EP2524063A1

EP2524063A1 - Alloy, protective layer, and component

Info

Publication number: EP2524063A1
Application number: EP11700398A
Authority: EP
Inventors: Friedhelm Schmitz; Werner Stamm
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2010-01-12
Filing date: 2011-01-10
Publication date: 2012-11-21
Also published as: US20120328900A1; EP2354260A1; WO2011086045A1

Abstract

Known protective layers having a high Cr content, as well as silicon, have brittle phases that become additionally brittle under the influence of carbon during use. The protective layer according to the invention has the composition of 18% to 20% cobalt (Co), 6% to 8% aluminum (Al), 0.5% to 0.7% yttrium (Y), 22% to 26% chromium (Cr), and the remainder nickel.

Description

Alloy, protective layer and component

The invention relates to an alloy according to claim 1, a protective layer for protecting a component against corrosion and / or oxidation, in particular at high temperatures, according to claim 10 and a component according to claim 11.

Protective layers for metallic components which are intended to increase their corrosion resistance and / or oxidation resistance are known in large numbers in the prior art. Most of these protective layers are known under the collective name MCrAlY, where M represents at least one of the elements selected from the group consisting of iron, cobalt and nickel and further essential components are chromium, aluminum and yttrium.

Typical coatings of this type are known from U.S. Patents 4,005,989 and 4,034,142.

The addition of rhenium (Re) to NiCoCrAlY alloys is also known.

The effort to increase the inlet temperatures both in stationary gas turbines and aircraft engines has in the field of gas turbines of great importance, since the inlet temperatures are important determinants of the achievable with gas turbines thermodynamic efficiencies. Conclusions The use of specially ent ^¬ Wrapped alloys as base materials for thermally highly onerous to components such as blades and vanes, particularly through the use of single-crystal superalloys, inlet temperatures of well above 1000 ° C are possible. Meanwhile, the prior art allows inlet temperatures of 950 ° C and more for stationary gas turbines and 1100 ° C and more in gas turbines of aircraft engines. Examples of the structure of a turbine blade with a einkri ^{¬-crystalline} substrate, which may itself be a complex structure, will become apparent from WO 91/01433 Al. While the physical capacity of the now escape ^¬ oped basic materials for highly stressed components with a view to possible further increases in the inlet temperatures is largely unproblematic to resort to protective layers need to achieve sufficient resistance to oxidation and corrosion. In addition to the sufficient chemical resistance of a protective layer under the attacks that are expected of flue gases at temperatures in the order of 1000 ° C, a protective layer must also have sufficient mechanical properties, not least in view of the mechanical interaction between the protective layer and the base material , to have. In particular, the protective layer must be sufficiently ductile in order to be able to follow any deformations of the base material and not to break, since in this way points of attack for oxidation and corrosion would be created.

Accordingly, it is an object of the present invention to provide an alloy and a protective layer which has good high-temperature resistance in corrosion and oxidation, has good long-term stability and, in addition, a mechanical stress to be expected particularly in a gas turbine at a high temperature well adjusted. The object is achieved by an alloy according to claim 1 and a protective layer according to claim 10.

Another object of the invention is to provide a component which has increased protection against corrosion and oxidation.

The object is also achieved by a component according to claim ^¬ 11, in particular a component of a gas turbine or steam turbine, the protection against corrosion and oxidation at high temperatures, a protective layer of vorbeschriebe ^¬ nen type has.

In the subclaims further advantageous measures are listed, which can be linked with each other in an advantageous manner mi each other.

The invention is inter alia based on the finding that the protective layer in the layer and in the transition region see be- shows protective layer and the base material brittle rhenium from ^¬ decisions. During operation, these brittle phases, which form increasingly with time and temperature, lead to pronounced longitudinal cracks in the layer as well as in the interface layer base material with subsequent detachment of the layer. By the interaction with carbon, which can hineindif ^¬ substantiate from the base material in the layer or during a heat treatment in the furnace by the surface diffuses into the layer, in addition, the brittleness of the rhenium precipitations increases. Oxidation of the rhenium phases further enhances the driving force for crack formation.

The invention will be explained in more detail below.

Show it

FIG. 1 shows a layer system with a protective layer,

FIG. 2 shows compositions of superalloys,

FIG. 3 shows a gas turbine,

Figure 4 shows a turbine blade and

Figure 5 is a combustion chamber.

The figures and the description represent only exemplary embodiments of the invention. According to the invention, a protective layer 7 (FIG

Protection of a component against corrosion and oxidation at a high temperature essentially the following elements would give the shares in Gew%):

18% to 22% cobalt (Co),

6% to 8% aluminum (AI),

0.5% to 0.7% yttrium (Y) and / or at least one equivalent metal from the group comprising scandium and the elements of the rare earths,

22% to 20% chromium (Cr),

Nickel (Ni) (NiCoCrAlY).

This listing is not exhaustive.

An advantageous embodiment consists of the elements

Nickel, cobalt, chromium, aluminum and yttrium

At higher oxidation load (pure combustion gas), more oxygen must be bound by yttrium, so that the protective aluminum oxide layer can not grow too fast, and then the yttrium value is advantageously up to 0.7wt%. However, the content of yttrium should generally not be too high in the alloy, otherwise this leads to embrittlement.

A preferred embodiment is: Ni - 20Co - 24Cr - 7A1 - 0.6Y. It should be noted that the proportions of the individual elements are specially tuned with regard to their effects, which are to be seen in particular in connection with the non-existent element rhenium. If the proportions are so large, can be dispensed with the addition of rhenium (Re), so that no rhenium precipitates form. There are advantageously no brittle phases during the use of the protective layer, so that the runtime behavior is improved and extended. In interaction with the reduction of the brittle phases, which have a negative effect especially under higher mechanical properties, by reducing the mechanical Stresses due to the selected nickel content improves the mechanical properties.

The protective layer, with good corrosion resistance, has a particularly good resistance to oxidation and is also distinguished by particularly good ductility properties, so that it is particularly qualified for use in a gas turbine 100 (FIG. 3) with a further increase in the inlet temperature.

The powders are applied for example by plasma spraying (APS, LPPS, VPS, ...). Other methods are also conceivable (PVD, CVD, cold gas spraying, ...).

The protective layer 7 described also acts as Haftvermitt ^¬ Lersch layer to a superalloy.

Preferably, only a single protective layer 7 is used for the component, ie no duplex layer for the bondcoat. In this protective layer 7 other layers insbeson ^¬ particular ceramic thermal barrier coatings 10 may be applied.

With a component 1, the protective layer 7 is advantageous ^¬ as applied to a substrate 4 made of a ^superalloy tion on nickel or cobalt base.

In particular the following composition is suitable as substrate (data in wt%):

0, 1% to 0.15% carbon

18% to 22% chrome

18% to 19% cobalt

0% to 2% tungsten

0% to 4% molybdenum

0% to 1.5% tantalum

0% to 1% niobium

1% to 3% aluminum

2% to 4% titanium

0% to 0.75% hafnium

optionally small amounts of boron and / or zirconium, balance

Nickel. Compositions of this type are be ^¬ known as casting alloys under the names GTD222, IN939, IN6203 and Udimet 500th

Further alternatives for the substrate 4 of the component 1, 120, 130, 155 are listed in FIG.

The thickness of the protective layer 7 on the component 1 is

preferably to a value between about lOOym and 300ym.

The protective layer 7 is particularly suitable for protecting the component 1, 120, 130, 155 against corrosion and oxidation, while the component at a material temperature of about 950 ° C, in aircraft turbines also about 1100 ° C, with a

Flue gas is applied.

The protective layer 7 according to the invention is thus particularly qualified for protecting a component of a gas turbine 100, in particular a guide blade 120, blade 130 or a heat shield element 155, which is acted upon with hot gas before or in the turbine of the gas turbine 100 or the steam turbine ^¬ .

The protective layer 7 can be used as an overlay (protective layer is the outer layer or as a bondcoat (protective layer is an intermediate layer).

It is preferably used as a "single" layer, i.e. there is no further metallic layer.

FIG. 1 shows a layer system 1 as a component.

The layer system 1 consists of a substrate 4.

The substrate 4 may be metallic and / or ceramic. Particularly in the case of turbine components, such as turbine runners 120 (FIG. 4) or guide vanes 130 (FIGS. 3, 4), heat shield elements 155 (FIG. 5) and other housing parts of a steam or gas turbine 100 (FIG. 3) Substrate 4 made of a nickel-, cobalt- or iron-based superalloy. Preferably, nickel-based superalloys are used.

On the substrate 4, the protective layer 7 according to the invention is present. It is preferably as "single" layer USAGE ^¬ det, ie there is no further metallic layer.

Preferably, this protective layer 7 is applied by plasma spraying (VPS, LPPS, APS1,...).

This can be used as outer layer (not shown) or intermediate layer (FIG. 1).

In the latter case, a ceramic thermal barrier coating 10 is present on the protective layer 7.

The protective layer 7 can be applied to newly produced components and refurbished components from the refurbishment.

Refurbishment means that components 1 are optionally separated from layers (thermal barrier coating) after use and that corrosion and oxidation products are removed, for example by acid treatment (acid stripping). If necessary, cracks still have to be repaired. Thereafter, such a component can be coated again because the substrate 4 is very expensive.

FIG. 3 shows by way of example a gas turbine 100 in a longitudinal partial section.

The gas turbine 100 has a rotatably mounted about a rotational axis 102 ^¬ rotor 103 having a shaft 101, which is also referred to as the turbine rotor.

Along the rotor 103 follow one another an intake housing 104, a compressor 105, for example, a toroidal combustion chamber 110, in particular annular combustion chamber, with a plurality of coaxially arranged burners 107, a turbine 108 and the exhaust housing 109th

The annular combustion chamber 110 communicates with an annular annular hot gas channel 111, for example. There, for example, four turbine stages 112 connected in series form the turbine 108. Each turbine stage 112 is formed, for example, from two blade ^rings . As seen in the direction of flow of a working medium 113, in the hot gas channel 111 of a row of guide vanes 115, a series 125 formed of rotor blades 120 follows.

The guide vanes 130 are fastened to an inner housing 138 of a stator 143, whereas the moving blades 120 of a row 125 are attached to the rotor 103 by means of a turbine disk 133, for example.

Coupled to the rotor 103 is a generator or work machine (not shown).

During operation of the gas turbine 100, air is sucked in by the compressor 105 through the intake housing 104 and compressed. The 105 ^¬ be compressed air provided at the turbine end of the compressor is ge ^¬ leads to the burners 107, where it is mixed with a fuel. The mixture is then burned to form the working fluid 113 in the combustion chamber 110. From there, the working medium 113 flows along the hot gas channel 111 past the guide vanes 130 and the rotor blades 120. On the rotor blades 120, the working medium 113 expands in a pulse-transmitting manner so that the rotor blades 120 drive the rotor 103 and drive the machine coupled to it.

The components exposed to the hot working medium 113 are subject to thermal loads during operation of the gas turbine 100. The guide vanes 130 and rotor blades 120 of the first turbine stage 112, viewed in the flow direction of the working medium 113, are subjected to the greatest thermal stress in addition to the heat shield elements lining the annular combustion chamber 110.

To withstand the prevailing temperatures, they can be cooled by means of a coolant.

Likewise, substrates of the components can have a directional structure, ie they are monocrystalline (SX structure) or have only longitudinal grains (DS structure). As a material for the components, in particular for the turbine blade ^¬ 120, 130 and components of the combustion chamber 110, for example, iron-, nickel- or cobalt-based superalloys are used.

Such superalloys are known, for example, from EP 1 204 776 B1, EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949.

The guide vane 130 has an inner housing 138 of the turbine 108 facing guide vane root (not Darge here provides ^¬) and a side opposite the guide-blade root vane root. The vane head faces the rotor 103 and fixed to a mounting ring 140 of the stator 143.

4 shows a perspective view of a rotor blade 120 or guide vane show ^¬ 130 of a turbomachine, which extends along a longitudinal axis of the 121st

The turbomachine may be a gas turbine of an aircraft or a power plant for power generation, a steam turbine or a compressor. The blade 120, 130 has along the ^longitudinal axis 121 to each other, a securing region 400, an adjoining blade or vane platform 403 and a blade 406 and a blade tip 415.

As a guide vane 130, the vane 130 may be pointed on its shovel 415 have a further platform (not Darge ^¬ asserted).

In the mounting region 400, a blade root 183 is formed, which serves for attachment of the blades 120, 130 to a shaft or a disc (not shown).

The blade root 183 is, for example, as a hammerhead out staltet ^¬. Other designs as Christmas tree or Schwalbenschwanzfuß are possible. The blade 120, 130 has for a medium which flows past the scene ^¬ felblatt 406 on a leading edge 409 and a ^trailing edge 412th In conventional blades 120, 130, in all regions 400, 403, 406 of the blade 120, 130, for example, ^massive metallic materials, in particular superalloys, are used.

The blade 120, 130 can hereby be manufactured by a casting process, also by directional solidification, by a forging process, by a milling process or combinations thereof.

Workpieces with a monocrystalline structure or structures are used as components for machines which are exposed to high mechanical, thermal and / or chemical stresses during operation.

The production of such monocrystalline workpieces takes place e.g. by directed solidification from the melt. These are casting processes in which the liquid metallic alloy is transformed into a monocrystalline structure, i. to the single-crystal workpiece, or directionally solidified.

Here, dendritic crystals are aligned along the heat flow and form either a columnar grain structure (columnar, ie grains that run the entire length of the workpiece and here, for general language use, referred to as directionally solidified) or a monocrystalline structure, ie the entire workpiece ^¬ is of a single crystal. In these methods, you have to transition to globular (polycrystalline) solidification avoided, since non-directional growth inevitably forms transverse and longitudinal grain boundaries ^¬ which solidified the directionally the good qualities or monocrystalline component nullify. The term "directionally solidified structures" generally refers to single crystals that have no grain boundaries or at most small angle grain boundaries, as well as stem crystal structures that have grain boundaries running in the longitudinal direction but no transverse grain boundaries. These second-mentioned crystalline structures are also known as directionally solidified structures.

Such methods are known from US Pat. No. 6,024,792 and EP 0 892 090 A1.

Likewise, the blades 120, 130 may have protection layers 7 ^{according to the} invention against corrosion or oxidation.

The density is preferably 95% of the theoretical

Density.

A protective aluminum oxide layer (TGO = thermal grown oxide layer) is formed on the MCrAlX layer (as an intermediate layer or as the outermost layer). On the MCrAlX may still be present a thermal barrier coating, which is preferably the outermost layer, and consists for example of Zr0 ₂ , Y2Ü3-Zr02, ie it is not, partially ^¬ or fully stabilized by yttria

and / or calcium oxide and / or magnesium oxide.

The thermal barrier coating covers the entire MCrAlX layer.

By suitable coating methods, e.g. Electron beam evaporation (EB-PVD) produces stalk-shaped grains in the thermal barrier coating.

Other coating methods are conceivable, for example atmospheric plasma spraying (APS), LPPS, VPS or CVD. The heat insulation layer may have ^¬ porous, micro- or macro-cracked ^compatible grains for better thermal shock resistance. The thermal barrier coating is therefore preferably more porous than the

MCrAlX layer.

The blade 120, 130 may be hollow or solid. If the blade 120, 130 is to be cooled, it is hollow and also has, if necessary, film cooling holes 418 ^(indicated by dashed lines) on.

5 shows a combustion chamber 110 of the gas turbine 100. The combustion chamber 110 is configured, for example, as so-called ^an annular ^combustion chamber, in which a plurality of in the circumferential direction about an axis of rotation 102 arranged burners 107 open into a common combustion chamber space 154, the flames 156 generate. For this purpose, the combustion chamber 110 is configured in its entirety as an annular structure, which is positioned around the axis of rotation 102 around. To achieve a comparatively high efficiency, the combustion chamber 110 is designed for a comparatively high temperature of the working medium M of about 1000 ° C to 1600 ° C. To even under these unfavorable for the materials operating parameters, a relatively long service life loan to enable the combustion chamber wall 153 is provided on its side facing the ^working medium M facing side with a formed from heat shield elements 155. liner.

Due to the high temperatures inside the combustion chamber 110 may also be provided for the heat shield elements 155 and for their holding elements, a cooling system. The heat shield elements 155 are then, for example, hollow and possibly still have cooling holes (not shown) which open into the combustion chamber space 154.

Each heat shield element 155 made of an alloy is equipped on the working fluid side with a particularly heat-resistant protective layer (MCrAlX layer and / or ceramic coating) or is made of high-temperature-resistant material (solid ceramic blocks).

These protective layers 7 may be similar to the turbine blades. On the MCrAlX, for example, a ceramic Wär ^¬ medämmschicht be present and consists for example of ZrÜ2, Y203-ZrÜ2, ie it is not, partially or fully ^¬ dig stabilized by yttrium and / or calcium oxide and / or magnesium oxide.

Other coating methods are conceivable, for example atmospheric plasma spraying (APS), LPPS, VPS or CVD. The heat insulation layer may have ^¬ porous, micro- or macro-cracked ^compatible grains for better thermal shock resistance.

Reprocessing (Refurbishment) means that turbine blades 120, 130, heat shield elements have to be removed from 155, after ^¬ A set of protective layers (for example by sandblasting). This is followed by removal of the corrosion and / or oxidation layers or products.

Optionally, cracks in the turbine blade 120, 130 or the heat shield element 155 are also repaired. This is followed by a re-coating of the turbine blades 120, 130, heat shield elements 155 and a renewed use of the turbine blades 120, 130 or the heat shield elements 155.

Claims

claims

1. Alloy

contains the following elements

(Data in wt%):

18% - 22% cobalt (Co),

in particular 19% - 21%,

22% - 26% chromium (Cr),

in particular 23% - 25%,

6% - 8% aluminum (AI),

especially 6.5% - 7.5%

0.5% - 0.7% of at least one element selected from the group umfas ^¬ send scandium and the rare earth elements,

especially yttrium (Y),

Nickel,

especially the rest of nickel.

2. Alloy according to claim 1,

containing 24wt% chromium.

3. Alloy according to claim 1 or 2,

containing 20% cobalt (Co).

4. Alloy according to one or more of claims 1 to 3, containing 0.6wt% yttrium,

5. Alloy according to one or more of claims 1 to 4, containing 7wt% aluminum.

6. Alloy according to one or more of the previous ones

Claims,

not containing rhenium.

7. Alloy according to one or more of the previous ones

Claims,

not containing silicon (Si).

8. Alloy according to one or more of the previous ones

Claims,

not containing zirconium (Zr) and / or

not containing titanium (Ti) and / or

not containing gallium (Ga) and / or

not containing germanium (Ge).

9. Alloy according to one or more of the previous ones

Claims,

consisting of cobalt (Co), chromium (Cr), aluminum (AI), yttrium (Y), nickel (Ni).

10. Protective layer for protecting a component (1) against Korro ^¬ sion and / or oxidation,

especially at high temperatures,

which has the composition of the alloy according to one or more of claims 1 to 9 and

which is present in particular as a single layer.

11. component,

in particular a component (120, 130, 155) of a gas turbine (100),

in particular in which a substrate (4) of the component (120, 130, 155) is nickel-based or cobalt-based,

that for protection against corrosion and oxidation at high temperatures has a protective layer (7) according to claim 10, in particular only a metallic protective layer (7) has on ^¬ and

wherein in particular the protective layer (7) is a ceramic j ^¬ specific heat-insulating layer (10) is applied.