Analyzing barrel surface damage in failed large caliber cannons

To elucidate the surface damage characteristics of artillery barrel bores, a dissected 155 mm failed barrel was analyzed. Utilizing macroscopic imaging, SEM and EBSD for characterization, distinct damage patterns were identified. The rifling and forcing cone regions predominantly exhibited fatigue crack patterns, while the mid-bore region also showed signs of fatigue cracks. Notably, the groove region demonstrated frictional wear features. Both the grooves and the lands region at the muzzle end were characterized by frictional wear. A significant finding was the presence of a heat-affected layer along the bore surface, extending from the breech end to the muzzle, with its thickness gradually decreasing. The radial hardness of the bore surface demonstrated a decreasing trend, with the hardness of the heat-affected layer being about double that of the matrix material. The formation of this layer was attributed to the high-energy impact loads the bore surface endures, involving a cycle of high temperature and rapid cooling. This process induces recrystallization, sub-grain structure formation, and continuous grain refinement alongside dislocation annihilation.