Note: Descriptions are shown in the official language in which they were submitted.
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Description
Method for Producing a Hole
The invention relates to a method for producing a hole as
claimed in claim 1, wherein a hole is produced in a component
by means of pulsed energy beams.
For many components, castings in particular, ablations
subsequently need to be carried out for instance to form
indentations or through-holes. Particularly for turbine
components which have film cooling holes for cooling, holes are
subsequently introduced after production of the component.
Such turbine components often also have layers, for example a
metallic layer or interlayer and/or a ceramic outer layer. The
film cooling holes must then be produced through the layers and
the substrate (casting).
US-A 6,172,331 and US-A 6,054,673 disclose a laser boring
method for introducing holes into layer systems, ultrashort
laser pulse lengths being used. A laser pulse length is found
from a particular laser pulse length range and the hole is
thereby produced.
DE 100 63 309 Al discloses a method for producing a cooling air
opening by means of the laser, in which the laser parameters
are adjusted so that material is ablated by sublimation.
US-A 5,939,010 discloses two alternative methods for producing
a multiplicity of holes. In one method (Figs 1, 2 of the US
patent) one hole is initially produced fully before the next
hole is produced. In the second method, the holes are produced
stepwise, by first producing a first subregion of a first hole
then a
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first subregion of a second hole etc. (Fig. 10 of the US
patent). Different pulse lengths may be used in the two
methods, but the pulse length used in a given method is always
the same. The two methods cannot be interlinked.
The cross-sectional area of the region to be ablated always
corresponds to the cross section of the hole to be produced.
US-A 5,073,687 discloses the use of a laser for producing a
hole in a component, which is formed by a substrate with a
copper layer on both sides. Initially a hole is produced
through the copper film by means of a longer pulse duration,
and then a hole is produced by means of shorter pulses in the
substrate consisting of a resin, a hole subsequently being
produced through a copper layer on the rear side with a higher
output power of the laser. The cross-sectional area of the
region to be ablated corresponds to the cross section of the
hole to be produced.
US Patent 6,479,788 Bl discloses a method for producing a hole,
in which longer pulses are used in a first step than in a
further step. The pulse duration is varied here in order to
produce an optimal rectangular shape in the hole. The cross-
sectional area of the beam is also increased as the pulse
length decreases.
The use of such ultrashort laser pulses is expensive and very
time-intensive owing to their low average powers.
It is therefore an object of the invention to overcome this
problem.
The object is achieved by a method as claimed in claim 1,
wherein different pulse lengths and pulse lengths of > 0.4 ms
for the longer pulse lengths are used.
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It is particularly advantageous for shorter pulses to be used
only in one of the first ablation steps, in order to generate
optimal properties in the outer surface region of the interface
since these are crucial for the outflow behavior of a medium
from the hole and for the flow behavior of a medium around this
hole.
In the interior of the hole, the properties of the interface
are less critical, so that longer pulses which cause
inhomogeneous interfaces may be used there.
Further advantageous measures of the method or the device are
listed in the dependent claims of the method.
The measures listed in the dependent claims may advantageously
be combined with one another in any desired way.
The invention will be explained in more detail with the aid of
the figures, in which:
Figure 1 shows a hole in a substrate,
Figure 2 shows a hole in a layer system,
Figure 3 shows a plan view of a through-hole to be
produced,
Figures 4 11 show ablation steps of the method according to
the invention,
Figures 12 - 15 show apparatus for carrying out the method,
Figure 16 shows a gas turbine,
Figure 17 shows a turbine blade and
Figure 18 shows a combustion chamber.
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Description of the Component with a Hole
Figure 1 shows a component 1 with a hole 7.
The component 1 consists of a substrate 4 (for example a
casting or DS or SX component).
The substrate 4 may be metallic and/or ceramic. Particularly in
the case of turbine components, for example turbine rotor
blades 120 or guide vanes 130 (Figs 16, 17), heat shield
elements 155 (Fig. 18) and other housing parts of a steam or
gas turbine 100 (Figure 16), but also an aircraft turbine, the
substrate 4 consists of a nickel-, cobalt- or iron-based
superalloy. In the case of turbine blades for aircraft, the
substrate 4 consists for example of titanium or a titanium
based alloy.
The substrate 4 comprises a hole 7, which is for example a
through-hole. It may however also be a blind hole. The hole 7
consists of a lower region 10 which starts from an inner side
of the component 1 and is for example designed symmetrically
(for example circularly, ovally or rectangularly), and an upper
region 13 which is optionally designed as a diffusor 13 on an
outer surface 14 of the substrate 4. The diffusor 13 represents
a widening of the cross section relative to the lower region 10
of the hole 7.
The hole 7 is for example a film cooling hole. In particular
the inner-lying surface 12 of the diffusor 13, i.e. in the
upper region of the hole 7, should be smooth in order to allow
optimal outflow of a medium, in particular a coolant from the
hole 7, because irregularities generate undesired turbulences
or deviations. Much less stringent requirements are placed on
the quality of the hole surface in the lower region 10 of the
hole 7, since the arriving flow behavior is affected only
little by this.
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Figure 2 shows a component 1 which is configured as a layer
system.
On the substrate 4, there is at least one layer 16.
This may for example be a metal alloy of the MCrAlX type, where
M stands for at least one element of the group ion, cobalt or
nickel. X stands for yttrium and/or at least one rare earth
element.
The layer 16 may also be ceramic.
The component 1 is preferably a layer system in which is also a
further layer 1611 on the MCrAlX layer 16', for example a
ceramic layer as a thermal barrier layer.
The thermal barrier layer 16" is for example a fully or
partially stabilized zirconium oxide layer, in particular an
EB-PVD layer or plasma sprayed (APS, LPPS, VPS), HVOF or CGS
(cold gas spraying) layer.
A hole 7 with the lower region 10 and the diffusor 13 is
likewise introduced in this layer system 1.
The following comments regarding production of the hole 7 apply
to substrates 4 with and without a layer 16 or layers 16',
16".
Figure 3 shows a plan view of a hole 7.
The lower region 10 could be produced by a machining
fabrication method. For the diffusor 13, on the other hand,
this would not be possible or would be possible only with very
great outlay.
The hole 7 may also extend at an acute angle to the surface 14
of the component 1.
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Method
Figures 4, 5 and 6 show ablation steps of the method according
to the invention.
According to the invention, energy beams 22 with different
pulse lengths are used during the method.
The energy beam may be an electron beam, laser beam or high-
pressure water jet. The use of a laser will be discussed below
merely by way of example.
Particularly in one of the first ablation steps, shorter pulses
(tpulse <<) preferably less than or equal to 500 ns, in
particular less than or equal to 100 ns are used. Pulse lengths
in the picosecond or femtosecond range may also be used.
When using shorter pulse lengths of less than or equal to 500
ns (nanoseconds), in particular less than or equal to 100 ns,
almost no melting takes place in the region of the interface.
No cracks are therefore formed on the inner surface 12 of the
diffusor 13, and exact plane geometries can thus be generated.
The shorter pulse lengths are all shorter in time than the
longer pulse lengths.
In one of the first ablation steps, a first subregion of the
hole 7 is produced in the component 1. This may for example
correspond at least partially or fully to the diffusor 13 (Figs
6, 9). The diffusor 13 is for the most part arranged in a
ceramic layer. In particular, a shorter pulse length is used
for producing the entire diffusor 13. In particular, a constant
shorter pulse length is used for producing the diffusor 13. The
time to produce the diffusor 13 corresponds for example to the
first ablation steps in the method.
For producing the diffusor 13, a laser 19, 19', 19" with its
laser beams 22, 22', 2211 is preferably displaced to and fro in
a lateral plane 43, as is represented
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for example in Figure 5. The diffusor 13 is displaced along a
displacement line 9, for example in the shape of a meander, in
order to ablate material here in a plane (step Fig. 4 to Fig.
6).
Preferably, but not necessarily, longer pulse lengths
(tpulse >) is greater than 0.4 ms, in particular greater than
0.5 ms and in particular 10 ms, are used to produce the
remaining lower region 10 of the hole once a metallic
interlayer 16' or the substrate 4 has been reached, as
represented in Figure 1 or 2.
The diffusor 13 is at least for the most part located in a
ceramic layer 1611, although it may also extend into a metallic
interlayer 16' and/or into the metallic substrate 4 so that
metallic material may likewise sometimes be ablated with
shorter pulse lengths.
In particular for producing the lower region 10 of the hole 7,
longer, in particular temporally constant pulse lengths are
used for the most part or entirely. The time to produce the
lower region 10 corresponds for example to the last ablation
steps in the method.
When using longer pulse lengths, the at least one laser 19,
19', 19" with its laser beams 22, 22', 2211 is preferably not
displaced to and fro in the plane 43. Since the energy is
distributed owing to thermal conduction in the material of the
layer 16 or of the substrate 4 and new energy is added by each
laser pulse, material is ablated over a large area by material
evaporation in such a way that the area in which the material
is ablated corresponds approximately to the cross-sectional
area A of the through-hole 7, 10 to be produced. This cross-
sectional area may be adjusted via the energy power and pulse
duration as well as the guiding of the laser beam 22 (position
of the focus at a horizontal distance from the surface 14).
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The laser pulse lengths of a single laser 19 or a plurality of
lasers 19', 19" may for example be varied continuously, for
example from the start to the end of the method. The method
begins with the ablation of material on the outer surface 14
and ends when the desired depth of the hole 7 is reached.
The layer is for example ablated progressively layer-by-layer
in planes 11 (Fig. 6) and in an axial direction 15.
Likewise, the pulse lengths may also be varied discontinuously.
Preferably only two different pulse lengths are used during the
method. For the shorter pulse lengths (for example < 500 ns)
the at least one laser 19, 19' is displaced, and for the longer
pulse lengths (for example 0.4 ms) for example it is not
displaced because the energy input in any case takes place over
a larger area than corresponds to the cross section of the
laser beam owing to thermal conduction.
During the processing, the remaining part of the surface may be
protected by a powder layer, in particular by masking according
to EP 1 510 593 Al. The powder (BN, Zr02) and the particle size
distribution according to EP 1 510 593 Al are part of this
disclosure for the use of masking.
This is expedient in particular when processing a metallic
substrate or a substrate with a metallic layer, which does not
yet have a ceramic layer.
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Laser Parameters
When using pulses with a particular pulse length, the output
power of the laser 19, 19', 1911 is for example constant.
For the longer pulse lengths, an output power of the laser 19,
19', 19" in excess of 100 watts, in particular 500 watts, is
used.
For the shorter pulse lengths, an output power of the laser 19,
19' less than 300 watts is used.
A laser 19, 19' with a wavelength of 532 nm is for example used
only to generate shorter laser pulses.
For the longer pulse lengths, in particular a laser pulse of
> 0.4 ms, in particular up to 1.2 ms, and an energy (joules) of
the laser pulse from 6 J to 21 J, in particular > 10 J, is
used, a power (kilowatts) of from 10 kW to 50 kW, in particular
20 kW, being preferred.
The shorter laser pulses have an energy in the single-figure or
two-figure millijoule (mJ) range, preferably in the single-
figure millijoule range, the power used usually lying
particularly in the single-figure kilowatt range.
Number of Lasers
The method may employ one laser, or two or more lasers 19',
191, which are used simultaneously or successively. The similar
or different lasers 19, 19', 191 have for example different
ranges in respect of their laser pulse lengths. For example a
first laser 19' may generate laser pulse lengths of less than
or equal to 500 ns, in particular less than 100 ns, and a
second laser 1911 may generate laser pulse lengths of more than
100 ns, in particular more than 500 ns.
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In order to produce a hole 7, the first laser 19' is used
first. The second laser 19" is then used for the further
processing, or vice versa.
For producing the through-hole 7, it is also possible to use
only one laser. In particular, a laser 19 is used which for
example has a wavelength of 1064 nm and can generate both the
longer laser pulses and the shorter laser pulses.
Sequence of Hole Regions to be Produced
Figure 7 shows a cross section through a hole 7.
Here, coarse processing is initially carried out with laser
pulse lengths of more than 100 ns, in particular more than 500
ns, and fine processing is carried out with laser pulse lengths
of less than or equal to 500 ns, in particular less than or
equal to 100 ns.
The lower region 10 of the hole 7 is processed fully and only a
region of the diffusor 13 is processed for the most part with a
laser 19 which has laser pulse lengths of more than 100 ns, in
particular greater than or equal to 500 ns (first ablation
steps).
In order to fabricate the hole 7 or the diffusor 13, only a
thin outer edge region 28 in the vicinity of the diffusor 13
still needs then needs to be processed by means of a laser 19,
19', 19" which can generate laser pulse lengths of less than
or equal to 500 ns, in particular less than 100 ns (last
ablation steps).
The laser beam 22, 22', 2211 is preferably displaced in this
case.
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Figure 8 shows a plan view of a hole 7 of the component 1.
The various lasers 19, 19', 19" or the different laser pulse
lengths of these lasers 19, 19', 19" are used in different
ablation steps.
First, for example, coarse processing is carried out with long
laser pulse lengths (> 100 ns, in particular > 500 ns). The
majority of the hole 7 is thereby produced. This in a region is
denoted by the reference 25. Only an outer edge region 28 of
the hole 7 or of the diffusor 13 must now be removed in order
to reach the final dimensions of the hole 7.
The laser beam 22, 22' is in this case displaced in the plane
of the surface 14.
The hole 7 or the diffusor 13 is not completed until the outer
edge region 28 has been processed by means of a laser 19, 19'
with shorter laser pulse lengths (<- 500 ns, in particular < 100
ns).
The contour 29 of the diffusor 13 is thus produced by shorter
laser pulses, so that the outer edge region 28 is ablated more
finely and more exactly and is therefore free from cracks and
melting.
The material is for example ablated in a plane 11
(perpendicularly to the axial direction 15).
Likewise, for the longer pulse lengths, the cross section A of
the region to be ablated when producing the hole 7 may be
reduced continuously in the depth direction of the substrate 4
to A', so that the outer edge region 28 is made smaller
compared with Figure 7 (Fig. 9). This is done by adjustments of
energy and pulse duration.
An alternative for producing the hole 7 consists in initially
producing the outer edge region 28 with shorter laser pulse
lengths (- 500 ns) to a depth in the axial direction 15 which
corresponds partly or fully to an extent of the diffusor 13 of
the hole 7 in this direction 15 (Fig. 10, the inner region 25
is indicated by dashes).
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The laser beam 22, 22' is displaced in the plane of the surface
14 in these first ablation steps.
Virtually no melting is therefore generated in the region of
the interface of the diffusor 13 and no cracks are formed
there, and exact geometries can thus be generated.
Only then is the inner region 25 ablated with longer pulse
lengths (> 100 ns, in particular > 500 ns) (last ablation
steps).
The method may be applied to newly produced components 1, which
have been cast for the first time.
The method may likewise be used for components 1 to be
refurbished.
Refurbishment means that components 1, which have been in use,
are for example separated from layers and are recoated again
after repair, for example filling cracks and removing oxidation
and corrosion products.
Here, for example, contaminants or coating material which has
been applied again (Fig. 11) and has entered the holes 7, is
removed by a laser 19, 19'. Alternatively, special shapes
(diffusors) are newly produced in the layer region after
recoating during the refurbishment.
Refurbishment
Figure 11 shows the refurbishment of a hole 7, wherein material
has penetrated into the already existing hole 7 during coating
of the substrate 4 with the material of the layer 16.
For example, the more deeply lying regions in the vicinity 10
of the hole 7 may be processed with a laser which has pulse
lengths of more than 100 ns, in particular more than 500 ns.
These regions are denoted by 25.
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The more critical edge region 28, for example in the vicinity
of the diffusor 13 on which contamination is present, is
processed by a laser 19' which has laser pulse lengths of less
than or equal to 500 ns, in particular less than 100 ns.
Device
Figures 12 to 15 show exemplary devices 40, in particular for
carrying out the method according to the invention.
The devices 40 consist of at least one optical component 35,
35', in particular at least one lens 35, 35' which directs at
least one laser beam 22, 22', 221 onto the substrate 4 in
order to produce the hole 7.
There are one, two or more lasers 19, 19', 191 . The laser
beams 22, 22', 2211 may be guided to the optics 35, 35' via
mirrors 31, 33.
The mirrors 31, 33 can be moved or rotated so that, for
example, only one laser 19', 191 can respectively send its
laser beams 22' or 2211 via the mirror 31 or 33 and the lens 35
onto the component 1.
The component 1, 120, 130, 155 or the optics 35, 35' or the
mirrors 31, 33 can be displaced in a direction 43 so that the
laser beam 22, 22' is displaced over the component 1, for
example according to Figure 5.
The lasers 19, 19', 19" may for example have a wavelength of
either 1064 nm or 532 nm. The lasers 19', 19" may have
different wavelengths: 1064 nm and 532 nm.
In respect of pulse length, the laser 19' is for example
adjustable to pulse lengths of 0.1 - 5 ms; conversely, the
laser 1911 to pulse lengths of 50 - 500 ns.
By moving the mirrors 31, 33 (Figs 12, 13, 14), the beam of the
laser 19', 19 " having those laser pulse lengths which are
required, for example to produce the outer edge region 28 or
the inner region 25, can respectively be delivered via the
optics 35 onto the component 1.
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Figure 12 shows two lasers 19', 191 1, two mirrors 31, 33 and
one optical component in the form of the lens 35.
If for example the outer edge region 28 is initially produced
according to Figure 6, then the first laser 19' with the
shorter laser pulse lengths will be connected up.
If the inner region 25 is then produced, then the first laser
19' will be disconnected by moving the mirror 31 and the second
laser 19" with its longer laser pulse lengths will be
connected up by moving the mirror 33.
Figure 13 shows a similar device as in Figure 12, although here
there are two optical components, here for example two lenses
35, 35', which make it possible to direct the laser beams 22',
2211 of the lasers 19', 19" simultaneously onto different
regions 15, 28 of the component 1, 120, 130, 155.
If for example an outer edge region 28 is being produced, the
laser beam 22' may be directed onto a first position of this
sleeve-shaped region 28 and onto a second position
diametrically opposite the first position, so that the
processing time is shortened considerably.
The optical component 35 may be used for the first laser beam
22' and the second optical component 35' for the second laser
beam 22 " .
According to this device 40, the lasers 19', 19" may be used
successively or simultaneously with equal or different laser
pulse lengths.
In Figure 14 there are no optical components in the form of
lenses, instead only mirrors 31, 33 which direct the laser
beams 22', 2211
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onto the component 1 and, by movement, are used to displace the
at least one laser beam 22', 2211 in a plane over the
component.
The lasers 19', 1911 may likewise be used simultaneously here.
According to this device 40, the lasers 191, 19" may be used
successively or simultaneously with equal or different laser
pulse lengths.
Figure 15 shows a device 40 with only one laser 19 in which the
laser beam 22 is directed for example via a mirror 31 onto a
component 1.
Here again, an optical component for example in the form of a
lens is not necessary. The laser beam 22 is for example
displaced over the surface of the component 1 by moving the
mirror 31. This is necessary when using shorter laser pulse
lengths. For the longer laser pulse lengths the laser beam 22
to need not necessarily be displaced, so that the mirror 31 is
not moved as it is in the method stage.
Nevertheless, a lens or two lenses 35, 35' may likewise be used
in the device according to Figure 15 in order to direct the
laser beam simultaneously onto different regions 25, 28 of the
component 1, 120, 130, 155.
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Components
Figure 16 shows a gas turbine 100 by way of example in a
partial longitudinal section.
The gas turbine 100 internally comprises a rotor 103, which
will also be referred to as the turbine rotor, mounted so as to
rotate about a rotation axis 102 and having a shaft 101.
Successively along the rotor 103, there are an intake manifold
104, a compressor 105, an e.g. toroidal combustion chamber 110,
in particular a ring combustion chamber, having a plurality of
burners 107 arranged coaxially, a turbine 108 and the exhaust
manifold 109.
The ring combustion chamber 110 communicates with an e.g.
annular hot gas channel 111. There, for example, four
successively connected turbine stages 112 form the turbine 108.
Each turbine stage 112 is formed for example by two blade
rings. As seen in the flow direction of a working medium 113, a
guide vane row 115 is followed in the hot gas channel 111 by a
row 125 formed by rotor blades 120.
The guide vanes 130 are fastened on an inner housing 138 of a
stator 143 while the rotor blades 120 of a row 125 are fitted
on the rotor 103, for example by means of a turbine disk 133.
Coupled to the rotor 103, there is a generator or a work engine
(not shown).
During operation of the gas turbine 100, air 135 is taken in
and compressed by the compressor 105 through the intake
manifold 104. The compressed air provided at the end of the
compressor 105 on the turbine side is delivered to the burners
107 and mixed there with a fuel. The mixture is then burnt to
form the working medium 113 in the combustion chamber 110. From
there,
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the working medium 113 flows along the hot gas channel 111 past
the guide vanes 130 and the rotor blades 120. At the rotor
blades 120, the working medium 113 expands by imparting
momentum, so that the rotor blades 120 drive the rotor 103 and
the work engine coupled to it.
During operation of the gas turbine 100, the components exposed
to the hot working medium 113 experience thermal loads. Apart
from the heat shield elements lining the ring combustion
chamber 110, the guide vanes 130 and rotor blades 120 of the
first turbine stage 112, as seen in the flow direction of the
working medium 113, are heated the most.
In order to withstand the temperatures prevailing there, they
may be cooled by means of a coolant.
Substrates of the components may likewise comprise a
directional structure, i.e. they are monocrystalline (SX
structure) or comprise only longitudinally directed grains (DS
structure).
Iron-, nickel- or cobalt-based superalloys used as material for
the components, in particular for the turbine blades 120, 130
and components of the combustion chamber 110.
Such superalloys are known for example from EP 1 204 776 Bl, EP
1 306 454, EP 1 319 729 Al, WO 99/67435 or WO 00/44949 are
used; with respect to the chemical composition of the alloys,
these documents are part of the disclosure.
The guide vane 130 comprises a guide vane root (not shown here)
facing the inner housing 138 of the turbine 108, and a guide
vane head lying opposite the guide vane root. The guide vane
head faces the rotor 103 and is fixed on a fastening ring 140
of the stator 143.
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Figure 17 shows a perspective view of a rotor blade 120 or
guide vane 130 of a turbomachine, which extends along a
longitudinal axis 121.
The turbomachine may be a gas turbine of an aircraft or of a
power plant for electricity generation, a steam turbine or a
compressor.
The blade 120, 130 comprises, successively along the
longitudinal axis 121, a fastening zone 400, a blade platform
403 adjacent thereto as well as a blade surface 406 and a blade
tip 415.
As a guide vane 130, the vane 130 may have a further platform
(not shown) at its vane tip 415.
A blade root 183 which is used to fasten the rotor blades 120,
130 on a shaft or a disk (not shown) is formed in the fastening
zone 400.
The blade root 183 is configured, for example, as a hammerhead.
Other configurations as a fir-tree or dovetail root are
possible.
The blade 120, 130 comprises a leading edge 409 and a trailing
edge 412 for a medium which flows past the blade surface 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 Al, WO 99/67435 or WO 00/44949; with
respect to the chemical composition of the alloy, these
documents are part of the disclosure.
The blades 120, 130 may in this case be manufactured by a
casting method, also by means of directional solidification, by
a forging
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method, by a machining method or combinations thereof.
Workpieces with a monocrystalline structure or structures are
used as components for machines which are exposed to heavy
mechanical, thermal and/or chemical loads during operation.
Such monocrystalline workpieces are manufactured, for example,
by directional solidification from the melts. These are casting
methods in which the liquid metal alloy is solidified to form a
monocrystalline structure, i.e. to form the monocrystalline
workpiece, or is directionally solidified.
Dendritic crystals are in this case aligned along the heat flux
and form either a rod crystalline grain structure (columnar,
i.e. grains which extend over the entire length of the
workpiece and in this case, according to general terminology
usage, are referred to as directionally solidified) or a
monocrystalline structure, i.e. the entire workpiece consists
of a single crystal. It is necessary to avoid the transition to
globulitic (polycrystalline) solidification in these methods,
since nondirectional growth will necessarily form transverse
and longitudinal grain boundaries which negate the beneficial
properties of the directionally solidified or monocrystalline
component.
When directionally solidified structures are referred to in
general, this is intended to mean both single crystals which
have no grain boundaries or at most small-angle grain
boundaries, and also rod crystal structures which, although
they do have grain boundaries extending in the longitudinal
direction, do not have any transverse grain boundaries. These
latter crystalline structures are also referred to as
directionally solidified structures.
Such methods are known from US-A 6,024,792 and EP 0 892 090 Al;
with respect to the solidification method, these documents are
part of the disclosure.
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The blades 120, 130 may likewise have coatings against
corrosion or oxidation, for example (MCrAlX; M is at least one
element from 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 rare earth element, or hafnium (Hf)). Such
alloys are known from EP 0 486 489 B1, EP 0 786 017 B1, EP 0
412 397 Bl or EP 1 306 454 Al which, with respect to the
chemical composition of the alloy, are intended to be part of
this disclosure.
The density may preferably be 95% of the theoretical density.
A protective aluminum oxide layer (TGO = thermal grown oxide
layer) is formed on the MCrAlX layer (as an interlayer or as
the outermost layer).
On the MCrAlX, there may furthermore be a thermal barrier
layer, which is preferably the outermost layer and consists for
example of Zr02, Yz03-ZrO2, i.e. it is not stabilized or is
partially or fully stabilized by yttrium oxide and/or calcium
oxide and/or magnesium oxide.
The thermal barrier layer covers the entire MCrAlX layer.
Rod-shaped grains are produced in the thermal barrier layer by
suitable coating methods, for example electron beam deposition
(EB-PVD).
Other coating methods may be envisaged, for example atmospheric
plasma spraying (APS), LPPS, VPS or CDV. The thermal barrier
layer may comprise produces porous, micro- or macro-cracked
grains for better thermal shock resistance. The thermal barrier
layer is thus preferably more porous than the MCrAlX layer.
The blade 120, 130 may be designed to be hollow or solid.
If the blade 120, 130 is intended to be cooled, it will be
hollow and optionally also comprise film cooling holes 418
(indicated by dashes) which are produced by the method
according to the invention.
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Figure 18 shows a combustion chamber 110 of a gas turbine 100.
The combustion chamber 110 is designed for example as a so-
called ring combustion chamber in which a multiplicity of
burners 107, which produce flames 156 and are arranged in the
circumferential direction around a rotation axis 102, open into
a common combustion chamber space 154. To this end, the
combustion chamber 110 as a whole is designed as an annular
structure which is positioned around the rotation axis 102.
In order to achieve a comparatively high efficiency, the
combustion chamber 110 is designed for a relatively high
temperature of the working medium M, i.e. about 1000 C to
1600 C. In order to permit a comparatively long operating time
even under these operating parameters which are unfavorable for
the materials, the combustion chamber wall 153 is provided with
an inner lining formed by heat shield elements 155 on its side
facing the working medium M.
Owing to the high temperatures inside the combustion chamber
110, a cooling system may also be provided for the heat shield
elements 155 or for their retaining elements. The heat shield
elements 155 are then hollow, for example, and optionally also
have film cooling holes (not shown) opening into the combustion
chamber space 154, which are produced by the method according
to the invention.
Each heat shield element 155 made of an alloy is equipped with
a particularly heat-resistant protective layer (MCrAlX layer
and/or ceramic coating) on the working medium side, or is made
of refractory material (solid ceramic blocks).
These protective layers may be similar to the turbine blades,
i.e. for example MCrAlX means: M is at least one element from
the group iron (Fe), cobalt (Co), nickel (Ni), X is an active
element and stands for yttrium (Y) and/or
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2005P20091WOUS
silicon and/or at least one rare earth element, 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 Al which, with respect to
the chemical composition of the alloy, are intended to be part
of this disclosure.
On the MCrAlX, there may furthermore be an e.g. ceramic thermal
barrier layer which consists for example of Zr02, Y203-ZrO2,
i.e. it is not stabilized or is partially or fully stabilized
by yttrium oxide and/or calcium oxide and/or magnesium oxide.
Rod shaped grains are produced in the thermal barrier layer by
suitable coating methods, for example electron beam deposition
(EB-PVD).
Other coating methods may be envisaged, for example atmospheric
plasma spraying (APS), LPPS, VPS or CVD. The thermal barrier
layer may comprise porous, micro- or macro-cracked grains for
better thermal shock resistance.
Refurbishment means that turbine blades 120, 130 and heat
shield elements 155 may need to have protective layers taken
off (for example by sandblasting) after their use. The
corrosion and/or oxidation layers or products are then removed.
Optionally, cracks in the turbine blade 120, 130 or the heat
shield element 155 are also repaired. The turbine blades 120,
130 or heat shield elements 155 are then recoated and the
turbine blades 120, 130 or the heat shield elements 155 are
used again.
