Atmospheric Plasma Spray

Atmospheric plasma spray - a cutting-edge technique

Atmospheric plasma spray (APS) is a cutting-edge materials processing technique that utilizes a high-temperature plasma to produce high-quality coatings on a variety of substrates. This technique involves the injection of fine particles of a material, such as metals, ceramics, or polymers, into a plasma stream generated by the ionization of a gas, typically argon, through an electric arc or radio frequency discharge. The plasma stream melts and accelerates the particles towards the substrate, where they solidify and form a dense, uniform coating.

The atmospheric plasma spray process offers numerous advantages over other coating techniques. It can produce coatings that are highly resistant to wear, corrosion, and thermal stress, and can withstand extreme temperatures and harsh environments. The coatings produced by atmospheric plasma spray are highly adherent to the substrate and have a uniform, fine-grained microstructure, which gives them exceptional mechanical properties. This makes them ideal for use in a wide range of applications, including aerospace, automotive, and energy industries.

Key benefits of atmospheric plasma spray

One of the key benefits of atmospheric plasma spray is its versatility. It can be used to deposit a wide range of materials, from metals and ceramics to polymers and composites, onto a variety of substrates, including metals, ceramics, and polymers. The coatings produced by atmospheric plasma spray are highly customizable, and their properties can be tailored to meet specific requirements. Other benefits include:

• Most flexible of all the thermal spray processes, with sufficient energy to melt any material — even materials with high melting points such as ceramics. 
• Excellent control of coating thickness and surface characteristics such as porosity and hardness 
• Widely used for high-volume production

Atmospheric plasma spray process description

A strong electric arc is generated between a positively charged pole (anode) and a negatively charged pole (cathode). This ionizes the flowing process gasses into the plasma state. The powder feedstock material is injected into the plasma jet, melting the powder particles and propelling them onto the workpiece surface. 

In addition to conventional atmospheric plasma spray guns, Oerlikon Metco has pioneered cascading arc plasma spray guns. Cascading arc spray guns constrain the arc between the anode and cathode, resulting in a more controlled spray plume. In turn, this results in more homogeneous heating of the plasma particles, and significantly increases the possible spray throughput (measured as deposit efficiency times spray rate). The resulting coatings are more reliable and can be applied faster. 

Atmospheric plasma spray process basics

• Heat source: arc 
• Feedstock: powder (ceramics, metals, alloys, blends, carbides and others) 
• Plasma temperature: approx. 16 000 °C (28 800 °F) 
• Particle velocity: up to 450 m/s (1 500 ft/s) 
• Approximate application rate: 4 to 8 kg/h (9 to 18 lb/h) 

Overall, atmospheric plasma spray is a highly advanced and versatile technique that offers a wide range of benefits for industrial applications. Its ability to produce high-quality coatings with exceptional mechanical and physical properties has made it a popular choice for a variety of industries, and it continues to be a key area of research and development in the field of materials science.

Plasma Coatings: Same, Same or Different?

Plasma coatings and coatings resulting from the atmospheric plasma spray (APS) process are related but not exactly the same. Plasma coatings, in a broader sense, refer to any coatings applied using a plasma-based technique, which can include various methods such as thermal spraying, chemical vapor deposition (CVD), physical vapor deposition (PVD), and others.

Materials used for plasma coatings vary depending on the specific application and desired properties of the coating. Some common materials include:

Ceramics: Such as alumina (Al2O3), zirconia (ZrO2), and titania (TiO2), which are often used for their high temperature resistance, wear resistance, and thermal insulation properties.

Metals and Alloys: Including nickel-based alloys, cobalt-based alloys, and stainless steels, which can provide corrosion resistance, wear resistance, and thermal barrier properties.

Carbides: Such as tungsten carbide (WC), chromium carbide (Cr3C2), and titanium carbide (TiC), known for their hardness and wear resistance.

Cermets: Combinations of ceramics and metals, offering a balance of properties such as hardness, toughness, and resistance to corrosion and wear.

Polymers: Some plasma coating techniques can also be used to apply polymer coatings, providing benefits such as chemical resistance, lubrication, and electrical insulation.

So, while coatings resulting from the APS process are a type of plasma coating, not all plasma coatings are produced using atmospheric plasma spray. There are other plasma-based coating techniques that utilize different processes and equipment.