| The corrosion resistence of sialon/SiC,Sialon/SiC (Z=2),Sialon/SiC (Z=3) and Si3N4/SiC products to the attack of H2O-H2-N2 gases was studied by the exposing to the gases at different temperature in the range of 900℃-1150℃for 100h.The changes in mass, in porosity and in bulk density were measured ,and the change in phases was determined by XRD as well as that in microstructure by SEM. The research is meaned to provide the application of these materials in the reduction of metal oxides by hydrogen a useful experimental basis. The results are as follows:(1) The causious gas to the four kinds of products in H2O-H2-N2 was the steamed H2O.(2) The stability areas for SiC,Si3N4,Si2N2O and SiO2 were plotted from the predominance area phase diagram for the Si-N-C-O-H system by thermodynamical calculation,from which it can be deduced that Si3N4 and SiC can be oxidized to SiO2 by steamed water as PH2O≈10-7-10-6MPa.While the Sialon phase in Sialon/SiC(Z=2) and Sialon/SiC (Z=3 ) can be oxidized to SiO2 and Al2O3 forming a protective film on the surfaces as the partial pressure of water vapor and hydrogen is controlled to be a certain proportion.( 3 ) The specific oxidation increment for the four materials were increased at the elevated oxidizing temperature. increased, and at the same oxidizing temperature,the turns from large to small of the specific oxidation increment for them was determined as Si3N4/SiC>Sialon/SiC (Z=2) >Sialon/SiC (Z=3) >Sialon/SiC.Namely the turns from strong to weak of the oxidizing resistance to water vapour is Sialon/SiC Sialon/SiC (Z=3) > Sialon/SiC (Z=2) >Si3N4/SiC. At the same temperature, the specific oxidation increment of the material was increased by the grown partial pressure of hydrogen in H2O-H2-N2 atmosphere. (4) Active oxidation mechanism for the SiC materials in the H2O-H2-N2 atmosphere was proposed not like the oxidation of the materials in oxygen and water vapor because there was Hydrogen that the oxidation products SiO2 of the materials were foretherly reduced by it to SiO vapour.(5) Sialon/SiC was found to be more resistenant to the oxidation of water vapor than Si3N4/SiC through SEM. EDS and XRD analysis, producing a layers composed of SiO2 and Al2O3 prohibiting the contact of the materials with gas.
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