Investigation of tungsten/MA956 steel diffusion bonding with an Nb/Ni composite interlayer

Abstract

Diffusion bonding is an effective method for joining dissimilar materials. In this study, dissimilar metals of MA956 steel and tungsten (W) were diffusion bonded with Ni/Nb composite interlayer. The experiments were carried out at [Formula: see text], 20 MPa for 20 min in vacuum by spark plasma sintering (SPS) technique. The microstructure and mechanical properties of the bonded joints were evaluated. SEM images and the results of elementary composition indicate that no intermetallics formed at Ni/MA956 steel and Nb/W interfaces, but [Formula: see text] and [Formula: see text] formed at the Nb/Ni interface. Compared with the directly bonded joint between W and MA956 steel, the average shear strength of the joint with Nb/Ni composite interlayer significantly increased to 270 MPa. Although the result of joint residual stresses simulation shows that the maximum residual stress was near the W substrate, the joints with composite interlayer in shear experiments fractured at Nb/Ni interface. The hardness changes along joint interfaces indicate the formation of intermetallic compounds and solid solution phases in the diffusion layers.