Gun barrel erosion studies utilizing ion beams

Abstract

Ion implantation and nuclear reaction analysis (NRA) have been utilized as tools to study the migrational behavior of selected erosive light elements (C, N, H) in gun barrel materials. This study was initiated to help provide more quantitative data on light element migration to aid erosion modelers, help promote use of environmentally friendly protective coatings, and better understand erosion mechanisms caused by hot, high pressure, light element propellant gases interacting with the bore surfaces of gun barrels. 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.