Wetting and interfacial phenomena of Ni-Ta alloys on CVD-SiC

When designing high-temperature brazing processes for ceramic materials, the interfacial phenomena between the liquid media and the adjoining surfaces must be known to design reliable joints. In order to assess the feasibility of using Ta-containing alloys for high-temperature brazing of SiC-based composites, the wetting of molten Ni-Ta alloys on ultra-pure chemical vapor deposited (CVD) SiC substrates has been investigated using the sessile drop technique. For all of the compositions and experimental conditions, good wetting was observed with fast spreading. The interfacial behavior is determined by the competition between the typical interfacial phenomena of the pure elements; specifically, either the dissolution of the ceramic phase by Ni or the formation of a new interfacial layer, TaC, by reaction between Ta and CVD-SiC, which prevails depends on the relative amount of the single element in the alloy.