HVOF: An Overview

What is HVOF?

HVOF (high velocity oxy fuel) coatings are applied through an HVOF spraying process using either a liquid or gas fuel HVOF gun. The process provides high bond strength, maximum hardness, high density, and greater coating thickness.

Which materials can have an HVOF coating?

HVOF coatings are used on materials such as:

Metals

Alloys

Ceramics

Composites

Tungsten carbide

Chrome carbide and chrome oxide

Carbides

Chilled iron composites

And other hard-to-grind materials

Why do I need a superabrasive for HVOF?

Like grinding ceramics, carbide, or other hardened materials, when grinding HVOF coatings, it is best to use a resin or vitrified bond diamond grinding wheel. Because HVOF coatings are denser and harder, they require a different approach to grind the material to achieve the required finishes and geometries.

Since diamond wheels are exceptionally hard, they can grind substantially higher levels of the coating compared to silicon-carbide and aluminum-oxide wheels. They maintain size and keep the conformity of the part better.

HVOF Applications & Industries

HVOF coatings can be utilized in many applications and industries to include:

Aerospace

Compressor repair

Pump repair

Paper mills

Oil fields for downhole mandrels

Valve repair

Maritime applications

How is HVOF quality defined?

HVOF coating quality is judged by measuring:

Porosity

Oxide content

Macro and micro hardness

Bond strength

Surface roughness

Recommended grinding method for HVOF coatings:

Typically, wet grinding is recommended for grinding HVOF because of the advantages it offers.

When wet grinding, a harder grinding wheel can be used without increasing the likelihood of heat cracking. It also minimizes surface particle detachment and achieves an optimal surface finish. The grinding wheel will not load up as quickly with wet grinding and requires lesser truing intervals.

In addition, wet grinding also aids in washing away debris residue. The concentration and filtration of the grinding fluid also has an effect on the surface finish.

Keys to success

The key to successfully grinding HVOF coatings is to follow the correct procedures. These include proper selection of the grinding wheel (grit size, grade, and bond type) and proper mounting, balancing, truing and dressing of the wheel prior to grinding.

Eagle’s Solutions

Our HVOF grinding wheels are customized and manufactured with HVOF coatings in mind. Based on your application, our engineers will formulate a solution with the correct bond system, grain, shape, and grit to achieve your operational goals.