AN ASSESSMENT OF THE HIGH-TEMPERATURE OXIDATION BEHAVIOR OF Fe-Cr STEELS IN WATER VAPOR AND STEAM

摘要

European and Japanese developments of technologies for coal-fired power plants employingrnadvanced steam conditions have resulted in Fe-Cr alloys that appear to have acceptable strength up torn620℃ (1148℉) or possibly 650℃ (1202℉). However, these alloys have relatively low Cr contents (uprnto 13 percent), which are marginal for the formation of protective oxide scales at these temperatures.rnSince there is no practical experience with alloys of this type in steam at elevated temperatures,rninformation on their oxidation behavior in steam, in particular their rate of oxidation, is needed. Thisrnpaper reports an assessment of the available information on steam oxidation of Fe-Cr alloys. It appearsrnthat the 9-12Cr and the 2-3Cr alloys oxidize at essentially the same rate at 550℃ (1022℉), but thernhigher-Cr alloys provide somewhat better protection at the higher temperatures of interest (up torn700℃/1292℉). However, the oxidation rates are still fast, since the predominant scales formed arernbased on magnetite. It will be important for lifetime prediction to determine if the scale growsrnaccording to a parabolic or linear rate law; this point is not well resolved by examination of existingrndata. Routes for promoting the formation of more protective, Cr-rich scales on the more highly-alloyedrnare being explored and some show good promise.