EP1840335A2 - Layer - Google Patents

Abstract

Alloy coatings comprise (wt%): chromium 20 -22; aluminum 10.5 - 11.5; yttrium 0.3 - 0.5; rhenium 1.5 - 2.5; and cobalt 1 -13, the remainder being nickel.

Description

The invention relates to a layer according to claim 1.

Electrolytic coating processes use an electrolyte in which the elements to be deposited are either dissolved in a solution or dispersed as powder particles in a solution.
However, alloys can be deposited poorly in this way.

It is therefore an object of the invention to overcome this problem.

The object is achieved by a layer according to claim 1.

Figur 1

eine Turbinenschaufel,

Figur 2

eine Brennkammer

Figur 3

eine Gasturbine und

Figur 4

Zusammensetzung von Legierungen, die aus einem erfindungsgemäßen Elektrolyten abscheidbar sind.

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FIG. 1

a turbine blade,

FIG. 2

a combustion chamber

FIG. 3

a gas turbine and

FIG. 4

Composition of alloys which can be deposited from an electrolyte according to the invention.

According to the invention, the electrolyte for the electrolytic deposition of an alloy is a solution of at least the element of the matrix material and furthermore contains dispersed powder. Solved means that the component is present as an ion in a solution (water, alcohol, acid, lye, ...).

The matrix material may be either cobalt or nickel. In addition to the matrix material, at least one further element of the alloy may be dissolved in the electrolyte. Thus, nickel and cobalt may be dissolved in the electrolyte.

The powder containing the further constituents of the alloy may have either chromium or aluminum or chromium and aluminum.
Likewise, the powder may comprise the elements chromium, aluminum and yttrium.
In addition to the elements chromium, aluminum and yttrium, silicon and / or rhenium may also be present as dispersed powder in the electrolyte.

In the case of so-called MCrAlX alloys, the matrix material consists of nickel or cobalt.
The alloy consists, for example, of at least three elements, in particular of at least five elements (for example NiCoCrAIX). The electrolyte contains, for example, at least one of the elements chromium, aluminum as a dispersed powder.

Also, melting point depressants such as B, Si, Hf, Zr may be dissolved in the electrolyte or may be present as a powder.

Likewise, coatings based on superalloys can be deposited with the electrolyte according to the invention.
For example, for an electrolyte to deposit a superalloy-based layer or repair a superalloy substrate, the powder still contains the elements titanium, tantalum, tungsten, molybdenum, niobium, boron, zirconium, or carbon.

With a corresponding electrolysis apparatus, layers can be deposited on a substrate by means of the electrolytes according to the invention. After the electrolytic production of the layer, a heat treatment can be carried out in order, for example, to achieve better bonding of the electrolytically produced layer to the substrate.
In a further step, further metallic and / or ceramic layers can be applied to the electrolytically produced layer.

A drawback with a prior art electrolytic process is that it is very difficult for an alloy to dissolve all components in the solution.
The other possibility, namely to disperse all constituents as powder in the solution, leads to the problem that the deposition process is very strongly determined by the powder particles of the matrix material, which occupy a large volume fraction. This often leads to an irregular or uncontrolled deposition of alloying elements with a smaller volume or weight fraction.
The electrolyte of the invention solves the problem in that the largest proportion (matrix material) of the alloy to be deposited is dissolved and the other elements are present as a powder.

Likewise, the electrolyte according to the invention opens up the possibility of varying the stoichiometry of the alloy during the electrolytic deposition by varying the proportions of powder by constantly increasing, for example by adding powder, the proportion of an alloying element and thus achieving a gradation in the concentration of this alloying element in the layer to be produced.

embodiments

• I. The desired composition of an MCrAlX alloy consists at least of (in wt%):
  • 20-22% chromium,
  • 10.5-11.5% aluminum,
  • 0.3-0.5% yttrium,
  • 1.5-2.5% rhenium,
  • 11-13% cobalt and
  • Rest of nickel.
    In this case cobalt and nickel are dissolved in the electrolyte and the powder which is added to the aqueous electrolyte consists, for example, of (in wt%)
    61.8% chromium,
    32.3% aluminum,
    0.9% yttrium and
    5% rhenium.
• II. Another MCrAlX alloy consists at least of (in wt%):
  • 27-29% chromium,
  • 7-8% aluminum,
  • 0.5-0.7% yttrium,
  • 0.3-0.7% silicon,
  • 29-31% nickel and
  • Balance cobalt.
    In this case, the elements cobalt and nickel are in turn dissolved in the electrolyte and the powder has, for example, the following weight distributions:
    76.5% chromium,
    20.5% aluminum,
    1.6% yttrium and
    1.4% silicon.
• III. Another embodiment of an MCrAlX alloy is
  16-18% chromium,
  12-13% aluminum,
  0.5-0.7% yttrium,
  0.3-0.5% silicon,
  21-23% cobalt and
  Rest of nickel.
  Again, cobalt and nickel are dissolved in the electrolyte and the powder has, for example, the following parts by weight:
  56.7% chromium,
  40% aluminum,
  2% yttrium,
  1.3% silicon.
• IV. Another exemplary embodiment of an MCrAlX alloy:
  • 16-18% chromium,
  • 9.5-11% aluminum,
  • 0.3-0.5% yttrium,
  • 1-1.8% rhenium,
  • 24-26% cobalt,
  • Rest of nickel.
  In turn, cobalt and nickel are dissolved in the electrolyte and the powder contains
  58.8% chromium,
  34.6% aluminum,
  1.4% yttrium and
  5.2% rhenium.

• 15 - 17% Chrom,
• 3,2 - 3,7% Aluminium,
• 3,2-3,7% Titan,
• 1,5-2,0% Tantal,
• 2,4-2,8% Wolfram,
• 1,5-2,0% Molybdän,
• 0,6-1,1% Niob,
• 0,0007-0,012% Bor,
• 0,015-0,06% Zirkonium,
• 8-9% Kobalt,
• Rest Nickel.

As an example of the composition of a superalloy, mention may be made here by way of example of IN 738 from FIG. 4 with the proportions:

• 15-17% chromium,
• 3.2 - 3.7% aluminum,
• 3.2-3.7% titanium,
• 1.5-2.0% tantalum,
• 2.4-2.8% tungsten,
• 1.5-2.0% molybdenum,
• 0.6-1.1% niobium,
• 0.0007-0.012% boron,
• 0.015-0.06% zirconium,
• 8-9% cobalt,
• Rest of nickel.

• 53,8% Chrom,
• 11,4% Aluminium,
• 11,4% Titan,
• 5,9% Tantal,
• 8,7% Wolfram,
• 5,9% Molybdän,
• 2,8% Niob,
• 0,03% Bor,
• 0,13% Zirkonium.

Here, cobalt and nickel, for example, are likewise dissolved again in the electrolyte, and the powder has, for example, the following constituents in wt%:

• 53.8% chromium,
• 11.4% aluminum,
• 11.4% titanium,
• 5.9% tantalum,
• 8.7% tungsten,
• 5.9% molybdenum,
• 2.8% niobium,
• 0.03% boron,
• 0.13% zirconium.

Other layers of superalloys according to FIG. 4 are also produced in this way.

1 shows a perspective view of a moving blade 120 or guide blade 130 of a turbomachine, which extends along a longitudinal axis 121.

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 consecutively a fastening region 400, a blade platform 403 adjoining thereto and an airfoil 406.
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 trailing 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 for example from EP 1 204 776 B1 . EP 1 306 454 . EP 1 319 729 A1 . WO 99/67435 or WO 00/44949 known; these references are part of the disclosure regarding the superalloy chemical compositions.
The blade 120, 130 can in this case by a casting process, also by means of directional solidification, by a forging process, be made by a milling method 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, for example, by directed solidification from the melt. These are casting methods in which the liquid metallic alloy solidifies into a monocrystalline structure, ie a single-crystal workpiece, or directionally.
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, in common parlance, referred to as directionally solidified) or a monocrystalline structure, ie the whole Workpiece consists of a single crystal. In these processes, it is necessary to avoid the transition to globulitic (polycrystalline) solidification, since non-directional growth necessarily produces transverse and longitudinal grain boundaries which negate the good properties of the directionally solidified or monocrystalline component.
The term generally refers to directionally solidified microstructures, which means both single crystals that have no grain boundaries or at most small angle grain boundaries, and stem crystal structures that have probably longitudinal grain boundaries but no transverse grain boundaries. These second-mentioned crystalline structures are also known as directionally solidified structures.
Such methods are known from U.S. Patent 6,024,792 and the EP 0 892 090 A1 known; these writings are part of the revelation.

Likewise, the blades 120, 130 may have coatings against corrosion or oxidation (MCrAlX; M is at least one element 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 the EP 0 486 489 B1 . EP 0 786 017 B1 . EP 0 412 397 B1 or EP 1 306 454 A1 whose chemical compositions are intended to be part of this disclosure. These layers can be applied electrolytically using the method according to the invention.

On the MCrAlX still a thermal barrier coating may be present and consists for example of ZrO ₂ , Y ₂ O ₄ -ZrO ₂ , ie it is not, partially or completely stabilized by yttria and / or calcium oxide and / or magnesium oxide.
By means of suitable coating processes, such as electron beam evaporation (EB-PVD), stalk-shaped grains are produced in the thermal barrier coating.

Refurbishment means that components 120, 130 may need to be deprotected after use (e.g., by sandblasting). This is followed by removal of the corrosion and / or oxidation layers or products. Optionally, even cracks in the component 120, 130 are repaired. This is followed by a re-coating of the component 120, 130 and a renewed use of the component 120, 130.

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

FIG. 2 shows a combustion chamber 110 of a gas turbine.
The combustion chamber 110 is configured, for example, as a so-called annular combustion chamber in which a plurality of circumferentially arranged about the rotation axis 102 around Burners 107 open into a common combustion chamber space. 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 enable a comparatively long service life even with these, for the materials unfavorable operating parameters, the combustion chamber wall 153 is provided on its side facing the working medium M side with an inner lining formed from heat shield elements 155.

Each heat shield element 155 is equipped on the working medium side with a particularly heat-resistant protective layer or made of high-temperature-resistant material. These may be solid ceramic stones or alloys with MCrAlX and / or ceramic coatings.
The materials of the combustion chamber wall and its coatings may be similar to the turbine blades.

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 combustion chamber 110 is designed in particular for detecting losses of the heat shield elements 155. For this purpose, a number of temperature sensors 158 are positioned between the combustion chamber wall 153 and the heat shield elements 155.

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

Along the rotor 103 follow one another a suction housing 104, a compressor 105, for example, a toroidal combustion chamber 110, in particular annular combustion chamber 106, with a plurality of coaxially arranged burners 107, a turbine 108 and the exhaust housing 109th
The ring combustion chamber 106 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 105 is sucked in 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. 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 seen in the flow direction of the working medium 113 first Turbine stage 112 is most thermally stressed in addition to the heat shield bricks lining the annular combustor 106.
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 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.

Also, the blades 120, 130 may be anti-corrosion coatings (MCrAlX; M is at least one element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and is yttrium (Y) and / or silicon and / or at least one element of the rare earths or hafnium). Such alloys are known from the EP 0 486 489 B1 . EP 0 786 017 B1 . EP 0 412 397 B1 or EP 1 306 454 A1 to be part of this revelation.

On the MCrAlX may still be present a thermal barrier coating, and consists for example of ZrO ₂ , Y ₂ O ₄ -ZrO ₂ , that is, it is not, partially or completely stabilized by yttria and / or calcium oxide and / or magnesium oxide. By means of suitable coating processes, such as electron beam evaporation (EB-PVD), stalk-shaped grains are produced in the thermal barrier coating.

The vane 130 has a guide vane foot (not shown here) facing the inner housing 138 of the turbine 108 and a vane head opposite the vane foot. The vane head faces the rotor 103 and fixed to a mounting ring 140 of the stator 143.

Claims (1)

layer
at least consisting of (in wt%): 20% -22% chromium, 10.5% -11.5% aluminum, 0.3% -0.5% yttrium, 1.5% -2.5% rhenium, 11% -13% cobalt and Rest of nickel.

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