The Repair of Magnesium Rotorcraft Components by Cold Spray

Abstract

The U.S. Army and Navy have experienced significant corrosion problems with magnesium alloys that are used to fabricate aircraft components. The most severe of these are associated with large and expensive transmission and gearbox housings for rotorcraft, which have to be removed prematurely because of corrosion, adversely affecting fleet readiness and safety. Many of the parts cannot be reclaimed because there is not an existing technology that can restore them adequately for service. The replacement of these parts is very expensive ranging in the millions of dollars every year. One common repair technique, used for some of those parts that can be salvaged, involves the use of aluminum shims, which are adhesively bonded over areas where the corrosion has been ground down and dimensional restoration is required. The U.S. Army Research Laboratory (ARL) Center for Cold Spray has developed a cold spray process to reclaim magnesium components that shows significant improvement over existing methods and is in the process of qualification for use on rotorcraft. The cold spray repair has been shown to have superior performance in the tests conducted to date, is inexpensive, can be incorporated into production, and has been modified for field repair, making it a feasible alternative over competing technologies. The work presented in this chapter represents the first two years of a three-year effort, which will result in the establishment of a demonstration cold spray facility at the Naval Air Depot at Cherry Point, North Carolina (NADEP-CP) where the overhaul and repair of Navy rotorcraft is accomplished. The program involved the participation of all branches of the U.S. Department of Defense, major U.S. helicopter companies, academia and international participation.