WO2018038738A1

WO2018038738A1 - Multi-layer protective coating enabling nickel diffusion

Info

Publication number: WO2018038738A1
Application number: PCT/US2016/048987
Authority: WO
Inventors: Sudhir Rajagopalan; Kirtan PATEL; Phillip DRAA; Atin SHARMA
Original assignee: Siemens Aktiengesellschaft
Priority date: 2016-08-26
Filing date: 2016-08-26
Publication date: 2018-03-01

Abstract

A component (10, 200, 300) is provided including a substrate (12, 202, 302); a first layer (16, 216, 316) disposed on the substrate (10, 202, 302) having a chromium-rich layer or an aluminum-rich layer; a second layer (18, 218, 318) disposed over the first layer (16, 216, 316) having the other of the chromium-rich layer and the aluminum-rich layer; and a nickel vehicle (20, 220, 320) associated with the second layer (18, 218, 318) to allow diffusion of nickel to the second layer (18, 218, 318).

Description

MULTI-LAYER PROTECTIVE COATING ENABLING NICKEL DIFFUSION

FIELD

The present invention relates to high temperature resistant materials for use in high temperature environments, such as gas turbines. More specifically, aspects of the present invention relate to coating systems for application onto components, such as gas turbine components, that allow nickel to diffuse to an aluminum-rich or chromium- rich layer. BACKGROUND

Gas turbines comprise a casing or cylinder for housing a compressor section, a combustion section, and a turbine section. A supply of air is compressed in the compressor section and directed into the combustion section. The compressed air enters the combustion inlet and is mixed with fuel. The air/fuel mixture is then combusted to produce high temperature and high pressure gas. This working gas is then ejected past the combustor transition and injected into the turbine section of the turbine.

The turbine section comprises rows of vanes which direct the working gas to airfoil portions of the turbine blades. The working gas travels through the turbine section, causing the turbine blades to rotate, thereby turning the rotor. The rotor is also attached to the compressor section, thereby turning the compressor and also an electrical generator for producing electricity. A high efficiency for the turbine is achieved by heating the gas flowing through the combustion section to as high a temperature as is practical. The hot gas and heat therefrom, however, may degrade the various metal turbine components, such as the combustor, transition ducts, vanes, ring segments, rotor discs, and turbine blades.

For this reason, strategies have been developed to protect gas turbine

components from extreme temperatures, such as the development and selection of high temperature materials adapted to withstand these extreme temperatures and cooling strategies to keep the components adequately cooled during operation. With respect to rotor discs, these discs, though not subjected to the highest temperatures in the system, have generally been made from steel. However, due to desired increased operating temperatures, discs formed from nickel (Ni)-based materials, e.g., Ni-based superalloys, are now being increasingly utilized.

However, at such increased operating temperatures, the oxidation and corrosion resistance of the Ni-based superalloys still may not be adequate. This may particularly true for newer generation alloys that typically include lower levels of aluminum and chromium, and thus may be more susceptible to oxidative corrosive attack. The bare surface of the alloy, and any flaw on it, may be exposed to the oxygen (and other contaminants) in the atmosphere inside the gas turbine. If the surface flaw develops into a crack under operating conditions, for example, the rate of crack growth and propagation is greatly increased if the opening crack tip is exposed to the oxygen.

Partly due to its susceptibility to crack tip oxygen embrittlement, the maximum

application temperature for some nickel-based alloys, e.g. , IN718, having relatively low aluminum and chromium concentrations is lower than desired.

SUMMARY

To address the above issues and others, the present inventors have developed a protective coating for components comprising at least two layers (an aluminum (Al)-rich layer and a chromium (Cr)-rich layer), and having a structural feature ("nickel vehicle" as described herein) to allow for nickel diffusion to the aluminum-rich layer and/or the chromium-rich layer upon processing, e.g., heating, of the subject elements. In this way, the protective coating is ultimately provided with at least one layer with a nickel and chromium-containing compound (Ni/Cr-containing compound) or a nickel and aluminum-containing compound (Ni/AI-containing compound) which provide the component with enhanced corrosion resistance properties. Further, aspects of the protective coating may increase the component's maximum operating temperature exposure limits and improve the component's high temperature surface-driven mechanical failure properties including, for example, high cycle fatigue (HCF) and the like.

In accordance with an aspect, there is provided a component comprising:

a substrate; a first layer disposed on the substrate comprising a chromium-rich layer or an aluminum-rich layer;

a second layer disposed over the first layer comprising the other of the chromium-rich layer and the aluminum-rich layer; and

a nickel vehicle associated with the second layer effective to allow an amount of nickel to diffuse to at least the second layer and form at least one of an

aluminum/nickel-containing compound and a chromium/nickel-containing compound upon an application of energy to at least the second layer and the nickel vehicle.

In accordance with another aspect, there is provided a component comprising: a nickel-based substrate;

a first layer disposed on the substrate comprising a chromium-rich layer or an aluminum-rich layer;

a plurality of passageways formed in the first layer, wherein the plurality of passageways comprise a material of the second layer therein such that the second layer is in contact with the nickel substrate.

In accordance with another aspect, there is provided a process for coating a component comprising:

depositing a first layer on a substrate, the first layer comprising a chromium-rich layer or an aluminum-rich layer;

depositing a second layer over the first layer, the first layer comprising the other of the chromium-rich layer and the aluminum-rich layer; and

providing a nickel vehicle associated with the second layer, wherein the nickel vehicle is effective to allow an amount of nickel to diffuse to at least the second layer and form at least one of an aluminum/nickel-containing compound and a

chromium/nickel-containing compound upon application of energy thereto; and

applying an amount of energy to at least the second layer and the nickel vehicle to move (diffuse) nickel from the nickel vehicle to the second layer to form at least one of an aluminum/nickel-containing compound (e.g., nickel aluminide) and a

chromium/nickel-containing compound (e.g. , nickel chromide) in the second layer. BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in the following description in view of the drawings that show:

FIG. 1 is a cross-sectional view of gas turbine in accordance with an aspect of the present invention.

FIG. 2 illustrates an embodiment of a coating system in accordance with an aspect of the present invention.

FIG. 3 illustrates an embodiment of a coating system in accordance with another aspect of the present invention.

FIG. 4 illustrates an embodiment of a coating system in accordance with yet another aspect of the present invention.

DETAI LED DESCRI PTION

Now referring to the figures, FIG. 1 shows, by way of example, a gas turbine engine 100 in the form of a longitudinal cross-section. In its interior, the gas turbine 100 has a rotor 103, which is mounted such that it rotates about an axis of rotation 102 and has a shaft, and is also known as a turbine rotor. An intake housing 104, a compressor 105, a combustion chamber 1 10, in particular an annular combustion chamber, with a plurality of coaxially arranged burners 107, a turbine section 108, and an exhaust casing 109 follow one another along the rotor 103. The combustion chamber 1 10 is in communication with a hot-gas duct 1 1 1 where, for example, there are four successive turbine stages 1 12.

Each turbine stage 1 12 is formed, for example, from two blade or vane rings. As seen in the direction of flow of a working medium 1 13, a row 125 formed from rotor blades 120 follows a row 1 15 of guide vanes in the hot-gas duct 1 1 1. The guide vanes 130 are secured to an inner housing 138 of a stator 143, whereas the rotor blades 120 of a row 125 are fitted to the rotor 103, for example, by a turbine disc 133. A generator or machine (not shown) may be coupled to the rotor 103.

In operation, the compressor 105 intakes air 135 through the intake housing 104 and compresses it. The compressed air, which is provided at the turbine-side end of the compressor 105, is passed to the burners 107 where it is mixed with a fuel. The mixture is then burned in the combustion chamber 1 1 0 to form the working medium 1 13. From there, the working medium 1 13 flows along the hot-gas duct 1 1 1 past the guide vanes 130 and the rotor blades 120. The working medium 1 13 expands at the rotor blades 120, transferring its momentum, so that the rotor blades 120 drive the rotor 103 and the rotor 103 drives the machine coupled to it.

Further, when the gas turbine 100 is operating, the components, which are exposed to the hot working medium 1 13, are subjected to significant thermal loads. The guide vanes 130 and rotor blades 120 of the first turbine stage 1 12, as seen in the direction of flow of the working medium 1 13, together with the heat shield elements, which line the annular combustion chamber 1 10, are subjected to the highest thermal loads. These components, as well as lower temperature components (e.g. , rotor discs 133) would benefit from a protective coating that provides both Type I and Type I I resistance.

By way of example, at temperatures of around 750° C to 950° C, a broad front attack can occur, thereby depleting unprotected substrate of its materials, e.g., Al and Cr. This may be referred to as Type I corrosion. In this instance, an Al-based coating may protect against type I corrosion. However, for type I I corrosion, localized pitting type corrosion is more likely. Type II corrosion, for example, may occur when molten salts in a gas stream combine with S0₂ and SO₃, and condense onto turbine

components, thereby resulting in small pits in the surface. In this instance, a Cr-based coating may protect against the type II corrosion. Aspects of the present invention provide both an aluminum-rich layer and a chromium-rich layer along with a nickel vehicle. The nickel vehicle ensures that nickel is provided to the aluminum-rich and chromium-rich layer such that upon heating or the like one or more corrosion-resistant Ni/AI-containing compounds (e.g., nickel aluminide) and one or more Ni/Cr-containing compounds (e.g., nickel chromide) are provided in their respective layers.

Referring to FIG. 2, there is shown a partial cross-sectional view of a component 10, which may be any component described previously herein and shown in FIG. 1 . In an exemplary embodiment, the component 10 comprises a turbine disc 133; however, it is understood that the present invention is not so limited. The component 10 comprises a substrate 12 and a coating system 14 thereon. In certain embodiments, the substrate 12 comprises a superalloy material. As used herein, the term "superalloy" may refer to a highly corrosion-resistant and oxidation-resistant alloy that exhibits excellent mechanical strength and resistance to creep even at high temperatures. Superalloys typically include a high nickel or cobalt content. Exemplary superalloys include, but are not limited to, alloys sold under the trademarks and brand names Hastelloy, Inconel alloys (e.g. IN 100, IN 700, IN 713C, IN 718, IN 738, IN 792, IN 939), Rene alloys (e.g., Rene N5, Rene 41 , Rene 80, Rene 108, Rene 142, Rene 220), Haynes alloys, Mar M, CM 247, CM 247 LC, C263, 718, X-750, ECY 768, 262, X45, PWA 1483 and CMSX (e.g. CMSX-4) single crystal alloys, GTD 1 1 1 , GTD 222, MGA 1400, MGA 2400, PSM 1 16, CMSX-8, CMSX-1 0, PWA 1484, Mar-M-200, PWA 1480, , Udimet 600, Udimet 500 and titanium aluminide.

In a particular embodiment, the substrate comprises a nickel-based alloy or a nickel-based superalloy material, such as IN 718, having relatively low levels of Al and Cr. IN 718, for example, has the following general composition in wt %: nickel (plus cobalt) 50.00-55.00; Cr 17-21 ; Nb (plus Ta) 4.75-5.5; Mb 2.8-3.3; Ti 0.65-1 .15; Al 0.2- 0.8; Co up to 1 .0 Co; up to 0.08 C; up to .35 Mn; up to .35 Si; up to .015 P; up to .015 S; up to .006 B; and up to 0.3 Cu.

In the embodiment of FIG. 2, the coating system 14 on the component 10 comprises a first layer 16 deposited on the substrate 12. The first layer 16 may be a chromium-rich layer or an aluminum-rich layer. On the first layer 16, there is deposited a second layer 18, which may comprise the other of the chromium-rich layer and the aluminum-rich layer. I n an embodiment, the first layer 16 comprises a chromium-rich layer and the second layer 18 comprises an aluminum-rich layer. In another

embodiment, the first layer 16 comprises an aluminum-rich layer and the second layer 18 comprises a chromium-rich layer.

The aluminum-rich layer (one of first layer 16 or second layer 18) comprises an amount of aluminum suitable to provide a desired corrosion resistance to the

component 10. By "aluminum-rich," it is meant that the first layer 16 or the second layer 18 (as the case may be) comprises an elemental aluminum content of at least 50 wt % in its "as-deposited" condition, and in an embodiment at least 85 wt %. In a particular embodiment, the first layer 16 or the second layer 18 has an elemental aluminum content of from 85 to about 95 wt % in its composition as-deposited. It is appreciated that nickel can form various aluminide intermetallic compounds with aluminum, such as N13AI , NiAl, and NiAI₃, after the application of energy, e.g., heat treatment, of the coating system. In certain embodiments, the Ni and Al amounts (and ratios thereof) may be modified so as to form the most corrosion / oxidation resistant compound(s) upon the heat-treatment. I n accordance with an aspect, the aluminum is present in the form of nickel aluminide (after completion of the application of energy, but not in the as- deposited form).

The chromium-rich layer (one of first layer 16 or second layer 18) comprises an amount of chromium suitable to provide a desired corrosion resistance to the

component 10. By "chromium-rich," it is meant that the first layer 16 or the second layer 18 comprises an elemental chromium content of at least 50 wt % in its "as deposited" composition as well, and in some embodiments at least 85 wt %. In a particular embodiment, the first layer 16 or the second layer 18 has an elemental chromium content of from 85 to about 95 wt % in its composition as deposited. In accordance with an aspect, after the application of energy, e.g., heat treatment, of the coating system chromium is present in the form of nickel chromide.

As will be explained in detail below, aspects of the present invention are directed to a path or source (hereinafter collectively "vehicle") for nickel to be included (by diffusion or the like) in the first and second layers 16, 18 upon the application of energy (e.g., heat treatment). Aluminum has a very low melting point (~ 660°C) and therefore Al alone may not be suitable for use at the temperatures of operation whereas NiAl, for example, has a melting point of ~1690°C. Accordingly, it is desirable to convert the aluminum as deposited into a nickel and aluminum-containing (Ni/AI) compound to increase the temperature and corrosion resistance of the material.

In the case of chromium as deposited (without nickel addition), chromium will tend to form chromium oxide which can provide oxidation resistance, but will not have good corrosion resistance. Thus, allowing the chromium to combine with nickel is advantageous as it produces an Ni/Cr compound (e.g., nickel chromide) with both excellent oxidation and corrosion resistance properties. It is noted that depositing nickel chromide and/or nickel aluminide (or like Ni/AI or Ni/Cr compounds) directly onto the component 10 would not be as desirable as the ease and control of such a process would be much more difficult than providing aluminum and chromium-rich layers with a nickel vehicle as proposed herein, wherein the nickel vehicle allows Ni to move by diffusion or otherwise into the layers during the application of energy (e.g., heat treatment).

Accordingly, aspects of the invention include a nickel vehicle 15 in the

component 10 that enables nickel to be provided to each of the first 16 and second layers 18 in an amount sufficient to form an Ni/AI or Ni/Cr compound therein, such as nickel aluminide or nickel chromide, respectively. In the embodiment of FIG. 1 , the substrate 12 comprises a nickel-based substrate and the first layer 16 is in direct contact with the nickel-based substrate 12, and hence may receive nickel by diffusion or otherwise from the substrate 12 upon the application of energy to the substrate 12 and the first layer 16. This would be the case, for example, in other two layer systems where a nickel-based substrate, for example, is in direct contact with a first layer of a deposited aluminum or chromium coating. However, in the absence of a nickel vehicle

15 as described herein, little or no nickel would be provided to a second layer 18 as it would be isolated from the substrate 12 by the first layer 16. To address this issue, aspects of the present invention provide a pathway for or source of nickel for travel of nickel to the second layer 18.

As shown in FIG. 2, in the first embodiment, the nickel vehicle 15 comprises a plurality of passageways 20, which extend from a surface of the substrate 12 so as to allow for the diffusion of nickel from the substrate 12 to the outer layer (second layer 18). In an embodiment, the plurality of passageways 20 are defined within the first layer

16 such that the material of the second layer 18 is disposed within the passageways 20. In this way, nickel contained in the base substrate 12 (when the substrate 12 comprises nickel) may diffuse from the substrate 12, particularly upon heating, to not only the first layer 16, but also the second layer 18 via the passageways 20.

The passageways 20 may comprise any suitable dimension and cross-sectional shape. In one aspect, the passageways 20 have a width of from 0.1 to 50 mm. In addition, the passageways may collectively provide any area fraction of a total surface area of covered by the first layer 16. In an embodiment, for example, an area fraction of the first layer 16 can be from 0.3 to 0.7 for a given area on the coated surface of the component (with the remainder left as passageways 20).

In addition, the passageways 20 may be provided in the first layer 16 in any suitable pattern on an exterior of the component 10. In an embodiment, the

passageways 20 may extend around a circumference of the component 10, or about a portion thereof. In an embodiment, at least some of the passageways 20 are formed in a linear path (in the same plane) about a circumference of the component 10.

Alternatively, the passageways 20 may be arranged in a serpentine pattern, staggered pattern, or any other desired pattern in the coating system 14. In addition, the remaining layers as described herein may also be deposited in any suitable pattern on the component 10. In the embodiment of FIG. 2, the first layer 16 and the second layer 18 may have any suitable thickness. In a particular embodiment, the first layer 16 and the second layer 18 each have a thickness of 100 microns or less, and in a further particular embodiment from 1 -10 microns.

In accordance with another aspect, the nickel vehicle 15 alternatively comprises a nickel-rich layer, which is associated with the second layer 18 such that nickel may be provided to the second layer from the nickel-rich layer, particularly upon the application of energy to the component 1 0. Referring now to FIG. 3, there is shown another embodiment of a component 200 in accordance with an aspect of the present invention. The component 200 comprises a substrate 202 having a coating system 215 thereon. The coating system 215 comprises a first layer 216 over the substrate 202, a second Iayer 218 over the first Iayer 216, and a nickel-rich layer 220 over the second Iayer 218. The first layer 216 comprises one of a Cr- rich layer and an aluminum-rich layer as defined herein. The second layer 218 may comprise the other of the chromium-rich layer and the aluminum-rich layer. In this embodiment, the nickel vehicle 215 comprises a nickel-rich layer 220 deposited over the second layer 218. In this way, an amount of nickel may be provided to the second layer 218 from the nickel-rich layer 220 sufficient to form an Ni/AI or an Ni/Cr-containing compound (as the case may be) in the second layer 218 upon processing of at least the layers 216, 218, 220. In an

embodiment, the movement of the nickel from the nickel-rich layer 220 to the second layer 218 by diffusion (or otherwise) takes place upon the application of an effective amount of energy thereto, such as by heating isothermally or with a temperature gradient from 500-800° C.

By "nickel-rich," it is meant that the nickel-rich layer 220 comprises an elemental nickel content of at least 50 wt % in its composition as deposited, and in an embodiment at least 80 wt %. I n a particular embodiment, the nickel-rich layer 220 has an elemental nickel content of from 85-95 wt % in its composition as deposited. The nickel-rich layer 220 may further have any suitable thickness. In an embodiment, the nickel-rich layer 220 comprises a thickness of about 100 micron or less, and in a particular embodiment from 1 -10 microns.

In the embodiment of FIG. 3, the first layer 216 may comprise a chromium-rich layer and the second layer 218 may comprise an aluminum-rich layer having a composition as described above for layers 16, 18. In another embodiment, the first layer 216 may comprise an aluminum-rich layer and the second layer 218 may comprise a chromium-rich layer having a composition as described above for layers 16, 18. In this embodiment also, the first layer 216 and the second layer 218 may have any suitable thickness. In an embodiment, the first layer 216 and the second layer 218 each have a thickness of 100 microns or less, and in a particular embodiment from 1 -10 microns. Further, the coating layers 216, 218, 220 may be disposed on the component in any suitable pattern - completely or only partially covering the subject component as needed.

In accordance with another aspect, the layers may be of same type and composition as described in the embodiment of FIG. 3 (substrate 202, first layer 216, second layer 218, and nickel-rich layer 220 but, in this instance, the nickel-rich layer may instead disposed between the first and second layers described herein vs. on top of the second layer (as in FIG. 3). Referring to FIG. 4, for example, there is shown a component 300 comprising a substrate 302 and a coating system 315 disposed on the substrate 302 as each layer is described herein. In this embodiment, the coating system 315 includes a first layer 316 disposed over the substrate 302, a nickel-rich layer 320 disposed over the first layer 316, and a second layer 318 disposed over the nickel-rich layer 320. In this way, nickel may be provided from the nickel-rich layer 320 to either or both of the first and second layers 316, 31 8 upon the application of energy (e.g., heating) of the layers 316, 318, 320 to ensure a sufficient amount of nickel is provided to the first and second layer 316, 318 in order to form a Ni-AI and/or Ni-Cr containing compound, e.g., nickel chromide and/or nickel aluminide, in the layers 316, 318.

In accordance with another aspect, the first and/or second layers in any of the embodiments described herein may be modified with other elements to enhance a property of the associated coating system such as oxidation resistance, corrosion resistance, mechanical strength, brittleness, temperature resistance, or the like.

Without limitation, any of the layers herein may be modified with elements such as hafnium, zirconium, yttrium, silicon, titanium, tantalum, cobalt, platinum, palladium, and rare earths (e.g. cerium, lanthanum, erbium, or ytterbium), and combinations thereof, to improve its corrosion resistance and other properties. In an embodiment, the sum of all additional elements (other than Al or Cr) is < 15 wt% (as deposited) when added to a particular layer, e.g., any or more of layers 16, 216, 316, 18, 218, 318, 220, and 320.

Although a single first layer, a single second layer, and a single nickel-rich layer

(when provided) are described in the above embodiments, it is appreciated that the present invention is not so limited. In certain embodiments, it may be desirable to repeatedly apply the layers in the same (or other sequence) such that the coating system includes a plurality of any one or more of any of the described layers. Further, it is appreciated that the embodiments described herein are not mutually exclusive. In certain embodiments, the passageways 20 may, if desired, also be included in the first layers 216, 316 shown in FIGS. 3 and 4, respectively. Additionally, in certain

embodiments, a nickel-rich layer 220, 320 may also be deposited over the second layer 18 shown in FIG. 1.

The layers and materials may be applied on the associated substrate 12, 202,

302 by any suitable technique known in the art for the material(s) being deposited. Without limitation, the depositing of any layer may be done by chemical vapor deposition (CVD) (e.g., plasma enhanced or plasma spray CVD), slurry coating, painting, cathodic arc deposition, filtered cathodic arc deposition, electroplating, or the like. Upon deposition of a single layer or of all the desired layers on the associated substrate, the layers or the coated component may be subjected to processing in order to promote diffusion of the nickel from the substrate (if present) and/or from the nickel layer (if present) to the aluminum-rich and/or chromium-rich layers. In an embodiment, the processing comprises applying an amount of energy, e.g., thermal energy, to the layers or component. In certain embodiments, this is done in a non-oxidizing

environment, such as in the presence of a flowing noble or inert gas. In another aspect, the layers or components as a whole subjected to heating, and the heating is done at a temperature of from about 500° C to about 800° C for a suitable duration effective to promote the formation of the nickel-aluminum and nickel-chromium compounds in the first layer 16, 216, 316 and second layer 18, 218, 31 8. In an embodiment, the processing, e.g., heating, is done for 1 to 10 hours, although the present invention is not so limited.

In the embodiments where the passageways 20 are provided, the passageways 20 may be formed by any suitable process. In an embodiment, the passageways 20 may be defined in the first layer 16 by the use of spacers or the like, or by mechanical application and then removal of the deposited coating in selected area. In a particular embodiment, for example, the passageways 20 may be formed by masking the surface of the component 1 0 where the passageways 20 are desired to be located, and then depositing the first layer 16 with the areas to define passageways 20 being masked. Thereafter, the masks may be removed and the subsequent second layer 18 deposited over the first layer 16 and within the passageways 20. I n another embodiment, the first layer 16 may be applied so as to cover a selected portion of the component.

Thereafter, selected portions of the first layer 16 may be removed by any suitable method, such as by mechanical or chemical methods to define the passageways 20. In an embodiment, the removing is done by mechanical stripping, such as by an abrasive water-jet or the like.

In some embodiments, the material of the first layer 16 forms the side walls that define the passageways 20. In still other embodiments, a suitable high temperature material (having the same or higher melting point) of the material of the second layer 18 is deposited and is used to define the sidewalls of the passageways 20.

The component 10, 200, 300 may be any type which could benefit from the described coating systems described herein. In an embodiment, the component 10, 200, 300 comprises a gas turbine component (FIG. 1 ). In a particular embodiment, the component 10, 200, 300 comprises a rotor disc 133 as described herein for a gas turbine. Rotor turbine discs formed from nickel-based substrates with light aluminum and chromium content may only have a maximum temperature capability of 580° C; however, with the coating systems described herein, the maximum temperature capability of the same component may be increased to 700°C or more.

While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.

Claims

CLAI MS What we claim is:

1 . A component (10, 200, 300) comprising:

a substrate (12, 202, 302);

a first layer (16, 216, 316) disposed on the substrate (10, 202, 302) comprising a chromium-rich layer or an aluminum-rich layer;

a second layer (18, 218, 318) disposed over the first layer (16, 216, 316) comprising the other of the chromium-rich layer and the aluminum-rich layer; and

a nickel vehicle (20, 220, 320) associated with the second layer (18, 218, 318) effective to allow an amount of nickel to move to at least the second layer (18, 218, 318) and form at least one of an aluminum/nickel-containing compound and a

chromium/nickel-containing compound upon an application of energy to at least the second layer (1 8, 218, 318) and the nickel vehicle (20, 220, 320).

2. The component (10, 200, 300) of claim 1 , wherein the substrate (10, 202, 302) comprises a nickel-based substrate, wherein the nickel vehicle (20, 220, 320) comprises a plurality of passageways (20) formed in the first layer (16, 216, 316), and wherein the plurality of passageways (20) comprise a material of the second layer (18, 218, 318) therein such that the material of the second layer (18, 218, 318) is in contact with the substrate (10, 202, 302).

3. The component (10, 200, 300) of claim 2, wherein the passageways (20) each comprise a maximum width of from 0.1 to 50 mm.

4. The component (10, 200, 300) of claim 2, wherein an area ratio of the first layer (16, 216, 316) with the passageways (20) formed therein to an area covered by the first layer (16, 216, 316) is from 0.3 to 0.7.

5. The component (10, 200, 300) of claim 1 , wherein the first layer (16, 216,

316) and the second layer (18, 218, 318) each have a thickness of 100 micron or less.

6. The component (10, 200, 300) of claim 5, wherein the first layer (16, 216, 316) has a thickness of from 1 -10 microns.

7. The component (10, 200, 300) of claim 5, wherein the second layer (18, 218, 318) has a thickness of from 1 -10 microns.

8. The component (10, 200, 300) of claim 1 , wherein the component (10, 200, 300) comprises a turbine disc (133).

9. The component (10, 200, 300) of claim 1 , wherein the nickel vehicle (20, 220, 320) comprises a nickel-rich layer (220) disposed over the second layer (218) such that nickel may diffuse from the nickel-rich layer (220) to the second layer (218) upon application of energy to at least the nickel-rich layer (218) and the second layer (220).

10. The component (10, 200, 300) of claim 1 , wherein the nickel vehicle (20, 220, 320) comprises a nickel-rich layer (320) disposed between the first layer (316) and the second layer (318) such that nickel may diffuse from the nickel-rich layer (320) to the second layer (318) upon application of energy to the layers (316, 318, 320).

1 1 . A component (1 0) comprising:

a nickel-based substrate (12);

a first layer (16) disposed on the substrate (12) comprising a chromium-rich layer or an aluminum-rich layer;

a second layer (18) disposed over the first layer (16) comprising the other of the chromium-rich layer and the aluminum-rich layer; and

a plurality of passageways (20) formed in the first layer (16), wherein the plurality of passageways (20) comprise a material of the second layer (18) therein such that the second layer (18) is in contact with the nickel substrate (12).

12. The component (10) of claim 1 1 , wherein each of the first layer (16) and the second layer (18) have a thickness of 1 00 micron or less.

13. The component (10) of claim 1 1 , wherein the component (10) comprises a turbine disc (133).

14. The component (10) of claim 1 1 , further comprising a nickel-rich layer (220, 320) disposed over the second layer (18).

15. The component (10) of claim 1 1 , wherein an area ratio of the first layer

(16) with the passageways (20) formed therein to an area covered by the first layer (16) is from 0.3 to 0.7.

16. The component (10) of claim 1 1 , wherein the passageways (20) each comprise a maximum width of from 0.1 to 50 mm.

17. A process for coating a component (10, 200, 300) comprising:

depositing a first layer (16, 216, 316) on a substrate (12, 202, 302), the first layer

(16, 216, 316) comprising a chromium-rich layer or an aluminum-rich layer;

depositing a second layer (18, 218, 318) over the first layer (16, 216, 316), the first layer (16, 216, 316) comprising the other of the chromium-rich layer and the aluminum-rich layer; and

providing a nickel vehicle (20, 220, 320) associated with the second layer (18, 218, 318), wherein the nickel vehicle (20, 220, 320) is effective to allow an amount of nickel to diffuse to at least the second layer (18, 218, 318) and form at least one of an aluminum/nickel-containing compound and a chromium/nickel-containing compound upon application of energy thereto; and

applying an amount of energy to at least the second layer (18, 218, 318) and the nickel vehicle (20, 220, 320) to move nickel from the nickel vehicle (20, 220, 320) to the second layer (18, 218, 318) to form at least one of an aluminum/nickel-containing compound (e.g., nickel aluminide) and a chromium/nickel-containing compound (e.g. , nickel chromide) in the second layer (18, 218, 318).

18. The process of claim 17, wherein the substrate (12, 202, 302) comprises a nickel-based substrate (12), wherein the nickel vehicle (20, 220, 320) comprises a plurality of passageways (20) formed in the first layer (16, 216, 316), and wherein the plurality of passageways (20) comprise a material of the second layer (18, 218, 318) therein such that the material of the second layer (18, 218, 318) is in contact with the substrate (12, 202, 302).

19. The process of claim 17, wherein the nickel vehicle (20, 220, 320) comprises a nickel-rich layer (220) disposed over the second layer (218) such that nickel may move from the nickel-rich layer (220) to the second layer (218) upon the applying an amount of energy.

20. The process of claim 17, wherein the nickel vehicle (20, 220, 320) comprises a nickel-rich layer (320) disposed between the first layer (316) and the second layer (318) such that nickel may move from the nickel-rich layer (320) to the second layer (318) upon the applying an amount of energy.