High pressure sintering of cubic boron nitride using Co–V–Al alloy as bonding media

•Homogenous cBN +(Co–V–Al) compact was sintered at 5.6 GPa and 1600 °C.•Addition of V into the catalyst increases the ratio of the cBN–cBN direct bonding.•Increase of Al content in Co–V–Al metal catalyst will decrease the hardness.

Fine-grained polycrystalline cubic boron nitride compacts were prepared using the mixture of cubic BN and Co–V–Al powders at 5.6 GPa and 1700 °C for 0.5 h. The weight percent of Co, V and Al to cubic BN powder was 10 wt.% or 20 wt.%. Results of electron dispersive spectrum were suggested that binder composition was changed from metallic binder of Co and V was dominant to VN and AlN mixture was dominant with increase of atomic percent of Al to BN in the sample. Microstructures of the sintered samples were observed by scanning electron microscope and back scattered electron image. The region of atomic weight ratio of Al to V that was about 1–5 showed homogeneously sintered microstructure of less than 3 μm of cubic BN grain size. The Vickers hardness trend that showed higher values in the region of atomic weight ratio of Al to V was about 1–5. The highest Vickers hardness resulted in the present study was about 40.7 GPa for the 20 wt.% metallic binder that contained a 1.39 atomic weight ratio of Al to V and 0.5–2 μm size of starting cubic BN powder was used.