Brazeability Study of an Additively Manufactured CuCrZr Alloy to Tungsten Using Various Cu-Based Fillers

This study investigates the brazeability of tungsten (W) and a CuCrZr alloy produced by means of additive manufacturing, using four different filler compositions from the Cu-Ge and Cu-Ti systems. The additive process resulted in a CuCrZr alloy with a columnar grain structure and a fine nanodispersion of Cr-rich strengthening precipitates. Brazing with W was performed using three Cu-Ge fillers: Cu13Ge, Cu19Ge, and Cu33Ge, at 1030, 900, and 775 °C, respectively. Increasing the Ge content reduced the brazing temperature but increased brittleness in the braze zone. Only with the highest Ge content (Cu33Ge) was a lack of metallic continuity at the interface observed. A fourth filler, Cu-20Ti, was used at 960 °C, but the braze zone exhibited cracks due to the presence of Ti-rich phases. The hardness of W remained unaffected after brazing. However, the CuCrZr alloy experienced softening caused by the loss of fine precipitate dispersion. To restore the required hardness for application, joints brazed with Cu13Ge and Cu19Ge—those with the best results—underwent post-brazing treatments including solution annealing, quenching, and aging. Cu13Ge joints showed optimal recovery with long annealing times (60 min), achieving a hardness of 116.2 ± 4.5 HV0.1 after aging for 120 min at 450 °C.