Brazing CoCrNi Medium-Entropy Alloy to Yttria-Stabilized Zirconia Ceramic: Microstructure and Mechanical Properties

The joining of CoCrNi medium-entropy alloy (MEA) to yttria-stabilized zirconia (YSZ) ceramic holds significant value due to their distinct performance advantages. In this study, the joining of CoCrNi MEA and YSZ was accomplished through vacuum brazing using AgCuTi filler metal. The influence of brazing temperature on the microstructure and mechanical properties of the joint was investigated, and the microstructure evolution mechanism was analyzed. The emblematic microstructure of the joint was CoCrNi/γ + σ (Co, Cr, Ni)/σ/ Ti (Co, Ni)₃/Ti (Co, Ni)/τ1/ Ag (s, s) + Cu (s, s)/Cu₂Ti₄O + Ni₂Ti₄O/TiO/YSZ. The Cu₂Ti₄O + Ni₂Ti₄O/TiO composite layer was crucial for mechanical properties of joints, and the thickness of Cu₂Ti₄O + Ni₂Ti₄O/TiO composite layer first increased and then tended to be stable as brazing temperature went up. The thickness of Cu₂Ti₄O + Ni₂Ti₄O/TiO composite layer reaches the maximum value when the brazing temperature is 850 °C, and the joint achieves a peak shear strength of 97.9 MPa correspondingly.