skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Creep and Corrosion Testing of Aluminide Coatings on Ferritic 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); Shared Research Equipment Collaborative Research Center
Sponsoring Org.:
FE USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
1003510
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Surface and Coatings Technology; Journal Volume: 201; Journal Issue: 7
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AIR; COATINGS; CORROSION; CREEP; HEAT TREATMENTS; STEELS; SUBSTRATES; TESTING; THIN FILMS

Citation Formats

Dryepondt, Sebastien N, Zhang, Ying, and Pint, Bruce A. Creep and Corrosion Testing of Aluminide Coatings on Ferritic Substrates. United States: N. p., 2006. Web. doi:10.1016/j.surfcoat.2006.07.258.
Dryepondt, Sebastien N, Zhang, Ying, & Pint, Bruce A. Creep and Corrosion Testing of Aluminide Coatings on Ferritic Substrates. United States. doi:10.1016/j.surfcoat.2006.07.258.
Dryepondt, Sebastien N, Zhang, Ying, and Pint, Bruce A. Sun . "Creep and Corrosion Testing of Aluminide Coatings on Ferritic Substrates". United States. doi:10.1016/j.surfcoat.2006.07.258.
@article{osti_1003510,
title = {Creep and Corrosion Testing of Aluminide Coatings on Ferritic 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 = {10.1016/j.surfcoat.2006.07.258},
journal = {Surface and Coatings Technology},
number = 7,
volume = 201,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • 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
  • This paper reports the successful co-deposition of inclusion-free chromium-modified aluminide coatings using a pack-cementation process. The substrate used was the nickel-base superalloy, Rene 80H. The coatings were of the outward-diffusion type; however, unlike the usual outward-diffusion coatings, the present coatings were relatively free of pack inclusions. The coatings consisted of [alpha]-Cr precipitates in a matrix of [beta]-NiAl. The morphology and distribution of the [alpha]-Cr precipitates could be adjusted to the extent that two types of coating structures could be obtained. The Type 1 coating structure contained lamellar [alpha]-Cr precipitates situated in the surface region of the coating, whereas the Typemore » 2 coating structure contained small, spheroidal [alpha]-Cr precipitates distributed throughout the outer of a two-layered coating. Both coating types exhibited significantly improved hot-corrosion resistance in a 0.1% SO[sub 2]-O[sub 2] environment at 900[degrees]C compared to a commercial aluminide coating. A study of the corrosion behavior of Type 1 coatings containing pack inclusions showed that the inclusions were deleterious to the corrosion resistance of the coatings. The corrosion behavior of chromium-aluminide coatings was dependent on both the distribution and amount of [alpha]-Cr precipitates in the coating.« less
  • The isothermal oxidation of reactive element (RE)-doped aluminide coatings on IN 713LC alloy substrates at 1100 C in air formed a continuous slow-growing [alpha]-Al[sub 2]O[sub 3] scale after 44 h of exposure. RE-free (reactive element-free) aluminide coatings were characterized by a cracked oxide scale which exposed an underlying voided coating surface. The cyclic oxidation behavior of Cr/RE-modified aluminide diffusion coatings on Rene 80 and IN 713LC alloy substrates, and of RE-doped aluminide coatings on IN 713LC alloy substrates, at 1100 C in static air was determined. Coatings deposited by the above pack (AP) arrangement, as opposed to the powder contactingmore » (PC) arrangement, showed improved resistance to cyclic oxidation attack. RE-doped and Cr/RE-modified aluminide coatings exhibited considerably more adherent protective Al[sub 2]O[sub 3] scales compared to undoped aluminide coatings. The hot corrosion behavior of Cr/RE-modified aluminide coatings on Rene 80 and Mar-M247 alloy substrates at 900 C in a 0.1 % sO[sub 2]/O[sub 2] gas mixture also was determined. The Cr/RE-modified aluminide coatings provided better resistance to hot corrosion attack (i.e., thin film studies) than a commercial low activity aluminide coating. Coating lifetimes were strongly dependent on the chromium surface composition, since a mixed (Al, Cr)[sub 2]O[sub 3] scale better resists attack by the molten salt.« less
  • a-Ta coatings on smooth and rough steel substrates (AISI 4340) were studied in an effort to assess the resulting porosity and corrosion behavior. While the long-range crystallographic orientation of the coatings was found to be affected by the surface roughness, the short-range structure was invariant. Peak broadening in X-ray diffraction patterns attributed to microstrain and particle size was observed for coatings on both types of substrates as compared to Ta powder. Although the roughness was two orders of magnitude greater for the coatings deposited on the rough substrates than the smooth ones, the porosity was not significantly different. Furthermore, electrochemicalmore » impedance behavior over long exposure times of coatings deposited on smooth and rough steel substrates was similar to that of Ta foil. These results demonstrate that substrate roughness appears to have little to no effect on the coating quality with respect to corrosion performance for 50 {micro}m coatings.« less