Reaction-driven formation of ZrC-SiC interlayers for high-strength joining of monolithic CVD β-SiC and SiCf/SiC composites

A reliable joining method for monolithic CVD β-SiC and SiC/SiC composites was developed using an in-situ formed ZrC-SiC interlayer. A ZrSi₂–C powder mixture was employed as the raw material, and joining was performed via field-assisted sintering technique (FAST). Initially, the joining conditions were optimised for CVD β-SiC ceramics by varying the interlayer composition (ZrSi₂ and ZrSi₂ + C) and processing temperature (1400–1650 °C). The joints produced using a non-stoichiometric mixture of raw materials (ZrSi₂:C = 1:1.5) at 1600 °C exhibited a uniform interlayer and the highest flexural strength (∼ 270 MPa). Furthermore, the joints maintained structural integrity up to 1400 °C and retained a flexural strength of 125 MPa at 1500 °C, without decomposition of the ZrC-SiC interlayer. Finally, the optimised joining conditions were successfully applied to SiC/SiC composites, yielding an apparent shear strength of ∼ 87 MPa.