Coating of Weapon Components with Bearing Material (Phase 1)

Abstract : Nodular iron pistons for the M174 Recoil Mechanism characteristically yield less-than-desirable service lives; the deficiency being attributed to a lack of fracture toughness of the iron. Consequently, cast steel pistons clad with a bearing material, required since the steel does not offer the built-in lubricity indigenous to nodular iron, were considered as an alternate material. Cost-effective Gas Metal Arc Welding (GMAW) processing techniques were developed to provide an aluminum-bronze bearing surface to the steel pistons. Concurrent laboratory tests were conducted on welded specimens to simulate live-firing performance. The tests included chemical, mechanical and metallurgical analyses. After development of the GMAW procedure, including selection of an aluminum-bronze bearing material, a coated steel piston was manufactured at Rock Island Arsenal and subjected to firing tests. Its performance in the Arsenal simulator followed by live-firing at Yuma Proving Ground exceeded all requirements. Future studies will provide more clad steel pistons for firing tests to verify material performance. In addition, strip welding and explosive bonding methods will be evaluated to determine the least cost method of cladding steel components with aluminum-bronze.