Brazing of high entropy ceramic to Nb using a CoFeCrNiCu high-entropy alloy filler: Interfacial microstructure and mechanism

Effective metallurgical bonding between the (HfZrTiTaNb)C high-entropy carbide ceramic and Nb was successfully established using CoFeCrNiCu as the filler material. The microstructure of the joint consists of (HfZrTiTaNb)C/FCC, Laves, Cu(s, s), NbC, and Nb(s, s)/Nb. The brazing mechanism of the joint was primarily contributed by the diffusion of Nb and C, leading to the formation of Laves and FCC phases at the joint center, and the development of NbC and Nb(s, s) diffusion zones on the Nb side. The composite microstructure of the joint, consisting of the soft FCC phase, hard Laves phase, and NbC, significantly enhances the joint strength. The maximum shear strength of the joint reached 61 MPa under the conditions of 1240 °C for 10 min. Additionally, the effects of brazing temperature and holding time on the microstructure and shear strength was discussed.