Friction welding of TiAl intermetallics and structural steel by applying Inconel 718 as interlayer

Inconel 718 with thickness ranged from 0.1-1.7 mm was chosen as interlayer to promote weldability in friction welding of TiAl intermetallics and structural steel such as AISI4140, in which the welded joint presents single fin showing less welding deformation on TiAl side. The correlations between tensile strength and the interlayer thickness were analyzed and fitted to a model. It indicates an optimum interlayer thickness ranged from 0.9-1.1 mm where the tensile strength reaches as high as 360 MPa. Otherwise, while the interlayer thickness decreases to 0.1 mm, brittle compounds of TiC, Al₂Ti₄C₂ and M₇C₃ are formed in the welded zone so that the tensile strength decays. Thicker interlayer should be also avoided as double joints may occur at TiAl-Inconel 718 and Inconel 718-AISI 4140, respectively, which lowers the tensile strength to some extent.