Pressureless sintered silicon carbide with enhanced mechanical properties obtained by the two-step sintering method

The Two-step sintering (TSS) method was applied to the pressureless sintering of commercial silicon carbide powder doped with boron and carbon. The microstructural and mechanical properties of TSS-SiC were compared to those of sintered SiC obtained with the conventional thermal cycle (CS-SiC). TSS-SiC was densified (97.7% T.D.) at 2050 °C instead of 2200 °C needed for CS-SiC (97% T.D.). Furthermore, TSS-SiC showed finer microstructure and enhanced mechanical properties. In particular, flexural strength of the TSS-SiC materials greatly increased up to 556 MPa, much higher than 341 MPa reached by CS-SiC.