The effect of the PyC interphase coating on the microwave heating sintered SiC/SiC composites

Abstract

SiC/SiC composites coated with the pyrolytic carbon (PyC) interphase coatings of different thickness were fabricated by polymer infiltration and pyrolysis (PIP) process using microwave sintering at 1100 °C assisted with the hot mould pressing pressure of 3 MPa. The effects of the PyC coating thickness on the densification, the flexural properties and microstructures of the fabricated SiC/SiC composites were investigated via the mercury intrusion test, the computed tomography (CT) technique and scanning electron microscopy (SEM). The results indicate that the preforms coated with thinner PyC coatings, which have better flexibility under the hot mould pressing process, bring SiC/SiC composites with higher densification degrees, due to their better flexibility under the hot press moulding process. Simultaneously, thicker PyC coatings result in weaker interphase debonding between SiC fibers and matrix quantified by the single fiber push-out test. Too thick or too thin PyC coatings both make against the flexural properties, as they will cause the debonding between SiC fibers and matrix too early or too late. The PyC coating thickness-0.20 μm is approximate for the better flexural properties.