No abstract

No abstract

The SHS-extrusion method, which combines the combustion processes in the mode of self-propagating high-temperature synthesis (SHS) and the subsequent high temperature shear deformation of the combustion products, was used to obtain metal-ceramic composite materials based on titanium boride with an iron matrix modified by additives of nanoaluminum nitride of grade SHS-Az. It was shown that small additions of nanoscale aluminum nitride powder (3 and 5 wt.%) to the initial mixture of the Ti-B-Fe system had a significant effect on the temperature and combustion rate of the system: the combustion rate decreased from 16 to 9 mm / s and the combustion temperature from 1830-1900°C to 1730-1780°C. The results of X-ray phase analysis showed that the modifying AlN nanopowder decomposed during the SHS process and interacted with titanium and iron matrix forming additional phases of TiN and AlFe 3. This is the main cause of the reduction of the temperature and combustion rate during synthesis. A refinement of the grains of titanium diboride in the modified samples from 0.5-2.5 μm to 0.1-1.5 μm was observed using a scanning electron microscope. Microhardness measurements showed that the obtained compact metal-ceramic materials modified with the nanoscale AlN powder had 10 % higher microhardness values compared to samples without additives.

Compact ceramic electrode materials based on the Ti‒B‒Fe system modified with nanosized particles of aluminum nitride (up to 15 wt. %) were obtained by SHS extrusion. The effect of additives on the combustion characteristics of the studied system, as well as on the structure and phase composition of the obtained materials, is studied. The addition of aluminum nitride increases the content of boride and nitride phases in the final product. It was found that the introduction of modifying nanosized particles of aluminum nitride into the initial charge leads to the grinding of grains of boride and nitride phases, which together increases the microhardness by 10 %, in comparison with unmodified samples.

Compact ceramic SHS-electrode materials based on titanium diboride modified with silicon nitride nanoparticles have been obtained by SHS-extrusion. The phase composition, structure, and physicomechanical properties of the obtained materials have been studied. The results of scanning electron microscopy showed that, in the modified samples, grain refinement of the main phase of titanium diboride is observed, as well as a change in the phase composition of the material. With the introduction of 5 wt. % nanosized particles of silicon nitride, in addition to the main wear-resistant phase TiB2, the formation of phases is observed: TiN, Fe2B and TiSi2 located in the FeTi intermetallic matrix. The average grain sizes of TiB2 and TiN are 0.5 – 2 mm and 2 mm, respectively. With the addition of 10 wt. % Si3N4, the structure of the material consists of TiB2 and TiN phases uniformly distributed in the FeTi intermetallic matrix, and a small amount of Si and B solid solutions. The TiB2 grain size does not exceed 0.5 – 1 mm, and the TiN phase has an average grain size about 0.5 – 1.5 mm. It is shown that the obtained modified ceramic SHS-electrode materials have higher microhardness and hardness compared to the material without Si3N4 additives.