Spall strength and damage formation in additively repaired 304L stainless steel

Additive manufacturing has the potential to make structural repairs of high-value parts a reality, but uncertainties regarding the strength of such repairs under shock loading represent a major barrier to practical implementation. Additive repair techniques can dramatically reduce downtime and unnecessary cost burdens from re-making parts that have incurred small, localized damage, but the mechanical behavior of the repair region must match that of the original part. The unique microstructure that results from repeated heating and cooling during an additive or multi-pass welding repair procedure often leads to dramatically different failure mechanisms, damage formation, and even variations in equation of state or shock wave propagation. In this work, 304L stainless steel samples were damaged via low-load mechanical impact, and subsequently repaired with semi-automated wire-fed laser additive manufacturing such that the damage site was filled. The repaired samples were tested under shock loading from a normal plate impact and soft recovered. The experimental results were used to quantify the performance of the repair relative to the original wrought material in order to better understand the influence of the unique additive material microstructure on the dynamic performance.