Synthesis and Comparison of Two cBN Composites with Starting Ternary Carbide Binders

Abstract

Ti3SiC2 and Ti3AlC2 are two promising binders for the ultrahard composite polycrystalline cubic boron nitride (PcBN). In this study, the cBN composites with Ti3SiC2 and Ti3AlC2 binders with different binder contents were synthesized under the same high pressure (~5.5 GPa) and high temperature (1350 °C) conditions. Their mechanical properties were measured separately, including Vickers hardness, bending hardening, and compression hardening. Together with XRD results, the phase compounds were also investigated. The decomposition and reaction processes were affected by binder content. Some new compounds formed during sintering, these compounds were TiC, TiSi2, SiC, TiB2, SiB4, TiB2, and TiC0.7N0.3 in Ti3SiC2-cBN composites, as well as TiC0.7N0.3, TiB2, and AlN in Ti3AlC2-cBN composites. The microstructure of the cracks surface was obtained after the bending tests, and was used to further investigate and compare their crack mode by SEM. The crack surface profile and elementary analysis on the oxidative surface were also discussed.