Superior ballistic performance of high-nitrogen steels against deformable and non-deformable projectiles

Hot-rolled high-nitrogen steel (HNS) plates were evaluated against AK-47 mild steel core (7.62 mm x 39 mm, deformable) and 14.5 mm armour piercing (AP) (14.5 mm x 114 mm, hard steel core) projectiles. The ballistic results of HNS plates were compared with conventionally used Rolled Homogeneous Armour (RHA) steel plates. The ballistic tests on HNS and RHA steel plates with different thicknesses were conducted against AK-47 mild steel core and 14.5 mm AP projectiles at velocities of 740 +/- 10 m/s and 1000 +/- 10 m/s respectively, in order to find out the minimum thickness required to stop the projectile without perforation. In comparison to RHA steel, HNS exhibited higher ballistic performance (in terms of minimum areal density required) against both AK-47 mild steel core and 14.5 mm armour piercing projectiles. The ballistic results against 14.5 mm AP was studied using an analytical model reported in literature. Detailed post ballistic (microstructural and hardness measurements) investigations were carried out to understand the ballistic performance of the two steels. Further, an attempt has been made to correlate the initial microstructure and mechanical properties with the failure mechanisms activated during ballistic impact and the resulting ballistic performance.