Railgun Tribology: Characterization and Control of Multishot Wear Debris

Railgun tribology describes the friction and wear sciences of interacting surfaces in relative motion. The novel tribological feature of railguns is the use of high-speed, high-current sliding electrical contacts for the conversion of the electrical energy in a current pulse into projectile kinetic energy. Several wear processes affect the life of components used to construct the bore of a railgun depending upon the severity of the duty cycle. Following multishot testing without refurbishment in solid-armature railguns, wear products have been observed to accumulate on the contact surfaces of rail conductors. Aluminum-alloy armatures produce wear debris that is chemically complex and structurally inhomogeneous. Because electromagnetic propulsion requires that electrical conduction take place across these debris layers, it is important to understand the factors that influence their structure. A critical question for repeatable and predictable railgun performance and for extended rail life is whether easy conduction occurs through these accumulated wear products. It is possible to control the dimensions and properties of these wear debris accumulations on rail contact surfaces using chemical and mechanical aids. Films of rapidly solidified aluminum with layered structures and high levels of gas porosity are the most common debris on copper rails. It is possible to control the structures of these films and to plow them away when they grow thick. Here, results of characterization and control of wear debris are presented and discussed