Post-Test Characterization of a Chromium-Plated Copper Conductor

Chromium-plated copper rails previously tested as electromagnetic launcher rail conductors were studied. As-received specimens were characterized. To simulate the effect of liquid aluminum that is generated at the sliding interface, aluminum hot-dipping experiments were performed at high temperature. In addition, a further reliquification and spreading experiment to examine aluminum wetting on chromium was conducted. Numerous cracks and voids were found on the chromium layer of as-received specimens, and no molten aluminum–chromium interaction was found at the armature footprint because of the protection provided by the Cr2O3 scale. It was found that cracking due to the coefficient of thermal expansion mismatch upon heating allows oxide-free surfaces to interact with molten aluminum, and oxide formation on the surface of the aluminum deposit prevents the spreading of the deposit.