- Program Areas
- Installation Energy and Water
- Environmental Restoration
- Munitions Response
- Resource Conservation and Resiliency
- Weapons Systems and Platforms
Green Machining of Weapons via Waterjet Technology
Mr. Frank Campo | U.S. Army Armament Research, Development and Engineering Command
The overall objective of this project is to use clean and environmentally friendly waterjet milling to rifle and hone explosively clad Ta-10W lined medium caliber gun barrels, with the technology being easily transferable to all caliber weapons. Medium caliber weapons require the use of chromium through hexavalent chromium plating. ESTCP project WP-201111 identified explosion bonding as a replacement to chromium and hexavalent chromium plating, and demonstrated that explosively bonded Ta-10W clad barrels outperformed chromium plated barrels by a factor of more than 4 to 1, resulting in a significant cost savings. An effective “production/manufacturing ready green” rifling method of explosively bonding Ta-10W lined barrels is the last critical component to full implementation of the chromium-free explosion bonding process and thus finally replacing the use of hexavalent chromium plating on medium caliber weapons.
Abrasive waterjet milling acts as a water-driven precision cutting and milling process. The cutting of the metal by the water jet is accomplished by adding abrasive particles (which are recycled) into the stream of water. Water jetting also provides a dynamic axial component at the nozzle in the form of high frequency pressure pulsations to increase the effectiveness of water jet technology not possible in traditional cutting tools. A high pressure nozzle travels straight down the inside of the gun-barrel with its output head pointed at the gun surface to be rifled. The gun-barrel is then rotated, following a predetermined rotational spin that follows the rifling profile for that particular barrel. The nozzle’s output has a design that contours the shape of the rifling profile as the water/garnet mixture sprays out at a controlled pressure. The major parameters that can be varied to change the dimensions and shape of the metal being cut are the water pressure, pass rate, garnet size, nozzle design, and nozzle angle. This project aims to demonstrate 3D waterjet machining technology on rifling of medium caliber Department of Defense (DoD) weapons, with the technology being transferable to manufacturing in almost all DoD weapons that use rifling and many DoD components and processes that require precision cutting.
The expected benefits to the Army for both large and medium caliber weapons would be significant. For medium caliber weapons, waterjet rifling will allow for the successful implementation of explosive bonding of refractory metal liners (Ta-10W) into a production environment, thus eliminating electroplating of chrome and the associated exposure issues related to hexavalent chromium. Significant environmental and energy savings throughout the weapon lifecycle will be realized with wide adoption of the explosion bonding process within all medium caliber weapons platforms once the rifling has been demonstrated. Hexavalent chromium waste is generated on all DoD sites whose weapons systems use chromium for bore protection. The elimination of a chrome plating bath and a waste treatment stream will provide further cost avoidance as well. Once implemented, all DoD and Government Owned/Contractor Operated (GOCO) sites and contractors that chrome plate on rifled weapons would see a cost savings of more than $25 million over 10 years on all chromium waste-stream treatment and clean-up costs. The process also avoids the creation of costly tooling (broaches) and the use of heavy metals and heat treatments (which often contain cyanide salts) used to make that tooling. The tool savings alone would be $22.5 million over 10 years. Abrasive waterjet technology also eliminates the waste water stream and recycling treatment of oils used in machining weapons. The total life cycle costs associated with waterjet technology would be less than 20% of the total lifecycle cost associated with rifling using broaches. (Anticipated Project Completion - 2018)