Interaction of Si3N4 with Ni-Cr alloy under N2 or Ar atmosphere

In relation to the joining of silicon nitride ceramics to metal, the interaction of Si3N4 with Ni-Cr alloy was investigated at temperatures from 1073 to 1573 K under N-2 or Ar atmosphere. Reaction rates were determined by thermogravimetry and reaction products were examined by X-ray diffraction. CrN, Ni3Si, Ni5Si2, Ni2Si and (Cr, Si)(3)Ni2Si were produced under N2 atmosphere. In addition to these products, Ni3Si2, Cr3Si and Cr5Si3 also were produced under Ar atmosphere. The reaction products were considered from the standpoint of thermodynamics. While the incubation period was observed under Ar atmosphere, it was not observed under Ng atmosphere. The initial rates obeyed a linear rate equation. The rates at the later stage of reaction described a parabolic rate equation. The reaction mechanism model was proposed. (C) 1998 Kluwer Academic Publishers.