Run-Through of Different Thermal Spray Coating Methods
Today, thermal spray coatings are utilized
in a number of different industries. These coatings consist of wire and molten
powder which are exposed to plasma or oxy fuel combustion. The fire from the spray
device will power the mixture that has been heated, and once it has been
sprayed onto metal, the mixture will retain a firm coating.
Thermal spray coatings are used in a wide
spectrum of many useful applications, which can include protecting airplanes,
buildings and other structures from extreme temperatures, chemicals or
environmental conditions such as humidity and rain. Here are the 5 most common
processes to generate thermal spray coatings today:
HVOF (High Velocity Oxy-Fuel Spraying)
HVOF is a process which makes use of a
torch that allows the flame to spread whenever the nozzle is used. This creates
rapid acceleration which speeds up the particles in the mixture. The end result
is an exceptionally thin coating which is evenly applied. Despite being thin,
this coating is strong and adheres well. Its resistance to corrosion is better
than plasma coatings, but it is not well suited for high temperatures.
Combustion Flame Spraying
Combustion flame thermal spray coating is
an excellent option for surfaces which aren’t designed to handle extreme
stress. The coating which results from this process is not strongly attached to
the surface since the spraying mechanism is powered by a lower flame velocity.
The flame will be generated via oxygen which has been combined with fuel, and
this will melt the mixture. Combustion flame spraying is popular for low
intensity applications due to its low cost.
Plasma Spraying
Plasma spraying makes use of the plasma
torch as the main tool for heating and spraying the coating. After the powder
material has been melted down, it is then placed on the product in a manner
which is similar to combustion flame spraying. The coatings which result from
plasma spraying may be a few micrometers thick to a few millimeters think. While
powder is the most widely used material, metals and ceramics are also used. The
plasma spraying process is highly popular due to its adaptability.
Vacuum Plasma Spraying
Vacuum plasma spraying is done in a
controlled environment, but utilizes low temperatures. This maintains the
vacuum while also reducing damage on the material. A variety of gas
combinations can be used to get the necessary pressure for spraying. Vacuum
plasma spraying is used for items such as car bumpers, the dashboard or housings
for door mirrors. This process can also be used for the pre-treatment of
polyethylene moldings, which provides adhesion for epoxy adhesives which are
water based.
Two-Wire Electric Arc Spraying
This thermal spray coating method utilizes
an arc point which is created between two wires which are electrically
conductive. Melting will occur at the point where the wires connect. The arc
allows for heating which in turn creates deposition and melting, similar to
combustion flame spraying which is used with a torch. Compressed air will be
used for spraying the coatings. This procedure is popular due to its cost
effectiveness, and will typically use aluminum or zinc as the base material.
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