高熱伝導SiCセラミックスの耐熱衝撃性

抄録

The thermal shock resistance of high thermal conductive SiC ceramics by the water quench method was studied in comparison with other SiC ceramics. The critical temperature difference (ΔT_C) of the flexural strength was dependent on the kinds of SiC ceramics. The high thermal conductive SiC ceramics had the highest ΔT_C value of 680°C. The hot-pressed SiC and pressureless-sintered SiC ceramics with smaller thermal conductivities had the ΔT_C values of 450° and 350°C, respectively. The thermal shock fracture resistance parameters (R′) calculated from the thermal conductivities at 500°C were 22kW/m for high thermal conductive SiC, 16kW/m for hot-pressed SiC and 12kW/m for pressureless-sintered SiC ceramics, which agreed qualitatively with the ΔT_C values. The ratio of the calculated stress intensity factor (K_I) for the crack initiation at the water quenching to the critical stress intensity factor (K_IC) obtained from the flexural strength was in the range of 60-80%, and were approximately constant in any examined SiC ceramics.