Gun bore erosion mechanisms revisited with laser pulse heating

Prior work has shown that laser pulse heating with appropriate energy and pulse duration reproduces many of the important degradation effects at chromium coated gun bore surfaces. Among these effects are recrystallization and grain growth in the chromium, major cracks in the chromium, a heat-affected zone in the steel substrate, oxidation of steel at the chromium crack tips, and initiation and propagation of blunt cracks into the heat-affected zone of the steel substrate. This report describes further studies of gun steel using laser pulse heating in air, argon, oxygen, nitrogen and hydrogen. The observed features include surface roughening, melting and oxidation-induced composition changes on the steel surface. Computer modeling of the laser pulse process was performed for the specimen configuration used in these experiments. Comparisons of laser pulse heating experiments with data from damaged surfaces of fired gun barrels offer new perspectives on gun bore degradation mechanisms.