Improvement of the shear strength of SiC joint with CaO–Al2O3–MgO–SiO2 glass filler by surface etching

In this study, CaO–Al 2 O 3 –MgO–SiO 2 glass was utilized to join SiC after surface polishing and etching, without the application of pressure. To join polished SiC at 1250 °C using CaO–Al 2 O 3 –MgO–SiO 2 glass proved unsuccessful. However, when polished SiC was joined at 1350 °C, the joint shear strength was 108.0 ± 15.5 MPa. Etching polished SiC with a NaOH–K 3 [Fe(CN) 6 ] solution effectively removed surface carbon, resulting in numerous micro-pits, that increased the joining area and improved the wettability of CaO–Al 2 O 3 –MgO–SiO 2 glass. The joint strengths of etched SiC joined at 1250 °C and 1350 °C were 29.0 ± 11.6 MPa and 125.1 ± 19.6 MPa, respectively. After ablation at 1200 °C for 10 min, the retained strength of the etched joints (joined at 1350 °C) was 61.9 ± 4.0 MPa, whereas the strength of the polished joints decreased to only 36.6 ± 10.7 MPa. Surface etching demonstrates the potential to significantly enhance the strength and high-temperature resistance of SiC joints.