Biomedical Engineering Reference
In-Depth Information
characteristics of materials, a large number of possibilities with potential
industrial applications remain unexplored.
One existing process for high-speed particle deposition is to create surface
coatings using thermal spray technology. This process consists of accelerating
particles to high speeds, with the particle material heated to its molten state to
aid in bonding with the substrate. While this process has useful applications in
industry, it has inherent limitations due to the heating of material. Among the
limitations of this process are oxidation and thermally induced stresses in the
applied surface coating. These factors limit the selection of materials available
for deposition in the thermal spray process.
One desirable characteristic of surface coatings is high hardness levels,
which would be useful in many industrial applications including machinery
and internal engine parts. Nanostructured materials, due to the small grain size,
exhibit very high hardness values when compared to the same material with
typical grain sizes. Hardness increases have been reported to be over 100%.
However, nanostructured materials cannot be deposited by thermal processes
without losing their nanostructured properties. This necessitates the need to
deposit these particles without the addition of heat. The deposition of
nanostructured materials through high-speed impacts may prove to be viable
process, and has shown promise in research. To further investigate the effect
of depositing nanostructured materials into a substrate through high-speed
impact, a cost-effective method of experimental testing is developed through
the use of a pneumatically-powered device.
2.
L
ITERATURE
S
URVEY
2.1. Methodology of the Literature Review
The discovery that metal particles could be deposited to a substrate
material was recognized by Max Ulrich Schoop in 1909, when he filed a
patent for metal spraying (Kogelschatz, 2004). Since this date, the process has
been used in many industrial applications, and much literature has been
published on the subject. While the thermal spray process was refined
throughout the twentieth century, it was not until the 1980's that Anatolli
Papyrin and his colleagues developed the cold spray process at the Russian
Academy of Sciences, and studied the process of depositing metal particles
onto a substrate below the melting point of the metal (Papyrin, 2001). In 1994
the first U.S. patent was issued for cold spray technology; research and
