Characteristic evaluation of liquid phase-sintered SiC materials by a nondestructive technique

The nondestructive properties of liquid phase-sintered silicon carbide (LPS-SiC) materials were investigated by an ultrasonic method, in conjunction with the examination of their mechanical properties and microstructures. The damage behaviors of LPS-SiC materials by the cyclic thermal shock were also examined. LPS-SiC materials were fabricated at the temperature of 1820 °C, using the additives of Al2O3, and Y2O3 particles. The compositional ratios of additive materials (Al2O3/Y2O3) for LPS-SiC materials were changed from 0.4 to 1.5 with the total amount maintained at 10 wt%. The LPS-SiC materials represented a good density of about 3.2 Mg/m3 and an average flexural strength of about 810 MPa at an additive composition ratio of 1.5. The properties of LPS-SiC materials such as density and flexural strength were more strongly correlated with the attenuation coefficient than with the velocity of ultrasonic wave. The attenuation coefficient of LPS-SiC materials also increased with the increase of thermal shock cycles, reflecting the increased microcrack density.