THE FORMATION OF INTERFACE PHASES IN THE DIFFUSION COUPLE TI-SIC

The interface reactions in the diffusion couple Ti-SiC have been inves tigated at 1673 K. The diffusion couples were prepared by depositing 1 mu m of Ti with MSIP on SiC substrates of 2 mm thickness and annealin g for up to 108 h under inert atmosphere. Thin film XRD, EPMA dimple e dge linescan profiling, TEM, as well as SEM and BSE micrographs served to analyse the phases formed by diffusion processes in the reaction z one. The intermediate ternary phase Ti3SiC2 (T1), already formed after 10 min of annealing, remained the major phase of the reaction zone ev en after 108 h annealing at 1673 K. After 1.5 h the small portion of T iSi2, formed after 10 min of annealing, was decomposed again, and a ph ase (Ti, Si)C1-x, which crystallized in the TiC1-x structure, was dete ctible in small amounts with a Ti/Si atomic ratio of up to 74/26. This phase only occurred in close proximity to the SiC substrate. The amou nt of (Ti, Si)C1-x did not markedly increase up to 108 h of annealing. It could be shown that the formation of Si-free TiC1-x observed in so me cases at the surface of the couple did not happen in the pure diffu sion couple Ti-SiC, but was always related to carbon intake from the g as phase.