Joining of SiC monoliths using a thin MAX phase tape and the elimination of joining layer by solid-state diffusion

This paper reports the joining of SiC monoliths using a thin MAX phase tape filler, such as Ti3AlC2 and Ti3SiC2, and the subsequent phenomena leading to the elimination of the joining layer via solid-state diffusion of the MAX phase into the SiC base material, particularly with the decomposition of the Ti3AlC2 filler. The base SiC monolith, showing ≥ 99% density, was fabricated by hot pressing SiC powder after adding 5 wt. % Al2O3-Y2O3 sintering additive. A butt-joint configuration was prepared and joined by hot pressing under a pressure of 3.5 MPa. The effects of the experimental parameters, including the type and thickness of the joining filler, temperature as well as the holding time, were examined carefully in terms of the microstructure, phase evolution and joining strength. The joining interface could be eliminated from the SiC base when the SiC monoliths were joined at 1900 °C using a thin Ti3AlC2 tape, showing a high joining strength ∼300 MPa. Moreover, fracture during the mechanical test occurred mainly at the base material rather than the joining interface, indicating excellent joining properties. These findings highlight the elimination of the joining interlayer, which might be ideal for practical applications because the absence of a joining filler helped preserve the excellent SiC mechanical properties of the joint.