Microstructure evolution and brazing mechanism of (Ti_0.2Zr_0.2Ta_0.2Nb_0.2Cr_0.2)C high entropy ceramic joint brazed with Ni-based filler

High-entropy ceramics (HECs) have attracted considerable interest due to their distinctive characteristics and promising applications. Developing reliable joining techniques is essential for facilitating their widespread application. In this study, a method for brazing high-entropy ceramic (Ti_0.2Zr_0.2Ta_0.2Nb_0.2Cr_0.2)C using nickel-based fillers was proposed, and the microstructural changes and shear strength of the brazed joints were studied in detail. The brazing seam primarily consisted of Cr₇Ni₃, Cr₂₃C₆, and Ni(s,s). The interfacial bonding was mainly influenced by the formation of a Cr₂₃C₆ reaction layer and the diffusion of Ni into the HEC matrix. Notably, the diffusion of Ni induced a phase transformation from the original HEC to an HEC(Ni diffused) phase with a similar lattice structure. This study presented a novel approach to addressing the issues of inadequate wettability and subpar joint strength in brazing connections of high-entropy ceramics. This facilitated the formation of a semi-coherent interface with a reduced lattice mismatch at the Cr₂₃C₆/HEC interface on the high-entropy ceramic side. Additionally, the favorable plastic deformation ability of Cr₂₃C₆ enhanced joint performance. Consequently, joints brazed at 1100 °C for 10 min achieved a maximum shear strength of 124 MPa.