Large caliber gun barrels for military tanks have a limited life due to erosion and corrosion. To mitigate these damages, the inner surface of the barrel has been electroplated with chromium (Cr) for many years. This process is environmentally unfriendly and produces significant amounts of toxic and carcinogenic waste that is very expensive to dispose of properly. Sponsored by the U.S. Army a few years ago, SwRI developed a Cylindrical Magnetron Sputtering (CMS) technology. In CMS, a solid material such as Cr or tantalum (Ta) (for higher temperatures) is sputter-deposited onto the inner surface of the barrel; therefore, it is an environmentally friendly process that has no toxic waste. SwRI has demonstrated the process on 12-inch long tubes.
The Israel Army has been using the U.S. Army Cr electroplating process. They are facing an urgent problem in that they have to move their gun barrel manufacturing facility to a new location in four years. However, they cannot move the Cr plating operation to the new location due to new stringent Environmental Protection Agency regulations. They learned about the SwRI work and are very interested in having SwRI reestablish the CMS technology and re-demonstrate Ta deposition on short sections of simulated gun barrels before submitting a formal proposal to them.
In this short project, SwRI re-established the CMS vacuum deposition system, re-designed and fabricated a cylindrical magnetron, which is the key component of the CMS process, purchased a Ta target and a few steel tube sections for the CMS deposition process and conducted a few deposition tests. The deposited tubes were sectioned and analyzed using various techniques. Finally, a few deposited tubes were sent to Israel for evaluation.
In this project, we reestablished the vacuum system, re-designed and established a cylindrical magnetron, and conducted a number of tests. We first studied the plasma cleaning process for cleaning both the target and the simulated gun barrel sections. Then we conducted a few deposition tests to deposit Ta on simulated gun barrel sections. Furthermore, we also studied another material Hastelloy C-276 as a potential replacement for both Cr (to eliminate Cr plating) and Ta (to reduce the cost). Finally, we deposited a thick Hastelloy C-276 coating on a tube and sent it to the Israeli Army for evaluation. Based on the results, we submitted a pre-proposal to Israeli Army.