Plasma Spray Coating Services

Some coatings will not melt in a combustion flame no matter how long you hold them there. Alumina, chromium oxide and zirconia need far more heat than an oxy-fuel gun can produce. That is the work our plasma spray coating services handle, along with carbides, metals and abradables on parts that cannot afford to warp.

Of all the thermal spray processes, plasma is the most flexible. We can put almost any ceramic, cermet or metal onto a wide range of substrates with a strong bond and very little heat going into the part. Our New Jersey shop has been doing it since 1944, with engineers, a materials laboratory and a machining department working in the same building.

How Plasma Spraying Works

A plasma gun strikes an electric arc between an electrode and a concentric nozzle while a high flow of inert gas runs along the arc. Depending on the material, we use nitrogen and hydrogen, or argon with hydrogen or helium. The arc turns that gas into a plume hot enough to melt refractory ceramics.

We inject powder into the plume near the nozzle. The expanding gas throws the molten particles forward at high speed, and they flatten against the prepared surface, building a well-bonded coating one pass at a time.

What engineers care about most is where the heat goes. It stays in the plume. The part itself is not heated above 250°F, so shafts stay straight, thin walls stay round and heat-treated parts keep their properties.

Advantages of Plasma Spray

The material list is close to unlimited. Metals, ceramics, cermets and refractory materials can all be sprayed, and our laboratory can blend materials when a job needs a special-purpose coating.

Substrates are just as varied. We coat steels, other metals, ceramics and some plastics, and we have even sprayed onto wood with good results. Depending on the materials, the bond can be mechanical, semi-fused or metallurgically fused.

Plasma can also build parts outright. By spraying onto a removable mandrel, we have made free-standing parts from tungsten, tungsten carbide, ceramics and other combinations.

Coating Systems We Apply

Our plasma work falls into five families. Each material below links to its data sheet.

Oxide Ceramics for Wear and Insulation

Alumina carries most of our dielectric work. We spray plasma white alumina and premium grade white alumina for electrical insulation and wear. The titania-modified grades, alumina-titania and nano alumina-titania, give up a little hardness for toughness. We also apply titanium dioxide.

Chromium Oxide Ceramics

Chromium oxide ranks among the hardest oxide ceramics in thermal spray, and we reach for it often when sliding wear is the problem. Our chromium oxide-silica blend is a close relative.

Thermal Barrier Ceramics

Zirconia slows the flow of heat into hot components. Our zirconia, titania and yttria composite is part of our thermal barrier coating work.

Carbides

When abrasion is the issue and plasma is the right process, we spray plasma tungsten carbide and plasma chromium carbide. If the goal is the densest possible carbide, our HVOF coating services are usually the better route.

Metallic Bond Coats and Abradables

Molybdenum-nickel-aluminum and nickel-iron-aluminum work as bond coats and buildup layers. For clearance control in turbines and compressors, our aluminum-polyester and aluminum-graphite systems produce abradable seal coatings.

Surface Preparation and Bond Coats

Plasma coatings grip the surface mechanically, so preparation sets the limit on how well they perform. We clean each part, take off any heavy oxidation and grit blast to a fresh, rough profile. Many parts are preheated afterward to drive off moisture.

Ceramic topcoats normally sit on a metallic bond coat. Alloys such as nickel-aluminum hold onto the substrate well and give the ceramic something compatible to bond to. The bond coat also helps the layer cope with the different rates at which metal and ceramic expand when heated.

Finishing Plasma Coatings to Size

We usually spray a little oversize and finish to the drawing. Ceramics and carbides are ground with diamond wheels, and many can be lapped or polished very smooth. Abradables are the exception: they are always machined, never ground.

That finishing happens in our own machining, grinding and lapping department. With turning up to 48 inches in diameter and grinding up to 30 inches, big rolls and shafts never leave the building between spraying and final size.

Plasma Spray vs. Other Processes

Choosing between plasma and HVOF usually comes down to the material. Plasma melts ceramics that HVOF cannot touch, while HVOF produces denser carbide and metal coatings.

Metalizing sprays wire and is a good fit for large structures and corrosion barriers, but it cannot apply ceramics.

Spray and fuse coatings form a full metallurgical bond, at the cost of heating the whole part. Plasma keeps the substrate under 250°F.

Where Plasma Spray Coatings Are Used

Typical jobs include salvaging worn parts, gas turbine and jet engine components, thermal barriers on hot section parts, printing rolls for laser engraving and piston rings. We also spray corrosion and wear resistant surfaces, insulate metal parts electrically, and build free-standing parts for research and development.

Valve balls show how spraying, machining and finishing fit together. For the U.S. Navy, a 6-axis robot coats each ball with alumina-titania ceramic. We then grind and polish it to a super-finish on dedicated valve ball grinding equipment, and an optional PTFE top layer adds low friction and anti-fouling properties. The full story is in our valve balls case study.

Why Work With A&A Coatings

Seven spray booths and an in-house laboratory let us run custom blends alongside production work. Complete machining, grinding and lapping are on site, with turning up to 48 inches in diameter. Over the years we have developed proprietary coatings in house, including Cerami-Pak for packaging and Microcoat for semiconductors. Our facility is certified under MIL-STD-1687A, the Navy thermal spray coating standard, and our quality system is written to MIL-I-45208 and audited by government agencies and prime contractors.

Request a Plasma Spray Quote

Tell us what the part is, what it is made of and what is making it fail. Include a drawing or photo, the coating thickness and finish you need, the quantity and your required date.

Upload files up to 8 MB through our quote form, call 888-679-5460 or reach our sales team.

FAQs

What materials can be plasma sprayed?

Nearly any ceramic, cermet or metal. We spray alumina, alumina-titania, chromium oxide, zirconia composites, titanium dioxide, tungsten carbide, chromium carbide, nickel and molybdenum alloys, and abradable blends. When no standard powder fits, our laboratory can mix materials for a special-purpose coating.

Will plasma spraying distort or weaken my part?

In most cases, no. The heat stays in the plume and the substrate stays below 250°F, so shafts stay straight, thin walls stay round and heat-treated parts keep their hardness. Fused coatings and welding put much more heat into the part.

Is plasma spray the same as a ceramic coating for cars?

No. Consumer ceramic coatings for vehicles are liquids wiped onto paint. Plasma spraying is an industrial process that applies hard ceramic or metal layers to machine components. A&A Coatings is an industrial job shop serving manufacturers, OEMs, maintenance teams and defense contractors, and we do not coat vehicle paint.

What surfaces can you plasma spray onto?

Most metals and many ceramics, plus some plastics. We have even sprayed wood with good results. Every surface is cleaned and grit blasted first, and the right bond coat depends on the substrate and the topcoat.

Can plasma spray restore a worn part to size?

Yes, and it is one of the most common reasons customers call. We build the worn area back up with a compatible coating, then machine or grind it to your drawing dimensions in house. That often costs far less than a replacement part.

Call 888-679-5460 to request a quote with A&A Coatings.