Brazing ZrB₂-SiC ceramics to Nb with a novel CoFeNiCrCu high entropy alloy

ZrB₂-SiC ceramic and Nb were brazed by using a novel high entropy alloy CoFeNiCrCu filler. Interfacial microstructure, mechanical properties and brazing mechanism of the joint were systematically investigated. It was found that the activity of Cr could be maintained during the brazing process due to the high-entropy mixing effect of CoFeNiCrCu. The newly generated Cr₂B had a tooth shape and it improved interfacial bonding between ZrB₂-SiC and Nb. A composite microstructure containing a soft FCC and hard Laves phase was formed in the joint due to the presence of Nb and this microstructure significantly enhanced the joint strength. Influences of brazing temperature on the interfacial reaction and shear strength of joint were also investigated. After being brazed at 1160 °C for 60 min, the maximum shear strengths of the joint were 216 and 94 MPa at room temperature and at 650 °C, respectively, indicating the successful use of the filler.