Gun barrel erosion studies utilizing ion beams

H depth profile measurements showed concentrations up to several atomic percent (at.%) in gun barrel materials after firing. Ion implanted 13C marker layers were used in conjunction with NRA to measure the low temperature diffusion of C in gun barrel steel, electroplated Cr, and Ta (a candidate coating for gun barrel liners), following controlled thermal annealing. Ion beam analysis also showed unexpectedly high (∼8 at.%) N concentrations in the near surface (0-2-μm depth) region of gun steel test nozzles exposed to test firings of high-N-containing propellants. This combustion-induced nitriding phenomena appear correlated with reduced erosion of these test nozzles, suggesting a competition between N and C interactions on gun steel surfaces.