This project will demonstrate the feasibility of switching to the environmentally sound cavitation stripping process to remove refractory metal coatings and electroplated chromium deposits on weapons system and components. 

This project will demonstrate a waterjet based cavitation stripping process for the removal of refractory metals (including chromium) on gun barrels by successfully removing electrodeposited chromium as well as tantalum that has been cold sprayed onto the inside of large caliber gun barrels. In cavitation stripping submerged high pressure water generates intense cavitation. Bubbles collapse on surface and generates a shock wave. The resulting shock wave will travel into the material and reflect off the coating-to-substrate interface. The following rarefaction wave can cause high tensile stresses in the coating so that it spalls off. The jet cleans away the coating where it can be filtered for recycling. The process is well suited for gun barrels where water can be contained within barrel.

The use of waterjet technology for cavitation stripping on large caliber weapon systems and components and precision machining (i.e. rifling) would result in significant benefits and cost savings for the Army. Any weapon system or part that is chromium or refractory metal coated (cold spray), which includes small, medium and large caliber gun barrels and numerous sub-parts often must have the chromium stripped off for various reasons. The only way to salvage these very expensive weapons and parts is to reverse electroplate the chromium coating off. This exposes the worker to toxic chromium plating bath fumes and risks contaminating the existing plating baths which then must be disposed of. The costs of the coated barrels and component parts are very significant and often they cannot be salvaged when the deposited coating cannot be removed. Cavitation stripping of these coatings will result in savings of millions of dollars in weapons value over a given year. The project will work with environmental subject matter experts assessing alternatives using the Lifecycle Cost Analysis framework implemented in a Sustainability Analysis. The output will serve to enable other researchers to consider life cycle impacts and costs and to avoid shifting the impact and costs along the supply chain or elsewhere in the Department of Defense.