Biomedical Engineering Reference
In-Depth Information
Figure 9.2
Process scheme of plasma spraying.
indicates a state of aggregation in which carriers of
positive and negative charges in equal concentration
exist freely due to the ionization of atoms at high
temperatures. Actually, temperatures of 12,000 K or
more are reached in the core region of the plasma,
although they dramatically decrease as a function of
the distance from the nozzle. Powder particles are fed
into the plasma jet using a gas carrier: as a result, they
are melted, highly accelerated, and propelled toward
the substrate surface, where they impact, spread, and
solidify, thus forming a typical lamellar structured
coating. Particle velocity can reach values up to
600 m/s, depending on the spraying method.
The physical processes are controlled by a large
number of parameters, some of the most important
being shown in
Fig. 9.3
. Coating characteristics, such
Figure 9.3
Plasma spray parameters and their interaction. Modified from Ref.
[21]
.
