APS Materials, Inc.

The APS Process

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)

Arc Plasma Spray
This 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 30000°F in most cases. The gas expands and rushes from the torch as an ionized "plasma". As shown in the figure below, powder is injected into the gas stream, where it melts and is spray-cast upon the substrate surface.

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The Arc-Plasma process: In Depth
Characteristics of Plasma-Sprayed Coatings
Benefits of Plasma coatings

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. Flow rates of the gas may be 60 cubic feet per hour and without any additional heat input; this creates a very low velocity as it exits from the front electrode (nozzle).

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 coatings on an equally wide variety of substrates.

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.

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Characteristics of Plasma Sprayed Coatings

Uniform deposits of rapidly quenched splats are collected to form coatings or near net shapes. Deposits may be machined to precise dimensions. APS can also process composite or graduated coatings of differing compositions without alloying or chemical activity, and thermally react them (with or without pressure) at a later time. The coating material, in powdered form, is injected into the forming plume of ionized gas.

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 coatings or structural shapes.

. Benefits of Plasma Sprayed 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.

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.

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