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Materials Science in Additive Manufacturing Laser absorption and printability of 90W-Ni-Fe

W-Ni-Fe as a structural material. The rapid development laser shadowing and expulsion. A recent study by Ge
of additive manufacturing (AM) provides a new method et al. proposed mesoscopic simulation to investigate
[14]
for W-Ni-Fe fabrication. AM is defined as a method of the influence of ceramic addition on the laser energy
printing components from three-dimensional (3D) model absorption and powder melting behaviors during LPBF of
data using a layer-wise manufacturing philosophy and TiC/Ti6Al4V composites, and they found that the addition
can be divided into seven divisions according to printing of 1 wt.% or 3 wt.% ceramic was beneficial to improving
mechanism and raw material . Laser powder bed fusion the laser absorptivity and the surface morphology of
[3]
(LPBF) is one of the most promising AM technologies due melted track. A high-fidelity model coupled with a
[15]
to its laser-induced complete melting mechanism [4,5] . As an ray-tracing method was constructed by Ren et al. to
efficient, digital, and highly flexible advanced technology, visualize the flow kinetics and reflection behavior during
LPBF has been applied in many fields such as military, LPBF of Cu-Cr-Zr alloy, which showed good agreement
aerospace, and biomedical, and has a laser beam with high with experiments in terms of track width and depth. The
energy to completely melt W particles, making it one of the above-mentioned and related studies have reported that
effective methods to prepare high-performance W-Ni-Fe laser absorptivity is vital for the subsequent metallurgical
components [3,6] . Nevertheless, the design of raw materials behavior and printing quality, and the absorption
has become a constraint to the development of LPBF- behavior and liquid-solid interface dynamics during
fabricated W-Ni-Fe parts [3,5,6] . LPBF are affected by the morphology and characteristics
of feedstock powder. Understanding the complex and
The previous studies indicate that powder properties interdependent laser-powder-melt pool interaction
have an important influence on LPBF-processed W parts. during LPBF is of great importance, which matters for the
Field et al. produced W specimens with two kinds of control of metallurgical defects and mechanical properties
[7]
high-purity W powders: the first powder was a chemically of LPBF-fabricated W-based parts [8,13,14,16] . However,
reduced powder with an irregular morphology, and few studies on laser absorption and melting behavior of
the second powder was a plasma-spheroidized powder W-based powders during LPBF have been reported, and
with highly spherical morphology. They found that W the mechanisms of the influence of powder morphology
powders with high sphericity had higher apparent power and characteristics on laser absorption behavior and
densities and enhanced the density of LPBF-fabricated W printability of 90W-Ni-Fe powder during LPBF remain
components. A 3D laser absorption model based on ray unknown.
tracing was established by Zhang et al. to investigate the
[8]
influence of W particle size and its distribution on the The in situ alloying of AM, as opposed to pre-alloyed
powder-to-laser absorptivity and underlying behavior. powder used for printing, provides a feasible way for AM
The simulation and experimental results indicated with multiple materials. The LPBF, due to its concentrated
that the absorptivity of the powder layers considerably laser energy input with sufficiently high thermal behavior,
exceeded the single powder particle value or the dense is expected to become one of the in situ alloying processes
solid material value, and smaller particle size improved the in the coming years [17-20] . In this work, the geometrical
laser absorptivity during LPBF-processed W parts. Braun optical ray-tracing (GO-RT) models and computational
et al. analyzed the processing of Mo and W by LPBF, fluid dynamics-based powder melting (CFD-PM) models
[9]
and they identified the oxygen in the powder as a cause were established to obtain an in-depth understanding
for cracks and residual porosity. Nevertheless, these studies of mechanisms during LPBF fabrication of W-based
mainly focused on pure W, and the effect of feedstock alloys. The nanoparticle-coated 90W-Ni-Fe powders for
powder characteristics on laser absorption behavior and LPBF were fabricated by mechanical mixing with ball
printing quality of LPBF-processed W-based alloys was milling, and the corresponding LPBF experiments were
rarely studied. It has been reported that nano-reinforcing carried out. The influence of the powder morphology
and characteristics on laser absorption behavior and
particles can effectively improve the printing quality of printability of LPBF 90W-Ni-Fe was investigated by
LPBF-fabricated W-based alloys [7,10-12] .
numerical and experimental methods, and the laser-
Several studies have been carried out on laser powder interaction mechanism and thermal behavior of
absorption and melting behavior during LPBF. Khairallah molten fluid were revealed. A good agreement was obtained
et al. used high-fidelity simulations, coupled with between the simulated and experimental results, and this
[13]
synchrotron experiments, to capture fast multitransient work provided a physical understanding of complex and
dynamics at the meso-nanosecond scale. They discovered interdependent laser-powder-melt pool interaction during
new spatter-induced defect formation mechanisms, which LPBF of 90W-Ni-Fe, aiming to form scientific guidance for
depend on the scan strategy and competition between LPBF fabricating high-quality W-based alloys.

Volume 1 Issue 2 (2022) 2 http://doi.org/10.18063/msam.v1i2.11