Flame Spray

What is Flame Spray?

Flame spray is divided into three subcategories, based on the form of the feedstock material, either powder-, wire-, or rod-flame spray. Flame spray utilizes combustible gasses to create the energy necessary to melt the coating material. Combustion is essentially unconfined, in that there is no extension nozzle in which acceleration can occur. Common fuel gases include hydrogen, acetylene, propane, natural gas, etc. The lower temperatures and velocities associated with conventional flame spraying typically result in higher oxides, porosity, and inclusions in coatings.

Download Flame Sprayed Coating Video (2.72 MB)

Materials

With the ability of flame spray to process wire, rod, or powders, a wide variety of materials can be made into coatings using the technologies of flame spray. Even high melting point oxide ceramics can be flame sprayed. Lower melting point materials are also flame sprayed. Some flame spray devices are designed to mainly deposit polymers such as nylons and polyesters to create very low porosity plastic coatings.

Industries

Flame spray can be commonly found in industries such as oil exploration, and agriculture. Flame spray and fuse coatings are produced in these industries to provide wear resistance along with excellent impact resistance. There are many other industries that use flame spray technology including aerospace, infrastructure, machine repair, etc.

Applications

An excellent use for flame spray is for producing spray and fuse coatings. These coatings are used where good wear resistance and excellent impact resistance are required such as with agricultural harvesting components, and oil drilling parts. A spray and fuse coating is produced by first depositing a wear resistant material using flame spraying. The coating material is designed to have a lower melting point, like a high temperature brazing material, than the metallic substrate it is deposited onto. After the coating is deposited the part and coating are heated to a temperature between its solidus and liquidus temperatures and it fuses (brazes) to the part creating a tenacious metallurgical bond. The majority of the porosity in the coating is also eliminated resulting in a dense very well bonded coating.

Metallurgical cross section of as-sprayed flame sprayed coatings		Metallurgical cross section of flame sprayed coating that has been heat treated