Synthesis and grain size control of cubic BN using Co–Cr–Al base alloy solvents under high pressure

• The P-T region of cBN formation in Co-(Cr, Mo)-Al and Co-(Cr, V)-Al was similar.
• Exchanging Mo to Cr in the solvent was effective to obtain 500 μm cBN crystals.
• Replacing Cr with V resulting fine grain cBN crystals to about 10 μm.
• Systematic change of grain size of cBN in Co-(Cr, V)-Al system was confirmed.

Cubic boron nitride (cBN)-metal composites were synthesized from hexagonal boron nitride (hBN) using Co–Cr–Al base alloy as infiltration solvents under high pressures and high temperatures. To control the grain size of the cBN crystals, Mo or V was used as a substitute of Cr in the base alloy. The pressure–temperature region of the cBN formation under Co–(Cr, Mo)–Al and Co–(Cr, V)–Al systems was determined at pressure between 4 and 6 GPa and temperature up to 1700 °C. It was confirmed that cBN was obtained at pressures above 4.4 GPa and temperatures above 1290 °C. The grain size of cBN synthesized using Co–(Cr, V)–Al solvent was relatively finer comparing with the ones synthesized with Co–Cr–(Mo)–Al alloy solvent. Under the Co–(Cr, V)–Al alloy solvent system where both Cr and V exist, the grain size of the synthesized cBN could be controlled by changing the composition of Cr and V in the solvent.

Optical photographs of the recovered cBN crystals at the hBN source-metal solvent interface of the sample obtained after HP–HT treatment. (a) sample with Co64–Cr20–V13–Al3 solvent, and (b) sample with Co49–Cr16–Mo32–Al3 solvent.Synthesis conditions were 4.2 GPa and 1300 °C for 1 h.Figure optionsDownload as PowerPoint slide