Preparation and properties of electroconductive Al2O3-based composites

Al2O3-based composites with the addition of 20 and 30 vol.% of TiN, TiC, TiB2 have been produced by hot pressing and by gas-pressure sintering. These electro-conductive, toughened and reinforced composites proved to be suitable for the manufacture of complex shapes by electrical discharge machining. Mechanical, electrical and thermal properties have been correlated to the microstructure and to the composition. The mechanical properties of the hot-pressed samples reveal an increase in fracture toughness of 30-70% and in flexural strength of some 70% in comparison with the Al2O3 matrix at room temperature. The oxidation, which takes place at the secondary phases, strongly affects the flexural strength at relatively high temperatures ( 700°C), limiting the potential operating temperature range for this type of composites.