New Type Superhard Material Made of Diamond and CBN

People often say that diamond is steadfast and immutable. Of course, it is true, in addition to the situation that they are used to cut iron, cobalt, nickel, chromium, vanadium at high temperatures. On the contrary, cubic boron nitride(CBN) has good chemical inertness, but its hardness is only half of diamond. In order to develop the superhard material suitable for various materials of industry, researchers in China have created the alloy of diamond and cubic boron nitride, which is a combination of excellent properties of two materials.

"Diamond and cubic boron nitride are very easy to form alloy to fill the defects on the performance of each other, because the two are similar in terms of lattice structure and characteristics of the covalence," Professor Duanwei from Sichauan University 's Institute of Atomic and Molecular Physics said. "However, this idea has never been confirmed, because the previous sample is too small to test their actual performance."

Professor He and collaborators from University of Nevada in the United States (University of Nevada) and Chinese Academy of Sciences, published this study on the Journal of Applied Physics created by American association of physics.

In order to synthesize diamond-CBN alloy, researchers mix diamond and cubic boron nitride powder, and put them in a vacuum furnace for calcining two hours under 1300 Kelvin temperature, and then compress them into small ball of 3.5mm in diameter under the pressure of more than 15, PASCAL conditions and under the condition of high temperature above 2000 degrees Kelvin. Small balls will turn cutting tools after grinding and sharpening.

Researchers tested the performance for cutting hardened steel and granite on the CNC lathe. They found that diamond-CBN alloy has great abrasion performance and tool life in cutting hardened steel samples that can rival polycrystalline cubic boron nitride, and it shows a significantly less wear and tear when cutting granite. In addition, this kind of alloy also shows better performance of high-speed cutting, which is more than any polycrystalline cubic boron nitride or polycrystalline diamonds for commercial use.