Oxidation behavior of Si3N4/TiC nanocomposite ceramic tool materials

Si3N4/TiC nanocomposite ceramic tool materials were fabricated by adding Si3N4 and TiC nanoparticles and with Al2O3 and Y2O3 as additives. The oxidation behavior of Si3N4/TiC nanocomposite ceramic tool materials in the temperature range of 800-1250°C was studied. The results show that the relationship between oxidation mass gain and oxidation time obeys the parabolic law. The oxidation mass gain increases with the increase of content of TiC. The composition of the surface layer of the materials after oxidation were investigated with X-ray diffraction. The results indicate that the surface oxidation layer is constituted of SiO2 and TiO2, and only a little Si3N4 or TiC phase can be found in the oxidation surface layer. This indicates that the surface layer is significantly covered with oxides after oxidation at 1250°C for 100h. There was no obvious decrease of bending strength of the 85% (in mass, with 15% nano-Si3N4) Si3N4/15% TiC sample after oxidation at 900°C for 100h, whereas the strength after oxidation at 1000°C for 100h decreases to 41% of the strength before oxidation. Scanning electron microscope observation indicates mat the initiation and extension of cracks are the main reasons for the decrease of strength.