Improving the mechanical properties of laser-welded joints of GH4169/Nb521 dissimilar materials by using a wedge-shaped Ni interlayer

• Laser-welded GH4169/Nb521 dissimilar material joints were successfully fabricated using a wedge-shaped Ni interlayer • Tensile properties were characterized under both room-temperature and elevated-temperature (500-950°C) conditions. • Post-weld heat treatment effects were evaluated through 950°C/30 min annealing experiments. • The microstructural mechanisms governing joint strengthening were systematically analyzed. Aiming to solve the problem of cracking caused by the brittle intermetallic compounds (IMCs) in the weld zone during the laser welding of ‘Ni - based alloy/Nb - based alloy’, a wedge-shaped Ni interlayer was fabricated via Electro-Spark Deposition (ESD) for laser welding of GH4169/Nb521 joints. The effects of wedge slopes on the microstructure and properties of the joints were investigated. This design effectively suppressed the formation of brittle Ni-Nb IMCs in the fusion zone, expanded the load-bearing area, and redirected stresses at the weak interface—shifting the dominant stress state from normal stress to a combination of normal stress and shear stress. The room - temperature tensile strength of the joint with a wedge slope of 1:6 reaches 391 MPa, which is 80 % of that of the Nb521 base metal. The room-temperature tensile joint failures mainly occur in Nb-rich regions adjacent to the Nb521/Ni interface, where contains significant quantities of Ni 3 Nb and Ni 6 Nb 7 IMCs. At 950 °C, the joint strength reaches 216 MPa with failure in FZ - Ni transition layer interface. The microhardness increase in Nb521 base metal at high temperature alters the joint’s microhardness distribution, weakening the IMC layer’s impact on joint performance.