STRUCTURE AND PROPERTIES OF POWDER MATERIALS BASED ON MECHANOSYNTHESIZED METAL MATRIX COMPOSITES Ni-TiC

Abstract

The article considers the mechanochemical preparation of TiC-Ni composites in reaction mixtures of Ti-C-Ni powders and the formation of the structure of materials during their sintering under pressure. The synthesis was carried out in an AGO-2 planetary ball mill with a mixture processing time of 12 and 20 min; their subsequent sintering was performed at a temperature of 950 °C and a pressure of 130 MPa. The results of diffraction studies are presented for structural-phase transformations in mixtures of equimolar composition of titanium and carbon depending on the nickel content in the range of 50–70 wt.%. It is established that an increase in the Ni concentration leads to a decrease in the size of the formed TiCx crystallites from 29 ± 1 to 16 ± 1 nm. A high carbon content TiC0.88–0.98 carbide is formed in Ti-C-(50 and 60 %)Ni compositions and non-stoichiometric TiC0.62–0.78 at 70 % Ni. The microstructure of dispersion-strengthened grains of the nickel solid solution is formed during sintering of TiC/(50–60 %)Ni mechanocomposites. Titanium carbide inclusions have a spherical shape and a diameter of 60–100 nm. When sintering TiC/70%Ni, depleted titanium carbide has a grain boundary distribution with the formation of large (~400 nm) agglomerates. The microhardness of sintered materials is in the range of 850–900 HV.