Microstructure and mechanical properties of SiCf/SiC joints brazed using CaO MgO Al2O3SiO2 glass

In this work, SiC fiber reinforced SiC matrix (SiCf/SiC) composites were joined using CaO-MgO-Al2O3-SiO2 glass (CMAS) at 1200-1400 degrees C in vacuum. The microstructures, phase composition, mechanical properties and thermal shock resistance of the joints were investigated by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), single-lap compressive shear test, and thermal shock test, respectively. The results showed that joints composed of CMAS glass were dense and crack-free, contributing to high shear strength of 45.7 MPa and good tightness at the brazing temperature of 1400 degrees C. In addition, a large number of SiCf/SiC composites was torn off by solder after the shear test, indicating that the bonding strength of joining interface was robust. After successive thermal shocking at 1200 degrees C for one, two, and three times, the shear strengths of the joints brazed at 1400 degrees C were 86.7%, 71.0%, and 57.7% of that without thermal shocking, respectively.