Enhancing the high-temperature performance of high-entropy ceramic/Zr-4 joints via Ni-assisted reactive brazing

Zr-4 alloys exhibit limited oxidation resistance at elevated temperatures, severely restricting their use in extreme environments. High-entropy ceramics (HECs), owing to their exceptional thermal stability and oxidation resistance, have emerged as promising candidates for protective cladding applications. However, reliable joining techniques and a comprehensive understanding of the interfacial phenomena between HECs and Zr-4 alloys are still lacking. In this study, reliable HEC/Zr-4 joints were successfully fabricated via reactive brazing using a pure Ni interlayer. Optimal joining of HEC and Zr-4 was achieved at 1100 °C for 10 min, forming a microstructure of HEC/TaC + ZrC/Zr₂Ni + Zr(s, s)/Zr-4. A continuous ZrC layer effectively alleviated thermal expansion mismatch, achieving high shear strengths of 118 MPa at room temperature (RT) and 109 MPa at 800 °C. Oxidation tests demonstrated that residual Ni at the interface facilitated the formation of a compact oxide layer, which significantly suppressed oxygen ingress. After oxidation at 900 °C for 4 h, the joints retained 90 % of their initial shear strength, indicating excellent high-temperature stability and oxidation resistance.