Microstructure and mechanical properties of inertia friction welded joints between alloy steel 42CrMo and cast Ni-based superalloy K418

The alloy steel 42CrMo and the cast Ni-based superalloy K418 were successfully joined by inertia friction welding. The effects of the initial flywheel kinetic energy on the microstructure and mechanical properties of the joints were investigated. The results showed that inertia friction welding is a rapid and efficient way to achieve metallurgical bonding between 42CrMo and K418. Intermetallic compounds Fe_0.64Ni_0.36, Ni–Fe–Cr, Ni₃ (Al, Ti) and MC-type carbides like NbC and TiC were observed at the interface containing a diffusion layer because of element diffusion. Elemental distribution analysis indicated that Fe and Ni were intermixed at the interface. The maximum tensile strength of the dissimilar 42CrMo/K418 joint was 772.19 MPa. Tensile fracture was identified to have occurred on the K418 side with brittle fracture features at an initial flywheel kinetic energy of 50.6 kJ. The origin and expansion of the cracks were mainly attributed to the MC carbides.