Page 61 - MSAM-3-1

Materials Science in Additive Manufacturing Customized scans and dwell time on AM 316L

by this technique is low. In contrast, the engineered net functional AM parts. The optimized parameters from the
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shaping (LENS) technique also offers flexibility, efficiency, previous study were utilized in this study, and two new
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and the ability to produce complex, large-scale parts print parameters – customized scan patterns and dwell
with a variety of materials in addition to better surface time between print layers – were added to get an in-depth
quality, making it valuable in various industries and understanding of the printing process.
applications. 2,16-19 Various process parameters including
layer thickness, print speed, laser power, printing patterns 2. Materials and methods
and orientations, cooling rate, etc., in AM can significantly 2.1. Materials
influence different properties of the produced parts. 1,9,10,13,14
Understanding how these process parameters influence The gas-atomized 316L SS from Carpenter Additive
properties is crucial for optimizing the AM process to meet (USA) was used to produce the test sample parts.
specific design requirements and quality standards for the Figure 1A shows the scanning electron microscopy
final printed parts. (SEM) images of the spherical gas-atomized 316L
SS powder, and Table 1 shows the energy dispersive
The LENS-based DED process has a default deposition X-ray spectroscopy (EDS) data of the 316L SS powder.
pattern, starting with the outer contour deposition and The particle size distribution (PSD) of D50= 58 μm
then proceeding to the alternative raster contour to create was recorded for the spherical powder based on SEM
hatch lines. 9,15,16 Ribeiro et al. studied different deposition image (Figure 1B). X-ray micro-computed tomography
strategies with the DED process and their influence (micro-CT) was performed, as elaborated in section 2.2,
on mechanical properties. There is a huge interest in with Skyscan 2214 Bruker micro-CT system (BRUKER,
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exploring alternative (customized) deposition patterns USA) using 0.5 mm Cu filter at 1.75 μm pixel resolution to
for the LENS-based DED process. In addition, with the assess the 316L SS powder quality. The 3D reconstructed
LENS-based DED technique, there is an opportunity to image of 316L SS powder is shown in Figure 2A, and the
explore inter-layer dwell time between each print layer X-Y cross-sectioned image in Figure 2B depicts a minor
so as to control the laser energy intensity to enable better trace of internal pores.
cooling rate control within the print layers. 18,20 Denlinger
et al. investigated the influence of inter-layer dwell time 2.2. Experimental methods
on distortion and residual stress in titanium and nickel MTS 500 hybrid AM tool built by Optomec was used to
alloys. While increasing the pause time between print deposit 316L SS powder onto 304 SS substrate to fabricate
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layers unavoidably lengthens the total printing time, it
merits consideration due to its potential influence on Table 1. Energy dispersive X‑ray spectroscopy data of 316L
microstructure and properties. stainless steel powder
In this study, an emphasis was placed on investigating Elements (wt. %)
the role of customized scan strategies and dwell time in Spot no. Fe Cr Ni Mo Si Mn
between the print layers of 316L stainless steel (SS) using the 1 65.47 18.93 11.89 1.73 0.96 0.56
DED technique. The current work is an extended research
of previous work, a parametric study summarizing the 2 64.52 19.43 12.18 1.95 0.94 0.81
optimization of process parameters to obtain fully dense 3 64.91 19.44 12.48 1.58 0.53 1.15

A B

Figure 1. (A) Scanning electron microscopy image with energy dispersive X-ray spectroscopy points, corresponding to energy dispersive spectroscopy
data in Table 1; (B) particle size distribution of 316L stainless steel powder.

Volume 3 Issue 1 (2024) 2 https://doi.org/10.36922/msam.2676