Toughening mechanism of NbC–Ni cermets by incorporating graphene-coated silicon carbide whiskers

Graphene-coated silicon carbide whisker (SiC w @MLG)-reinforced NbC-Ni cermets were successfully fabricated via high-energy ball milling combined with microwave sintering. The effect of SiC w @MLG content on the microstructural evolution and mechanical properties of the cermets was systematically investigated, with a particular focus on elucidating the underlying toughening mechanisms. Microstructural characterization revealed that multilayer graphene (MLG) formed a uniform and continuous coating on the surface of SiC w , and this core-shell structure remained stable in the NbC-Ni matrix. The cermet with 1.5 vol.% SiC w @MLG exhibited optimal mechanical performance, with a fracture toughness of 15.811 MPa·m 1/2 , a Vickers hardness of 1293 kg/mm 2 , and a flexural strength of 1360.6 MPa. These values are 22.65%, 24.69%, and 22.65% higher than those of the unreinforced cermet, respectively, representing significant improvements. The enhanced mechanical properties were primarily attributed to the synergistic effects of multiple mechanisms, including grain refinement, whisker pull-out, crack deflection, and crack bridging induced by the SiC w @MLG reinforcement. • SiC w @MLG-toughened NbC-Ni cermets were synthesized via integrated high-energy ball milling and microwave sintering methodologies. • The NbC-Ni cermet sample with the addition of 1.5 vol.% SiC w @MLG exhibits the optimal comprehensive mechanical properties, with a hardness, strength, and toughness of 1293 kg/mm 2 , 1360.6 MPa, and 15.811 MPa·m 1 / 2 , respectively. • SiC w @MLG enhances the comprehensive mechanical properties of NbC-Ni cermets through mechanisms including limited solid solution of SiC whiskers, SiC whisker pull-out, as well as crack bridging and deflection.