The effect of SiC whiskers addition on the microstructure and mechanical properties of a (Hf-Ta-Zr-Nb-Ti)C-SiC composite

High-energy ball milling of carbide powders, mixing with SiC whiskers, and following spark plasma sintering was used for the processing of a (Hf-Ta-Zr-Nb-Ti)C-SiC composite. A high relative density composite (99.4%) was achieved consisting of a single-phase high-entropy carbide (HEC) matrix and homogenously distributed SiC phase with evident degradation of the whiskers to particles. The grain size of the HEC matrix was in the range of 1.0-5.0 & mu;m and the diameter of the SiC phase was about 0.5-6.0 & mu;m with a low aspect ratio. The nano-hardness of the HEC matrix and SiC phase was about 38 GPa and 42 GPa, respectively. The microhardness increased with SiC addition from 24.4 to 28.7 GPa together with the indentation fracture resistance from 2.68 to 3.16 MPa m1/2 in comparison with the monolithic HEC of similar relative density and grain size. The toughening mechanisms were revealed to be crack deflection, crack branching, and crack bridging.