Microstructure and mechanical properties of diffusion bonded single crystal to polycrystalline Ni-based superalloys joint

Bonding of a single crystal Ni-based superalloy to a polycrystalline Ni-based superalloy was carried out through diffusion bonding and the microstructure and mechanical properties of the joint were investigated. A diffusion zone with a width of 35 μm was formed due to elements diffusion. From the single crystal substrate to the diffusion zone, the shape of γ′ phase changed from cuboidal to columnar. The hardness of the diffusion zone was a bit higher, which can be attributed to the precipitation of the fine γ′-strengthening phases. The average shear strength of 433 MPa was obtained and the fracture presented a plastic characteristic.