Wetting of SiC by Al-Ti alloys and joining by in-situ formation of interfacial Ti3Si(Al)C-2

Two pressureless and reliable procedures for brazing SiC-based materials have been designed. The joining was obtained by the in-situ formation of a Ti3Si(Al)C-2 MAX phase using simple Al-Ti interlayers. Wettability studies were conducted using several Al-Ti alloys in contact with SiC at 1500 degrees C. The interfacial microstructures and thermodynamic analysis demonstrated that liquid Al3Ti in contact with SiC formed a well-bonded Ti3Si(Al)C-2 interfacial layer. These findings guided the design of two joining methods: one consisted of the simple infiltration of Al3Ti into the brazing seam, while an Al3Ti paste/Ti/Al3Ti paste interlayer assembly was designed for the second process. Sound interfaces without cracks were obtained in both processes. The average shear strength was very high, 296 MPa, for the infiltration method; the drawback was the presence of residual Al. Joining through Al3Ti/Ti/Al3Ti interlayers avoided the presence of low-temperature melting phases, with lower shear strength: 85 or 89 MPa depending on the testing method.