Diffusion kinetics of the carburization and silicidation of $Ti3SiC2$ Available to Purchase

The ternary carbide $Ti3SiC2$ possesses a unique set of properties that could render it a material of considerable technological impact. The motivation for this work was to enhance the hardness and oxidation resistance of $Ti3SiC2$ by altering its surface chemistry. Reaction of $Ti3SiC2$ with single crystal Si wafers in the 1200–1350 °C temperature range resulted in the formation of a dense surface layer composed of a two phase mixture of $TiSi2$ and SiC. This layer grows in two distinct morphologies; an outer layer with fine (1–5 μm) SiC particles and an inner coarser (10–15 μm) one. The overall growth rates of the layers were parabolic. Comparison with previously published results supports the conclusion that diffusion of Si through $TiSi2$ is rate limiting. In the 1400–1600 °C temperature range, reaction of $Ti3SiC2$ with graphite foils resulted in the formation of a 15 vol. % porous surface layer of $TiCx$ (where $x>0.8$⁠). It is shown that the carburization kinetics are rate limited by the diffusion of C through $TiCx.$ Both carburization and silicidation increased surface hardness, the latter also enhanced the oxidation resistance by about three orders of magnitude.