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

A reliable joining method for monolithic CVD β-SiC and SiCf/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. 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 SiCf/SiC composites, yielding a shear strength of ~87 MPa, which exceeded that of the reference unjoined materials.