Effect of sintering temperature on BaO–Al 2 O 3 –SiO 2 glass ceramic coating for carbon fibre reinforced silicon carbide matrix composites

BaO–Al₂O₃–SiO₂ (BAS) glass ceramic coatings were prepared on carbon fibre reinforced silicon carbide matrix composites (C/SiC) by in situ sintering. The effect of sintering temperature on the final phase and microstructure of the coatings were studied. The results show that higher degree of crystallisation in the BAS glass is achieved at higher sintering temperatures and more crystalloids are melted by the residual glass with low viscosity at the same time. Considering these two factors, the crystallinity of BAS glass ceramic should have a peak value at a specific sintering temperature. The sample sintered at 1473 K has an obvious transition layer of 40 μm in thickness between the coating and the composite, which enhances the adhesion strength between them. The oxidation resistance of C/SiC composites with BAS protective coatings was characterised using isothermal oxidation tests at 1773 K for 15 min. The weight loss of the composites with BAS coatings is decreased with the increase of the sintering temperature.