Tailoring mechanical properties of Mo-SiC composites through controlled phase formation during reactive spark plasma sintering

The present study investigates the sintering behavior of Mo-xSiC reactive composites (x= 10-40 vol%) using reactive spark plasma sintering (RSPS) at 1700 degrees C for 5 min. The microstructure, phase formation, and mechanical properties of the fabricated composites were evaluated. X-ray diffraction (XRD) analysis reveals the formation of various compounds, including Mo2C, Mo3Si, and Mo 4.8 Si 3 C 0.6 , which increase in intensity with increasing SiC content. It was found that composites with 10 vol% and 15 vol% SiC still contained unreacted Mo phase, whereas larger amounts of SiC resulted in no remaining Mo. Conversely, unreacted SiC particles were detected in all composites. Field-emission scanning electron microscopy (FESEM) and energy-dispersive spectroscopy (EDS) analysis confirm the presence of multiple phases. The flexural strength of the composites exhibits complex relationships with SiC content, with Mo-10 vol% SiC and Mo-15 vol% SiC composites showing superior strength (585+32 MPa and 618+21 MPa) due to the presence of unreacted Mo phase. The strength decreased with increasing SiC content, likely due to the formation of brittle intermetallic phases. Hardness increased with SiC content, with a significant improvement in Mo-20 vol% SiC composite (12.88 + 0.21 GPa), but decreased thereafter. Fracture toughness followed a different trend, decreasing with increasing SiC content due to the elimination of ductile Mo phase and the formation of brittle phases. Therefore Mo-10 vol% SiC and Mo-15 vol% SiC composites exhibited the highest fracture toughness values of 8.34+0.68 MPa.m1/2 and 7.99+0.37 MPa.m1/ 2 , respectively.