Analysis of Railgun Barrel Material

The effect of the number of shots on multiple-launch railgun barrel material performance under significantly high current conditions was studied. Material analysis was conducted on rail samples from four sets of experiments involving increasing number of shots. Cross sections of samples from two locations in the copper rail were examined using a variety of metallographic techniques. During each shot a thin film of molten aluminum from the armature deposited on the rail surface. The deposit became thicker and multilayered with increasing number of shots and was thicker in the bottom half of the vertically oriented rails than in the top half. Preferential removal of material occurred along both rail edges, which resulted in the formation of grooves over the length of the rails. Grooves were deeper near the top edge of the rails compared to the bottom edge. A proposed mechanism for grooving is dissolution of the rail material into molten aluminum flowing toward the rail interior due to aerodynamic drag and over the rail edge due to surface tension effects, assisted by extremely high rail edge temperatures. Asymmetry in the armature-rail gap due to magnetic interactions with the support structure may be the cause of asymmetry in deposit thickness and groove depth