AbstractThe effect of aging treatment on the microstructures and mechanical properties of new groove T92/Super 304H dissimilar steel joints is studied in this paper. The experimental results show that the heat-affected zone (HAZ) of T92 is mainly composed of coarse-grained and fine-grained martensitic, whereas the microstructure of Super 304H HAZ and weld seam exhibit an austenitic structure. Aging treatment increases the nucleation and growth of second phase particles of the weld joints, especially at T92 side. The weld joints have a low tensile strength (<700 Mpa) and a high tensile strength (>700 Mpa) when the tensile fractures are located at weld seam and T92 base metal, respectively. With increasing aging time, the hardness and tensile strength of the weld joints initially decrease, then increase, and finally stabilize. Moreover, the weld joints have a maximum hardness value at the T92 heat-affected zone. At room temperature condition, the impact absorbed energy reaches the minimum value, which is related to the coarse grain containing equiaxed dendrites in the weld seam.