Direct joining of pressureless solid-phase sintered silicon carbide ceramics

The development of a direct joining process for pressureless solid-phase sintered silicon carbide (PSS-SiC) with excellent high temperature properties and corrosion resistance is essential for obtaining highly reliable joints, but little attention has been paid to it and the joining process and mechanism are still unclear. In this study, PSS-SiC joints were successfully fabricated via direct joining using spark plasma sintering at a relatively low temperature in a short time. The effects of the joining temperature, uniaxial pressure, and holding time on the microstructure and shear strength of the joints are systematically discussed. The results showed that the joining temperature played a key role in the joining behavior of the joints. When the joining temperature, uniaxial pressure, and holding time were 1650 °C, 25 MPa, and 5 min, respectively, a reliable joint with a comparable shear strength to that of the PSS-SiC matrix was obtained. Moreover, by analyzing the fracture surfaces of the joints obtained at different temperatures, the microstructure evolution during the direct joining process can be disclosed; thus, the joining mechanism was revealed reasonably. The developed direct joining process is expected to expand the applications of high-performance SiC components.