Improved Austenitic Steels for Power Plant Applications
Using alloy design principles, an austenitic alloy, with base composition of Fe-16Cr-16Ni-2Mn-1Mo (in weight percent, wt%), was formulated to which up to 5 wt% Si and/or Al were added specifically to improve the oxidation resistance. Cyclic oxidation tests were carried out in air at 700 and 800 C for 1000 hours. For comparison, Fe-18Cr-8Ni type-304 stainless steel alloys was also tested. The results showed that at 700 C, all the alloys were twice as oxidation resistant as the type-304 alloy (i.e., the experimental alloys showed weight gains about half that of type-304). Surprisingly, at 800 C, alloys that contained both Al and Si additions were less oxidation resistant than the type-304 alloy. However, alloys containing only Si additions were significantly more oxidation resistant than the type 304 alloys (i.e., showed weight gains 4 times less than the type-304 alloy). Further, alloys with only Si additions pre-oxidized at 800 C, showed zero weight gain in subsequent testing for 1000 hours at 700 C. This implies the potential for producing in-situ protective coating for these alloys. Preliminary exposure tests (1%H2S at 700 C for 360 hrs) indicated that the Si-modified alloys are more sulfidation resistant than type-304 alloy. The mechanical properties of the alloys, modified with carbide forming elements, were also evaluated; and at 600, 700 and 800 C the yield stresses of the carbide modified alloys were twice that of type-304 stainless steel. In this temperature range, the tensile properties of these alloys were comparable to literature values for type-347 stainless steel. It should be emphasized that the microstructures of the carbide forming alloys were not optimized with respect to grain size, carbide size and/or carbide distribution. Also, presented are initial results of vari-strain weld tests used to determine parameters for joining these alloys.
- Research Organization:
- Albany Research Center (ARC), Albany, OR (United States)
- Sponsoring Organization:
- USDOE Office of Fossil Energy (FE)
- OSTI ID:
- 807846
- Report Number(s):
- DOE/ARC-2002-008; TRN: US200706%%876
- Resource Relation:
- Conference: 16th Annual Conference on Fossil Energy Materials, Baltimore, MD, April 22-24, 2002; Other Information: Also available at http://www.netl.doe.gov/publications/proceedings/02/materials/alman.pdf; Related Information: US Patent 6,475,310 B1 issued Nov. 5, 2002
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALLOYS
AUSTENITIC STEELS
CARBIDES
GRAIN SIZE
MECHANICAL PROPERTIES
OXIDATION
POWER PLANTS
PROTECTIVE COATINGS
STAINLESS STEELS
STRESSES
SULFIDATION
TENSILE PROPERTIES
TESTING
austenitic steels
austenitic alloys
power plants
oxidation resistance
creep resistance
corrosion resistance