Enhancement of porous carbon preforms for high carbon phase content and excellent tribological properties of graphite/SiC composites

The pore characteristics and microstructure of porous carbon preform plays a critical role in determining the carbon content and overall performance of graphite/SiC composites produced by reactive melt infiltration (RMI). Here, the green bodies were prepared by compression molding of carbon-composite-powders (PFC@G), which is phenol-formaldehyde resin derived glassy carbon coated graphite particles. Polymer infiltration and pyrolysis (PIP) process was then applied to green bodies modified the internal structure of the obtained porous carbon preforms, repair microcracks, fully enclose the PFC@G, and improve strength. This approach reduces the consumption of PFC@G during RMI, resulting in samples with higher carbon content and improved mechanical properties. The strength of the porous carbon preforms increased from 4 MPa to 77 MPa with the number of impregnation cycles. The samples produced after three impregnation cycles exhibit a flexural strength of 97 MPa, a carbon content of 61 vol%, and excellent self-lubricating properties, with a low friction coefficient (∼0.12) and wear rate (∼10⁻⁶ mm³·N⁻¹·m⁻¹). It also demonstrates high thermal conductivity (81 W·m⁻¹·K⁻¹), and favorable oxidation resistance (5 % weight loss after 30 mins at 900 °C).