Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3649225 A
Publication typeGrant
Publication dateMar 14, 1972
Filing dateNov 17, 1969
Priority dateNov 17, 1969
Publication numberUS 3649225 A, US 3649225A, US-A-3649225, US3649225 A, US3649225A
InventorsAlfred E Simmons Jr
Original AssigneeUnited Aircraft Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Composite coating for the superalloys
US 3649225 A
Abstract
Improved operating lifetimes are provided for the superalloys through use of a composite coating comprising a chromium or chromium-rich interlayer adjacent the superalloy substrate surface and an oxidation-resistant outer layer comprising an alloy of iron, cobalt and/or nickel alloyed with selected amounts of chromium, aluminum and yttrium.
Images(1)
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

United States Patent Simmons, Jr.

[45] Mar. 14, 1972 [54] COMPOSITE COATING FOR THE 3,041,040 6/1962 Levinstein ....29/ 198 SUPERALLOYS 2,861,327 11/1958 Bechtold ....29/19s 3,552,953 l/197l Lemkey... ....75/l7l [721 lnvemorl Alfred slmmons, East Hartford 3,215,512 11/1965 Coad ..29/191 Conn.

[73] Assignee: United Aircraft Corporation, East Hart- Primary Emfniner flyland Bizot ford, Conn. Attorney-Richard N. James [22] Filed: NOV. 17, 196 [57] ABSTRACT [21] Appl. No.: 877,321

Improved operating lifetimes are provided for the superalloys [52] U.S. Cl. ..29/194, 29/1966, 29/198 hr gh use of a omp ite coa ing comprising a chromium or [51] Int. Cl ..B32b 15/00 chromium-rich interlayer adjacent the superalloy substrate [58] Field of Search ..29/ 198, 194, 196.6; 75/171 surface and an oxidation-resistant outer layer comprising an alloy of iron, cobalt and/or nickel alloyed with selected [56] References Cited amounts of chromium, aluminum and yttrium.

UNlTED STATES PATENTS 4 Claims, 1 Drawing Figure 2,993,264 7/1961 Grenoble ..29/198 KVPPf/l/T f/V/Nf fifQV/Pf/Wf/VZJ l \1 Q 1% Q \s COMPOSITE COATING FOR THE SUPERALLOYS BACKGROUND OF THE INVENTION The present invention relates in general to high-temperature, oxidation-resistant coatings for the superalloys, particularly as applied to gas turbine engine components.

A limiting factor in the application of many of the superalloys to demanding environments such as those encountered by jet engine hardware is their susceptibility to high-temperature oxidation and corrosion. For this reason these alloys are generally provided with suitable surface coatings for increased oxidation resistance. For current operating conditions the most widely used coatings have been provided by reacting aluminum with the alloy to form surface aluminides which preferentially oxidize to form surface oxides through which the transport rates of the oxidizing species are low. Typical of processes of this type is that described in the US. Pat. No. to Joseph 3,102,044.

Both turbine blade and vane life in existing engines, and the extent of power increases requiring higher engine operating temperatures, are largely limited by the durability of the coatings. In the past, the inadequacy of current coatings to give long term protection against corrosion at very high temperatures has prevented use of some of the stronger nickelbase alloys, such as B-l900, in applications where their properties otherwise indicate the desirability of their use.

At high temperatures in the dynamic oxidizing environment of a gas turbine engine, temperature fluctuations caused by the mixing of hot combustion gases with cooler secondary air, or those associated with variations in engine power levels, give rise to thermally induced strains in the coatings at the metaloxide interface which are sufficiently large to spall the protective oxide layer. Furthermore, at a temperature of about 2,000 F nickel and the nickel-base superalloys begin to exhibit a great alloying affinity for the usual coating constituents, and particularly for aluminum, as recognized in the US. Pat. No. to Maxwell 3,450,212. Thus, a loss of coating protection in a dynamic oxidizing environment at very high temperature, involves both an inward and an outward loss of one or more of the protective species.

In a series of copending applications of the present assig'nee, there are described a number of coating compositions for the superalloys which have doubled the endurance of the coated components at high temperature and have in addition permitted engine performance increases associated with the higher temperatures of current interest. In application Ser. No. 731,650, filed May 23, 1968 for an Iron Base Coating for the Superalloys, now US, Pat. No. 3,542,530 there is described a preferred coating alloy comprising, by weight, 25-29 percent chromium, 12-14 percent aluminum, 0.6-0.9 percent yttrium, balance iron, hereinafter referred to as the FeCrAlY coating. In application Ser. No. 795,616 filed Jan. 31, 1969 for a Cobalt Base Coating for the Superalloys, there is described a preferred coating composition comprising, by weight, 19-24 percent chromium, 13-17 percent aluminum, 0.6-0.9 percent yttrium, balance cobalt, hereinafter referred to as the CoCrAlY coating. A NiCrAlY coating comprising, by weight, 20-35 percent chromium, 15-20 percent aluminum, 0.050.3 percent yttrium, balance nickel is disclosed in application Ser. No. 734,740 filed June 5, 1968. All of the above coating alloys are resistant of oxidation, thermal spalling, and to interdifiusion with the substrate when compared to alternative coating schemes. However, it has been found that even with these advanced coatings there exists a measure of coating-substrate interdiffusion.

It is known that, in some instances, improved coating performance may be obtained through coating processes involving multiple surface treatments. In the U.S. Pat. No. to Gibson 2,809,127, the surface of an alloy is first chromized and then aluminized to increase the oxidation resistance at high temperature. As in the case of Joseph, supra, the basic oxidation protection in Gibson is dependent upon the reaction of aluminum with the constituents of the substrate at the surface to be protected.

SUMMARY OF THE INVENTION It is the object of the present invention to provide an improved coating for the superalloys characterized by long term durability in dynamic oxidizing environments at very high temperatures. There is provided a composite coating comprising a chromium or predominantly chromium interlayer at the superalloy surface to be protected and an outer layer of highoxidation resistance comprising an alloy of iron, cobalt or nickel containing selected amounts of chromium, aluminum and a rare earth element such as yttrium.

In a preferred embodiment of the invention, the composite coating comprises an interlayer of chromium and an outer layer consisting essentially of, by weight, 25-29 percent chromium, 12-14 percent aluminum, 0.60.9 percent yttrium, balance iron.

In another preferred embodiment, the composite coating comprises an interlayer of chromium and an outer layer consisting essentially of, by weight, 19-24 percent chromium, 13-17 percent aluminum, 0.60.9 percent yttrium, balance cobalt.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a chart comparing the various coatings for the nickel-base superalloys in terms of durability.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the generation of the FeCrAlY, CoCrAlY and NiCrAlY coating alloys, and as currently provided in production jet engines, component surface protection has nonnally been provided by exposing the substrate to aluminum or aluminum vapor at high temperature and promoting a reaction of the aluminum with one or more of the substrate constituents to form protective aluminides. In the FeCrAlY-type coating system, the oxidation protection is effected, not by a coatingsubstrate reaction, but rather by the coating alloy per se. The coating alloy of itself is oxidation-resistant and relatively immune to thermal spalling and no intermediate coatings are required in terms of the basic function which the coating is to provide, nor in fact is any interdiffusion of substrate or intermediate layer constituents into the coating desired. In the present composite coating, an interlayer of chromium is provided to specifically reduce the outer coating-substrate interdifiusion and by so doing to improve the durability of the coating as demonstrated by an increased operating lifetime for a component so coated.

Thus, the durability of the FeCrAlY-type coatings have been found to be limited not by deficiencies in the oxidationerosion resistance of the coatings per se, but rather is a function of the extent of aluminum depletion in the coating resultant from the coating-substrate interdifi'usion, particularly at temperatures in excess of about 2,000 F.

It was found that a substantial improvement in the endurance of the FeCrAlY-type coatings can be provided by interposing an interlayer of chromium or a predominantly chromium alloy between the outer coating and the substrate to act as a diffusion barrier therebetween, minimizing the depletion of aluminum in the outer coating by this mechanism. This chromium interlayer may be produced by any of the available methods for generating such coatings or surface layers including electroplating, electroplating plus diffusion heat treatment, pack cementation, plasma spray, slurry spray, or any other technique providing a predominantly chromium layer at or on the substrate surface. It is relatively immaterial how the interlayer formed subject, however, to the requirement that the process be one yielding an interlayer composed primarily of chromium.

The FeCrAlY-type outer coatings are typically applied utilizing vacuum vapor deposition methods and apparatus. As explained, the efficacy of these coatings is dependent upon the correct coating alloy composition being deposited on the surface to be protected. These coatings are characterized by high-melting points as alloyed and by diverse melting points insofar as the elemental constituents are concerned. Care must taken in the coating formation process to provide all of the desired coating alloy species in the correct proportions in the coating as applied. Satisfactory results have been attained by vapor deposition in a vacuum utilizing an electron beam heat source, as suggested in the U.S. Pat. No. to Steigerwald 2,746,420.

It should be noted that it is the unique combination comprising the composite coating that provides the coating endurance improvements established by test. One of the incidents of the undesirable coating-substrate interdiffusion, in addition to aluminum depletion in the coating, is contamination of the substrate by the coating constituents. The use of the chromium interlayer has been found not only to prevent such detrimental contamination by the coating elements but also to provide none of itself. In addition, the chromium interlayer adjacent the FeCrAlY coating has appeared to provide no observable detrimental effect on the coating alloy itself nor on its adherence to the substrate.

Tests conducted on several nickel-base superalloy substrates, including such superalloys as B4900, MAR M200, and NX 188, and on the cobalt-base superalloys such as MAR M302, have indicated that coating life improvements on the order of 50 percent are achieved, as graphically illustrated in the drawing.

EXAMPLE Various nickel-base and cobalt-base superalloy parts to be coated were embedded in a pack of blended powders composed of, by weight, 84.5 percent alumina, 15 percent chromium, and 0.5 percent ammonium chloride. After purging with argon, the pack was sealed and the parts were chromized at 2,l F. for 4 hours. In general, surface buildups of 0002-0005 in. resulted from pack chromizing under these conditions.

Subsequent to the chromizing operation, parts were mounted in the vacuum chamber of electron beam melting apparatus, preheated, and coated by vapor deposition from a molten pool of coating material in a vacuum of Torr or better to typical outer coating thicknesses of 0001-0005 in.

Following deposition of the outer coating, the coated cobalt-base substrates were heat treated at 1,900 F. for about an hour in vacuum with a cool in a nonoxidizing atmosphere at a rate equivalent to air cool. The nickel-base superalloy substrates after coating, and the cobalt-base superalloy substrates after coating and heat treatment, as coated, were dry glass bead peened at N for about 2 minutes in accordance with AMS 2,430. Subsequent to peening the coated parts were heated to 1,975 F. in dry argon or hydrogen, or vacuum; held at heat for 4 hours; and cooled at a rate equivalent to air coolmg.

A variety of superalloy substrates were provided with several composite coating combinations, particularly with respect to the outer coating composition. After extensive testing, it was determined that the preferred FeCrAlY outer coating chemistry conformed to the following:

Component percent by weight chromium 25-29 aluminum 10.5-12.5 yttrium 0.4-0.9

oxygen 0.03 max. nitrogen 0.01 max. hydrogen 0.01 max.

0.5 max.

remainder other elements, total iron The most preferred CoCrAlY coating in the composite coating consisted of:

broader aspects it is not limited to the exact details described, for obvious modifications will occur to those skilled in the art.

What is claimed is:

l. A composite article resistant to oxidation at high temperature comprising:

a substrate selected from the group consisting of the hightemperature nickel-base and cobalt-base alloys having strengths suitable for structural applications in a gas turbine engine environment,

an interlayer, adjacent the substrate surface and bonded thereto, selected from the group consisting of chromium and its alloys,

and an oxidation resistant outer layer thereover, bonded to the interlayer, which consists essentially of chromium, aluminum, at least one rare earth element, and at least one element selected from the group consisting of iron, cobalt, and nickel.

2. A composite article according to claim 1 wherein: in the outer layer,

the chromium content is 1 5-30 weight percent,

the aluminum content is l0-20 weight percent,

the rare earth element is yttrium,

and the yttrium content is at least 0.1 weight percent.

3. A coated gas turbine engine component comprising:

a substrate selected from the group consisting of the high temperature, high-strength nickel-base and cobalt-base alloys,

an interlayer, adjacent the substrate surface and bonded thereto, selected from the group consisting of chromium and its alloys,

and an oxidation resistant outer layer superimposed on and bonded to the interlayer, the outer layer consisting essentially of, by weight, 25-29 percent chromium, 10-14 percent aluminum, 0.4-0.9 percent yttrium, balance substantially iron.

4. A coated gas turbine engine component comprising:

a substrate selected from the group consisting of the high temperature, high-strength nickel-base and cobalt-base alloys,

an interlayer, adjacent the substrate surface and bonded thereto, selected from the group consisting of chromium and its alloys,

and an oxidation resistant outer layer superimposed on and bonded to the interlayer, the outer layer consisting essentially of, by weight, 21-25 percent chromium, 10-1 5 percent aluminum, 0.4-0.9 percent yttrium, balance substantially cobalt.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2861327 *Sep 12, 1956Nov 25, 1958Westinghouse Electric CorpApplying protective metal coatings on molybdenum
US2993264 *Dec 23, 1955Jul 25, 1961Gen ElectricProtective coating for molybdenum
US3041040 *Dec 23, 1955Jun 26, 1962Gen ElectricMetal clad blade
US3215512 *Jun 9, 1961Nov 2, 1965Texas Instruments IncComposite refractory articles
US3552953 *Jan 10, 1969Jan 5, 1971United Aircraft CorpCobalt-chromium base alloy and articles produced therefrom
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3755887 *Nov 12, 1971Sep 4, 1973Continental Can CoMethod of making cobalt alloy steel composite article
US3849865 *Oct 16, 1972Nov 26, 1974NasaMethod of protecting the surface of a substrate
US3869779 *Jan 24, 1974Mar 11, 1975NasaDuplex aluminized coatings
US3904382 *Jun 17, 1974Sep 9, 1975Gen ElectricCorrosion-resistant coating for superalloys
US3918139 *Jul 10, 1974Nov 11, 1975United Technologies CorpMCrAlY type coating alloy
US3928026 *May 13, 1974Dec 23, 1975United Technologies CorpHigh temperature nicocraly coatings
US3957454 *Nov 15, 1974May 18, 1976General Electric CompanyIron, cobalt, nickel, aluminum, hot corrosion resistant
US4005989 *Jan 13, 1976Feb 1, 1977United Technologies CorporationCoated superalloy article
US4022587 *Sep 8, 1975May 10, 1977Cabot CorporationChromium, aluminum, yttrium, lanthanum, cerium
US4029477 *Oct 29, 1975Jun 14, 1977General Electric CompanyCoated Ni-Cr base dispersion-modified alloy article
US4080486 *Sep 24, 1974Mar 21, 1978General Electric CompanyCoating system for superalloys
US4109061 *Dec 8, 1977Aug 22, 1978United Technologies CorporationMethod for altering the composition and structure of aluminum bearing overlay alloy coatings during deposition from metallic vapor
US4144380 *Aug 10, 1977Mar 13, 1979General Electric CompanyCladdings of high-temperature austenitic alloys for use in gas turbine buckets and vanes
US4148936 *Nov 21, 1977Apr 10, 1979General Electric CompanyMethod for diffusion coating an Fe-Ni base alloy with chromium
US4218007 *Feb 22, 1979Aug 19, 1980General Electric CompanyMethod of diffusion bonding duplex sheet cladding to superalloy substrates
US4743514 *Jun 29, 1983May 10, 1988Allied-Signal Inc.Nickel base alloy
US4963440 *Jan 19, 1989Oct 16, 1990Kabushiki Kaisha Kobe Seiko ShoCorrosion resistance
US5197852 *May 31, 1990Mar 30, 1993General Electric CompanyNozzle band overhang cooling
US5384200 *Apr 18, 1994Jan 24, 1995Detroit Diesel CorporationThermal barrier coating and method of depositing the same on combustion chamber component surfaces
US5499905 *Mar 20, 1995Mar 19, 1996Siemens AktiengesellschaftMetallic component of a gas turbine installation having protective coatings
US5500252 *May 10, 1995Mar 19, 1996Rolls-Royce PlcAluminum, chromium alloy
US5987882 *Apr 19, 1996Nov 23, 1999Engelhard CorporationTurbocharger and oxidation catalyst
US6006516 *Apr 11, 1997Dec 28, 1999Engelhard CorporationSystem for reduction of harmful exhaust emissions from diesel engines
US6256984 *Sep 7, 1999Jul 10, 2001Engelhard CorporationSystem for reduction of harmful exhaust emissions from diesel engines
US6391479 *Dec 21, 2000May 21, 2002General Electric CompanyCoating interlayer for improved compatibility between HR-120 and aluminum-containing oxidation resistant metallic coatings
US6422008Apr 16, 2001Jul 23, 2002Engelhard CorporationSystem for reduction of harmful exhaust emissions from diesel engines
US6655369Aug 1, 2001Dec 2, 2003Diesel Engine Transformations LlcCatalytic combustion surfaces and method for creating catalytic combustion surfaces
US6793968Feb 17, 2000Sep 21, 2004Siemens AktiengesellschaftMethod and device for coating a product
US7455913Jan 10, 2006Nov 25, 2008United Technologies CorporationThermal barrier coating compositions, processes for applying same and articles coated with same
US7527048Dec 2, 2003May 5, 2009Diesel Engine Transformation LlcCatalytic combustion surfaces and method for creating catalytic combustion surfaces
US7579087Jan 10, 2006Aug 25, 2009United Technologies CorporationHeat treatment; flame spraying; vapor deposition; sputtering; for resistance sand related stress in turbomachinery
US7622195Jan 10, 2006Nov 24, 2009United Technologies CorporationThermal barrier coating compositions, processes for applying same and articles coated with same
US7758914 *May 27, 2005Jul 20, 2010SnecmaRepairing the chromium/aluminum (C1A) protective coating on a worn zone of a turboprop blade by removing the coating and painting the exposed superalloy substrate with a paint containing a platinoid metal and chromium; vapor aluminizing the prelayer; cost efficiency; fuel efficiency; aircraft
US8007899Apr 9, 2010Aug 30, 2011United Technologies CorporationSegmented abradable coatings and process(es) for applying the same
US8182881Dec 24, 2008May 22, 2012United Technologies CorporationMethods for reducing stress when applying coatings, processes for applying the same and their coated articles
US8475598 *Dec 20, 2011Jul 2, 2013United Technologies CorporationStrip process for superalloys
US8529999Aug 24, 2009Sep 10, 2013United Technologies CorporationThermal barrier coating application processes
US8802199Dec 31, 2009Aug 12, 2014United Technologies CorporationMethod for microstructure control of ceramic thermal spray coating
US8808852Jul 11, 2007Aug 19, 2014United Technologies CorporationProcess for controlling fatigue debit of a coated article
US20120156366 *Dec 20, 2011Jun 21, 2012United Technologies CorporationStrip Process for Superalloys
US20120321905 *Dec 21, 2010Dec 20, 2012Friedhelm SchmitzNano and micro structured ceramic thermal barrier coating
DE2520192A1 *May 6, 1975Nov 27, 1975United Technologies CorpHitzbestaendige nicocraly-beschichtungen
DE3006103A1 *Feb 19, 1980Sep 4, 1980Gen ElectricVerfahren zum diffusionsverbinden eines doppelblechueberzuges mit einem substrat aus einer superlegierung
DE3229293A1 *Aug 5, 1982Mar 24, 1983United Technologies CorpDeckbelaege fuer superlegierungen
EP0082660A1 *Dec 14, 1982Jun 29, 1983United Kingdom Atomic Energy AuthorityApparatus for use in liquid alkali environment
EP1033417A1 *Mar 4, 1999Sep 6, 2000Siemens AktiengesellschaftProcess and apparatus for coating a product, especially a high temperature gas turbine component
EP1217096A2 *Dec 10, 2001Jun 26, 2002General Electric CompanyInterlayer between HR-120 and aluminium-containing oxidation resistant metallic coatings
EP1752553A2Aug 4, 2006Feb 14, 2007United Technologies CorporationMethod for microstructure control of ceramic thermal spray coating
EP1788125A2 *Nov 22, 2006May 23, 2007United Technologies CorporationStrip process for superalloys
EP1829984A1Mar 1, 2007Sep 5, 2007United Technologies CorporationHigh Density Thermal Barrier Coating
EP1939326A2Dec 11, 2007Jul 2, 2008United Technologies CorporationProcess for preventing the formation of secondary reaction zone in susceptible articles, and articles manufactured using same
EP2014786A1Jul 9, 2008Jan 14, 2009United Technologies CorporationProcess for controlling fatigue debit of a coated article
EP2204465A2Sep 21, 2009Jul 7, 2010United Technologies CorporationApparatus for reducing stress when applying coatings, processes for applying the same and their coated articles
WO1989007159A1 *Jan 19, 1989Aug 10, 1989Siemens AgMetallic object, in particular gas turbine blade with protective coating
WO2000052220A1 *Feb 17, 2000Sep 8, 2000Helge ReymannMethod and device for coating a product
Classifications
U.S. Classification428/651, 428/656, 428/938, 428/667
International ClassificationC22C38/18, C23C28/02, C23C14/58, C23C14/16
Cooperative ClassificationC23C28/023, C23C14/16, C22C38/18, Y10S428/938, C23C14/5886, C23C14/58, C23C14/5806
European ClassificationC22C38/18, C23C14/58, C23C14/58L, C23C14/58B, C23C28/02B, C23C14/16