Flash joining of alumina ceramics by spark plasma sintering with Ni and Ti interlayers

Manufacturing ceramics has limitations regarding product size, shape, and quality. Ceramic-to-ceramic joining techniques are employed to overcome these limitations and enable the fabrication of multi-material components as well as intricate or large shapes. This study investigated direct and interlayer-assisted field-assisted solid-state diffusion bonding of alumina ceramics. Experiments were carried out on alumina-alumina, alumina-nickel-alumina, and alumina-titanium-alumina sandwich structures, following finite element simulations that evaluated the associated residual stresses. Samples were joined at different temperatures for 5 min with 54.7 MPa in low vacuum via spark plasma sintering. The joint interface and microstructure were examined using scanning electron microscopy, backscattered electron imaging, energy-dispersive X-ray spectroscopy, X-ray diffraction, and nanoindentation. The alumina-alumina system failed to form a continuous joint interface over the temperature range of 1200 to 1500 °C. Joining was obtained for the alumina-nickel-alumina system at temperatures between 1000 and 1300 °C, and for the alumina-titanium-alumina system at temperatures between 1100 and 1400 °C. No reaction layer was observable in the alumina-nickel-alumina samples, while intermetallic compounds formed at the interface of the alumina-titanium-alumina system.