Microstructure and Properties of Diamond/SiC Composites Via Hot Molding Forming and CVI Densifying

In order to improve the mechanical properties and thermal conductivity, diamond/SiC composites are fabricated using hot molding forming and chemical vapor infiltration (CVI) densifying. The effects of diamond particle size and grain gradation (maximum particle size of 50–500 µm) on microstructure, mechanical properties, and thermophysical properties of diamond/SiC composites are investigated. The results indicate that the thermal conductivity of composites can be obviously enhanced and the maximum value is 257 W · m⁻¹· K⁻¹ using large diamond particle size and grain gradation. The value is 2.22 times higher than that of the diamond/SiC composites prepared using tape-casting and CVI process (116 W · m⁻¹· K⁻¹). The maximal density, flexural strength, and fracture toughness are found to be 3.16 g cm⁻³, 248.33 MPa, and 4.65 MPa^.m^1/2, respectively. The fracture mechanism of the composites is transferred from diamond particles’ trans-granular fracture to interfacial debonding due to stronger combination between the diamond and the CVI-SiC matrix. Furthermore, JD50 sample has the highest flexural strength (248.33 MPa), fracture toughness (4.65 MPa · m^1/2), and equivalent CTE (4.0 × 10⁻⁶ K⁻¹) compared with other samples. Additionally, its thermal conductivity is also relatively high, making it a suitable high thermal conductivity material.