MBe Internation - Plasma spray

The Plasma Spray process is probably the most versatile of all the major Thermal Spray processes. This is predominantly due to the extremely high heat source temperatures available.

Schematic diagram of the plasma spray process

Also, because no combustion is taking place to provide the heat source, very low oxide coatings can be produced, even in atmosphere.

Temperatures in the range of 8,000°C to 15,000°C can be achieved. By adjusting the dwell time of the particles in the heat source, we can apply a thermal energy to almost any stable element or compound sufficient to cause melting.

The plasma spray heat source is a high temperature, inert flow of varying gas combinations which provides excellent heat transfer properties for the powdered material; and in some cases, wire.

The Plasma Spray process is most commonly associated with powder as it’s feed stock but some wire derivatives have been developed over the years.

Plasma spray properties table

Principle of operation

The Plasma Spray process relies on the principle of ionisation to create the heat source. The plasma gas is passed through the plasma chamber and subjected to a high intensity DC electric arc. The energy from the DC electric arc is transferred to the gas which causes the gas to ionise (enter the plasma condition). It is the recombination of the gas atoms which creates the extremely high temperatures as the gas reverts back from the plasma condition into it’s original state.

The most common gases used are Argon and Nitrogen (primary gas) but different combinations are used to create different heat transfer characteristics. Hydrogen and Helium are often used as “secondary” gases.

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