Kuryliak T. Improving the process of producing diamond - tungsten carbide nanocomposite by modifying diamond nanopowder with tungsten-containing compounds.

The thesis is devoted to the solution of the scientific and technical problem of improving the process of obtaining nanocomposite of diamond - tungsten carbide as a wear-resistant polycrystalline diamond material for working elements of the cutting tools due to activating sintering of the material by increasing the amount of W-C bonds on the surface of diamond nanoparticles as a result of modifying the surface of the initial nanopowders of the diamond with tungsten-containing compounds. The process for producing tungsten diamond-carbide nanocomposite has been improved due to developing a new method of modifying diamond nanopowders with tungsten-containing compounds before adding a basic binder under normal pressure. The essence of the new method of modification is that along with the tungsten trioxide the tungsten-containing solution (aqueous solution of ammonium tungstate), i.e an additional modifying agent, is added, which increases the number of W-C bonds on the surface of diamond particles and improves the bond between the particles. The results of research of interaction in the C-W-O system are defended. The thermodynamics have been analyzed and the kinetics of reactions of oxidation of a diamond with atmospheric oxygen in the presence of tungsten has been studied. It was found that tungsten trioxide reacts with diamond and a W-C bond is formed on the surface that inhibits the process of oxidation of diamond and, in conditions of sintering of nanocomposites, excludes its graphitization through the gas phase. It has been shown that the use of soluble ammonium tungstate as a medium for the preparation of an initial mixture of diamond and tungsten trioxide nanopowders activates sintering of nanocomposite of diamond- tungsten carbide. At optimal temperature the density of the composite increases by 6%, the porosity decreases by 1.7 times, thereby the hardness of the composite is 1.2 times more the hardness of the base nanocomposite.