THE APS PLASMA SPRAY COATING PROCESS
Plasma Spray Coating
The plasma spray coating process is the most advanced of the thermal spray processes. Plasma Spray processes use a plasma generator as a thermal and kinetic energy source to spray-cast droplets of molten materials against an appropriate substrate. An inert gas is injected into an arc chamber framed by two concentric water-cooled electrodes, ionizing the gas and creating temperatures up to 30,000°F in most cases. The gas expands and rushes from the torch as an ionized “plasma”. As shown in the figure to the right, powder is injected into the gas stream, where it melts and is spray-cast upon the substrate surface.
Benefits of Plasma Spray Coatings
The plasma spray process enables the generation of advanced materials, offers solutions to interface stresses, and provides a new method of fabricating near net shapes. Our coatings often exhibit higher tensile strengths, improved corrosion resistance, and better wear properties than other methods. Unique properties, such as dielectric and oxide free, are easily obtainable using the plasma spray process. Feel free to get in touch with us to see what our plasma spray process can do for your company.
The Arc Plasma Process: In Depth
This figure illustrates the basic principles of plasma spray torch operation. An inert gas, (nitrogen, argon, helium,) or mixtures including trace amounts of hydrogen, is passed between two concentric water-cooled electrodes.
The plasma is initiated by a momentary “trigger”, a spark that is created by a separate radio frequency (RF) generator. The arc in the arc-chamber is then sustained by a charged DC power source capable of sustaining at least 1000 amps of current and generates temperatures that can achieve 30000°F in conventional equipment or 60000°F in high energy plasma equipment.
This means that nearly any material that has a melting point below these temperatures can be processed using this method. In addition, substrate temperatures may be controlled to <100 degrees C during deposition, making it possible to put a wide variety of plasma coatings on an equally wide variety of substrates. Coating thicknesses from 1 to 100 mils can be achieved.
The “DC” arc (estimated 17,000oC max. temperature) causes rapid expansion of the inert gases (arc-gas), and the heated plasma issues from the front nozzle rush from the front nozzle at a velocity of Mach I (1100 ft/sec) in conventional equipment or Mach II (2200 ft/sec) in high energy equipment. In certain special cases, gas velocities of Mach III (3300 ft/sec) can be achieved. The powder which is to be spray-cast onto the substrate is injected into the plasma stream either within the confines of the nozzle or externally to the nozzle by use of an appropriate carrier gas.
On Board Processes:
- Combustion Flame Wire and Powder Spray
- Inert Chamber Plasma Spray (ICPS)
- Shrouded Plasma Spray (SPS)
- Atmospheric Plasma spray
- Two-wire Arc Spray
- Low Pressure Plasma spray (LPPS)
- Hypervelocity Oxy-Fuel Combustion Spray (HVOF)
APS can process any solid material that exhibits a liquid phase at atmospheric pressure, including incongruent melting systems. Metals, ceramics, cermets, semiconductors, and salts can be formed into spray coatings or structural shapes.
At APS we understand the uniqueness of our industry. In order to best serve our customers, we employ a cooperative approach to engineering that is equally unique. The engineering staff at APS educates the client’s technical staff as they research, develop, and specify the materials and coating process. Confidentiality is maintained as our staff works closely with the client. Care to learn more about our process?