Surface engineering of SiCf/SiC composites by selective thermal removal

Surface engineering based on the Selective Thermal Removal (STR) of SiC fibers from SiCf/SiC composites was used to obtain a brush-like surface in view of joining processes. As observed through 3D confocal microscopy, the thermal treatment led to a selective removal of the surface fibers so that the specific surface increased. Wetting tests were performed using a Ag-Cu-Ti brazing alloy. The STR led to a negligible increase in the contact angles, which ranged from 16° to 21° for as-received composites and increased to 28° for composites after STR. Microstructural observations showed that the brazing alloy perfectly adhered to the brush-like surfaces were giving a mechanical interlocking expected to enhance the strength of the joint.