Investigation of tungsten/EUROFER97 diffusion bonding using Nb interlayer

Diffusion boning is a preferred method to join tungsten and EUROFER97 for the manufacturing of some components in the fusion technology. To reduce the interfacial residual stresses induced during the diffusion bonding by the large mismatch of their coefficients of thermal expansion, a Nb plate is introduced as an interlayer. The diffusion bonding experiment was conducted for 1 h at 1050 °C and with a pressure which yield at the EUROFER97 side to a calculated creep strain of 8%. Investigations of the bonded specimens show a hard reaction layer consisted of niobium carbides (Nb2C and Nb6C5) at the interface between EUROFER97 and Nb, which can weaken the bonding interface especially at RT. At a testing temperature of 550 °C, the strength of the bonded specimens is improved and close to that of EUROFER97. An improvement in toughness is also observed by means of Charpy impact tests.