Evaluation of feasibility of tungsten/oxide dispersion strengthened steel bonding with vanadium insert

A diffusion bonding (DB) technique to reduce thermal expansion coefficient mismatch between tungsten (W and oxide dispersion strengthened ferritic steel (ODS-FS) was developed by applying a vanadium (V) alloy as an insert material. In order to suppress phase precipitation at the interface, DB of ODS-FS and V4Cr4Ti was carried out by introducing a Ti insert as a diffusion barrier between V4Cr4Ti and ODS-FS, and examined feasibility of W/V/Ti/ODS-FS joint for application to fusion reactor components by comparing the three-point bending strength and microstructure between the joints with and without a Ti diffusion barrier layer. It is shown that the fracture strength of the joint without a Ti insert was decreased by 25% after aging at 700°C for 100 h, but that with a Ti insert shows no change after the aging treatment up to 1000 h. The result indicates that the introduction of a Ti insert leads to the prevention of the formation of phase during aging and resultant control of the degradation of the bonding strength.