Characterization of diffusion bonded joint between titanium and 304 stainless steel using a Ni interlayer

Solid-state diffusion bonded joints were prepared between commercially pure titanium and 304 stainless steel with nickel as an intermediate material in the temperature range of 800–950 °C for 10.8 ks under a 3 MPa uniaxial pressure in vacuum. The interface microstructures and reaction products of the transition joints were investigated by optical and scanning electron microscopy. Up to 850 °C processing temperature, a 300-μm nickel interlayer completely restricts the diffusion of titanium to stainless steel. However, the nickel interlayer cannot block the diffusion of Ti to the stainless side and λ + χ + α-Fe, λ + FeTi and λ + FeTi + β-Ti phase mixtures are formed at the SS–Ni interface, when bonding was processed at 900 °C and above. These reaction products were confirmed by X-ray diffraction. A maximum tensile strength of ∼ 270 MPa and shear strength of ∼ 194 MPa, along with 6.2% ductility, were obtained for the diffusion bonded joint processed at 850 °C. Fracture surface observation in SEM using EDS demonstrates that failure occurred through the Ni–Ti interface of the joints when processed up to 850 °C and through the SS–Ni interface when processed at and above 900 °C.