Effect of single alloying element (Ti, Nb, V, Cu) on microstructure and mechanical properties of dissimilar TiAl/Ni-based superalloy laser joints

Abstract

Dissimilar welding of TiAl-based alloy and Ni-based superalloy with different single alloying element (Ti, Nb, V, Cu) was performed by laser. Detailed effects of alloying element on microstructural characterization and mechanical properties of the joints were investigated. The results showed that laser welding of TiAl/Ni-based superalloy was not achieved by using Ti filler metal. The large number of Ni0.35Al0.30Ti0.35 brittle phases in the joint was the main factor of affecting the weldability of joint. Laser welding was not achieved a better connection by using Nb filler metal, and macrocracks existed in the weld, which mainly attributed to the formation of AlNbNi, AlNbNi2 and Cr2Nb intermetallics. The dissimilar metals was successfully welded by using V filler metal, and (V,Cr) solid solution and (V,Cr)/AlNi2Ti eutectic phase were formed in the weld zone. The average tensile strength of the joint was 140 MPa and the joint fracture occurred on Ni-based superalloy side, owing to the fine (V,Cr)/AlNi2Ti eutectic phase. The dissimilar metals was successfully welded by using Cu filler metal, and Cu solid solution and Al(Ni,Cu)2Ti/Cr eutectic phase were formed in the weld zone. The average tensile strength of the joint was 155 MPa and the joint fracture occurred on TiAl alloy side where more AlCuTi and AlCu2Ti formation has.