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Materials Science in Additive Manufacturing Cold spray additive manufacturing of Cu-based materials

reducing adherence with metal. There is also a mismatch cold spray coatings to prove its superiority in terms of
in the thermal expansion coefficient of metal and ceramic, quality, sustainability, and economy as compared to other
which makes the bonding difficult and may also result available methods for producing coatings.
in interfacial cracks. Cold spray is an excellent technique Fukumoto et al. reported the study of deposition
[23]
for making an effective metal-ceramic interface because behavior and efficiency of cold-sprayed copper coatings
it is a low-temperature process that avoids any melting of with respect to changes in substrate temperature, particle
particles or phase transformations. The effectiveness of velocity, gas pressure, and gas temperature. The copper
adherence between metal-ceramic interfaces produced by particles have mean sizes 5, 10, and 15 µm. According to
the cold spray technique can have a great effect on their their observations, the 5 µm copper particles produced an
mechanical and tribological properties . increase in particle velocity with an increase in gas pressure
[21]
The powder particles, having a velocity greater than during the cold spraying process. However, the effect of gas
the critical velocity, get deposited on the substrate. These temperature was not significant on particle velocity. The
powder particles with high supersonic velocity bombard particle velocity was highest for 5 µm copper particles and
the surface of a substrate and essentially perform the lowest for 15 µm copper particles; this observation shows
desired work of removing the oxide layer on the substrate, that particle velocity significantly varies with particle mean
enhancing the bonding of coatings to the substrate in size. Moreover, higher copper particle velocity leads to
the presence of ceramic particles along with the metal better deposition efficiency.
particles, enhancing the bonding characteristics. The In the same study, it was also reported that an increase
ceramic particles do not deform themselves, but they in the temperature of the substrate could lead to improved
distort the ductile metal matrix and enhance the bonding. deposition. This increase was even more pronounced when
These ceramic particles may also break into fragments and, both pressures of the gas and substrate temperature were
hence, get embedded in the metal matrix all around, which increased. Figure 3 shows the increase in deposition of
may eventually increase the hardness of the coatings. The copper particles with respect to the substrate temperature
cermet particles serve the following functions: (i) Cleaning and pressure. This observation could be of good use in
the nozzle, (ii) activating the sprayed surface, and (iii) designing the parameters for cold spray deposition .
[23]
densifying the structure [3,22] .
Borchers et al. studied the deformation behavior of
[24]
2. Pure copper cold spray coatings cold-sprayed copper coatings by focusing on various areas
in the coating microstructures seen in the transmission
Copper as an element specifically known for its exceptional electron microscopy micrographs (Figure 4). The regions
electrical and thermal conductivities is greatly used for marked as A, B, C, and D in the micrograph correspond to
thermal and electrical applications commercially in the copper particle-particle boundaries. Region “D” shows
various industries. Several studies have been conducted
to explore the properties of pure copper and copper-based

Figure 3. Deposition of copper particles with respect to substrate
temperature and gas pressure . (Reprinted from Journal of Thermal
[23]
Spray Technology, 16, Fukumoto, M., Wada, H., Tanabe, K., Yamada, M.,
Yamaguchi, E., Niwa, A., Sugimoto, M., and Izawa, M., Effect of Substrate
Temperature on Deposition Behavior of Copper Particles on Substrate
Surfaces in the Cold Spray Process, 643-650-108, 2007, with permission
Figure 2. Parameters for successful Cu-MMC cold spray coatings. from Springer Nature).

Volume 1 Issue 2 (2022) 4 https://doi.org/10.18063/msam.v1i2.12