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Title: Creep and Corrosion Testing of Aluminide Coatings on Ferritic-Martensitic Substrates

Abstract

Pack and chemical vapor deposited (CVD) aluminide coatings on commercial ferritic-martensitic Fe-9Cr-2W steel are being investigated by creep and corrosion testing at 650 C. Results from different coating thicknesses show that the coated region makes no contribution to the creep strength. The creep behavior of uncoated material was studied after various heat treatments to simulate the coating process and typical secondary heat treatments. Alternating creep and corrosion exposures showed little effect on the creep strength of uncoated material but coated materials became progressively weaker. The coatings were protective in wet air at 650 C after creep testing.

Authors:
 [1];  [2];  [1]
  1. ORNL
  2. Tennessee Technological University
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); High Temperature Materials Laboratory; Shared Research Equipment Collaborative Research Center
Sponsoring Org.:
FE USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
931295
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: NACE Corrosion 2007, Nashville, TN, USA, 20070313, 20070317
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AIR; COATINGS; CORROSION; CREEP; HEAT TREATMENTS; STEELS; SUBSTRATES; TESTING; Ferritic steel; oxidation; creep; aluminide coatings

Citation Formats

Dryepondt, Sebastien N, Zhang, Ying, and Pint, Bruce A. Creep and Corrosion Testing of Aluminide Coatings on Ferritic-Martensitic Substrates. United States: N. p., 2007. Web.
Dryepondt, Sebastien N, Zhang, Ying, & Pint, Bruce A. Creep and Corrosion Testing of Aluminide Coatings on Ferritic-Martensitic Substrates. United States.
Dryepondt, Sebastien N, Zhang, Ying, and Pint, Bruce A. Mon . "Creep and Corrosion Testing of Aluminide Coatings on Ferritic-Martensitic Substrates". United States. doi:.
@article{osti_931295,
title = {Creep and Corrosion Testing of Aluminide Coatings on Ferritic-Martensitic Substrates},
author = {Dryepondt, Sebastien N and Zhang, Ying and Pint, Bruce A},
abstractNote = {Pack and chemical vapor deposited (CVD) aluminide coatings on commercial ferritic-martensitic Fe-9Cr-2W steel are being investigated by creep and corrosion testing at 650 C. Results from different coating thicknesses show that the coated region makes no contribution to the creep strength. The creep behavior of uncoated material was studied after various heat treatments to simulate the coating process and typical secondary heat treatments. Alternating creep and corrosion exposures showed little effect on the creep strength of uncoated material but coated materials became progressively weaker. The coatings were protective in wet air at 650 C after creep testing.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • Pack and chemical vapor deposited (CVD) aluminide coatings on commercial ferritic-martensitic Fe-9Cr-2W steel are being investigated by creep and corrosion testing at 650 C. Results from different coating thicknesses show that the coated region makes no contribution to the creep strength. The creep behavior of uncoated material was studied after various heat treatments to simulate the coating process and typical secondary heat treatments. Alternating creep and corrosion exposures showed little effect on the creep strength of uncoated material but coated materials became progressively weaker. The coatings were protective in wet air at 650 C after creep testing.
  • The creep behavior of various pack cementation aluminide coatings on Grade 91 ferritic-martensitic steel was investigated at 650 C in laboratory air. The coatings were fabricated in two temperature regimes, i.e., 650 or 700 C (low temperature) and 1050 C(high temperature), and consisted of a range of Al levels and thicknesses. For comparison, uncoated specimens heat-treated at 1050 C to simulate the high temperature coating cycle also were included in the creep test. All coated specimens showed a reduction in creep resistance, with 16 51% decrease in rupture life compared to the as-received bare substrate alloy. However, the specimens heat-treatedmore » at 1050 C exhibited the lowest creep resistance among all tested samples, with a surprisingly short rupture time of < 25 h, much shorter than the specimen coated at 1050 C. Factors responsible for the reduction in creep resistance of both coated and heat-treated specimens were discussed.« less
  • A pack cementation process was developed to coat commercial 9% Cr ferritic-martensitic steel T91 at temperatures below its normal tempering temperature to avoid any potential detrimental effect on the mechanical properties of the coated alloy. In order to prevent the formation of Fe{sub 2}Al{sub 5} coatings, the Al activity in the pack cementation process was reduced by substituting the pure Al masteralloy with binary Cr-Al masteralloys containing either 15 or 25 wt.% Al. When the Cr-25Al masteralloy was used, a duplex coating was formed at 700 C, consisting of a thin Fe{sub 2}Al{sub 5} outer layer and an inner layermore » of FeAl. With the Cr-15Al masteralloy, an FeAl coating of {approx} 12 {micro}m thick was achieved at 700 C. The pack aluminide coatings fabricated at 700 C are being evaluated in air + 10 vol.% H{sub 2}O at 650 C and 700 C to determine their long-term oxidation performance.« less
  • Corrosion behavior of the F-M (ferritic-martensitic) steels (T91, T92, T122) and Fe-base ODS (oxide dispersion strengthened) alloy (MA956{sup TM}) were evaluated in an aerated (8 ppm D.O.) SCW (supercritical water) at the temperature range between 300 and 627 deg C under 25 MPa. In aerated SCW the weight change of the F-M steel specimens became greater as the test temperature increased. However, the extent of the weight change at 350 deg C, just below the critical temperature appeared not to be less than those at 550 deg C. And the weight changes of all the F-M steel specimens in themore » deaerated SCW (for 347 hrs in 100 ppb D.O. for 347 hrs, and in 10 ppb D.O. for 432 hrs) tended to converge to about 1 mgcm{sup -2}. In aerated or deaerated conditions 20Cr Fe-base ODS alloy appeared to be very resistant to a SCW corrosion at all the test temperatures up to 500 hrs. Stress corrosion cracking (SCC) behavior of 9Cr F-M steels (T91 and T92) was investigated by CERT (Constant Extension Rate Test) in SCW at various temperatures and D.O. levels with different strain rates. T91 did not show any evidence of a SCC in a fully deaerated (below 10 ppb D.O.) SCW at 500, 550, and 600 deg C at the test conditions. T92 specimens were tested at 500 deg C in SCW with different D.O. levels. The strain rate did not seem to affect the SCC behavior of the T92 steel, but D.O. in SCW seems to affect the SCC behavior to some extent. The total elongation of T92 in SCW of 100 ppb or of 500 ppb D.O. was significantly smaller than that at a fully deaerated (below 10 ppb D.O.) SCW (about 15 vs. 20%), and it appears to provide a clue to a SCC on the fracture surface after the CERT test. (authors)« less
  • Russian ferritic/martensitic (F/M) steels EP-450, EP-852 and EP-823 were irradiated in the BN-350 fast reactor in the form of gas-pressurized creep tubes. The first steel is used in Russia for hexagonal wrappers in fast reactors. The other steels were developed for compatibility with Pb-Bi coolants and serve to enhance our understanding of the general behavior of this class of steels. In an earlier paper we published data on irradiation creep of EP-450 and EP-823 at temperatures between 390 and 520C, with dpa levels ranging from 20 to 60 dpa. In the current paper new data on the irradiation creep andmore » swelling of EP-450 and EP-852 at temperatures between 305 and 335C and doses ranging from 61 to 89 dpa are presented. Where comparisons are possible, it appears that these steels exhibit behavior that is very consistent with that of Western steels. Swelling is relatively low at high neutron exposure and confined to temperatures <420C, but may be camouflaged somewhat by precipitation-related densification. These irradiation creep studies confirm that the creep compliance of F/M steels is about one-half that of austenitic steels.« less