The objective of this project was to develop cold spray coating as an environmentally benign process to replace hard chromium and nickel electroplating used for localized repair of weapons system components.
The approach that the Cold Spray Team has taken was not just to develop a specific coating or set of coatings to replace Cr and Ni electroplates, but also to develop and deploy a holistic approach to cold spray development that would employ all the modern computational an analytical tools at our disposal to develop and optimize the powders, spray equipment, and deposition conditions to bring cold spray coating technology to production rapidly and reliably. The research team has therefore developed modeling and computational methods to determine the optimum powder design, gun design and process parameters.
The research team has also developed the necessary infrastructure for successful production of additional equipment, powders, and coatings for fully industrializing cold spray.
This work has utilized the capabilities of a diverse team led by the US Army Research Laboratory.
The resultant coatings have been evaluated in wear tests, and several tungsten carbide and chromium carbide composite coatings have been shown to be superior in performance to hard chrome and nickel electroplates.
In addition to improved wear, these cold spray coatings appear to be able to be built up in thicknesses that would allow them to be used directly for repairs that would replace the current sulfamate nickel/ hard chrome coatings currently used to bring badly worn or corroded components back to print dimensions.
Finally, not only have powders been developed and demonstrated, but also new applicator and nozzle designs have been developed which are ideally suited to the materials of interest, but can also deposit coatings in hard to coat areas. Specifically, short nozzles and specialty applicators have been produced which can get coatings into gaps or bores as small as two inches in diameter, and has the potential to coat bores as small as 1.5 inches.
The primary benefit of the cold spray development approach that the research team has created in this program is the capability of designing, not just the coatings, but the powders, equipment and deposition processes to bring viable coatings to the market rapidly and successfully. This will make it easier for organizations to increase the speed with which changes can be made in response to environmental and market drivers. Specifically, as regulatory requirements change powder and coating composition changes can be made to accommodate the new requirements.
The improved performance of composite cold spray coatings will reduce sustainment cost and increase readiness by producing repairs that are more reliable and long-lasting, while reducing the Environmental Safety and Occupational Health burdens on the sustainment community. The powders and equipment developed have furthermore been evaluated using Commercial Off-The-Shelf Cold Spray systems that have or are planned to be installed at several military depots including Corpus Christi, Letterkenny, Pearl Harbor, and Puget Sound as well as several contractor and supplier facilities which support the Department of Defense.