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

Abstract

Soft TiB2-BN-C hetero-modulus ceramics were sintered with the assistance of in-situ reactions during the hot pressing of TiN-B4 C precursors. TiB2 formation was observed already after the hot pressing at 1100◦ C, remaining the only phase identifiable by XRD even after sintering at 1500◦ 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 B4 C to TiN. Reactive sintering route allows almost full densification of TiB2-BN-C composite ceramics at 1900◦ C. The processes enable the formation of multilayer h-BN nanosheets inside the TiB2 matrix. The manufactured TiB2-33BN-13C ceramic with K1C = 5.3 MPa·m1/2 and HV = 1.6 GPa is extremely thermal shock-resistant at least up to quenching temperature differential of 800◦ C. The sintered UHTC composite can be machined into complex geometry components.