Studies of the Joining-Relevant Interfacial Properties in the Si-Ti/C and Si-Ti/SiC Systems

Reactive melt infiltration of Si-based alloys into C preforms and SiC/C composites may be an affordable alternative route to fabricate highly performant lightweighting metal matrix and ceramic matrix composites (CMCs), as well as to obtain reliable and long-term stable joints. In order to optimize reactive infiltration process and to tailor the joint microstructures, the knowledge of interfacial phenomena including thermodynamics, kinetics and surface properties of involved phases (i.e., metals and ceramics) as well as wettability and reactivity occurring between dissimilar materials is of crucial importance. In the present work, the feasibility study of a novel brazing method using Si-Ti alloys as filler for SiCf/SiC is reported and supported by the analysis of microstructural evolution and interfacial phenomena observed during the joining process. Namely, the CMC joining was successfully obtained via the reactive infiltration approach. The results obtained were critically discussed and compared with the know-how coming from the previously carried out investigations on the wetting and reactivity of Si-Ti melts in contact with glassy-C and HIP-SiC substrates. In particular, the microstructural evolution of the Si-Ti/C and Si-Ti/SiC interfaces during wetting tests and at the joint of CMC parts was analyzed and related to the operating conditions.