Reactive diffusion between monocrystalline 6H-SiC and chromium

Interface reactions between chromium and monocrystalline 6H-SiC were studied in the temperature range of 1000-1200 degrees C for 24-192 h duration. The reaction layers were characterised by XRD and SEM/EDX techniques. The sequence of reaction layers as observed in the diffusion couples, Cr/Cr23C6/Cr7C3/Cr7C3 + Cr3Si/Cr3Si/Cr5Si3C/SiC, could be related to the isothermal section at 1000 degrees C. A stability diagram was constructed for the Cr-Si-C system at 1000 degrees C, based on the available thermodynamic data by plotting the logarithm of activities of C as a function of relative mole fractions of X(Si) and X(Cr). Based on the thermodynamic calculations and the stability map, interpretations pertaining to the observed diffusion paths are discussed.