Residual stress-induced deformation and fatigue crack growth in weld-repaired high-strength low-alloy steel with soft buffer layer

Residual stresses (RS) in a bulk weld-repaired steel structure and thin samples sliced from the welded-section are different due to inevitable variations in the stiffness and boundary conditions. In this study, thin extended compact tension (E-CT) samples for fatigue crack growth measurements were sliced from three extensively weld-repaired high-strength low-alloy (HSLA) blocks with three different welding conditions, i.e. welding with a 4 or 10 mm thick soft buffer layer (BL) and welding without the soft BL. Deformation in the thin E-CT samples with notches due to the partial release of welding-induced RS) was measured, and then the samples were used to measure the fatigue crack growth. In this study, we reported detailed measurements of residual stress-induced (RS-induced) deformation in thin test samples and corresponding fatigue crack growth behavior of an extensively weld-repaired HSLA with or without a thin BL. Three groups of E-CT samples were prepared: weld-repaired HSLA without BL, and weld-repaired HSLA with a 10 mm or 4 mm BL. The RS-induced deformation and corresponding fatigue crack growth were measured, and studied together with the influence of BL. The results showed that the incorporation of a 4 mm BL had a profound influence on reduction of the RS-induced deformation, and the incorporation of a 10 mm BL had a significant influence on the fatigue crack growth behavior in the parent metal, heat-affected-zone and weld metal. Detailed SEM observations show that fatigue characteristics of the weld-repaired HSLA were also influenced by the buffer layer and welding-induced RS.