Saturday, January 27, 2018

The Process Of Tungsten Carbide Coatings And Their Application In The Industrial Market

By Richard Patterson


Recently, the hard chromium coatings are phased out due to various performance limitations associated with them. This has been influenced by the wide application of viable high-velocity oxygen fuel tungsten carbide coatings which have gained supremacy in the engineering community, both the military and the civilian aerospace. This is because of its adhesive and cohesive abilities and forms durable coatings which are anti-wear to abrasive processes like galling and corrosion.

Similarly, the carbide coatings are also used in plasma sprays where they produce a relatively finer texture depending on the mode of application. In such instances, the flame spray is warranted as a secondary operation for fusibility purposes and to provide a metallurgic coating. Therefore, the carbide as a powdered feed-stock ensures consistent production in its application when HVOF thermal or plasma sprays are used.

The process of application is usually initiated by a jet of combusted high-pressure fuel gas together with oxygen gas. It is then pressurized more in pressure chambers where it jets out via a small diameter-nozzle at an accelerating velocity in a long gas barrel. It is thus mixed with carbide powder at nozzle point where the two attains a supersonic speed.

The speeding mixture of the powder and the gases impart terrific amounts of the motion energy, including the kinetic energy on the on the injected powder particles. This makes the energetic particles to strike the surface making the velocity to yield zero and also the adoption of the kinetic energy which makes them cling instantly to the workpiece in question. This results in the formation of a very dense, cohesive and adhesive coating. Therefore, low porosity and a high bond strength coating are realized.

Some critical instances demand a specified coating texture. It is thus achieved through mixing the carbide powder with the selected binder material containing the desired characteristics. The resulting compound manifest increased hardness due to its higher boiling point. It is thus sprayed by a high-velocity oxygen thermal spray resulting in the formation of a hard and resistant to corrosion coating.

The binder material and chemical technique selected determines the resulting coating characteristics and its ability to curb irritating processes like corrosion, erosion, and abrasion in drastic wear conditions. Through the above technique, it renders it applicable in various industries processes like in paper production where the desired paper output is solely determined by the nature of the rolling surface.

Similarly, the coating is applicable in power generation mostly where coal is the chief fuel source. This is because the component surfaces must be keenly protected from extreme cases of gouging like an abrasion. Also, the coating is also widely used in steel and metal products throughout the entire process. It thus accrues a benefit in that it dramatically manifests reduced maintenance costs and advanced production quality.

Lastly, the adoption of the tungsten carbide coating technology has revealed endless benefits. This is because it is the most durable and efficient mode of coating in that it serves the metal substrate extremely longer time duration. Still, it overpowers the former conventional chrome plating due to its faster deposition rate and does not undergo lengthy processes of embrittlement-treatment.




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