Nano-infiltration and transient eutectic (NITE) joining of SiC ceramics applied for the harsh environments

To expand the application of SiC/SiC joints under extreme conditions, Nano-Infiltration and Transient Eutectic (NITE) joining technology with AlN-Y2O3 as a sintering additive was successfully developed. The rheological properties of the slurry and the microstructure evolution of the joints were systematically characterized by rheometer, SEM, EDS, EBSD, and TEM, respectively. Both room-temperature and high-temperature flexural strength was measured to evaluate the mechanical properties of the joints. An immersion test with concentrated nitric acids was performed to evaluate the corrosion resistance of the joints. The defect-free joining layer was composed of a dense α-SiC phase, a small amount of YAG(Y3Al5O12) distributed in the triangular grain boundary, and a Y-Al-O glass phase from AlN-Y2O3. The mechanism of NITE joining could be attributed to the incoherent growth of the newly generated α-SiC in the joining layer along the α-SiC substrate. The maximum room-temperature strength of the joints was 320.5 ± 37.6 MPa. When the test temperatures were 1000 °C, 1200 °C, and 1400 °C, the flexural strength reached 238.7 ± 33.1 MPa, 215.5 ± 52.5 MPa, and 166.9 ± 52.0 MPa, respectively. After immersing the joints in a concentrated HNO3 for 168 h, the flexural strength was 173.3 ± 12.6 MPa. The joints' excellent mechanical properties and corrosion resistance reveal great application potential under extreme conditions.