Page 69 - MSAM-1-2

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

from copper particles by the Van der Waals forces, which observed in copper-MoS -WC wear track. Furthermore,
2
became an advantage for cold spraying and enhanced wear the subsurface microstructures of copper-MoS -WC wear
2
resistance characteristics . tracks suggested that the WC particles also served as load
[53]
In Figure 14, worn areas of copper and its composite bearers and protected the rest of the surface from severe
coatings are shown . The graphene copper composite plastic deformation. The presence of the ultrafine grains
[53]
coatings had a better friction coefficient of 0.46, and only around the WC particles proved it. While for the
copper coatings had a friction coefficient of 0.6, as shown copper-MoS coatings, the ultrafine grains were present
2
in Figure 15. Furthermore, the wear rates for graphene everywhere on the worn surface. The cracks on copper-
copper composite coatings were 5.2 × 10 mm /Nm and MoS wear tracks were again due to the already work
-4
3
2
that for pure copper coatings were 8.6 × 10 mm /Nm . hardened ultrafine grains present all over the surface of the
3
-4
[53]
wear track.
4.5. Copper-MoS composite coatings
2 4.6. Copper-TiB composite coatings
Metal matrix composites that have good wear resistance 2
and self-lubricating properties can be used for making Copper-TiB composite fabrication has received much
2
bearings . In this material type, MoS particles can play attention due to its vivid applications that require properties
[54]
2
an effective role in reducing friction and wear rate . The such as electrical conductivity, thermal conductivity, wear
[55]
addition of ceramic particles into self-lubricating metal
matrix composites is a good practice to ameliorate the wear
resistance and strength of these composites [56-61] . Moreover,
cold spray can be a beneficial method for spraying metal
matrix composites powder feedstock containing MoS
2
because there could be no decomposition or phase
transformations of solid lubricant MoS as the cold spray
2
process does not involve very high temperatures. Brittle
compounds such as Cu S and CuMo S may cause an
2 3
2
increase in friction and wear, eliminating the purpose
of solid lubricant when the Cu-MoS composites are
2
fabricated through sintering .
[62]
Zhang et al. studied the sliding wear behavior of
[63]
copper-MoS and copper-MoS -WC cold spray coatings.
2
2
As reported, the sliding wear experiment done showed that
copper-MoS -WC coatings had low friction and wear rate Figure 17. Copper-43 vol.% TiB feedstock powders formed as product
2
2
compared to copper-MoS coatings. The tungsten carbide after the SHS reaction for cold spraying . (Reprinted from Composites
[70]
2
particles helped reduce the friction; wear became uniform Science and Technology, 67(11), Kim, J. S., Kwon, Y. S., Lomovsky, O. I.,
throughout the wear track, as shown in Figure 16. The Dudina, D. V., Kosarev, V. F., Klinkov, S. V., Kwon, D. H., and Smurov,
I., Cold spraying of in situ produced TiB2–Cu nanocomposite powders,
tungsten carbide particles embedded in the coating had a 2292 – 2296, 2007, with permission from Elsevier).
thin layer of copper, which could be an advantage because
the function of hard particles like tungsten carbide is not A B
only to reduce friction but also to not serve as abrasives
during wearing by having direct contact. In that work,
the authors did not use a high volume percent of tungsten
carbide in the coatings; probably, because tungsten carbide
particles can compromise the bond strength. As far as
copper-MoS coatings were concerned, the MoS particles
2
2
smeared out during sliding and replenishing the particles
continued with sliding. However, for copper-MoS -WC Figure 18. Microstructures of copper-43 vol.% TiB cold spray coating:
2
2
coatings, more wear debris accumulation due to WC (A) Etched with (NH ) S O aqueous solution and (B) etched with FeCl 3
8
4 2 2
[70]
particles suggests a low wear rate. There was an active aqueous solution . (Reprinted from Composites Science and Technology,
transfer of material due to rapid wear debris removal in 67(11), Kim, J. S., Kwon, Y. S., Lomovsky, O. I., Dudina, D. V., Kosarev,
V. F., Klinkov, S. V., Kwon, D. H., and Smurov, I., Cold spraying of in
the case of copper-MoS coatings. This led to detachments situ produced TiB2–Cu nanocomposite powders, 2292 – 2296, 2007, with
2
and cracks on copper-MoS wear tracks, which was not permission from Elsevier).
2
Volume 1 Issue 2 (2022) 13 https://doi.org/10.18063/msam.v1i2.12