Double-layer coated Csf/SiC composite fabricated by LPBF/LSI with improved mechanical properties through fiber damage prevention and crack propagation inhibition

Abstract

The C_sf/SiC composites are fabricated by Laser powder bed fusion/liquid silicon infiltration (LPBF/LSI). To prevent the C_sf from being eroded by molten Si, and optimize the interface between the fiber and matrix, a pyrolytic carbon-silicon carbide (PyC-SiC) double-coated layer is synthesized on the surface of C_sf. The SiC layer prevents the diffusion of molten Si, thereby shielding fibers from erosion. The PyC layer can form a weak bonding interface between the matrix and fibers, facilitating fiber extraction at crack tips during material fracture. The double-layer coating's dual action mechanism of fiber damage prevention and crack propagation inhibition significantly enhances the strength and fracture toughness of C_sf/SiC composites. C_sf/SiC composites with double-layer coated fibers exhibit a maximum bending strength of 257.11 MPa and a maximum fracture toughness of 3.60 MPa·m^1/2, marking respective improvements of 8.51 % and 16.12 % compared to the C_sf/SiC composites with original fibers.