Effect of Sintering Temperature and Applied Pressure on the Properties of Boron Carbide-Silicon Carbide Composites

Abstract: To obtain high density boron carbide-silicon carbide composites, the spark plasma sintering method was used. 50% B₄C–1.5% C–48.5% SiC mixture compositions were sintered at four different temperatures (1800, 1850, 1900, 1950°C) under 50 MPa pressure and four different applied pressures (20, 30, 40, and 50 MPa) at a constant temperature of 1950°C. The boron carbide-silicon carbide composites reached full density (>99% th. density) at 1950°C and under 50 MPa pressure. Samples were characterized using SEM, XRD, and ultrasound analysis. Density, Vickers hardness, Berkovich hardness and fracture toughness were also evaluated. Ultrasound analysis showed that increasing the sintering temperature and applied pressure increased the elastic modulus, shear, and bulk modulus of the composites. The samples densified at 1950°C under 50 MPa pressure, had 409 GPa elastic modulus, 176 GPa shear modulus, and 203 GPa bulk modulus. With increasing sintering temperature and pressure, the hardness and fracture toughness of the composites also increased. Vickers hardness values dramatically increased from 17.55 GPa (1800°C) to 30.78 GPa (1950°C) with increasing sintering temperature. The highest Berkovich hardness value was obtained as 37.37 GPa in the sample sintered at 1950°C under 50 MPa. The highest calculated fracture toughness values were 2.64 MPa m^1/2 (1950°C under 50 MPa).