This work presents a process of technological preparation of powders in order to modify them and obtain a superhard ceramic cutting tool from the nanocomposite material Al2O3-TiC-Ni.
Alumina powders, nickel oxide and titanium carbide were used as substrates and as a consequence of technological preparation of this powders, the grain boundaries of the high-purity alumina powder are modified by segregation of the Nickel(II) oxide phases and by the formation of well-distributed Titanium carbide nanoparticles.
The presence of these phases at the grain boundaries (GBs) drastically affects the evolution of the microstructure, and the properties of the resulting materials.
Thus high dense composites with microstructures formed by an alumina matrix and a very homogeneous distribution of nanophases can be obtained by using spark plasma sintering (SPS) technology. SPS provides a high rate of solidification of the powder composition and high quality and uniform distribution comes be achieved using significantly lower sintering temperature than in other sintering methods.
The nickel content in the final product was limited to 2%, and 25% for titanium carbide. Titanium carbide content was selected to be 25 vol.% for being a concentration over the percolation threshold (fc ~ 16 vol.%). This concentration of the third phase in the form of nano-sized titanium carbide provides the necessary electrical conductivity of this superhard material and consequently suitable for electrical discharge machining.
This composition and method of sintering allows to obtain nanocomposite with required properties of wear resistance and conductivity with high hardness (HV = 25,6 ± 0,7 GPa), flexural strength (σf = 537 ± 88 MPa) and density (ρ= 4,27 ± 0,01 g/cm3).