Microstructure and properties of SiC_f/SiC joint brazed by Y-Al-Si-O glass

In this study, SiC fiber reinforced SiC ceramic matrix composites (SiC_f/SiC) were joined by Y-Al-Si-O glass. The effects of the composition of Y-Al-Si-O glass, brazing temperature and holding time on microstructure and properties of SiC_f/SiC joint were investigated. Based on the investigated results, the brazing process was optimized. The results showed that the wettability of Y30 glass (SiO₂ 55 wt%, Al₂O₃ 15 wt%, Y₂O₃ 30 wt%,) and SiC_f/SiC was good and the wetting angle was ~ 9.84°. With the increase of the temperature from 1300 °C to 1400 °C, the crystal phase decreased and Y-Al-Si-O glass phase increased gradually in the joint brazed by Y30 glass. The joint layer brazed by Y30 glass at 1400 °C contained only amorphous phase, and the joint layer with smooth and defect-free structure is beneficial to its airtightness. The shear strength of the joint brazed by Y30 glass increased with the increase of the brazing temperature from 1300 °C to 1400 °C, and the shear strength reached the maximum at 1400 °C. The effect of holding time on the shear strength of the joint brazed by Y30 glass at 1400 °C was largely insignificant. The optimized joining process of the SiC_f/SiC brazed by Y-Al-Si-O glass was that the brazing agent is Y30 glass, the brazing temperature and the holding time were 1400 °C and 0 min, respectively. With optimized process, the shear strength of the joint was ~ 38.85 MPa. With the increase of thermal shock times, the shear strength of the joint with optimized process declined gradually because the cracks occurred in the interface near the SiC_f/SiC and gradually propagated to the joint layer.