A study of the solid state reaction between silicon carbide and iron

The solid state reaction between SiC and Fe annealed in an Ar–20 vol.% H2 atmosphere in the temperature range from 1073 to 1373 K for times from 0.5 to 40 h had been studied. The reaction products of Fe3Si, Fe(Si), and the graphitic carbon precipitates were generated. The reaction zone is composed of the band structure, i.e. the modulated carbon precipitation zone (M-CPZ)/the random carbon precipitation zone (R-CPZ)/the carbon precipitation free zone (C-PFZ) from the SiC terminal to the Fe terminal, when annealed at 1173 K and above. The formation of the M-CPZ is due to the discontinuous decomposition of SiC. The microhardness values across the reaction zone are the function of the carbon content/microstructure in the M-CPZ and the R-CPZ, and the function of the silicon concentration in the C-PFZ. The reaction follows the parabolic growth law indicating the diffusion-controlled reaction kinetics. The reaction rate constant, K=4.9×10−4 exp(−(180×103)/RT) m2 s−1 is calculated which is in the same order of magnitude as DFe3SiFe in the temperature range used. The apparent activation energy, 180 kJ mol−1, is believed to be that of the diffusion of Fe in Fe3Si. It indicates that Fe diffusion in Fe3Si is the dominating diffusion species of the reaction.