抄録
Using mixed powder compacts, the products and mechanism of the reaction between Si3N4 and 18%Cr-8%Ni austenitic stainless steel (SUS304L) have been investigated under a nitrogen or an argon atmosphere at temperatures from 873 to 1573K.
Under a nitrogen atmosphere, the reaction of chromium in SUS304L with nitrogen gas yielded Cr2N and CrN. During a long time heating, silicon was dissolved in SUS304L as a solid solution by the solid-state reaction between Si3N4 and SUS304L. The occurrence of such products resulted in the austenite-ferrite transformation of SUS304L. Above 1373K, iron silicide, Fe3Si, also was produced.
Under an argon atmosphere, Cr2N was produced and silicon was dissolved in SUS304L at lower temperatures. At higher temperatures and on prolonged heating, iron silicides were produced in the following order: Fe3Si, Fe5Si3 and FeSi. Both chromium and nickel as the constituents of SUS304L are considered to form the solid solution with iron silicides.
Initial rate was described by a linear rate law, and the activation energy was 199kJ/mol below 1373K and 97kJ/mol above 1423K. The rate is considered to be controlled by a gas-phase diffusion or/and an interfacial reaction. The rate at the late stage of reaction obeyed a parabolic rate law. The activation energies were 521kJ/mol in the Fe3Si region and 494kJ/mol in the Fe5Si3 region. The reaction rate is considered to be determined by the solid-state diffusion through the reaction layer formed around the particles of SUS304L.
