1997 Volume 105 Issue 1220 Pages 317-321
In relation to the joining of silicon nitride ceramics to metal, the reaction products and reaction mechanism between Si3N4 and Fe-Cr alloy have been investigated under Ar atmosphere at temperatures from 1223 to 1573K. Using Si3N4/Fe-62.5mass%Cr alloy powder mixture, the reaction rates were thermogravimetrically determined, and the reaction products were identified by X-ray diffraction. Cr2N was produced below 1273K. Above 1273K, the solid solution and silicides were produced, resulting in the mass loss. At higher temperatures and on prolonged heating, the silicides changed in the following order: Cr3Si, Cr5Si3 and CrSi. Two types of Cr5Si3 were found; hexagonal crystal above 1323K and tetragonal crystal above 1423K. Iron is considered to form the solid solution with chromium silicides. The initial rate was described by the linear rate law. The activation energy was 264kJ/mol. An interfacial reaction may be the rate-determining step. When the alloy particles were covered with the reaction product layer, the kinetics obeyed the parabolic rate law. The reaction rate is probably controlled by the solid-state diffusion through the reaction layer.
