A Comparative Study on the Ballistic Performance and Failure Mechanisms of High-Nitrogen Steel and RHA Steel Against Tungsten Heavy Alloy Penetrators

Abstract

Traditionally, medium-carbon, low-alloy steels with tempered martensitic microstructures are widely used in structural armor applications. There have been continuous attempts to develop alternative structural armor materials that can provide further weight reduction of armored vehicles. In this context, high-nitrogen steel (HNS) plates with austenitic microstructures were studied against a full-scale tungsten heavy alloy penetrator (500 mm in length and 25 mm in diameter), and the results were compared with those of rolled homogeneous armor steels with tempered martensitic microstructures. The ballistic trials on HNS and RHA steel plates were carried out against a WHA penetrator at velocities of 1630 ± 20 m/s (at a 0° angle of attack and a distance of 100 m) to determine the depth of penetration. HNS exhibited higher ballistic performance (i.e., a lower normalized depth of penetration) against WHA long-rod projectiles than RHA steel. The ballistic results were analyzed with the help of the initial mechanical properties and operating failure mechanisms. The better ballistic performance of HNS against tungsten heavy alloy can be primarily attributed to its higher dynamic flow stress. Post-ballistic hardness measurements on crater cross sections indicated that a higher volume of material was involved in energy dissipation in the HNS target than in the RHA steel target. Microstructural analysis showed that adiabatic shear band-induced cracking played an important role in the failure of both steel targets.