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摘要
Fe-Cralloys (Cr: 9-30 wt%) were subjected to cyclic oxidation in Ar-20%O(2), Ar-20%O(2)-5%H(2)O and Ar-10%H(2)-5%H(2)O (partial pressure of oxygen, p(O2) = 1.1 x 10(-16)atm). Oxidation weight change measurement showed that in general, increasing Cr content reduced the oxidation rate. At Cr <= 17%Cr, breakaway oxidation was observed. However, for Cr >= 25%, the weight gain became very low due to formation of Cr(2)O(3) layer. Adding 5%H(2)O to Ar-20%O(2) accelerated the oxidation rate of alloys with Cr <= 20%. However, this accelerating effect did not appear in high chromium content alloys. XRD analysis showed that for alloys with Cr < 20%, wustite and spinel were formed at low p(O2), while at high p(O2), hematite, iron oxide and spinel were formed. For high Crcontent alloy only Cr(2)O(3) was detected. Cross-section analysis showed that the spinel was formed by internal oxidation. The thickness and size of this internal oxide zone increased with increasing Crcontent. A dense chromia layer was observed when the Crcontent was above 25%. The oxides scales formed in water vapour were more porous and less compact than the scale formed in dry oxygen. The accelerating effect of water vapour on Fe-Croxidation is discussed in terms of gas-solid interactions.
- 出版日期2010-4
