Microstructure Evolution and Tensile Properties of Ti3Al/Ni-based Superalloy Welded Joint

In the present work, the dissimilar joining of a Ti3Al-based alloy to a Ni-based superalloy was attempted by gas tungsten arc (GTA) welding technology. Sound joints were successfully achieved by using a Cu-Ni alloy as filler material. According to X-ray energy dispersive spectroscopy and X-ray diffraction analysis results three transitional layers at the weld/Ti3Al interface were verified as follows: Ti2AlNb phase dissolved with Cu and Ni; Al(Cu,Ni)2Ti, (Cu,Ni)2Ti and (Nb,Ti) solid solution; Cu-rich phase and a complex multi-element phase. The In718/weld interface is characterized by solid solutions of Ni, Cu, Cr, Fe and Nb. The average tensile strength of the as-welded joints at room temperature is 163 MPa, and after a post-weld heat treatment it is increased slightly to 177 MPa. The fracture occurred at the surfacial layer of the joined Ti3Al base alloy, indicating that the Ti2AlNb layer dissolved with Cu and Ni is the weak link of the Ti3Al/In718 joint.