Effect of Vickers indented load and microstructure on hardness, bending strength and fracture toughness in sintered silicon carbide ceramics

Vickers hardness, four-point bending tests and fracture toughness evaluation by indentation methods were conducted on reaction and normal sintered silicon carbide (SiC-R and SiC-N) ceramics. To investigate the microstructure on the hardness Hv, the bending strength σf and the fracture toughness KIC, three kinds of SiC-N materials (SiC-NA, NB and NC) with different sintered temperature were prepared. The Hv and the σf decreased with increasing the indentation load P for all materials. The σf was smaller than other materials for the smooth specimens, and the variation of the σf of the material SiC-R was larger than other materials for the smooth and the indented pre-cracked specimens in all cases. The KIC by ISB method and by IF method were almost equal in the same P condition, and the KIC by IF method decreased with increasing the P and saturated in the range of P ≥ 10N for three SiC-N materials