Functional Graded Conductor Rails for Electromagnetic Launchers

The US Navy is pursuing the development of an electromagnetic rail gun (EMRG) for long range naval surface fire support. Such guns have been built and operated successfully on a test basis, however several obstacles prevent them from usage in the field. One specific obstacle is the development of suitable materials for the conductor rails. Copper and Cu alloys have been materials of choice for electrical and thermal conductivity considerations. However, abrasion, rail arcs, balloting loads and molten armature metals easily degrade bare Cu surfaces. As a result multiple firings are not possible without significant barrel repair. In order to maximize electrical/thermal conductivity, Cu alloys are likely inescapable. In order to minimize damage to Cu rail, a material with a high melting temperature and high density is essential. Therefore, a rail structure that most practically meets these requirements would have a Cu-based core and a refractory metal surface. However, issues associated with coefficient of thermal expansion mismatch have challenged the production of such a structure via conventional manufacturing techniques. During a Phase I investigation, the ability to form a functionally graded Cu/refractory metal conductor rail surface will be evaluated. The ability to form net-shape, non-planar geometries and the feasibility to grade the through thickness properties will also be investigated.