Optimizing δ-ferrite structure to enhance high-temperature elongation in ER308L stainless steel deposited metal

As the size and weight of crucial equipment in third-generation nuclear power plants increase, the demand for high-temperature plasticity in welds has become more critical. This study examines the effect of varying δ-ferrite content on the high-temperature tensile properties of 308L austenitic stainless steel deposited metal at 350°C. The results reveal that as the δ-ferrite content decreased from 11.6 to 7.4%, the ferrite morphology shifted from continuous lathy and network structures to a discontinuous skeletal form. Correspondingly, 350°C high-temperature elongation increased from 26 to 32%, while tensile strength remained stable across all specimens, exhibiting good strength and plasticity at room temperature. The discontinuous skeletal δ-ferrite (7.4%) suppresses interfacial crack propagation during high-temperature tensile testing, thereby improving the high-temperature ductility.