Effect of Coarse SiC Particles on Thermal Shock Resistance of Recrystallized Silicon Carbide Ceramics

The effects of coarse particles of silicon carbide (SiC) addition on the thermal shock resistance of recrystallized silicon carbide(R-SiC) were investigated.The thermal shock resistance of the ceramics with different formulas was evaluated through residual strength measurement by thermal shock (water quenching) tests at different temperatures.The average linear thermal expansion coefficient of the R-SiC ceramics was tested at 30-120℃.The microstructure of the ceramics was analyzed by SEM and the thermal shock damage mechanism was investigated.The results show that as the increase of the coarse particle SiC (250 μm) addition,the density and critical thermal shock temperature difference of the R-SiC ceramics increased first and then decreased.The ceramic with 50 wt % addition of 250 μm SiC particles had the maximum density of 2.60 g·cm-3,the minimum thermal expansion coefficient of 4.60×10-6/℃,the best thermal shock resistance and critical thermal shock temperature difference of 395℃.A large number of microcracks formed during the R-SiC thermal shock process as the addition of 250 μm SiC particles which absorbed rapidly elastic energy deposited in the material and improved its thermal shock resistance.