Original Date: 07/13/1992
Revision Date: 01/18/2007

Benet Laboratories has several refractory metal coatings (including chromium and tantalum) coatings under research and development. Chromium is a good refractory metal coating because it is extremely hard with a high melting temperature (1875 degrees C) and provides excellent resistance to wear, erosion, and corrosion. The use of electrodeposits such as chromium plating and refractory metals to protect ordnance materials is an established industrial practice. Refractory metals are used to protect gun barrels from the erosive and corrosive environment inside a gun tube after firing. When the projectile is fired, extreme temperatures, pressures, and gases are produced near the breech end of the gun. These conditions, coupled with stresses, expose the gun barrel to extreme friction, wear, erosion and corrosion.

High contraction (HC) chromium is the current industry standard for protecting the bore surface of gun barrels. For corrosion protection, a softer, crack-free electrodeposited chromium coating -- called low contraction (LC) chromium -- has been developed by Benet. LC chromium shows negligible contraction after heating, and since it is stronger and contains few cracks, is more suitable than HC chromium for protecting a metal against wear and erosion.

The refractory metals have extremely high melting points. Because of the continued increase in propellant flame temperatures, Benet Labs continues to develop techniques for depositing these materials onto the bore of large caliber guns. Benet is currently focusing on the ion-based physical vapor deposition process, known as sputtering, to deposit the material tantalum onto the bore surface of gun barrels. Benet Laboratories' goal is to find the material/process which will provide coatings with the highest erosion and thermal protection.

For more information see the Point of Contact for this survey.