Microstructure and Mechanical Performance of Diffusion Bonding Joints of 316L Ss with Ni Interlayer

The diffusion bonding of 316L stainless steel with Ni interlayer in the temperature range of 850-1050°C, under a uniaxial pressure 10 MPa for 60 min is investigated. The diffusion bonds have been evaluated light microscopy, SEM, X-ray diffraction and tensile test. The main result is that the introduction of the interlayer may reduce the room temperature strength but increase the high temperature strength. This is attributed to the transformation of Fe0.64Ni0.36 formed in bonding process into FeNi3 at high temperature. Kirkendall voids are formed in the Ni interlayer near the interface where the specimen fractured. Fractographic study indicates that the fracture mode of the joints is strongly affected by the bonding and testing temperature. The fracture is a mixed mode of brittle and ductile fracture in high temperature tensile test, while it is brittle fracture at room temperature.