steel with 6 wt.% TiB powder was used and other
2
can be overcome by adding reinforcement particles such as parameters such as laser spot size and scanning strategy
SiC, TiC, and TiB to form MMCs that have significantly were kept constant. Optical microscopy and scanning
2
higher strength and hardness [12,14-17] . Among the various electron microscopy (SEM) were used to evaluate the
reinforcement particles, TiB is considered one of the most microstructure of the samples. Finally, the density and
2
suitable due to its compatibility with 316L stainless steel . Vickers hardness of the samples were also determined and
[18]
TiB has high thermal stability, chemical resistance, and discussed.
2
wettability with molten steel . 2. Materials and methods
[19]
One of the main challenges of the DED process is the
optimization of the variables involved. The part properties 2.1. Powder preparation
from DED process is highly dependent on these variables Gas atomized 316L stainless steel powder with particle size
such as scanning paths and build part geometry as well distribution 40–100 µm from TLS Technik (Germany) was
as process parameters . Variation in these variables tumble mixed with 6 wt.% TiB nanoparticles. The powder
[20]
2
will cause a significant change in microstructure and mixture was mixed for 8 h at 60 rpm using the Inversina
mechanical properties of DED parts. Mukherjee et al. 2L Tumbler Mixer (Bioengineering AG, Switzerland). The
observed changes in the thermal distortion of AM parts chemical composition of the 316L stainless steel powder is
with process parameters, build geometry, and material . listed in Table 1.
[21]
Saboori et al. also demonstrated that the microstructure The powders before and after mixing were examined
and tensile strength of 316L stainless steel cuboids created using SEM to ensure that the TiB particles adhere to
by DED varied depending on the deposition strategy due the 316L stainless steel particles and are homogeneously
2
to the differences in cooling rate .
[22]
dispersed. TiB particles were observed to be evenly coated
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There have been some studies on the effects of variables and distributed on the 316L stainless steel particles. The
on MMCs using 316L stainless steel as the matrix. Ertugrul
et al. showed that using proper powder preparation, the Table 1. Chemical composition of 316L stainless steel
addition of TiC particles increased the hardness by about powder
100 HV as compared to pure 316L stainless steel . Wu
[14]
et al. showed that increasing the SiC content in 316L Material Chemical composition (wt.%)
stainless steel MMCs would result in higher hardness but 316L C Mn P S Si Cr Ni Mo Fe
lower corrosion resistance . Other researchers such as 0.03 2 0.045 0.03 1 16-18 10-14 2-3 Bal.
[12]

Volume 1 Issue 2 (2022) 2 http://doi.org/10.18063/msam.v1i2.13