US3595712A - Processing of aluminide-coated nickel-base superalloys - Google Patents

Processing of aluminide-coated nickel-base superalloys Download PDF

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Publication number
US3595712A
US3595712A US765777A US3595712DA US3595712A US 3595712 A US3595712 A US 3595712A US 765777 A US765777 A US 765777A US 3595712D A US3595712D A US 3595712DA US 3595712 A US3595712 A US 3595712A
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United States
Prior art keywords
coating
substrate
aluminide
processing
coated
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Expired - Lifetime
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US765777A
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English (en)
Inventor
Donald H Boone
Cornelius P Sullivan
Clifford H Wells
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RTX Corp
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United Aircraft Corp
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
    • C23C10/60—After-treatment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12736—Al-base component
    • Y10T428/1275—Next to Group VIII or IB metal-base component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12861—Group VIII or IB metal-base component
    • Y10T428/12944—Ni-base component

Definitions

  • the present invention relates in general to the hightemperature, oxidation-resistant coatings, particularly the aluminide coatings as applied to the superalloys. It has specific utility in the processing of those coated gas turbine engine components formed from the nickel-base superalloys.
  • the aluminide coatings generally derive their protectivity from intermetallic compounds of aluminum which in turn are protected by a layer of aluminum oxide formed by high temperature oxidation of the coating. Gradually, the oxide is lost by a process of erosive spalling, but a reoxidation occurs and the protective function is reestablished. Accordingly, the substrate remains protected as long as sufcient aluminum is retained in the coating to provide the preferential oxidation mechanism leading to the formation of aluminum oxide.
  • the protective character of the coating is, hence, a function of its aluminum content, the higher aluminum contents leading to improved component lifetimes in terms of oxidation behavior when viewed in the light of the progressive oxidation-erosion-reoxidation mechanism.
  • the typical aluminide coating may be formed in a number of ways, but the more Widely used methods are those involving slurry-diffusion or pack cementation.
  • a typical slurry process utilizing a Udimet 700 substrate, a mixture of aluminum and silicon powders in a ratio of 9 to 1 is suspended in a cellulose acetate vehicle and applied by spray gun to the mechanically-abraded surface of a fully machined and heat treated article. After volatilization of the vehicle and reaction of the mixture with the substrate by exposure to an elevated temperature for a few minutes, the article is given the following heat treaatment: diffusion at 19757 F. for 4 hours; plus 15500 F. for 24 hours; plus 1400 F. for 16 hours.
  • the desired aluminide coating is generated by embedding the parts in a pack consisting of 15 percent aluminum powder, 3 percent ammonium chloride and 82 percent alumina and heating the pack to a temperature of perhaps l800 F.
  • Both coating mechanisms proceed mainly by diffusion of aluminum into the substrate. Although the particular coating composition achieved rellects to some extent the structural and compositional characteristics of the substrate alloy, microstructural examination of a large number of contemporary coating-substrate systems indicates that most, if not all, aluminide coatings on the nickelbase superalloys are formed on and protect by similar mechanisms regardless of the method by which the coating is achieved.
  • the ⁇ aluminide coating comprises a polycrystalline matrix of high aluminum content NiAl phase) together with a variety of interspersed second phases.
  • This aluminide phase having an aluminum content of typically "3U-40 weight percent aluminum is characterized by very low ductility at temperatures below 1500D yF. and, hence, is susceptible to crack formation.
  • This low ductility is a function of the high aluminum content and results in a high brittle-ductile transition temperature usually within or above the designed component critical strain range.
  • the substrate adjacent to the coating is altered in composition by withdrawal of species by the coating in a diffusion mechanism.
  • enrichment of cobalt and chromium occurs and subsequent heat treatment or engine operation results in the precipitation of an undesirable sigma (a) phase at the substrate surface.
  • the primary object of the present invention is to improve the fatigue properties of aluminide coatings and coated articles, particularly in their application to the nickel-base snperalloys and gas turbine engine components fabricated therefrom.
  • the foregoing object and other objects ⁇ of the invention are achieved by altering the coating composition and/or structure particularly through the inducement of information of more optimum types, amounts and distribution of the various phases present in the coating and/or a minimization of the more detrimental phases by suitable processing.
  • the processing is selected to reduce the localized aluminum content of the coating whereby, in addition to t-he reduction of brittle aluminide phases, and/or the formation of a ductile NigAl 'y' phase grain boundary layer, there is an improved distribution of second phases in the structure.
  • the substrate surface prior to coating is mechanically cleaned so as to furnish a surface roughness not exceeding about microns/ inch.
  • the preferred processing contemplates an intermediate elevated temperature heat treatment between the usual coating and substrate precipitation heat treatments, this intermediate heat treatment being conducted in the temperature range where the sigma or other detrimental phases are not stable.
  • This heat treatment results in an advantageous homogenization of the aluminide and the secondary phases in the coating and a reduction in the localized aluminum content of the coating.
  • the particular temperature level selected for this intermediate heat treatment or high temperature anneal is both a function of the substrate composition and of the intended environment of the coated article and as such falls coincident with the substrate solutionizing temperature range.
  • the present process in an overall sequence hence involves coating of a substrate with or without prior full heat treatment thereof, usually but not necessarily including the usual short term heat treatment to set the coating; an intermediate high temperature anneal at the substrate solutionizing temperature; and a precipitation heat treatment cycle.
  • a particular preferred coating process for Udimet 700 components thus becomes; coating, including on an optional basis, a diffusion heat treatment at 1975 F. for 4 hours; an intermediate heat treatment at 2140* F. for 4 hours; air cool plus 1975 F. for 4 hoursair cool plus 1550 F. for 24 hours; air cool plus 1400 F. for 16 hours; and air cool.
  • the preferred processing becomes: coating, including on an optional basis, a diffusion heat treatment at 1975o F. for 4 hours; an intermediate heat treatment at 2200 F. for 2 hours; air cool plus 1600" F. for 32 hours; and air cool.
  • the drawing is a graph depicting the results of low cycle fatigue testing of wrought Udimet 700 at 1700 F. with the sample in various conditions of processing.
  • nickel-base superalloys will be understood to have reference to those multiphase alloys of the y-y type characterized by high strengths in the temperature regimes of 16002100 F. or higher. Some of the currently available alloys of this type are those listed below.
  • TAB LE Nominal composition (percent by wt.)
  • MAR-M200 9% Cr, 10% Co, 2% Ti, 5% Al, 12.5% W, 1% Co, .15% C,
  • aluminide coatings thus generated all depend for their protective effect upon the formation of an outer layer of aluminum oxide during exposure of the coating to a high temperature oxidizing environment.
  • the specific composition of the coating and, to a lesser extent, the morphology of the secondary phases (carbides, etc.) wary somewhat as a function of substrate composition resulting from an interdiffusion of species in the coating process.
  • the overall effect of these variations in microstructure and composition do not alter the basic principles involved in the coating and protective mechanisms.
  • the brittle-ductile transition temperature for the improved coating is lowered to a less critical temperature range.
  • the coatings have as a matter of practice been applied to the fully heat treated blade or vane. This, of course, has involved a prior component heat treatment cycle prior to coating.
  • a prior component heat treatment cycle prior to coating In accordance with the present invention, through utilization of a high temperature anneal after coating, it is now possible to heat treat the coating and substrate simultaneously and, accordingly, the prior substrate heat treatments may be eliminated.
  • coating may be effected on the blades and vanes as-wrought, as-machined or as-cast. Not only is the fatigue behavior of the coating improved but the overall processing cycle is considerably simplified with the consequent considerable cost savings in generation of the coated article.
  • the overall processing sequence comprises coating the substrate; annealing the coated substrate at about the substrate solutionizing temperature; and precipitation heat treating the coated article.
  • the substrate surface is processed to achieve a surface roughness less than about I65 microns/inch, a smoother coating results and further improvement in fatigue crack initiation resistance is attained.
  • the annealing is conducted to reduce the localized aluminum content of the coating and to promote the formation of the ductile NiaAl'y phase of the aluminide in the coating.
  • the surface of the article to be aluminized is provided with a surface roughness not exceeding about 65 microns per inch.
  • the intermediate heat treatment is conducted to provide a localized aluminum content in the coating less than about 25 percent by weight.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
US765777A 1968-10-08 1968-10-08 Processing of aluminide-coated nickel-base superalloys Expired - Lifetime US3595712A (en)

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US76577768A 1968-10-08 1968-10-08

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US3595712A true US3595712A (en) 1971-07-27

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US (1) US3595712A (enrdf_load_stackoverflow)
CA (1) CA925414A (enrdf_load_stackoverflow)
DE (1) DE1948031A1 (enrdf_load_stackoverflow)
FR (1) FR2020132A1 (enrdf_load_stackoverflow)
GB (1) GB1266241A (enrdf_load_stackoverflow)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3839898A (en) * 1972-11-22 1974-10-08 United Aircraft Corp Determination of thermal profile history of high temperature parts
US3953647A (en) * 1973-10-05 1976-04-27 United Technologies Corporation Graphite fiber reinforced metal matrix composite
US4087589A (en) * 1975-10-14 1978-05-02 General Electric Company Coated article
US4142023A (en) * 1975-12-16 1979-02-27 United Technologies Corporation Method for forming a single-phase nickel aluminide coating on a nickel-base superalloy substrate
US4314880A (en) * 1980-02-08 1982-02-09 The United States Department Of America As Represented By The United States Department Of Energy Hydrogen permeation resistant barrier
US4362696A (en) * 1979-05-21 1982-12-07 The United States Of America As Represented By The United States Department Of Energy Corrosion-resistant fuel cladding allow for liquid metal fast breeder reactors
US5334416A (en) * 1991-12-30 1994-08-02 Pohang Iron & Steel Co., Ltd. Heat resistant stainless steel coated by diffusion of aluminum and the coating method thereof
US20070169913A1 (en) * 2003-04-03 2007-07-26 Joachim Bamberg Method to manufacture components for gas turbines
US20120302811A1 (en) * 2004-03-23 2012-11-29 Velocys Inc. Catalysts Having Catalytic Material Applied Directly to Thermally-Grown Alumina and Catalytic Methods Using Same; Improved Methods of Oxidative Dehydrogenation
CN104439977A (zh) * 2014-12-03 2015-03-25 北京航星机器制造有限公司 一种对称裙板类铸造铝合金零件的快速制造方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6035992B2 (ja) * 1980-05-02 1985-08-17 株式会社日立製作所 Ｎｉ合金のＡｌコ−テイング方法

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3839898A (en) * 1972-11-22 1974-10-08 United Aircraft Corp Determination of thermal profile history of high temperature parts
US3953647A (en) * 1973-10-05 1976-04-27 United Technologies Corporation Graphite fiber reinforced metal matrix composite
US4087589A (en) * 1975-10-14 1978-05-02 General Electric Company Coated article
US4142023A (en) * 1975-12-16 1979-02-27 United Technologies Corporation Method for forming a single-phase nickel aluminide coating on a nickel-base superalloy substrate
US4362696A (en) * 1979-05-21 1982-12-07 The United States Of America As Represented By The United States Department Of Energy Corrosion-resistant fuel cladding allow for liquid metal fast breeder reactors
US4314880A (en) * 1980-02-08 1982-02-09 The United States Department Of America As Represented By The United States Department Of Energy Hydrogen permeation resistant barrier
US5334416A (en) * 1991-12-30 1994-08-02 Pohang Iron & Steel Co., Ltd. Heat resistant stainless steel coated by diffusion of aluminum and the coating method thereof
US20070169913A1 (en) * 2003-04-03 2007-07-26 Joachim Bamberg Method to manufacture components for gas turbines
US20120302811A1 (en) * 2004-03-23 2012-11-29 Velocys Inc. Catalysts Having Catalytic Material Applied Directly to Thermally-Grown Alumina and Catalytic Methods Using Same; Improved Methods of Oxidative Dehydrogenation
US9011781B2 (en) * 2004-03-23 2015-04-21 Velocys, Inc. Catalysts having catalytic material applied directly to thermally-grown alumina and catalytic methods using same; improved methods of oxidative dehydrogenation
CN104439977A (zh) * 2014-12-03 2015-03-25 北京航星机器制造有限公司 一种对称裙板类铸造铝合金零件的快速制造方法

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Publication number Publication date
CA925414A (en) 1973-05-01
GB1266241A (enrdf_load_stackoverflow) 1972-03-08
DE1948031A1 (de) 1970-04-23
FR2020132A1 (enrdf_load_stackoverflow) 1970-07-10

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