Effects of minor alloying additions on the formation of protective scales under sulfidizing conditions at 700 degree C
- Battelle Columbus Div., OH (USA)
- Pacific Northwest Lab., Richland, WA (USA)
Effects of Al, Si, Mn, Y, and Hf on the formation of protective scales have been investigated in environments simulating substoichiometric combustion of high-S coal, and an oxidizing flue gas. Minor additions were made to three clean alloys bases: Fe-25Cr, Fe-25Cr-20Ni, and Fe-25Cr-6Al, by conventional alloying, and by powder metallurgical routes involving rapid solidification or high-energy milling. Scales formed at 700{degree}C were compared with those formed on the unalloyed base alloys, in terms of weight change, scale morphology and composition. Alumina scales on the Fe-25Cr-6Al-base alloys proved the most effective as a group, with excellent protection being provided for more than 6000 h in aggressively sulfidizing conditions. Chromia scales formed on Fe-25Cr-base alloys were markedly more effective than those on equivalent Fe-25Cr-20Ni-base alloys prepared by conventional casting. Observations of initial stages of corrosion of the base alloys indicated that a major difference was that the protective scales formed on the FeCr alloy were of the M{sub 2}O{sub 3}-type, whereas those that led to inferior protection on the FeCrNi alloy were of the M{sub 3}O{sub 4}-type, and led to the inclusion of higher levels of Fe in the nominally protective scale. It is postulated that alloy modifications that can promote the exclusive formation of M{sub 2}O{sub 3}-type scales alloys should also enhance their sulfidation resistance. 23 refs., 107 figs., 16 tabs.
- Research Organization:
- Oak Ridge National Lab., TN (USA); Battelle Columbus Div., OH (USA); Pacific Northwest Lab., Richland, WA (USA)
- Sponsoring Organization:
- DOE/FE
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 6407418
- Report Number(s):
- ORNL/Sub-86-57444/02; ON: DE91002861
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
20 FOSSIL-FUELED POWER PLANTS
ALUMINIUM ALLOYS
SCALING
CHROMIUM ALLOYS
COMBUSTORS
CORROSION
IRON BASE ALLOYS
NICKEL ALLOYS
ALUMINIUM
ALUMINIUM OXIDES
BOILERS
CHROMIUM OXIDES
FOSSIL-FUEL POWER PLANTS
HAFNIUM
MANGANESE
METALLURGICAL EFFECTS
MICROSTRUCTURE
PROGRESS REPORT
SILICON
SULFIDATION
YTTRIUM
YTTRIUM OXIDES
ALLOYS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
CRYSTAL STRUCTURE
DOCUMENT TYPES
ELEMENTS
IRON ALLOYS
METALS
OXIDES
OXYGEN COMPOUNDS
POWER PLANTS
SEMIMETALS
THERMAL POWER PLANTS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
YTTRIUM COMPOUNDS
014000* - Coal
Lignite
& Peat- Combustion
360105 - Metals & Alloys- Corrosion & Erosion
200104 - Fossil-Fueled Power Plants- Components