Sintering behavior and mechanical properties of spark plasma sintered ߖSiAlON/TiN nanocomposites

In this study, fully dense β-SiAlON/TiN composites were produced by Spark Plasma Sintering (SPS) method. Si3N4, Al2O3, AlN and TiO2 powders were used as precursors. Starting powders were mixed with high energy ball milling and then were sintered by SPS method (at 1750 °C under pressure of 30 MPa for 12 min.). The milled powders had an average particle size of below ~ 155 nm. The XRD patterns of SPS-ed composites showed that the entire β-SiAlON phase constituent was in the form of Si4Al2O2N6 phase and cubic TiN phase can be formed by the phase transformation of TiO2 in relation with other precursors. FESEM micrographs confirmed that TiN particles were distributed homogeneously throughout β-SiAlON matrix. Mechanical properties evaluation revealed that by adding micro sized TiO2, optimal mechanical properties with a hardness ~14.6 GPa and a fracture toughness ~ 6.3 MPa m1/2 were obtained. The improvement in the fracture toughness was attributed to the presence of the crack deflection as the dominant toughening mechanism in the SPS-ed β-SiAlON/TiN composites.