| Abstract: | The corrosion behaviour of Fe-Cr, Ni-Cr and Fe-Cr-Ni alloys was studied in simulated liquefaction environments over the temperature range of 623 to 723 K. Corrosion of alloys in these environments was controlled by both sulfidation and oxidation. In the slurry, the oxygen potential was apparently higher and the corrosion rate was smaller in comparison with those in the gas phase in the solvent only environment. An oxygen-rich brown coal caused much smaller corrosion than a sub-bituminous coal. With regard to the effect of the alloy compositions, chromium content controlled the corrosion rate. The Fe-Cr-Ni austenitic alloys were the most resistant. The Fe-Cr alloys with high chromium content were fairly resistant, although they may be relatively sensitive to the variation of the environments such as temperature and H2S content. Ni-Cr alloys of less than 20% Cr may have high corrosion rate due to their fast sulfidation. The structure of the scales formed on the alloys can be reasonably explained by the phase stability diagram of Metal-O-S system. |
