Control of the interface reaction between silicon carbide and iron

Abstract

Two methods of the oxidation of silicon carbide (SiC) and alloying the Fe matrix with Cr had been investigated to control the interface reaction between SiC and Fe. The oxide membrane on the SiC piece is thermodynamically stable, and effectively controls the interface reaction between SiC and Fe. However, the interface of the oxidized-SiC/Fe couple is instable at 1273 K. The point-like reaction zone was generated when the couple was annealed for 5 h. The reaction zone is mainly composed of Fe 3Si, Cr 3Si, M 7C 3-type carbide (M=Cr, Fe), and the graphitic carbon precipitates, when the SiC/Fe–20 Cr alloy couple was annealed at 1373 K for 20 h. The structure of the reaction zone is the SiC reaction zone (SRZ), the metal reaction zone (MRZ) from the SiC side to the Fe side. The SRZ has high Si, Fe concentrations, and a low Cr concentration. The bright matrix of the SRZ is mainly composed of Fe 3Si, in which the carbon precipitations are distributed randomly. The MRZ has no carbon precipitates, which is only composed of M 7C 3. The interface reaction of SiC/Fe–20 Cr follows a parabolic kinetics with the reaction rate constant, K=1.9×10 −4 exp(−(235×10 3)/RT) (m 2 s −1). Compared with that of SiC/Fe, the interface reaction kinetics of SiC/Fe–20 Cr has a higher Q value and a lower K 0 value. The interface reaction of SiC/Fe–20 Cr is reduced. It is attributed to that the MRZ inhibits the transport of the Fe atoms in the reaction zone during the annealing process.