Effect of hydrogen on diffusion bonding of TiAl-based intermetallics and Ni-based superalloy using hydrogenated Ti6Al4V interlayer

The diffusion bonding of TiAl-based intermetallics and Ni-based superalloys using hydrogenated Ti6Al4V interlayer was carried out. The effect of hydrogen on diffusion bonding at different heating rates and the microstructure of hydrogenated Ti6Al4V interlayer after bonding were investigated by using SEM, EPMA, XRD and TG/DSC. It was observed that the fast heating rate promotes improvement of diffusion bonding quality. Specifically, the bonding parameters decreased and the shear strength dramatically increased in comparison with the direct diffusion bonding of the two certain materials. Phase transformation of the hydrogenated Ti6Al4V interlayer performed differently when the heating rate changed from 50 °C/min to 1200 °C/min. The addition of hydrogen optimizes the interface contact and facilitated the elements diffusion. However, the hydrogen in hydrogenated Ti6Al4V starts to escape before bonding at slow heating rate, which weakens the positive effect of hydrogen addition. The fast heating rate prevents the escape of most hydrogen before achieving the bonding temperature, which facilitates the diffusion bonding process.