Reaction Sintering of Machinable TiB2-BN-C Ceramics with In-Situ Formed h-BN Nanostructure

Soft TiB2-BN-C hetero-modulus ceramics were sintered with the assistance of in-situ reactions during the hot pressing of TiN-B4C precursors. TiB2 formation was observed already after the hot pressing at 1100 degrees C, remaining the only phase identifiable by XRD even after sintering at 1500 degrees C. Analysis of reaction kinetics allows us to assume that the most probable reaction controlling stage is boron atoms sublimation and gas phase transfer from B4C to TiN. Reactive sintering route allows almost full densification of TiB2-BN-C composite ceramics at 1900 degrees C. The processes enable the formation of multilayer h-BN nanosheets inside the TiB2 matrix. The manufactured TiB2-33BN-13C ceramic with K-1C = 5.3 MPa center dot m(1/2) and H-V = 1.6 GPa is extremely thermal shock-resistant at least up to quenching temperature differential of 800 degrees C. The sintered UHTC composite can be machined into complex geometry components.