Plasma Services (APS) Atmospheric Plasma Spraying

The plasma spraying process involves the latent heat of ionized inert gas (Plasma) being used to create the heat source. The most common gas used to create the plasma is argon. This is referred to as the primary gas.

PLASMA EXPLAINED
Plasma is often referred to as the fourth state of matter. Plasma, like the other three states of matter (Solid, Liquid and gas) has it's own unique properties. Just as most substrates will become solid if cooled enough, any substance will become a plasma if heated enough. In a plasma the electrons are stripped from the atoms creating a substance that resembles a gas but that conducts electricity. Plasma occur naturally on earth in electrical discharge, lightning bolts, aurora borealis and solar winds.

How does it work

Argon flows between the electrode and nozzle. A high frequency or high voltage alternating electric arc is struck between the nozzle and the electrode, which ionizes the gas stream. By increasing the arc current, the arc thickens and increases the degree of ionization. This has the effect of increasing the power and also, due to the expansion of gas, an increase in the velocity of gas stream.

With a plasma created by argon only it requires a very large arc current (Typically 800 to 1,000 amps) to create sufficient power to melt most materials. With this level of arc current the velocity may be too high to allow materials with a high melting point to be made molten. Therefore, to increase the power to a level sufficiently enough to melt ceramic materials it is necessary to change the thermal and electrical properties of the gas stream. This is generally done by adding a secondary gas to the plasma gas stream (usually Hydrogen).
Once the appropriate gas stream has been established for the material being sprayed, the feed stock (material in various powder forms) is injected into the gas stream.

Plasma spray advantage

There is a wide range of coating materials that meet a wide variety of different needs, with nearly all materials available in a suitable powder form.
Higher quality coatings such as flame or electrical arc spraying.
Many types of substrate material, including metals, ceramics, plastics, glass, and composite materials can be coated using plasma spraying.
The high temperature of a plasma jet makes it particularly suitable for spraying coatings of refractory metals and ceramics, including ZrO2, B4C and tungsten.
A broader powder particle size range can be used, typically 5-100µm, compared with HVOF spraying.
Plasma spraying is a well-established coating process that is widely available and well understood.

Typical plasma spray coating applications / industry

Compared to other processes

There are materials such as ceramics that require tremendous amount of energy to soften and transform into a desired coating. Such materials to be deposited (which come in powder form) are heated in the plasma stream at temperatures around 16,500 degrees C and subsequently sprayed at Mach 2 speeds onto the surface to be coated.

The inherent versatility and control of the process permits the deposition of a wide variety of spray materials including metals, alloys, ceramics (oxides, carbides) and cermets. Such coatings offer excellent properties for abrasion, high temperature, corrosion, electrical conductivity, EMI shielding, release properties, repair of worn parts and more!

TSS s.r.l is unique in its ability to work with its customers and provide them with a custom engineered solution for their specific surface engineering requirements. 

Due to our vast 30 years experience in the field of thermal spray coatings as well as the capabilities of our laboratory facilities, engineering department, and machining facilities, TSS s.r.l is highly capable of assisting you in any phase of thermal spray coatings.

High Definition PLASMA (APS) video1 (44Mb)

High Definition PLASMA (APS) video2 (44Mb)