Exploratory metallurgical evaluation of worn rails from a 90 mm electromagnetic railgun

A set of rails made from a copper chromium zirconium alloy were retired after approximately 88 shots most with aluminum plasma driven armatures. One rail was sectioned and a metallurgical analysis was performed to determine the effects of service conditions on the material. Analytical techniques included measurement of hardness, electrical conductivity, macroetching for grain structure observation, microscopic and penetrant inspection of surface conditions, scanning electron microscopy, and other techniques. In addition, a sample of boning chips removed in sizing the bore of a working gun were analyzed with chemical and metallurgical techniques. The analysis showed that electrical conductivity ranged from 69.0 to 88.2% IACS, hardness ranged from 60.8 to 72.2 Rockwell B, microhardness averaged 144 DPH within 3 mm of the bore, and the bore was covered with an adherent deposit. No evidence of surface melting was observed.<>