Diffusion brazing of tungsten and steel using Ti–Ni liquid phase forming interlayer

A diffusion brazing process, for joining of tungsten (W) to steel using liquid phase forming interlayer, was developed for divertor application. Ti–Ni liquid forming interlayer was designed to overcome the large differences in physical properties between W and steel, and to eliminate the need for a high bonding pressure to achieve intimate contact between the bonded surfaces. The diffusion brazing experiment was conducted at 1050 °C for 1 h under 0.2 MPa uniaxial pressure of contact. Metallographic analysis revealed that a good bonding was obtained at both the W/Ni and Ni/steel interfaces, and the reaction products were identified in the diffusion zone. A hard reaction layer containing TiC with a high hardness value of about 20.3 GPa was found at the Ni/steel interface. Joint tensile strength at different testing temperatures was evaluated and all the fracture occurred in the brittle carbide layer