Joining of ZrB2-based ultra-high-temperature ceramic composites using Pd-based braze alloys

Hot-pressed ZrB2–SiC and composites with carbon (ZSC) or SCS-9a SiC fibers (ZSS) were joined using Pd-base brazes, Palco (65% Pd–35% Co) and Palni (60% Pd–40% Ni). Joint integrity was exhibited by the defect-free ZS/Palco/ZS joints with large interaction zones. The ZSS/Palco and ZSC/Palco joints revealed substantial chemical interaction and interfacial cracking due to residual stresses. The joints with Palni exhibited either poor wetting/bonding or cracking. The ZS/Palco joints displayed high Knoop hardness within the ZS region and lower hardness within the Palco interlayer.