Effect of Z values on the microstructure and mechanical properties of post-sintered reaction bonded β-SiAlON

β-SiAlON materials with different Z values (Z=0.5-3) were fabricated by a reaction bonding combining post-sintering route using raw materials of Si, Al₂O₃, AlN, etc. The reaction bonded β-SiAlON (RB-β-SiAlON) were post-sintered at 1,750°C for 6 h. Apparent porosity, bulk density, bending strength and Vicker's hardness of the samples before and after post-sintering were tested. XRD results showed that the phase composition of both RB-β-SiAlON and post-sintered RB-β-SiAlON (PSRB-β-SiAlON) were β-SiAlON. For RB-β-SiAlON, the apparent porosity was decreased with the increase of Z values, while the strength and hardness was increased accordingly. After the post-sintering procedure, nearly full densified PSRB-β-SiAlON was obtained and the mechanical properties were significantly improved. The bending strength and Vicker's hardness of the PSRB-β-SiAlON (Z=0.5) achieved 510MPa and 16.5GPa, respectively, which were as 2.7 and 6.7 times high as those of the corresponding RB-β-SiAlON. However, the strength and hardness of PSRB-β-SiAlON decreased with the increase of Z value due to the grain growth.