High strength and high toughness Csf/SiC composites prepared by laser powder bed fusion/ reactive melt infiltration with the impregnation of boron-and silicone-containing phenolic resin

Abstract

Laser powder bed fusion (LPBF) has emerged as an effective method for preparing complex structured silicon carbide (SiC) ceramics. However, the SiC components demonstrate low strength and high brittleness, which remain major challenges limiting its application. To overcome this limitation, short carbon fiber reinforced silicon carbide (Csf/SiC) composites are prepared by combining LPBF and phenolic resin binder impregnation (PRBI)-reactive melt infiltration (RMI), in which high char yield boron-and silicone-containing phenolic resin (BSiPF) impregnation is used to adjust the carbon density of green bodies and to reduce the pore size of green bodies. By optimizing the impregnation process, the carbon density can be brought close to the theoretical optimal value of 0.84 g/cm3, and the reduction of the pore size is conducive to the improvement of the reaction rate at the early stage of the reaction, which enhance the SiC phase content of Csf/SiC composites obtained by RMI. Meanwhile, the application of BSiPF results in a protective pyrolytic carbon (PyC) coating on the surface of Csf, which can reduce the erosion of Csf by molten Si during the RMI process, thus improving the fracture toughness of Csf/SiC composites. The final Csf/SiC composites exhibit the enhanced bulk density, bending strength and fracture toughness, reaching 2.90 ± 0.01 g/cm3, 257 ± 20 MPa, 3.52 ± 0.15 MPa m1/2, respectively. This study provides a new strategy for effective impregnation technique for the additive manufacturing (AM) of high strength and high toughness SiC composites.