Development of brazing foils to join monocrystalline tungsten alloys with ODS-EUROFER steel

Results on rapidly solidified filler metals for brazing W with W and monocrystalline W with EUROFER steel (FS) are presented. Rapidly quenched powder-type filler metals based on Tibal–V–Cr–Be were developed to braze polycrystalline W with monocrystalline W. In addition, Febal–Ta–Ge–Si–B–Pd alloys were developed to braze monocrystalline W with FS for helium gas cooled divertors and plasma-facing components. The W to FS brazed joints were fabricated under vacuum at 1150 °C, using a Ta spacer of 0.1 mm in thickness to account for the different thermal expansions. The monocrystalline tungsten as well as the related brazed joints withstood 30 cycles between 750 °C/20 min and air cooling/3–5 min.