Effect of loading configuration on tensile and fatigue behavior of dissimilar resistance spot welds of selective laser-melted maraging steels

Unlike conventional wrought or cast martensitic steels, which are prone to embrittlement and hydrogen cracking, 3D-printed martensitic steels exhibit exceptional weldability due to their tailored microstructural homogeneity and reduced precipitate segregation. This study investigated resistance spot welds (RSWs) in additively manufactured martensitic steel under complex loading conditions, specifically coach peel and KSII configurations. The results reveal that the weld nugget undergoes significant softening due to high-temperature remelting and the dissolution of strengthening precipitates, which reduces precipitation hardening and promotes grain coarsening. Finite element analysis (FEA) of coach peel specimens demonstrated a load-dependent transition in the shear-to-tensile stress ratio, with shear stress dominating at low loads, leading to interfacial fracture, while tensile stress becomes dominant at high loads, resulting in failure within the sheet metal. Furthermore, by extending Dong’s structural stress approach, this study highlights that the diameter of the weld nugget and sheet thickness are critical factors influencing fatigue life, with a strong correlation (R 2 = 0.90). These findings provide new insights into the optimization of weld design and performance for resistance spot welds in a 3D-printed martensitic steel underlining the potential for improved weld reliability and structural performance under complex loading conditions.