EP2376677A1

EP2376677A1 - Mcralx layer having differing chromium and aluminum content

Info

Publication number: EP2376677A1
Application number: EP09795967A
Authority: EP
Inventors: Friedhelm Schmitz; Werner Stamm
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2009-01-08
Filing date: 2009-12-14
Publication date: 2011-10-19
Also published as: CN102272354A; EP2698450A1; WO2010079049A1; EP2206805A1; CN102272354B; RU2011133090A; US20110268987A1; JP2012514692A

Abstract

The invention relates to a two-ply MCrAlX layer wherein the contents of nickel and cobalt, but also Cr, Al and Y, differ significantly, in order to improve both oxidation resistance and thermal-mechanical strength.

Description

MCrAlX layer with different chrome and

aluminum contents

The invention relates to a two-layer MCrAlX layer in which the chromium and aluminum contents differ.

Ni and Co base materials are used in the hot gas path of gas turbines. However, because of their optimization to the highest possible strength, these materials often lack sufficient oxidation and high temperature corrosion resistance in the hot gas. The materials must therefore be protected with suitable protective coatings against hot gas attack. To increase the turbine inlet temperature, a ceramic layer of zirconium oxide is additionally applied to thermal insulation on thermally highly stressed components. The underlying metallic layer serves as an adhesive layer for the ceramic thermal insulation layer and as an oxidation protection layer for the base material.

To solve this problem, as described above, protective coatings are applied to the hottest components by means of thermal spraying or EB-PVD methods. These usually consist of so-called MCrAlX coating layers which, in addition to Ni and / or Co, also contain chromium, aluminum, silicon, rhenium or rare earths such as yttrium. However, as the surface temperatures on the protective layer continue to rise, damage can occur which leads to the failure of the layer or to the flaking off of the thermal insulation layer. It is therefore necessary to develop a protective layer at increasing temperatures on the layer surface, which under these difficult conditions has an improved oxidation resistance combined with a sufficiently good thermo-mechanical resistance. This can only be achieved by a very balanced chemical composition of the protective layer. In particular, the elements Ni, Co, Cr, Al are of importance here. Because these elements are due to Diffusion also xn interaction mxt the base material are, xst dxes also berεckssexchtigen. Due to the high level of raw material extrusion, especially the special alloying elements, a cost-optimized composition must be ensured.

The object of the invention is to solve the above-mentioned problem. The object is achieved by a layer system according to claim 1 and 2.

In the dependent claims further advantageous measures are listed, which can be combined with each other in order to achieve further advantages. Show it:

1, 2 Ausfuhrungsbexspiele the layer system, Figure 3 exne gas turbine,

FIG. 4 is a perspective view of a turbine blade, FIG. 5 is a perspective view of a combustion chamber, and FIG. 6 is a list of superalloys.

The figures and the description thereto represent only exporting examples of the invention.

FIG. 1 shows a first example. The component 1, 120, 130, 155 has a substrate 4. Particularly in the case of gas turbines 100 (FIG. 3) for applications at high temperatures, the substrate 4 has a superalloy, in particular according to FIG.

On the substrate 4, a metallic protective layer 13 is present.

According to the invention, the metallic protective layer 13 comprises two MCrAlX- different in their chemical composition. Schxchten 7, 10, wherein the outer layer 10 preferably has a higher chromium content.

Also preferably, the alumimum content of the outer layer 10 is higher than the Alumimumgehalt the underlying layer. 7

The difference in chromium content for the two layers 7, 10 is preferably (at least in absolute terms) preferably at least 1 wt% (| Cr (7) - Cr (10) |> 1 wt%). The difference in alum content for the two layers 7,

10 is preferably (in absolute terms) preferably at least lwt% (| A1 (7) - Al (IO) | ≥ lwt%), more preferably at least 2wt%.

The protective layer 13 preferably consists only of two different MCrAlX layers 7, 10.

Thus, a metallic protective layer 13 is proposed, which has a better oxidation resistance than the previously used MCrAlX layers compared to the layers used hitherto with simultaneously the same good thermomechanical properties

Behavior. This is achieved by using a duplex layer system which has different requirements for optimized diffusion interaction with the base material and, on the other hand, forms an optimized TGO layer at the phase boundary with the ceramic. A different chemical composition of the two MCrAlX alloys used achieves this goal.

The chromium content of the inner layer 7 is higher than that of the outer layer 10, the aluminum content of the outer layer 10 being higher than the Alummium content of the inner layer 7. The same is preferably true for a layer system 7, 10 containing yttrium (Y). Higher yttrium content means at least one absolute difference of 0.15wt%, (| Y (7) - Y (IO) | ≥ 0.15wt s). The inner layer 7 close to the base material (substrate 4) preferably has the following basic composition (in wt-o): Ni about 38 t in the chemical composition of the powder or ingot used. to about 66.6% and Co from 8% to 22%. This basic composition means that despite a high Cr content of 21% to 29 ^ little or no α-Cr phases occur and a good ductility of the layer is maintained. The relatively high Cr and Y content acts as a getter for sulfur in the base material and is said to prevent a damaging effect on the TGO. The relatively low Al content of 4% to 9% requires the ductility behavior of layer 7, but also leads to a low interdiffusion with the base material (substrate). On the other hand, it is still high enough to favorably influence the life of a thermal insulation layer 16, since there is sufficient Al for subsequent diffusion. The phases occurring at this concentration of the main alloying constituents in the new and operationally stressed state are Y (gamma), Y 'and β (beta). The yttrium content should preferably be greater than 0.4wt to 0.9wt and also a gettering effect for sulfur. In addition, the yttrium should also be able to diffuse into the overlying outer layer 10. Optionally, the layer can also Re up to 1- ,. contained in order to further delay interdiffusion.

The outer MCrAlX layer 10 located above has a thickness that is preferably the same as the first layer 7 within the scope of the manufacturing tolerances.

This basic composition, in conjunction with a lowered Cr content of preferably around 20 Wt ⁵ and an Al content of preferably 11.5 wt s, leads to an excellent AlyO cover layer formation, which is further enhanced by the low contents of Si of 0.2%. 0.4% and Y from 0.1% - 0.2% in terms of

Training and liability is supported. The low Y content avoids internal oxidation of the yttrium and does not form a growth latent in the initial phase of the oxidation the MCrAlX. This leads to less Schrcht growth, and damrt low aluminum consumption. Dre Bild 10 essentially has a phase composition of gamma, beta, is thermally stable and avoids brittle phases, which in turn leads to good ductility properties of MCrAlX layer 10.

Preferably, the MCrAlX layers 7, 10 are NiCoCrAlY layers.

The protective layer 13 has two superimposed layers, preferably with the composition of layer 7 (in wt s):

Ni, Co 8% - 22 ² - preferably 19 ⁵ - - 21O, very preferably 20 ^c -,

Cr 21 ² - - 29s preferably 23 ^ - 25%, very preferably 24 ^r -,

Al 4% - 9%, preferably 6f - 8, most preferably 7-,

Y 0.4-0.0-s, preferably> 0.4-σ-0.6-_>, very preferably 0.5-0,

preferably 0-o, preferably the list above (Ni, Co, Cr, Al, Y, Re) is final, and with the composition of outer layer 10:

Co,

preferably 34-36%, most preferably 35%

Cr 17 ^a - 24 ", preferably 19% - 21%, most preferably 20%,

Al 9% - 14%, preferably 11% - 12%, most preferably 11.5%, preferably 0.1% - 0.2s, optxonal preferably 0.2% to 0.4 t, very preferably 0.3 t, preferably the above list (Co, Ni, Cr, Al, Y, Si) is conclusive.

Other elements, such as Hf, Zr, P and other trace elements, can provide up to 0.3% positive properties through mutual interaction.

FIG. 3 shows by way of example a gas turbine 100 in a longitudinal section. The gas turbine 100 has inside a rotatably mounted about a rotation axis 102 rotor 103 with a shaft, which is also referred to as a turbine runner.

Along the rotor 103 follow one another Ansauggehause 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. In the direction of flow of a working medium 113, a series of guide vanes 115 follows a series of vanes 120 in the hot gas duct 111 of a row of vanes 115.

In this case, the guide vanes 130 are fastened to an inner housing 138 of a stator 143, whereas the rotor 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 105 is sucked and compressed by the compressor 105 through the intake housing 104. The compressed air provided at the turbine-side end of the compressor 105 is supplied 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. The working medium 113 expands on the rotor blades 120 in a pulse-transmitting manner so that the rotor blades 120 drive the rotor 103 and drive the machine which is coupled to it ,

The components exposed to the hot working medium 113 are subject to thermal loads during the operation of the gas turbine 100. The guide vanes 130 and rotor blades 120 of the first turbine stage 112, viewed in the direction of flow 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.

In order to withstand the temperatures prevailing there, they can be cooled by means of a coolant. Likewise, substrates of the components may have a directional structure, i. they are monocrystalline (SX structure) or have only slow-moving grains (DS structure).

As the 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 vane 130 has a Leitschaufelfuß facing the Innengehause 138 of the turbine 108 (not shown here) and a Leitschaufelfuß the opposite vane head on. The vane head is the rotor 103 facing and fixed to a mounting ring 140 of the stator 143.

FIG. 4 shows a perspective view of a moving blade 120 or guide blade 130 of a turbomachine that extends along a longitudinal axis 121.

The turbomachine may be a gas turbine of an aircraft or power plant for power generation, a steam turbine or a compressor.

The blade 120, 130 has along the longitudinal axis 121 in succession a fastening region 400, an adjacent blade platform 403 and an airfoil 406 and a blade tip 415.

As a guide blade 130, the blade 130 may have at its blade tip 415 another platform (not shown).

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 designed, for example, as a hammer head. Other designs as Christmas tree or Schwalbenschwanzfuß are possible.

The blade 120, 130 has a leading edge 409 and a downstream edge 412 for a medium flowing past the airfoil 406.

In conventional blades 120, 130, for example, solid metallic materials, in particular superalloys, are used in all regions 400, 403, 406 of the blade 120, 130. 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 blade 120, 130 can be made by a casting process, also by directional solidification, by a forging process, by a Frasverfahren or combinations thereof.

Single-crystalline structures or structures are used as components for machines that are subject to high mechanical, thermal and / or chemical stresses during operation. The production of such einkπstallinen workpieces is done for example by directed solidification from the melt. These are casting processes in which the liquid metallic alloy solidifies to a monocrystalline structure, ie to a single-crystalline workpiece, or directionally. Here, dendritic crystals are aligned along the warm flow and form either a prismatic crystalline grain structure (columnar, ie grains that run the entire length of the workpiece and here, in common usage, are referred to as directionally solidified) or a monocrystalline structure, ie the whole The work consists of a single crystal. In these processes, one must avoid the transition to globulitic (polycrystalline) solidification, since by undirected growth necessarily transverse and longitudinal grain boundaries form, which negate the good properties of the directionally solidified or einkπstalliiien component. Is generally of directionally solidified Gef diegen the speech, so are both single crystals meant that have no grain boundaries or at most small angle grain boundaries, as well as Stangelkπstallstrukturen, which probably have in the longitudinal direction grain boundaries, 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, blades 120, 130 may have coatings against corrosion or oxidation, e.g. M is at least one element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and stands for yttrium (Y) and / or silicon and / or at least one element of the rare ones Earth, or hafnium (Hf)). Such alloys are known from EP 0 486 489 B1, EP 0 786 017 B1, EP 0 412 397 B1 or EP 1 306 454 A1, which should be part of this disclosure with regard to the chemical composition of the alloy. The density is preferably 95? the theoretical density.

On the MCrAlX layer (as an intermediate layer or as outermost layer), a protective aluminum oxide layer (TGO = thermal grown oxide layer) is formed.

Preferably, the layer composition comprises Co-30Ni-28Cr-8A1-0, 6Y-0, 7Si or Co-28Ni-24Cr-10Al-0, 6Y. In addition to these cobalt-based protective coatings, nickel-based protective layers such as Ni-10Cr-12Al-0.6Y-3Re or Ni-12Co-21Cr-IIAl-O, 4Y-2Re or Ni-25Co-17Cr-10Al-0.4Y-1 are also preferably used , 5RE.

On the MCrAlX may still be present a thermal insulation layer, which is preferably the outermost layer, and consists for example of ZrO ₂ , Y ₂ OsZrO ₂ , ie it is not, partially or completely stabilized by yttria and / or calcium oxide and / or magnesium oxide , The thermal insulation layer covers the entire MCrAlX layer. Suitable coating processes, such as electron beam evaporation (EB-PVD), are used to produce protuberant grains in the thermal insulation layer.

Other coating methods are conceivable, for example atmospheric plasma spraying (APS), LPPS, VPS or CVD. The thermal insulation layer can have porous, microporous or macroporous corns for better thermal shock resistance. The thermal insulation layer is therefore preferably more porous than the MCrAlX layer. The blade 120, 130 may be hollow or solid. When the blade 120, 130 is to be cooled, it is hollow and possibly still has film cooling holes 418 (indicated by dashed lines).

FIG. 5 shows a combustion chamber 110 of the gas turbine 100. The combustion chamber 110 is designed, for example, as a so-called annular combustion chamber, in which a multiplicity of burners 107 arranged around an axis of rotation 102 in circumferential direction pass into a common combustion chamber space 154, which produce flames 156 , 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. In order to allow a comparatively long service life for these concrete substrates which are unfavorable for the materials, the combustion chamber wall 153 is provided on its side facing the working medium M with an inner lining formed of heat shield elements 155.

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 m cooler holes (not shown) which are still in contact with the combustion chamber space 154.

Each heat shield element 155 made of an alloy is equipped on the working medium 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 may be similar to the Turbmenschaufein, so for example, MCrAlX means: M is at least an element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and stands for yttrium (Y) and / or silicon and / or at least one element of the rare earths, or hafnium (Hf) , Such alloys are known from EP 0 486 489 B1, EP 0 786 017 Bl, EP 0 412 397 B1 or EP 1 306 454 A1.

On the MCrAlX, for example, a ceramic thermal barrier layer may be present and consists for example of ZrCv, Y _/ O-ZrCv, ie it is not, partially or completely stabilized by yttrium oxide and / or calcium oxide and / or magnesium oxide.

By suitable coating methods, e.g. Electron Beam Evaporation (EB-PVD) produces proton grains in the thermal insulation layer.

Other coating methods are conceivable, e.g. atmospheric plasma spraying (APS), LPPS, VPS or CVD. The thermal insulation layer may have porous, microporous or macroporous grains for better thermal shock resistance.

Refurbishment means that turbine blades 120, 130, heat shield elements 155 may need to be deprotected (e.g., by sandblasting) after use. 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. Thereafter, a re-coating of the Turbmenschaufein 120, 130, heat shield elements 155 and a renewed use of

Turbomachine 120, 130 or the heat shield elements 155.

Claims

claims

A layered system (1, 120, 130, 155) comprising a substrate (4) and a two-layer MCrAlX layer (13) comprising (13): an outer MCrAlX layer (10) and an inner MCrAlX layer ( 7), wherein the chromium content of the outer MCrAlX layer (10) is lower than the chromium content of the inner MCrAlX layer (7) and wherein the alummium content of the outer MCrAlX layer (10) is higher than the alummium content of the inner MCrAlX layer ( 7) in which the inner MCrAlX layer (7) has (in wt%):

Co: 8 o - 22 ή, preferably 19% - 21 ή,

Cr: 21 ^r - - 29%, preferably 23 ^r - - 25%,

Al: 4 ° - - 9 ° -, preferably 6 ° - - 8 ^& , Y: 0,4- - 0,9-, preferably 0,4- - 0,6-,

Re: 0-υ-1, 0-o, preferably 0- _u ,

Ni, in particular the rest of nickel (Ni).

2. Layer system (1, 120, 130, 155), comprising a substrate (4) and a two-layer MCrAlX layer (13), which (13) comprises: an outer MCrAlX layer (10) and an inner MCrAlX layer ( 7), wherein X represents at least yttrium (Y), and wherein the yttrium content of the outer layer (10) is less than the Y content of the inner layer (7) in which the inner MCrAlX layer (7) comprises (7) in wt%):

Co: 8% -22%, preferably 19% -21%,

Cr: 21 ^C <- 29%, preferably 23 ^C <- 25%,

Al: 4% - 9%, preferably 6% - 8 ° -, Y: 0.4 & - 0.9 ^, preferably 0.4 ^ - 0.6%,

Re: 0% - 1.0%, preferably 0%,

Ni, in particular the rest of nickel (Ni).

3. Layer system according to claim 1 or 2, wherein the outer MCrAlX protective layer (10) has the following composition: Ni: 29-: - 39-6, preferably 34-: - 36-6, Cr: 17-: - 24- 6, preferably 19-: - 21-6, Al: 9% - 14-j, preferably 11% - 12-j, Y: 0.05-έ. - 0.5-i, preferably 0.1t, - 0.2 -, ,, optionally Si: 0, 1-J - 1.1 ^, preferably 0.2% - 0.4%, Co, preferably the remainder Co ,

4. Layer system according to claim 1, 2 or 3, above which the outer NiCoCrAlX layer (10) comprises at least one element from the group hafnium (Hf), zirconium (Zr), phosphorus (P), in particular at least 0.05wt ^c _ ,, in particular up to a percentage of 0.3wt-s.

5. Layer system according to claim 1, 2, 3 or 4, wherein the MCrAlX layer (13) is only two-ply (7, 10).

6. Layer system according to claim 1, 2, 3, 4 or 5, wherein the inner MCrAlX layer (7) has the same layer thickness as the outer MCrAlX layer (10).

7. A layer system according to claim 1, 2, 3, 4 or 5, wherein the outer MCrAlX layer (10) is significantly thinner than the inner MCrAlX layer (7).

8. Layer system according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the MCrAlX layer (7, 10) comprises a NiCoCrAlX layer (7, 10), in particular consists thereof, wherein X = Y, Re.

9. Layer system according to claim 3, wherein the proportion of silicon (Si) in the outer layer (10) amounts to 0.2wt% to 0.4wtt>.

10. Layer system according to claim 3, wherein the proportion of silicon (Si) in the outer layer (10) amounts to 0.7wt% to l, 0wts.

11. A layer system according to claim 1 or 3, wherein the outer layer (10) has no silicon (Si).

12. Layer system according to claim 2, wherein the Y content of the outer layer (10) 0.05wt ^ to less than 0.4wt%, in particular 0, lwt% to 0.2wt% amounts.

13. A layer system according to claim 2, wherein the Y content for the inner layer (7) amounts to greater than 0.4wt ° ό to 0.9wtή, in particular to 0,6wt ° ό.

14. A layer system according to claim 1, 2, 3 or 4, wherein an outer ceramic thermal barrier layer (16) is provided on the double-layered MCrAlX layer (13).

15. Layer system according to one or more of the preceding claims, in which the layer system consists of: a substrate (4) of a two-layered MCrAlX layer (7, 10), a ceramic thermal dam layer (16) on the MCrAlX layer (7, 10) and optionally a TGO layer on the outer MCrAlX

Layer (10).

16. Layer system according to one or more of the preceding claims, wherein the layer system consists of: a substrate (4) of a two-layer MCrAlX layer (7, 10), and optionally a TGO layer on the outer MCrAlX layer (10).

17. A layer system according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 13, 14, 15 or 16, wherein X = yttrium.