High strength and self-lubrication graphite/SiC composites

For the reaction-formed graphite/SiC composites, the presence of cracks and poor mechanical properties seriously affect their reliability as wear resistant or sealing materials. In this work, a porous carbon preform was pressure formed first by carbon-composite-powder (PFC@G) and carbon black, impregnated with resin and carbonized subsequently, which can heal the micro-cracks, increased the strength of porous carbon preforms and finally reduce the reactivity of liquid Si and carbon during the reaction forming process. The results show that the modified porous carbon preform has a 4.8 % reduction in porosity and a 3.98 times increase in compressive strength. After reactive melt infiltration, the prepared graphite/SiC composites had a compact and isotropic structure and obtained the highest carbon content of 66.18 vol%. In addition, the coupling effect of the PFC@G size on the carbon content and mechanical properties of composites was studied. With the decreasing of the PFC@G size, the mechanical properties of the composites increased and the carbon content decreased. The sample with a carbon content of 48 vol% and a bending strength of 137 MPa exhibited excellent self-lubrication properties.