The microstructure and mechanical properties of high-hardness armor-grade steel joints are significantly influenced by welding consumables, directly impacting ballistic performance.

Welding these steels poses challenges such as heat-affected zone (HAZ) softening and hydrogen-induced cracking (HIC). To address HIC concerns, designers employ austenitic stainless steel (ASS) consumables due to the higher hydrogen solubility in the austenite phase compared to the ferrite phase. However, the low hardness and strength of ASS joints adversely affect ballistic properties.

In this study, two methods were employed to enhance the ballistic properties of ASS weld joints: (i) localized strain hardening through laser shot peening and (ii) sub-zero treatment of the weld joints.

Both methods demonstrated a significant improvement in mechanical properties (hardness and tensile properties) by over 20%. However, sub-zero treatment exhibited superior ballistic performance compared to laser shot peening, attributed to the greater depth of low-temperature treatment (15 mm vs. 1 mm).

Microstructure studies revealed that both laser shock peening and sub-zero treatments increased the hardness of austenitic stainless-steel welds through strain hardening. This concurrent enhancement of dynamic flow stress further improved the ballistic properties of the weld joint.

This article is shared by S. Naveen Kumar, V. Balasubramanian, Malarvizhi, Hafeezur Rahman and V. Balaguru