U.S. patent application number 11/636682 was filed with the patent office on 2007-12-20 for component comprising a masking layer.
This patent application is currently assigned to SIEMENS AKTIENGESELLSCHAFT. Invention is credited to Nigel-Philip Cox, Oliver Dernovsek, Ralph Reiche.
Application Number | 20070292719 11/636682 |
Document ID | / |
Family ID | 28051773 |
Filed Date | 2007-12-20 |
United States Patent
Application |
20070292719 |
Kind Code |
A1 |
Cox; Nigel-Philip ; et
al. |
December 20, 2007 |
Component comprising a masking layer
Abstract
Masking layers for components according to the prior art react
with the base material of the component and/or are difficult to
remove again. The component according to the invention has a
masking layer which can very easily be removed following coating of
the components, since on the one hand the bonding between the
masking layer and the base material of the component is poor, or
the masking layer can easily be removed through penetration of a
liquid.
Inventors: |
Cox; Nigel-Philip; (Berlin,
DE) ; Dernovsek; Oliver; (Munchen, DE) ;
Reiche; Ralph; (Berlin, DE) |
Correspondence
Address: |
SIEMENS CORPORATION;INTELLECTUAL PROPERTY DEPARTMENT
170 WOOD AVENUE SOUTH
ISELIN
NJ
08830
US
|
Assignee: |
SIEMENS AKTIENGESELLSCHAFT
|
Family ID: |
28051773 |
Appl. No.: |
11/636682 |
Filed: |
December 8, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10511250 |
Oct 8, 2004 |
7163747 |
|
|
PCT/EP03/03283 |
Mar 28, 2003 |
|
|
|
11636682 |
Dec 8, 2006 |
|
|
|
Current U.S.
Class: |
428/701 |
Current CPC
Class: |
Y10T 428/31504 20150401;
Y10T 428/31536 20150401; Y10T 428/25 20150115; C23C 10/04 20130101;
C23C 16/042 20130101; Y10T 428/31663 20150401; C23C 4/01 20160101;
C23C 8/04 20130101 |
Class at
Publication: |
428/701 |
International
Class: |
B32B 9/00 20060101
B32B009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 10, 2002 |
EP |
02008045.3 |
Claims
1-32. (canceled)
33. A turbine component, comprising: a masking layer arranged on a
portion of the component that contains carbon at an outer surface
of the masking layer; and a plurality of material layers arranged
on the masking layer that forms a ceramic layer or a ceramic
precursor layer on the component and the plurality of material
layers chemically reacts with the masking layer to aid in the
removal of a portion of the masking layer material.
34. The turbine component as claimed in claim 33, wherein the
turbine component is a blade or vane.
35. The turbine component as claimed in claim 33, wherein the
material layers are a ceramic thermal barrier coating.
36. The turbine component as claimed in claim 35, wherein the
thermal barrier coating comprises a bond coat.
37. The turbine component as claimed in claim 33, wherein the
masking layer comprises three sub-layers, a first sub-layer
arranged on a base material of the component and provides bonding
to the base material of the component, a second gradient sub-layer
arranged on the first sub-layer, and a third reactive sub-layer
arranged on the gradient layer and adapted to react with the layers
of material applied to the component.
38. The turbine component as claimed in claim 37, wherein the first
sub-layer comprises carbosilane.
39. The turbine component as claimed in claim 37, wherein the
gradient layer comprises polysiloxane, a metal, or a metal-ceramic
composite.
40. The turbine component as claimed in claim 37, wherein the
gradient layer comprises polysiloxane, the metal, and a
metal-ceramic composite.
41. The turbine component as claimed in claim 37, wherein a filler
material is added to the gradient sub-layer to inhibit
thermo-mechanical stresses in the masking layer.
42. The turbine component as claimed in claim 41, wherein a filler
material is added to the gradient sub-layer to prevent
thermo-mechanical stresses in the masking layer.
43. The turbine component as claimed in claim 37, wherein a filler
material is added to the gradient sub-layer to inhibit
thermo-mechanical stresses between the masking layer and a
substrate of the component.
44. The component as claimed in claim 33, wherein the masking layer
is a gradient layer.
45. A turbine blade or vane, comprising: a first functional layer
arranged on a base material of the component that promotes bonding
to the component base material; a gradient layer arranged on the
first functional layer that promotes a dense and a crack free
coating of the component; and a reactive layer arranged to the
gradient layer that reacts with the first functional and gradient
layers to promote removal of the first functional and gradient
layers.
46. The turbine blade or vane as claimed in claim 45, wherein the
reactive layer reacts with the gradient layers to form a water
soluble layer.
47. The turbine blade or vane as claimed in claim 45, wherein the
first functional layer comprises carbosilane.
48. The turbine blade or vane as claimed in claim 45, wherein the
gradient layer comprises polysiloxane, a metal, and a metal-ceramic
composite.
49. The turbine blade or vane as claimed in claim 45, wherein the
first functional layer is applied to a portion of the base
material.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP03/03283, filed Mar. 28, 2003 and claims the
benefit thereof. The International Application claims the benefits
of European application No. 02008045.3 EP filed Apr. 10, 2002, both
of the applications are incorporated by reference herein in their
entirety.
FIELD OF THE INVENTION
[0002] The invention relates generally to a coated component having
a masking layer.
BACKGROUND OF THE INVENTION
[0003] Components, such as for example turbine blades and vanes, in
particular for gas turbines, are coated in particular in the main
blade region, since they are exposed to high thermal loads.
[0004] Lower temperatures prevail in the base or securing region of
the turbine blade or vane, and consequently there is no need for a
coating in the form of a thermal barrier coating there. Ceramic
coatings are even undesirable in this region, since the base has to
be fitted accurately into a metallic disk.
[0005] Masks in accordance with the prior art which are intended to
prevent coating are often difficult to remove again, since the
material of the mask bonds well to the base material of the turbine
blade or vane or there is an undesired diffusion of elements out of
the masking layer into the base material of the turbine blade or
vane.
SUMMARY OF THE INVENTION
[0006] Therefore, it is an object of the present invention to
provide a masking layer which, following desired coating of the
turbine blade or vane, can easily be removed again in the undesired
regions without the base material or the geometry of the turbine
blade or vane being affected in the masked region.
[0007] The object is achieved by a turbine blade or vane as
described in the claims. A ceramic is applied direct to the base
material of the turbine blade or vane.
[0008] Thermal barrier coatings which are applied to a turbine
blade or vane in the main blade region generally have intermediate
layers between a substrate, i.e. the base material of the turbine
blade or vane, and the thermal barrier coating, such as for example
what are known as bonding layers, for example metallic MCrAlY, or
diffusion barriers.
[0009] These intermediate layers are dispensed with at the masking
in order to prevent good bonding of the masking layer. The masking
layer is formed in particular from ceramic, since the brittle
ceramic can be removed by simple processes, such as for example
sand blasting, dry ice blasting. The material for the ceramic is
selected in such a way that there is little or no diffusion from
the ceramic into the substrate.
[0010] The object of the invention is also achieved by a turbine
blade or vane as described in the claims. The masking layer reacts
with the material of the material that is to be applied and is
therefore easy to remove.
[0011] Further advantageous configurations of the component
according to the invention as described in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] In the drawing:
[0013] FIG. 1 shows a turbine blade or vane in accordance with the
prior art,
[0014] FIG. 2 shows process steps involved in the production of a
coating in accordance with the prior art,
[0015] FIG. 3 shows a masking layer of a turbine blade or vane
according to the invention,
[0016] FIG. 4 shows a further masking layer of a turbine blade or
vane according to the invention,
[0017] FIGS. 5, 6 show a masking layer which reacts with material
of layers which are to be applied, and FIGS. 7, 8 show how the
masking layer can easily be removed again following a reaction.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Identical reference numerals have the same meaning
throughout the various figures.
[0019] FIG. 1 shows a perspective view of a turbine blade or vane
1, in particular a rotor blade for a gas turbine, which extends
along a longitudinal axis 4. In succession along the longitudinal
axis 4, the turbine blade 1 has a securing region 7, an adjoining
blade platform 10 and a main blade region 13.
[0020] The securing region 7 is designed as a blade root 16 which
is used to secure the turbine blade 1 to a shaft (not shown in more
detail) of a turbine machine (likewise not shown in more detail).
The blade root 16 is designed, for example, in the form of a
hammerhead. Other configurations, for example as a fir-tree root or
dovetail root are also possible.
[0021] In conventional turbine blades 1, solid metallic materials,
in particular nickel- or cobalt-base superalloys, are used in all
regions of the turbine blade. The turbine blade may in this case be
produced by a casting process, by a forging process, by a milling
process or by combinations of the above.
[0022] In particular the securing region 7 is made from metal,
since this region is clamped in an accurately fitting manner into a
corresponding shape in a disk. Brittle ceramic coatings would flake
off and alter the geometry in the securing region.
[0023] The main blade region 13 is coated, for example, with a
thermal barrier coating, it being possible for further layers, such
as for example bonding layers (MCrAlY layers), to be arranged
between the base material of the turbine blade 1.
[0024] A component according to the invention in the form of a
turbine blade or vane 1 may be a guide vane or rotor blade of any
desired turbine, in particular a steam or gas turbine.
[0025] FIG. 2 shows what happens when the surface of the blade 1
does not have a masking layer 25 (FIG. 3). The material 22 of an
interlayer 19 (MCrAlY), which has been applied in any desired form
to a surface of the turbine blade 1, for example by plasma
spraying, by PVD or CVD or by dipping in a liquid metal or
application of powder, so as to form the interlayer 19, leads to a
reaction of the material 22 with the turbine blade 1 and to good
bonding of the interlayer 19 to the base material of the turbine
blade 1.
[0026] When the interlayer 19 is to be removed again, for example
because it is undesired in the securing region 7, it therefore
presents considerable problems, since the geometry of the securing
region 7 changes as a result of partial removal of the base
material of the substrate 40.
[0027] FIG. 3 shows a component according to the invention in the
form of a turbine blade 1 with a masking layer 25. By way of
example, first of all a first functional layer 28 is applied to the
turbine blade 1. This first functional layer is, for example, a
polycarbosilane layer with a thickness in the nanometer range,
which crosslinks at 200.degree. C. in air, allowing good bonding to
the base material 40 of the turbine blade 1.
[0028] By way of example, a gradient layer 31 is applied to the
first functional layer 28, the material used for the gradient layer
31 being a mixture of polysiloxane and a metal-ceramic and/or
metal.
[0029] The gradient layer 31 may, for example, be applied in the
form of a slip with layer thicknesses of 10-30 .mu.m and can
likewise be crosslinked at approximately 200.degree. C. in air.
[0030] A further powder, in particular of the composition MCrAlY,
where M stands for Fe, Co, Ni, is added as a metallic filler to
this material of the gradient layer 31, since such a filler, on
account of its expansion coefficient, is used as an interlayer
(bonding layer) between base material 40 and ceramic thermal
barrier coating.
[0031] A reactive layer 34, consisting, for example, of a pure
carbon precursor, is applied to the gradient layer. The
crosslinking within the reactive layer 34 takes place at
180.degree. C. in air.
[0032] The crosslinked layers 28, 31, 34 are converted into a
ceramic by what is known as the pyrolysis process as a result of a
heat treatment at 1000.degree. C. under an argon atmosphere. On
account of the change in density of the organometallic precursor,
such as for example the polysiloxane, having a density of 1
g/cm.sup.3, to a silicon oxicarbide phase (SiOC) with a density of
approx. 2.3 g/cm.sup.3, a 10-30 .mu.m thick, dense and crack-free
coating is not possible. Therefore, metallic or ceramic fillers are
added to the polymer, for example in a proportion of 30-50% by
volume, in order to deliberately control the phase transformation
of the polymer and the crack formation which are taking place and
to minimize or eliminate the thermomechanical stresses caused by
different coefficients of thermal expansion at the interface
between metal (turbine blade 1) and masking layer 25.
[0033] The required thermal stability of the masking layer is
provided by the thermal phase transformation of the polycarbosilane
into the corresponding high-temperature-resistant SiOC or graphite
phase.
[0034] During the coating process, a material 22 is applied to the
main blade region 13 of the turbine blade 1 and to the masking
layer 25. The material 22 reacts with the reactive layer 34 to form
a reaction layer 43, i.e. to form a material which is able to
withstand high temperatures but, for example, is soluble in water,
i.e. can easily be removed.
[0035] The material 22 is, for example, aluminum, which is applied
to the turbine blade 1 in order to form an aluminide layer. An
aluminide layer of this type can be applied by plasma spraying or
processes as described in EP patent 0 525 545 B1 and EP patent 0
861 919 B1.
[0036] In the case of aluminum, the carbon of the reactive layer 34
reacts with aluminum to form Al.sub.4C.sub.3. If the main blade
region 13 is completely coated, the entire blade, in particular the
securing region 7, can be introduced into water, with the result
that the water-soluble reaction layer 43 which has reacted with the
material 22 is dissolved.
[0037] The underlying layers 28, 31 can easily be removed by dry
ice blasting, and consequently the removal processes do not cause
any change in the geometry in the securing region 7. Aluminum is
applied to a turbine blade 1 during refurbishment for example, i.e.
inter alia during removal of used MCrAlY layers.
[0038] As an alternative to the three-layer structure shown here by
way of example, the masking layer 25 may also be a gradient layer
which has a graduated structure, i.e. on the substrate 40 the
composition is selected in such a way as to allow good bonding, and
at the outer surface the composition is such that it reacts with
the material 22 of layers which are yet to be applied.
[0039] FIG. 4 shows a component according to the invention in the
form of a turbine blade 1 having a masking layer 25.
[0040] A ceramic layer 37, which forms the masking layer 25, is
applied direct to the, for example, metallic turbine blade 1.
[0041] This ceramic layer may, for example, be an oxide ceramic
which is matched to the coefficient of thermal expansion of the
substrate.
[0042] There are no further layers, in particular no bonding
layers, between the ceramic layer 37 and the metallic substrate 40
of the turbine blade 1, and consequently the ceramic layer 25, 37
can be removed by gentle introduction of energy, such as for
example sand blasting or dry ice blasting. The dense ceramic layer
37 also forms a diffusion barrier during a process of coating the
turbine blade 1 with other layers, such as for example bonding
layers or thermal barrier coatings.
[0043] The masking layer 25 may also only react with the material
22 of layers which are yet to be applied, for example to form a
brittle layer 43, for example a ceramic layer 37. The ceramic layer
37 may also form only after a further heat treatment (pyrolysis),
by way of example.
[0044] Brittle layers 43 of this type can be removed by simple
processes, such as thermal shock processes or sand blasting or dry
ice blasting, i.e. by blasting processes which introduce energy but
do not have an abrasive action.
[0045] It is particularly advantageous if the masking layer 25
reacts with the material 22 of layers which are to be applied to
form a water-soluble layer 43.
[0046] Further layers may in this case be present beneath the top
layer of the masking layer, i.e. the masking layer 25 may be a
multilayer structure. In this case, it is possible for a joining
layer to be applied direct to the substrate 40 of the coated
component and for a gradient layer also to be applied, allowing
matching to coefficients of thermal expansion, so that the masking
layer 25 remains crack-free even during masking, and consequently
it is impossible for any material to reach the substrate 40 of the
component which is to be coated.
[0047] FIG. 5 shows a turbine blade 1 having a substrate 40 to
which a masking layer 25 has been applied. The material of the
masking layer does not react and diffuse with the material of the
substrate 40 at the elevated temperatures of the coating
process.
[0048] During the coating process, material 22 comes into contact
with the masking layer 25 and reacts with the latter. The reaction
may also take place in a subsequent heat treatment, if the reaction
temperature is higher than the substrate temperature during the
coating operation. The reaction layer 43 which is formed in this
way (FIG. 6) can easily be removed again following the process of
coating the turbine blade, since it is, for example, brittle or
water-soluble. The material 22 therefore also comes into contact
with the unmasked regions of the substrate 40 of the turbine blade
1 and forms a desired coating 55 (FIG. 6).
[0049] FIG. 7 shows a water bath 46 into which a turbine blade
having a water-soluble layer 43 has been introduced. Its water
solubility allows the layer 43 to be removed easily, so that after
the turbine blade 1 has been taken out of the water bath an
uncoated part and a desired coated part 55 of the turbine blade 1
are present. The reaction layer 43 may also be removed by water
blasting, in which case once again a small amount of energy is
introduced.
[0050] The, for example, brittle reaction layer 43 may also be
removed by the introduction of energy from a blasting gun 49
(ultrasound, dry ice blaster, sand blaster) (FIG. 8).
* * * * *