Transport properties in chromium and Fe-Cr alloys exposed to oxygen-sulfur environments.

摘要

The diffusivities of oxygen and sulfur in thermally grown oxides of pure Cr ad model alloys of Fe-25 wt.% Cr and Fe-25 wt.% Cr-Re (Re = 1 wt.% of Ce or V) have been determined by means of electrical conductivity measurement. For pure Cr(sub 2)O(sub 3), electrical conductivity of the oxide decreased owing to doping with a tracer amount of sulfur at temperatures investigated between 700 and 950(degree)C and PO2 = 10(sup (minus)4) atm. The measured diffusivity of sulfur in Cr(sup 2)O(sub 3) was at least one order of magnitude higher at 900(degree)C and at temperatures <750(degree)C, four orders of magnitude higher than that of oxygen. The activation energy of oxygen is 3.53 eV, whereas the value for sulfur (0.8 eV) is much lower. The solubility of sulfur decreased with an increase temperature, in general, but was almost constant below 800(degree)C. 20 refs., 15 figs., 1 tab.