Poltoratskiy V. Formation of abrasive superhard composite materials based on diamond and cubic boron nitride structured by carbon binder at sub-atmospheric pressures

The thesis is devoted to the actual scientific and technical problem of creating abrasive superhard composite materials based on diamond and cubic boron nitride due to structuring the powder material by carbon binder at sub-atmospheric pressures. It results in increase of efficiency of grinding and polishing tools based on superhard materials (SHM). It was found that during the formation of the carbon binder from carbon-containing gas (methane) on the surface of particles in the diamond and cubic boron nitride compacts the filamentous carbon particles (whiskers), which bind the particles together, are formed under such conditions: temperature – 1273 - 1523 K; gas pressure – 2.5•104 – 5.1•104 Pa; gas flow rate – 3.1•10-5 – 4.7•10-5 m3/s. It was ascertained that the formation in the structure of the compacts, specifically in space between the grains of initial SHM, globular and filamentous carbon results in increased thermal stability of the compacts, the strength of the compacts is not decreased at heating to 1474 K in argon. It was found that just addition to initial powders the micron powders of diamond or cBN of grain sizes: 3/2, 2/1, 1/0 results in increase of strength of composite by 20 % due to decrease of pore size of the composite. Experimental-industrial test showed advantages of the developed composite materials, a significant increase of durability of the grinding tool and its application.