The formation of interface phases in the diffusion couple Ti-SiC

The interface reactions in the diffusion couple Ti-SiC have been investigated at 1673 K. The diffusion couples were prepared by depositing 1 μm of Ti with MSIP on SiC substrates of 2 mm thickness and annealing for up to 108 h under inert atmosphere. Thin film XRD, EPMA dimple edge linescan profiling, TEM, as well as SEM and BSE micrographs served to analyse the phases formed by diffusion processes in the reaction zone. The intermediate ternary phase Ti 3 SiC 2 (T1), already formed after 10 min of annealing, remained the major phase of the reaction zone even after 108 h annealing at 1673 K. After 1.5 h the small portion of TiSi 2 , formed after 10 min of annealing, was decomposed again, and a phase (Ti, Si)C 1-x , which crystallized in the TiC 1-x structure, was detectible 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 amount of (Ti, Si)C 1-x did not markedly increase up to 108 h of annealing. It could be shown that the formation of Si-free TiC 1-x observed in some cases at the surface of the couple did not happen in the pure diffusion couple Ti-SiC, but was always related to carbon intake from the gas phase.