DIFFUSION KINETICS OF THE CARBURIZATION AND SILICIDATION OF TI3SIC2

The ternary carbide Ti3SiC2 possesses a unique set of properties that could render it a material of considerable technological impact. The m otivation for this work was to enhance the hardness and oxidation resi stance of Ti3SiC2 by altering its surface chemistry. Reaction of Ti3Si C2 with single crystal Si wafers in the 1200-1350 degrees C temperatur e 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 distinc t morphologies; an outer layer with fine (1-5 mu m) SiC particles and an inner coarser (10-15 mu m) one. The overall growth rates of the lay ers were parabolic. Comparison with previously published results suppo rts the conclusion that diffusion of Si through TiSi2 is rate limiting . In the 1400-1600 degrees C temperature range, reaction of Ti3SiC2 wi th graphite foils resulted in the formation of a 15 vol. % porous surf ace layer of TIG, (where x>0.8). It is shown that the carburization ki netics are rate limited by the diffusion of C through TiCx,. Both carb urization and silicidation increased surface hardness, the latter also enhanced the oxidation resistance by about three orders of magnitude. (C) 1998 American Institute of Physics.