U.S. patent application number 12/774033 was filed with the patent office on 2010-08-26 for material composition for producing a coating for a component made from a metallic base material, and coated metallic component.
Invention is credited to Rene Jabado, Daniel Kortvelyessy, Ursus Kruger, Ralph Reiche, Michael Rindler, Jan Steinbach, Raymond Ullrich.
Application Number | 20100212541 12/774033 |
Document ID | / |
Family ID | 34926852 |
Filed Date | 2010-08-26 |
United States Patent
Application |
20100212541 |
Kind Code |
A1 |
Jabado; Rene ; et
al. |
August 26, 2010 |
Material Composition for Producing a Coating for a Component made
from a Metallic Base Material, and Coated Metallic Component
Abstract
The invention relates to a material composition that is used for
producing a coating for a component, especially a turbine
component, which is made of a metallic basic material, i.e. a metal
or a metal alloy. Said material composition comprises a matrix
material for forming a basic coating matrix and at least one filler
for adjusting desired coating proportions or coating
characteristics. The matrix material can be provided especially
with basic glass ceramic properties. The inventive material
composition is characterized in that the matrix material and/or the
filler contains nanoparticles
Inventors: |
Jabado; Rene; (Berlin,
DE) ; Kruger; Ursus; (Berlin, DE) ;
Kortvelyessy; Daniel; (Berlin, DE) ; Reiche;
Ralph; (Berlin, DE) ; Rindler; Michael;
(Schoneiche, DE) ; Steinbach; Jan; (Berlin,
DE) ; Ullrich; Raymond; (Schonwalde, DE) |
Correspondence
Address: |
SIEMENS CORPORATION;INTELLECTUAL PROPERTY DEPARTMENT
170 WOOD AVENUE SOUTH
ISELIN
NJ
08830
US
|
Family ID: |
34926852 |
Appl. No.: |
12/774033 |
Filed: |
May 5, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11664742 |
Apr 5, 2007 |
7744351 |
|
|
PCT/EP2005/054277 |
Aug 31, 2005 |
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12774033 |
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Current U.S.
Class: |
106/14.05 |
Current CPC
Class: |
C23C 22/74 20130101;
C23C 18/127 20130101; B82Y 30/00 20130101; Y02T 50/67 20130101;
Y02T 50/60 20130101; C23C 18/1216 20130101 |
Class at
Publication: |
106/14.05 |
International
Class: |
C09D 5/08 20060101
C09D005/08; C09D 5/10 20060101 C09D005/10 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2004 |
EP |
04023702.6 |
Claims
1. A material composition for the production of a coating for a
metallic turbine component, comprising: a matrix material
comprising an inorganic binder forming a base matrix of the
coating; and a filler material comprising metal or metal alloy
particles selected to be less noble than the base material to
create a sacrificial anode action when in use in a turbine, wherein
the matrix material or the filler material comprise nanoparticles
with particle sizes of less than 75 nm in a quantity effective to
produce a top surface having a degree of smoothness adequate for
use in the turbine as a top surface of the component with no
overlying top coating, wherein the coating comprises at least two
layers across its depth, the layers containing different nanoscale
pigment types to provide a color indication of wear.
2. The material composition as claimed in claim 1, wherein the
particle sizes of the nanoparticles are between 20 nm to 50 nm.
3. The material composition as claimed in claim 2, wherein solid
constituents of the matrix material are in the form of
nanoparticles.
4. The material composition as claimed in claim 3, wherein the
nanoparticles comprise at least one of the following materials: Al,
CrO.sub.3, MgO, Al.sub.2O.sub.3, and H.sub.3BO.sub.3.
5. The material composition as claimed in claim 2, wherein the
metal or metal alloy particles comprise at least one of the
following metals: Al, Mg, Fe, Ni, Co, Ti, and Zn.
6. The material composition as claimed in claim 2, wherein the
metal or metal alloy particles are deactivated.
7. The material composition as claimed in claim 8, wherein the
metal or metal alloy particles, for the deactivation, comprises an
oxide layer, a phosphate layer or a deactivation layer.
8. The material composition as claimed in claim 9, wherein the
filler material comprises hard-material particles as
nanoparticles.
9. The material composition as claimed in claim 10, wherein the
hard-material particles comprise at least one of the following
materials: diamond, silicon carbide, cubic boron nitride, and
corundum.
10. The material composition as claimed in claim 9, wherein the
filler material comprises thermally stable particles as
nanoparticles.
11. The material composition as claimed in claim 10, wherein the
thermally stable particles comprise at least one of the following
materials: ZrO.sub.2, SiO.sub.2, Al.sub.2O.sub.3, and
(Al.sub.xSi.sub.y)O.sub.z.
12. The material composition as claimed in claim 9, wherein the
filler material comprises dry lubricants as nanoparticles.
13. The material composition as claimed in claim 12, wherein the
dry lubricants comprise at least one of the following materials:
graphite, MoS.sub.2, WS.sub.2, and ZrO.sub.xN.sub.y.
14. The material composition as claimed in claim 9, wherein the
filler material comprises colored pigments of at least one pigment
type as nanoparticles.
15. The material composition as claimed in claim 14, wherein the
filler material comprises a mixture of various pigment types as
nanoparticles.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of 11/664,742 filed Apr. 5,
2007, which is the US National Stage of International Application
No. PCT/EP2005/054277, filed Aug. 31, 2005 and claims the benefit
thereof. The International Application claims the benefits of
European application No. 04023702.6 filed Oct. 5, 2004, both of the
applications are incorporated by reference herein in their
entirety.
FIELD OF INVENTION
[0002] The present invention relates to a material composition for
producing a coating for a component, in particular for a component
of a gas turbine installation, such as for example a compressor
blade or vane, which is made from a metallic base material. The
present invention also comprises a coated metallic component. The
invention is suitable, for example, for use in gas turbine
installations, in particular for use in compressors of gas turbine
installations.
BACKGROUND OF THE INVENTION
[0003] In its simplest form, a gas turbine installation comprises a
compressor, a combustion chamber and a turbine. Intake air is
compressed in the compressor, and fuel is then added to it. This is
followed by combustion of this mixture in the combustion chamber,
with the combustion exhaust gases being fed to the turbine, where
their thermal energy is withdrawn and converted into mechanical
energy. The compressor is generally driven by the turbine and
comprises a multiplicity of compressor blades or vanes.
[0004] During compression of the air in the compressor, water may
be formed, which under certain circumstances combines with other
elements contained in the air to form an electrolyte which can lead
to corrosion and erosion at the compressor blades or vanes. To
prevent this corrosion and/or erosion, therefore, compressor blades
or vanes are generally provided with coatings. Coatings which are
particularly suitable in this context are those which comprise a
for example phosphate-bonded base matrix with metal particles, such
as for example aluminum particles, dispersibly distributed therein.
The protective effect of a coating of this type is that the metal
particles embedded in the base coating, together with the (more
noble) metal of the compressor blade or vane and the electrolyte,
from a galvanic cell, in which the metal particles form what are
known as sacrificial anodes. The oxidation or corrosion then takes
place in the sacrificial anodes, i.e. in the metal particles, and
not in the metal of the compressor blade or vane.
[0005] The phosphate-bonded base matrix has glass-ceramic
properties, is thermally stable, is likewise resistant to the
corrosion, and also provides protection against mechanical effects,
such as abrasion and erosion.
[0006] In addition to the metal particles, the coating may contain
further particles as fillers. By way of example, mention may be
made at this point of dye particles.
[0007] Other types of coatings may be considered as well as
phosphate-bonded coatings. EP 0 142 418 B1, EP 0 905 279 A1 and EP
0 995 816 A1 describe chromate/phosphate-based coatings. EP 1 096
040 A2 describes a phosphate/borate-based coating, and EP 0 933 446
B1 describes a phosphate/permanganate-based coating. The coatings
described use particle additions with particle sizes of >1 .mu.m
Therefore, the coatings have layer structures with grain sizes of
over 1 .mu.m. To obtain a smooth blade or vane outer surface,
therefore, a particularly suitable outer coating, known as the top
coat, is applied above a primer layer, known as the base coat, of
this type.
SUMMARY OF INVENTION
[0008] It is an object of the present invention to provide a
material composition which is advantageous compared to the prior
art for the production of a coating of a component made from a
metallic base material, in particular a turbine component, more
particularly a compressor blade or vane or a turbine blade or
vane.
[0009] A further object of the present invention is to provide an
advantageous coated metallic component, in particular a turbine
component, and more particularly a compressor blade or vane or
turbine blade or vane.
[0010] The first object is achieved by the process as claimed in
the claims, and the second object is achieved by the coated
component as claimed in the claims. The dependent claims contain
advantageous configurations of the invention and can be combined
with one another in any desired way.
[0011] A material composition according to the invention for the
production of a coating for a component, in particular for a
turbine component which is made from a metallic base material, i.e.
from a metal or a metal alloy comprises a matrix material to form a
base matrix of the coating, and at least one filler material for
setting desired coating properties and/or coating features. The
matrix material may in particular have glass-ceramic base
properties. The material composition according to the invention is
distinguished by the fact that the matrix material and/or the
filler material comprise(s) nanoparticles with particle sizes of
less than 1 .mu.m. It is preferable for the particle sizes of the
nanoparticles to be in the range from 50 .mu.m to 200 .mu.m.
[0012] The use of nanoparticles serves, inter alia, to set an
ultrafine layer microstructure. It is in this way possible to
improve properties which are dependent on grain size, for example
fracture toughness, strength, resistance to thermal shocks, etc.,
of the layer microstructure. On account of their high surface
energy, materials with a grain size in the nanometer range have an
extremely high sintering activity. The high number of interfacial
atoms and the short diffusion paths in the nanoparticles mean that
sintering of the material composition is possible at a temperature
which is approx. 20% to 40% lower than the melting temperature of
the volume-forming material. This in turn is beneficial to the
grain growth in the material.
[0013] Moreover, it has been found that nanostructured materials
used to protect against corrosion are more resistant to corrosive
media than the coarse-grained coatings of the prior art. The
improved corrosion protection for metals is caused by the presence
of a greater number of uniformly finely distributed defects in the
passive film, which are located primarily at the grain boundaries.
The ultrafine distribution of the defects prevents a high local
accumulation of harmful anions (for example chloride, sulphate,
etc.). As a result, a greater force is required for anion
accumulation and subsequent acidification, with the result that a
higher anodic potential is required for stable hole growth.
[0014] The material composition with nanoparticles also has other
properties which differ greatly from those of coarse-grained
material compositions, i.e. compositions with particle sizes of
over For example, the typical hardness of metals with particle
sizes of approx. 10 .mu.m is higher by a factor of 2 to 7 than the
same metal with particle sizes of approx. 1 .mu.m. Moreover, the
hard-soft phenomenon of nanostructured materials occurs: hard
material becomes more ductile, soft material becomes harder. On
account of this hard-soft phenomenon, the material composition
according to the invention can produce coatings of reduced
brittleness.
[0015] In one configuration of the invention, solid constituents of
the matrix material are in the form of nanoparticles. Forming the
solid constituents of the matrix material as nanoparticles
increases the thermal stability, the corrosion resistance as well
as the resistance to mechanical effects of a coating produced from
the material composition. Moreover, the use of nanoparticles in the
matrix material, in particular in conjunction with the use of
nanoparticles in the filler material, allows the production of
smoother coatings than with the coarse-grained material
compositions of the prior art. There is then no longer any need for
a top coat. The costs and time required to coat a component can be
reduced as a result of elimination of the process steps for
production of the top coat.
[0016] Suitable nanoparticles for the matrix material are in
particular--although not exclusively--materials comprising aluminum
(Al), chromium trioxide (CrO.sub.3), magnesium oxide (MgO),
aluminum oxide (Al.sub.2O.sub.3) and/or boric acid
(H.sub.3BO.sub.3).
[0017] In a further configuration of the present invention, the
filler material comprises metal or metal alloy particles as
nanoparticles. As a function of the metallic base material, these
particles can be selected in such a manner as to provide a
sacrificial anode effect. In other words, the metal or metal alloy
of the nanoparticles can be less noble than the metal or metal
alloy of the metal base material.
[0018] Depending on the metallic base material, the metal or metal
alloy particles may comprise at least one of the following metals:
aluminum (Al), magnesium (Mg), Iron (Fe), nickel (Ni), cobalt (Co),
titanium (Ti) and zinc (Zn). The metals listed are particularly
suitable for the coating of blades or vanes which are made from
iron-base, nickel-base or cobalt-base superalloy. Alloys of this
type typically comprise chromium, titanium, tantalum, aluminum,
tungsten and further elements with excellent resistance to high
temperatures combined, at the same time, with a high strength.
Iron-based base alloys are used in particular to produce compressor
blades or vanes, whereas nickel-based or cobalt-based base alloys
are used in particular to produce the turbine blades or vanes. An
example of a gas turbine blade or vane produced from a superalloy
is given in U.S. Pat. No. 5,611,670. Therefore, reference is
explicitly made to the disclosure of said document with regard to
the composition of possible superalloys for turbine blades or
vanes.
[0019] Since, on account of their small size, the metal or metal
alloy particles have a particularly high reactivity, it is
advantageous for them to be deactivated. The deactivation can be
realized, for example, by the metal or metal alloy particles
comprising an oxide layer, a phosphate layer or a deactivation
layer which is compatible with the matrix material and/or further
fillers, for example chromate, borate, etc. The deactivation layer
can be produced in situ during production of the nanoparticles.
This may take place, for example, by controlled addition of
precursor compounds or gases. The deactivation of metallic
nanoparticles is described, for example, in US 2003/0108459 A1 and
in WO 01/58625 A1. Therefore, reference is made to the disclosure
of these documents with regard to the deactivation of the metal or
metal alloy particles.
[0020] In a further configuration of the present invention, the
filler material comprises hard-material particles as nanoparticles.
The hard-material particles may in particular comprise at least one
of the following materials: diamond, silicon carbide (SiC), cubic
boron nitride (BN), corundum, etc. The nanoscale hard-material
particles can be used to increase the resistance of a coating
produced using the material composition according to the invention
to mechanical effects.
[0021] In yet another configuration of the present invention, the
filler material comprises thermally stable particles as
nanoparticles. Suitable thermally stable nanoparticles are in
particular zirconium oxide (ZrO.sub.2), silicon oxide (SiO.sub.2),
aluminum oxide (Al.sub.2O.sub.3), aluminum-silicon oxide
(Al.sub.xSi.sub.y)O.sub.z, etc. The nanoscale thermally stable
particles can be used to increase the ability of a coating produced
using the material composition according to the invention to
withstand thermal stresses.
[0022] Moreover, in a further configuration of the material
composition according to the invention, the filler material may
comprise dry lubricants as nanoparticles. Example of suitable dry
lubricants include graphite, molybdenum sulfide MoS.sub.2, tungsten
sulfide WS.sub.2, ZrO.sub.xN.sub.y, etc. The dry lubricants can be
used to increase the ware resistance of a coating produced using
the material composition according to the invention.
[0023] Finally, in yet another configuration of the material
composition according to the invention, the filler material may
comprise colored pigments of at least one pigment type as
nanoparticles. The colored pigments can be used to realize a
decorative or informative coloring of a coated component.
Furthermore, the colored pigments can also contribute to improving
the corrosion protection, the thermal stability and the ware
resistance of the coated component.
[0024] The filler material may also comprise a mixture of various
pigment types as nanoparticles, so that a large number of different
colors can be realized.
[0025] A further aspect of the present invention provides a coated
metallic component having a coating which has been produced from
the material composition according to the invention.
[0026] In one particular configuration of the coated component, its
coating has at least two layers, which contain different nanoscale
pigment types. It is in this way possible, for example during
maintenance or repair work carried out on the component, to use the
color to recognize whether or not the top layer of the coating is
present. This makes it possible to recognize to what extent the
coating is still providing protection, and therefore obviates the
need for unnecessary recoating.
[0027] The coated metallic component according to the invention may
be configured, for example as a component of a turbine
installation, in particular as a compressor blade or vane or as a
turbine blade or vane.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Further features, properties and advantages of the present
invention will emerge from the following description of exemplary
embodiments with reference to the accompanying figures, in
which:
[0029] FIG. 1 shows an exert from a diagrammatic illustration of a
coated compressor blade or vane.
[0030] FIG. 2 shows an exert from a diagrammatic illustration of a
coated compressor blade or vane.
[0031] FIG. 3 shows a partial longitudinal section through an
example of a gas turbine.
[0032] FIG. 4 shows a perspective view of a rotor blade or guide
vane of a turbomachine.
DETAILED DESCRIPTION OF INVENTION
[0033] FIG. 1 diagrammatically depicts an excerpt from a compressor
blade or vane 1 as used in a compressor of a gas turbine
installation. The base material 3 and a coating 5 applied to the
base material 3 can be recognized.
[0034] The base material 3 of the compressor blade or vane 1 may be
produced, for example, from a superalloy. Superalloys are alloys
based on iron, nickel or cobalt, which typically comprise chromium,
titanium, tantalum, aluminum, tungsten and further elements with an
excellent resistance to high temperatures combined, at the same
time, with a high strength. An example of a gas turbine blade or
vane produced from a superalloy is disclosed, for example, in U.S.
Pat. No. 5,611,670. Therefore, reference is made to said document
with regard to the composition of suitable superalloys. In the
present exemplary embodiment, the base material is an iron-based
alloy.
[0035] The coating 5 is an inorganic coating to protect the
compressor blade or vane 1 against corrosion and wear. It comprises
an inorganic binder made from chromate/phosphate compounds and
metal particles, for example spheroid aluminum particles,
dispersively distributed in the binder, as a pigment.
[0036] The coating can be effected, for example, by spraying on the
following material composition: 7% by weight chromium trioxide
(CrO.sub.3), 25% by weight phosphoric acid (H.sub.3PO.sub.4), 6% by
weight magnesium oxide (MgO) and 62% by weight water (H.sub.2O) as
binder and aluminum particles with a mean diameter in the range
from 90 to 110 .mu.m as pigment. The production of aluminum
particles of this type is described, for example, in WO 01/58625
A1. Therefore, reference is made to the disclosure of said document
with regard to the production of the nanoscale aluminum particles.
The composition of the binder and of further suitable
chromate/phosphate-based binders are described in EP 0 142 418 B1.
Furthermore, further possible coating compositions based on
chromate/phosphate are described in EP 0 905 279 A1 and in EP 0 995
816 A1. Therefore, reference is made to said documents with regard
to the chemical composition of chromate/phosphate-based
coatings.
[0037] Unlike in the coating compositions mentioned therein,
however, in the coating composition according to the invention
described with reference to FIG. 1, the pigment is realized in the
form of nanoscale particles. In the documents mentioned, by
contrast, the diameters of the filler particles are in the
.mu.m-range.
[0038] The nanoscale metal particles or metal alloy particles added
are used in particular as sacrificial anodes of the coating.
Therefore, as a function of the composition of the base material,
the metal should be selected in such a way that it is less noble
than the base alloy, in order to ensure the sacrificial anode
action. It is therefore preferable to use aluminum.
[0039] After the coating composition described has been sprayed
onto the base material 3 of the compressor blade or vane 1, the
composition is allowed to dry out, so that the binder then forms
the layer matrix in which the nanoscale aluminum particles are
embedded.
[0040] In a modification of the exemplary embodiment described,
instead of the aluminum particles or in addition to the aluminum
particles, it is also possible for the solid constituents of the
binder, i.e. in the present exemplary embodiment for example the
chromium trioxide and the magnesium oxide, to be in the form of
nanoscale particles.
[0041] In general, the use of nanoscale particles serves to set an
ultrafine layer microstructure. It is in this way possible to
produce particularly smooth coatings, with the result that in the
exemplary embodiment illustrated in FIG. 1 a top coat is not
required.
[0042] As an alternative or in addition to the nanoscale pigments
and/or aluminum particles, it is also possible for nanoscale
hard-material particles, for example diamond, silicon carbide
(SiC), etc. to be added to the coating described, in order to
increase the resistance to mechanical effects, for example abrasion
or erosion. It is also possible to add temperature-resistant
nanoscale compounds, such as for example zirconium oxide
(ZrO.sub.2), silicon oxide (SiO.sub.2), etc., in order to increase
the ability of the coating to withstand thermal stresses. Finally,
it is also possible to add nanoscale dry lubricants, for example
graphite, molybdenum sulphide (MoS.sub.2), etc., in order to set
the coating wear resistance.
[0043] FIG. 2 shows an excerpt from a coated compressor blade or
vane 10 as a second exemplary embodiment of the present invention.
The figure illustrates the base material 13, which can be of the
same structure as the base material 3 of the first exemplary
embodiment, as well as a coating 15 applied to the base material
13. In the second exemplary embodiment, the coating comprises a
first layer 17 and a second layer 19 applied above the first layer
17. The chemical composition of both the first layer 17 and the
second layer 19 of the coating 15 corresponds to the coating 5 of
the first exemplary embodiment.
[0044] Unlike in the coating 5 of the first exemplary embodiment,
suitable colored pigments in the form of nanoscale colored pigment
particles have additionally been added to the coating 15 of the
second exemplary embodiment. Colored pigments are described, for
example, in EP 0 905 279 A1, or are known as "color index" pigments
(The Society of Dyers and Colorists). The desired coloring of the
coating which is to be achieved through the addition of the colored
pigments can be achieved by mixing various types of colored
pigments. Unlike the known colored pigments, the colored pigments
in the material composition according to the invention are added in
the form of nanoscale particles.
[0045] In the present exemplary embodiment, a different type of
colored pigment is added to the first layer 17 of the coating 5
from the type of colored pigment added to the second layer 19. It
is in this way possible, when inspecting a blade or vane which has
already been in operation, to use the color to ascertain the extent
to which the coating has worn away. As soon as the second layer 19
has worn away, the color of the coating changes. It is in this way
possible to demonstrate the need to refurbish the compressor blade
or vane. Of course, it is also possible to use more than two
differently colored layers.
[0046] The coating compositions described thus far have contained
chromate/phosphate-based binders. However, alternative coating
compositions may also comprise binders based on phosphate/borate or
phosphate/permanganate.
[0047] By way of example, a suitable phosphate/borate-based binder
may include the following constituents: water, phosphoric acid,
boron oxide, zinc oxide and aluminum hydroxide. In a binder of this
type too, the solid constituents may be in the form of nanoscale
particles. It is in turn possible for nanoparticles, for example
aluminum particles or other metal particles with nanoscale
dimensions, i.e. with dimensions of less than 75 nm, preferably
between 50 nm and 75 nm or preferably between 20 nm and 75 nm, in
particular between 20 nm and 50 nm, to be added to the binder. As
an alternative or in addition, it is possible for the nanoscale
hard-material particles which have already been mentioned above
and/or the abovementioned temperature-resistant particles and/or
the abovementioned dry lubricants and/or the abovementioned
nanoscale colored pigments to be added. Suitable compositions of
phosphate/borate-based binders are described, for example, in EP 1
096 040 A2. Therefore, reference is made to the disclosure of said
document with regard to the composition of possible binders for the
coating composition according to the invention.
[0048] A suitable phosphate/permanganate-based binder may, for
example, comprise the following constituents: 67% by weight water,
2% by weight magnesium permanganate, 23% by weight of 85% strength
phosphoric acid and 8% by weight aluminum hydroxide. As in the
other coatings described, the solid constituents of the binder
composition may be in the form of nanoscale particles. Moreover,
all the additions which have been mentioned in connection with the
other exemplary embodiments in the form of nanoscale particles can
also be added. Other possible chemical compositions for coatings
based on phosphate/permanganate are described in EP 0 933 446 B1.
Therefore, reference is made to the disclosure of said document
with regard to suitable chemical compositions of possible binders
for the coating composition according to the invention.
[0049] In the exemplary embodiments, the solids of the binders are
in the form of nanoscale particles. However, it is also possible
for the solids of the binder not to be in the form of nanoscale
particles. In this case, one or more of the abovementioned
additives are present, with at least one of the additives being in
the form of nanoscale particles.
[0050] FIG. 3 shows, by way of example, a partial longitudinal
section through a gas turbine 100. In the interior, the gas turbine
100 has a rotor 103 which is mounted such that it can rotate about
an axis of rotation 102 and is also referred to as the turbine
rotor. An intake housing 104, a compressor 105, a, for example,
toroidal combustion chamber 110, in particular an annular
combustion chamber 106, with a plurality of coaxially arranged
burners 107, a turbine 108 and the exhaust-gas housing 109 follow
one another along the rotor 103.
[0051] The annular combustion chamber 106 is in communication with
a, for example, annular hot-gas passage 111, where, by way of
example, four successive turbine stages 112 form the turbine
108.
[0052] Each turbine stage 112 is formed, for example, from two
blade or vane rings. As seen in the direction of flow of a working
medium 113, in the hot-gas passage 111 a row of guide vanes 115 is
followed by a row 125 formed from rotor blades 120.
[0053] 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 means of a turbine disk 133.
[0054] A generator (not shown) is coupled to the rotor 103.
[0055] While the gas turbine 100 is operating, the compressor 105
sucks in air 135 through the intake housing 104 and compresses it.
The compressed air provided at the turbine-side end of the
compressor 105 is passed to the burners 107, where it is mixed with
a fuel. The mix is then burnt in the combustion chamber 110,
forming the working medium 113. From there, the working medium 113
flows along the hot-gas passage 111 past the guide vanes 130 and
the rotor blades 120. The working medium 113 is expanded at the
rotor blades 120, transferring its momentum, so that the rotor
blades 120 drive the rotor 103 and the latter in turn drives the
generator coupled to it.
[0056] While the gas turbine 100 is operating, the components which
are exposed to the hot working medium 113 are subject to thermal
stresses. The guide vanes 130 and rotor blades 120 of the first
turbine stage 112, as seen in the direction of flow of the working
medium 113, together with the heat shield bricks which line the
annular combustion chamber 106, are subject to the highest thermal
stresses.
[0057] To be able to withstand the temperatures which prevail
there, they can be cooled by means of a coolant.
[0058] Substrates of the components may likewise have a directional
structure, i.e. they are in single-crystal form (SX structure) or
have only longitudinally oriented grains (DS structure).
[0059] By way of example, iron-base, nickel-base or cobalt-base
superalloys are used as material for the components, in particular
for the turbine blade or vane 120, 130 and components of the
combustion chamber 110. Superalloys of this type 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; these documents form part of the
disclosure.
[0060] The blades or vanes 120, 130 may also have coatings which
protect against corrosion (MCrAlX; M is at least one element
selected from the group consisting of iron (Fe), cobalt (Co),
nickel (Ni), X is an active element and represents yttrium (Y)
and/or silicon and/or at least one rare earth element or hafnium).
Alloys of this type 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 are intended to form
part of the present disclosure.
[0061] A thermal barrier coating, consisting for example of
ZrO.sub.2, Y.sub.2O.sub.4-ZrO.sub.2, i.e. unstabilized, partially
stabilized or completely stabilized by yttrium oxide and/or calcium
oxide and/or magnesium oxide, may also be present on the MCrAlX.
Columnar grains are produced in the thermal barrier coating by
suitable coating processes, such as for example electron beam
physical vapor deposition (EB-PVD).
[0062] The guide vane 130 has a guide vane root (not shown here),
which faces the inner housing 138 of the turbine 108, and a guide
vane head which is at the opposite end from the guide vane root.
The guide vane head faces the rotor 103 and is fixed to a securing
ring 140 of the stator 143.
[0063] FIG. 4 shows a perspective view of a rotor blade 120 or
guide vane 130 of a turbomachine, which extends along a
longitudinal axis 121.
[0064] The turbomachine may be a gas turbine of an aircraft or of a
power plant for generating electricity, a steam turbine or a
compressor.
[0065] The blade or vane 120, 130 has, in succession along the
longitudinal axis 121, a securing region 400, an adjoining blade or
vane platform 403 and a main blade or vane part 406. As a guide
vane 130, the vane 130 may have a further platform (not shown) at
its vane tip 415.
[0066] A blade or vane root 183, which is used to secure the rotor
blades 120, 130 to a shaft or a disk (not shown), is formed in the
securing region 400.
[0067] The blade or vane root 183 is designed, for example, in
hammerhead form. Other configurations, such as a fir-tree or
dovetail root, are possible.
[0068] The blade or vane 120, 130 has a leading edge 409 and a
trailing edge 412 for a medium which flows past the main blade or
vane part 406.
[0069] In the case of conventional blades or vanes 120, 130, by way
of example solid metallic materials, in particular superalloys, are
used in all regions 400, 403, 406 of the blade or vane 120, 130.
Superalloys of this type 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;
these documents form part of the disclosure. The blade or vane 120,
130 may in this case be produced by a casting process, also by
means of directional solidification, by a forging process, by a
milling process or combinations thereof.
[0070] Workpieces with a single-crystal structure or structures are
used as components for machines which, in operation, are exposed to
high mechanical, thermal and/or chemical stresses. Single-crystal
workpieces of this type are produced, for example, by directional
solidification from the melt. This involves casting processes in
which the liquid metallic alloy solidifies to form the
single-crystal structure, i.e. the single-crystal workpiece, or
solidifies directionally. In this case, dendritic crystals are
oriented along the direction of heat flow and form either a
columnar crystalline grain structure (i.e. grains which run over
the entire length of the workpiece and are referred to here, in
accordance with the language customarily used, as directionally
solidified) or a single-crystal structure, i.e. the entire
workpiece consists of one single crystal. In these processes, a
transition to globular (polycrystalline) solidification needs to be
avoided, since non-directional growth inevitably forms transverse
and longitudinal grain boundaries, which negate the favorable
properties of the directionally solidified or single-crystal
component.
[0071] Where the text refers in general terms to directionally
solidified microstructures, this is to be understood as meaning
both single crystals, which do not have any grain boundaries or at
most have small-angle grain boundaries, and columnar crystal
structures, which do have grain boundaries running in the
longitudinal direction but do not have any transverse grain
boundaries. This second form of crystalline structures is also
described as directionally solidified microstructures
(directionally solidified structures). Processes of this type are
known from U.S. Pat. No. 6,024,792 and EP 0 892 090 A1; these
documents form part of the disclosure.
[0072] The blades or vanes 120, 130 may likewise have layers
protecting against corrosion or oxidation (MCrAlX; M is at least
one element selected from the group consisting of iron (Fe), cobalt
(Co), nickel (Ni), X is an active element and represents yttrium
(Y) and/or silicon and/or at least one rare earth element, or
hafnium (Hf)). Alloys of this type 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 are
intended to form part of the present disclosure.
[0073] It is also possible for a thermal barrier coating,
consisting for example of ZrO.sub.2, Y.sub.2O.sub.4-ZrO.sub.2, i.e.
unstabilized, partially stabilized or completely stabilized by
yttrium oxide and/or calcium oxide and/or magnesium oxide, to be
present on the MCrAlX. Columnar grains are produced in the thermal
barrier coating by means of suitable coating processes, such as for
example electron beam physical vapor deposition (EB-PVD).
[0074] Refurbishment means that after they have been used,
protective layers may have to be removed from components 120, 130
(e.g. by sand-blasting). Then, the corrosion and/or oxidation
layers and products are removed. If appropriate, cracks in the
component 120, 130 are also repaired. This is followed by recoating
of the component 120, 130, after which the component 120, 130 can
be reused.
[0075] The blade or vane 120, 130 may be hollow or solid in form.
If the blade or vane 120, 130 is to be cooled, it is hollow and may
also have film-cooling holes 418 (indicated by dashed lines).
* * * * *