Impact of sandwich joint on mechanical and ballistic performance of high-hardness armor steels

Abstract This study investigates the mechanical and ballistic performance of welded armor steel joints using two distinct filler materials, focusing on fully austenitic and sandwich joint configurations. Robotic gas metal arc welding (GMAW) was utilized to achieve precise and consistent welding parameters. The analysis thoroughly examined microstructure, hardness, tensile strength, Charpy impact toughness, and ballistic resistance. The fully austenitic joint offered excellent ductility and energy absorption but lacked the hardness to withstand ballistic impacts, resulting in complete penetration in the weld region. Conversely, the sandwich design, combining the exceptional toughness of the ASS layer with the superior hardness of the hard-faced interlayer, achieved excellent ballistic performance by resulting in only partial penetration (11 mm/15 mm of thickness). However, sandwich design led to a reduction in yield strength (41%), tensile strength (27%), elongation (62%), and toughness (48%) compared to the austenitic joint. It is also important to point out that in both designs, the heat-affected zone (HAZ) maintained hardness levels that were compliant with military standards (lower than 15.9 mm), ensuring structural reliability under impact conditions. Ballistic tests also confirmed that HAZ regions in both designs provided ballistic protection with a maximum penetration of 6.8 mm/15 mm. These findings underscore the balance between hardness and ductility in welded armor steels, offering critical insights for refining welding designs in defence applications. The study concludes that the sandwich design provides a robust solution for applications demanding high ballistic resistance, with potential implications for the defence industry in establishing new standards for welded armor steel joints.