Microstructure and Mechanical Properties of Self-Composed Si<sub>3</sub>N<sub>4</sub>-TiN Ceramics Prepared from Si, TiC and TiO<sub>2</sub> Mixed Powder

Abstract

Microstructure and mechanical properties of the self-composed Si3N4-TiN ceramics prepared from Si, TiC and TiO2 mixed powder compacts were studied. Si3N4 matrix and TiN particles were formed during the sintering process of the ceramics. The results were compared with the reaction bonded Si3N4-TiN ceramics prepared from Si and TiN mixed powder compacts. The TiN particles in the self-composed Si3N4-TiN ceramics were finely and homogeneously distributed in comparison with those in the reaction bonded Si3N4-TiN ceramics. The fracture toughness was 5.0MPa·m1/2 in Si3N4 ceramics, which incresed with addition of TiN particles. Fracture toughness of 6.3 and 5.9MPa·m1/2 were obtained at 20vol% TiN for the self-composed Si3N4-TiN ceramics and the reaction bonded Si3N4-TiN ceramics, respectively. The incresed fracture toughness is probably due to the thermal expansion coefficient difference between the Si3N4 and TiN. The fracture strength was 930MPa in Si3N4 ceramics and it was retained up to 20vol% TiN in the self-composed Si3N4-TiN ceramics, whereas in the reaction bonded Si3N4-TiN ceramics the fracture strength was 350MPa at 20vol% TiN, only 40% of the initial value. This is possibly attributed to the difference in the distribution of TiN particles between two-ceramics.