U.S. patent application number 10/972310 was filed with the patent office on 2005-05-26 for electrolytic process for depositing a graduated layer on a substrate, and component.
Invention is credited to Kruger, Ursus, Reiche, Ralph, Steinbach, Jan.
Application Number | 20050109626 10/972310 |
Document ID | / |
Family ID | 34384623 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050109626 |
Kind Code |
A1 |
Kruger, Ursus ; et
al. |
May 26, 2005 |
Electrolytic process for depositing a graduated layer on a
substrate, and component
Abstract
This invention relates to an electrolytic process for the
deposition of a graduated layer on a substrate. The process
includes depositing a composite material having a first constituent
and a second constituent forming a graduated layer on a substrate,
introducing the substrate into an electrolyte for a period of time,
varying the fist and second constituents of the electrolyte during
the period of time to achieve the graduated layer, and using a
current/voltage pulse for the electrolytic deposition such that an
optimized deposition of the constituents occurs.
Inventors: |
Kruger, Ursus; (Berlin,
DE) ; Reiche, Ralph; (Berlin, DE) ; Steinbach,
Jan; (Berlin, DE) |
Correspondence
Address: |
SIEMENS CORPORATION
INTELLECTUAL PROPERTY DEPARTMENT
170 WOOD AVENUE SOUTH
ISELIN
NJ
08830
US
|
Family ID: |
34384623 |
Appl. No.: |
10/972310 |
Filed: |
October 22, 2004 |
Current U.S.
Class: |
205/102 ;
205/238; 428/409 |
Current CPC
Class: |
C25D 5/10 20130101; Y10T
428/31 20150115; C25D 5/20 20130101; F01D 5/005 20130101; C25D 5/00
20130101; C25D 5/18 20130101; C25D 15/02 20130101; C25D 21/14
20130101; F01D 5/288 20130101 |
Class at
Publication: |
205/102 ;
205/238; 428/409 |
International
Class: |
C25D 005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2003 |
EP |
03024373.7 |
Claims
1-22. (canceled)
23. An electrolytic process for depositing a composite material on
a substrate, comprising: introducing the substrate into an
electrolyte containing a first constituent; electrolytically
depositing the first constituent on the substrate to create a first
layer; introducing a second constituent into the electrolyte;
electrolytically depositing the second constituent on the first
layer to create a second layer; varying a concentration of the fist
and second constituents of the electrolyte to achieve a graduated
layer; and using a current/voltage pulse to cause the electrolytic
deposition such that an optimized deposition of the constituents
occurs.
24. The process as claimed in claim 23, wherein the substrate is
arranged in a vessel filled with the electrolyte and the variation
in the composition of the electrolyte during the period of time is
effected by feeding the constituents into the vessel.
25. The process as claimed in claim 23, wherein the substrate is
arranged in the vessel and the variation in the composition of the
electrolyte during the period of time is effected by the
electrolyte comprising the first constituent such that the first
constituent is partially removed and the second constituent being
supplied.
26. The process as claimed in claim 23, wherein the first
constituent is metallic.
27. The process as claimed in claim 23, wherein the first
constituent is an alloy.
28. The process as claimed in claim 23, wherein in the first
constituent is a ceramic.
29. The process as claimed in claim 23, wherein the second
constituent is a ceramic.
30. The process as claimed in claim 23, wherein the second
constituent is metallic.
31. The process as claimed in claim 23, wherein the electrolyte is
mechanically vibrated by an ultrasound probe.
32. The process as claimed in claim 23, wherein the current/voltage
pulse and a time profile are used for the electrolytic
deposition.
33. The process as claimed in claim 23, wherein positive and
negative current/voltage pulses are used for the electrolytic
deposition.
34. The process as claimed in claim 23, wherein a plurality of
current/voltage pulses are combined in a sequence and are used for
the electrolytic deposition.
35. The process as claimed in claim 34, wherein the sequence
comprises different blocks and a block comprises a plurality of
current pulses.
36. The process as claimed in claim 35, wherein the block is
defined by a number of current pulses, a pulse duration, a pulse
interval, a current level, and a time profile.
37. The process as claimed in claim 35, wherein the block is
matched to the first or second constituent of the alloy to optimize
the deposition of the constituent.
38. The process as claimed in claim 35, wherein the block is
matched to the first or second constituent of the alloy to achieve
the optimum composition of the constituents.
39. The process as claimed in claim 23, wherein the layer deposited
on the substrate is an MCrA1/X alloy, where M is an element
selected from the group consisting of iron, cobalt or nickel, and X
is yttrium, or at least one rare earth element.
40. The process as claimed in claim 38, wherein an alloy layer that
is produced and gradients in the material composition are
influenced by a variation in the current/voltage pulse or the
sequence during the period of time.
41. The process as claimed in claim 23, wherein a base current is
superimposed on the current pulses and the intervals.
42. The process as claimed in claim 23, wherein a base current is
superimposed on the current pulses or the intervals.
43. The process as claimed in claim 23, wherein the substrate is a
component of a steam turbine or a gas turbine.
44. The process as claimed in claim 43, wherein the substrate is a
component having no service history or a refurbished component.
45. The process as claimed in claim 23, wherein the current/voltage
pulse to cause the electrolytic deposition creates an optimized
deposition of the constituents occurs.
46. A coated turbine component, comprising: a substrate; a first
layer comprised of a first constituent electrolytically deposited
on the substrate; a second layer comprised of a second constituent
electrolytically deposited on the first layer; and a graduated
layer between the first and second layer produced by varying the
concentration of the first and second constituent with the largest
concentration of the first constituent toward the substrate and the
largest concentration of the second constituent toward the second
layer.
47. The component as claimed in claim 46, wherein a first graduated
layer of a first material is applied to the substrate and a second
graduated layer is applied to the first graduated layer, the
concentration of the first material decreasing in the layer
starting from the substrate.
48. The component as claimed in claim 46, wherein the concentration
of the substrate in the first graduated layer decreases and the
concentration of the first material in the first graduated layer
increases.
Description
[0001] The invention relates to an electrolytic process for the
deposition of a graduated layer on a substrate as claimed in claim
1 and to a component produced using this process as claimed in
claim 21.
[0002] There are various known processes for applying layers to a
substrate. These include, for example, plasma spraying,
electroplating or evaporation coating, inter alia.
[0003] An article by G. Devaray in Bulletin of Electrochemistry 8
(8), 1992, pp. 390-392 entitled "Electro deposited composites--a
review on new technologies for aerospace and other field" gives an
overview of processes for the electrochemical deposition of
layers.
[0004] DE 101 13 767 A1 discloses an electrolytic plating
process.
[0005] DE 39 43 669 C2 discloses a process and an apparatus for
electrolytic surface treatment in which the mass fractions used for
coating are intimately mixed by vibratory motion and/or rotary
motion, so that a uniform electrolytic layer is deposited.
[0006] Further electrolytic processes for coating are known from GB
2 167 446 A, EP 443 877 A1 and from the article by J. Zahavi et al.
in Plating and Surface Finishing, January 1982, pp. 76 ff.
"Properties of electrodeposited composite coatings" in which
undissolved particles in the electrolyte are used to also deposit
these particles in the layer.
[0007] In Electrochemical Society Proceedings Vol. 95-18, pp. 543
ff. von Sarhadi et al. entitled "Development of a low current
density electroplating bath . . . "describes the use of baths which
contain cobalt, nickel or iron compounds.
[0008] U.S. Pat. No. 6,375,823 B1 describes an electrolytic coating
method which uses an ultrasound probe.
[0009] DE 195 45 231 A1 describes a process for the electrolytic
deposition of metal layers in which a pulsed current or pulsed
voltage method is used. However, this is employed only in order to
reduce aging phenomena in deposition baths.
[0010] U.S. 2001/00 54 559 A1 discloses an electrolytic coating
process which uses pulsed currents in order to prevent the
undesired evolution of hydrogen during electrolytic coatings of
metals.
[0011] DE 196 53 681 C2 discloses a process for the electrolytic
deposition of a pure copper layer in which a pulsed current or
pulsed voltage method is used.
[0012] DE 100 61 186 C1 describes a process for electrolytic
deposition in which periodic current pulses are used.
[0013] In the article entitled "Electrodeposited composite coatings
for protection from high temperature corrosion" in Trans IMF 1987,
65, 21 ff, V. Sova describes an electrolytic deposition process in
which particles which are undissolved in the electrolyte are used
for the layer which is to be applied. The use of pulsed currents is
also described.
[0014] Under the conditions of some intended uses, layers applied
with the known processes have poor bonding with respect to the
substrate. Moreover, it is only possible to deposit materials of a
constant composition.
[0015] Therefore, it is an object of the invention to overcome the
abovementioned problems.
[0016] The object is achieved by an electrolytic process for
depositing a graduated layer on a substrate as claimed in claim 1
and a component as claimed in claim 21.
[0017] The variation in the composition of the electrolyte over the
course of time in order to produce graduated layers improves the
bonding of layers to the substrate and if appropriate to one
another, since abrupt transitions in the material can be
avoided.
[0018] Further advantageous configurations of the process and of
the component are listed in the subclaims. The process steps of the
subclaims and the measures aimed at improving the component can
advantageously be combined with one another.
[0019] Exemplary embodiments of the invention are explained in more
detail in the figures, in which:
[0020] FIG. 1 shows an apparatus with which the process according
to the invention can be carried out,
[0021] FIG. 2 shows a sequence of current/voltage pulses which can
be used for a process according to the invention,
[0022] FIG. 3 shows the profile of the process according to the
invention over the course of time,
[0023] FIGS. 4a,b,c show various examples for a gradient layer,
[0024] FIG. 5 shows a gas turbine, and
[0025] FIG. 6 shows a combustion chamber.
[0026] FIG. 1 diagrammatically depicts, by way of example, an
apparatus 1 which can be used to carry out the process according to
the invention. An electrolyte 7, an electrode 10 and a component as
substrate 13 that is to be coated are arranged in a vessel 4.
[0027] The substrate 13 that is to be coated is, for example, a
turbine component (turbine blade or vane 120, 130 (FIG. 5), a
combustion chamber lining 155 (FIG. 6) or another housing part of a
steam or gas turbine 100 (FIG. 5)) made from an iron-, nickel- or
cobalt-base superalloy and may already have a layer (MCrAlX) on its
surface.
[0028] The component 13 may either be newly produced or
refurbished. Refurbishment means that components, after they have
been used, are if appropriate separated from layers (thermal
barrier coating), and corrosion and oxidation products are removed,
for example by an acid treatment (acid stripping). Cracks may also
have to be repaired. Then, a component of this type can be coated
again. Refurbishment is of economic interest since the substrate 13
is very expensive.
[0029] The substrate 13 and the electrode 10 are electrically
conductively connected to a current or voltage source 16 via
electrical supply conductors 19. The current or voltage source 16
can generate pulsed electric currents or voltages (FIG. 2).
[0030] The electrolyte 7 contains, by way of example, the
individual constituents 28, 31 of an alloy which are to be
deposited on the substrate 13. For example, the electrolyte 7
contains the first constituent 28 and the second constituent 31 of
an alloy. The constituents 28, 31 are deposited on the substrate 13
by suitable selection of the process parameters (FIG. 2). The
constituents 28, 31 may be metallic and/or ceramic. It is also
possible for all the constituents to be only metallic or only
ceramic.
[0031] It is also possible for gradients in the chemical
composition to be produced in the layer that is to be produced, by
suitable selection of the process parameters. By way of example, an
alloy MCrAlX is deposited on the substrate 13, M standing for at
least one element selected from the group consisting of iron,
cobalt or nickel. The alloying elements Cr, Al, X and optionally
further elements are introduced either by the addition of suitable
soluble salts to the electrolyte or by the suspension of
fine-grained, insoluble powders in the electroplating bath, which
are deposited as solid particles. By way of example, at least two
constituents are dissolved in the electrolyte 7, for example in the
form of salts.
[0032] A subsequent thermal process allows the deposited layer to
be homogenized or densified or allows specific phases to be set in
the layer.
[0033] An ultrasound probe 22, which may be arranged in the
electrolyte 7 and is controlled by an ultrasound emitter 25,
improves the hydrodynamics and the mixing of the constituents 28,
31 in the region of the substrate 13 and accelerates the deposition
process.
[0034] The current/voltage level, the pulse duration and the pulse
interval can be defined for each constituent 28, 31 of the
alloy.
[0035] FIG. 2 shows an example of a sequence of current pulses
which are repeated. A sequence 34 comprises at least two blocks 37.
Each block 37 comprises at least one, in particular two or more,
current pulses 40. A current pulse 40 is characterized by its
duration t.sub.on, its level I.sub.max and its shape (square-wave,
delta, etc.). Other important process parameters are the intervals
between the individual current pulses 40 (t.sub.off) and the
intervals between the blocks 37.
[0036] The sequence 34 comprises, for example, a first block 37 of
three current pulses 40, between each of which there is an
interval. This is followed by a second block 37, which has a higher
current level and comprises six current pulses 40. After a further
interval, there follow four current pulses 40 in the opposite
direction, i.e. with a reversed polarity, in order to correct the
alloy composition, the hydrogen desorption or to achieve
activation.
[0037] The sequence 34 is finished by a further block 37 of four
current pulses. The sequence 34 can be repeated a number of times
and can also be varied over the course of time.
[0038] The individual pulse times t.sub.on are preferably of the
order of magnitude of approximately 1 to 100 milliseconds. The time
duration of the block 37 is of the order of magnitude of up to 10
seconds, so that up to 5 000 pulses are emitted in one block
37.
[0039] The application of a low potential (base current) both
during the pulse sequences and during the intervals is optionally
possible. This avoids interruption to the electrodeposition, which
may cause inhomogeneities.
[0040] The parameters of a block 37 are matched to a constituent
28, 31 of the alloy, in order to optimize the deposition of this
constituent 28, 31. This can be determined in individual tests. An
optimized block 37 leads to optimized deposition of the constituent
optimized for this block 37, i.e. the duration and nature of the
deposition are improved. However, the other constituents are also
deposited.
[0041] This optimization can be carried out for at least one
further constituent, for example all the constituents 31, of the
alloy. This results in an optimized composition of the constituents
28, 31.
[0042] The proportion of the constituents 28, 31 in the layer that
is to be applied can be defined, for example, by the duration of
the individual blocks 37. Gradients can also be produced in the
layer. This is achieved by correspondingly lengthening or
shortening the parameters of the block 37 which is optimally
matched to a constituent 28, 31.
[0043] It is also possible for further nonalloy constituents, such
as for example secondary phases, to be contained in the electrolyte
7 and deposited.
[0044] FIG. 3 shows the profile of the process according to the
invention over the course of time. The apparatus 1 has an
electrolyte 7, the first constituent 28 of which is, for example,
metallic and has a composition MCrAlX.
[0045] The constituents 28, 31 of the electrolyte 7 are understood
to be particles, dissolved salts, if appropriate with the addition
of wetting agents or additives, which result in the constituents
28, 31 in the layer that is to be produced. An MCrAlX layer is
electrolytically deposited on the component 13 in a known way. Over
the course of time, at least one second, further constituent 31 is
fed into the vessel 4 and to the electrolyte 7, and its
concentration is increased, so that the composition of the
electrolyte 7 changes. This can take place in one step or
alternatively the concentration of the constituent 13 is
continuously increased over the course of time, so that the
percentage concentration of the first constituent 28 decreases. In
this way, the composition of the electrolyte 7 is varied over the
course of time. Therefore, the component 13 does not have to be
introduced into different vessels 4 holding different electrolytes
7. The second constituent 31 may also be present in the electrolyte
7 from the outset and its concentration can then be increased
further. It is also possible to vary the concentration of wetting
agents and further additives.
[0046] If appropriate, in addition to the addition of the
constituent 31, it is also possible for the composition of the
electrolyte 7 to be varied by means of an outlet valve 40 through
which electrolyte 7 containing the constituent 28 is discharged, so
that as a result the concentration of the further constituent 31 in
the electrolyte 7 likewise rises.
[0047] The further constituent 31 is likewise deposited, resulting
in a layer which is graduated according to the increase in the
concentration of the constituent 31. The graduated layer is a
composite material. At the start of the process, a matrix is formed
comprising the constituent 28, and this matrix contains the
secondary phase 31, the proportion of which within the matrix may
vary.
[0048] The proportion of the constituent 31 can also be increased
by, in an inverse arrangement, the matrix being formed by the
constituent 31 and the secondary phase being formed by the
constituent 28.
[0049] FIG. 4 shows, by way of example, layer systems which can
form as a result of the variation in the composition of the
electrolyte 7 over the course of time.
[0050] FIG. 4a shows a substrate 50 on which a layer 53 has been
electrolytically deposited.
[0051] In a first process step, only the constituents 28 were
deposited, as has been explained in connection with the first
process step in FIG. 3. A layer 54, the composition of which
comprises only the constituent 28, is formed. In a further process
step, the concentration of the further constituent 31 was increased
in a step, so that the material composition of the layer 55 to be
deposited changes. Therefore, a further layer 55, which includes
the constituents of the electrolyte 7 comprising the constituents
28, 31, is formed on the layer 54. A layer system 53 is formed.
[0052] Graduated layers can also be produced by continuously
increasing the addition of the constituent 31 in the electrolyte 7
over the course of time t or discharging the electrolyte 7
comprising the constituent 28. The result, therefore, by way of
example, is a layer as illustrated in FIG. 4b. Once again,
initially only a layer which results from the constituent 28 of the
electrolyte has been formed on the substrate 50. A continuous or
discontinuous increase in the constituent 31 in the electrolyte 7
over the course of time causes the concentration (c31) of this
constituent 31 in the layer 55 to increase toward the outside.
[0053] However, it is also possible for the constituent 31 to be
added to the electrolyte 7 from the outset, so that a concentration
gradient is formed starting directly from the substrate 50.
[0054] FIG. 4c shows a further layer system 53, which has been
produced using the process according to the invention. The layer
system 53 has multiply graduated layers 54, 55. For example, in a
first layer 54 on the substrate 50, the concentration of the
material of the substrate 50 decreases in the outward direction to
a defined level, in this case zero, by the end of the layer 54 or
earlier. At the same time, the concentration of the constituent 28
of the first layer 54 rises. After the concentration of the
constituent 28 has reached 100%, for example, the concentration of
the constituent 28 decreases again in the second layer 55. The
concentration of the constituent 28 can drop to zero or a value
other than zero. At the same time, the concentration of the
constituent 31 in the layer 55 rises accordingly.
[0055] The substrate 50 consists, for example, of an iron-, nickel-
or cobalt-base superalloy, the layer 54 may be an MCrAlX layer to
which a ceramic thermal barrier coating 55 (ZrO.sub.2) has been
applied.
[0056] The concentration of the constituents 28, 31 may in addition
also be influenced by varying the deposition parameters, such as
current density, voltage, pulse duration and interval duration, by
these parameters of the current/voltage pulses being specifically
matched to the deposition properties of the constituents 28,
31.
[0057] FIG. 5 shows a longitudinal section through part of a gas
turbine 100.
[0058] 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.
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. The annular combustion chamber 106 is in communication
with an, for example, annular hot-gas duct 111. There, by way of
example, four series-connected turbine stages 112 form the turbine
108. Each turbine stage 112 is formed from two rings of blades or
vanes. As seen in the direction of flow of a working medium 113, a
row 125 formed from rotor blades 120 follows a row 115 of guide
vanes in the hot-gas duct 111.
[0059] The guide vanes 130 are secured to the stator 143, whereas
the rotor blades 120 of a row 125 are mounted on the rotor 103 by
means of a turbine disk 133. A generator or working machine (not
shown) is coupled to the rotor 103.
[0060] While the gas turbine 100 is operating, the compressor 105
sucks in air 135 through the intake housing 104 and compresses this
air. The compressed air provided at the turbine-side end of the
compressor 105 is fed to the burners 107, where it is mixed with a
fuel. The mixture is then burnt so as to form the working medium
113 in the combustion chamber 110. From there, the working medium
113 flows along the hot-gas duct 111 past the guide vanes 130 and
the rotor blades 120. The working medium 113 expands at the rotor
blades 120, transferring its momentum, so that the rotor blades 120
drive the rotor 103 and the latter drives the working machine
coupled to it.
[0061] While the gas turbine 100 is operating, the components which
are exposed to the hot working medium 113 are subject to thermal
loads. 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, and also the heat shield bricks which line the annular
combustion chamber 106, are subject to the highest thermal loads.
In particular, they have a substrate, a directional structure, i.e.
they are single-crystalline (SX) or longitudinally directed
(directionally solidified (DS) structure). To withstand the
temperatures prevailing there, they are cooled by means of a
coolant. It is also possible for the blades and vanes 120, 130 to
have coatings protecting against corrosion (MCrAlX; M=Fe, Co, Ni,
X.dbd.Y, rare earths) and heat (thermal barrier coating, for
example of ZrO.sub.2 or Y.sub.2O.sub.4-ZrO.sub.2 in the form of
columnar grains (EB-PVD)), which are graduated and are produced
using the process described above.
[0062] The guide vane 130 has a guide vane root (not shown here)
facing the inner housing 138 of the turbine 108 and a guide vane
head on the opposite side 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. 6 shows a combustion chamber of a gas turbine. The
combustion chamber 110 is designed, for example, as what is known
as an annular combustion chamber, in which a multiplicity of
burners 102, which are arranged around the turbine shaft 103 in the
circumferential direction, open out into a common combustion
chamber space. For this purpose, the overall combustion chamber 110
is designed as an annular structure which is positioned around the
turbine shaft 103.
[0064] To achieve a relatively high efficiency, the combustion
chamber 110 is designed for a relatively high temperature of the
working medium M of approximately 1 000.degree. C. to 1 600.degree.
C. To allow a relatively long operating time even at these
operating parameters, which are unfavorable for the materials, the
combustion chamber wall 153 is provided, on its side which faces
the working medium M, with an inner lining formed from heat shield
elements 155. On the working medium side, each heat shield element
155 is equipped with a particularly heat-resistant protective
layer, which can be produced in accordance with the invention, or
is made from material which is able to withstand high temperatures.
Moreover, on account of the high temperatures in the interior of
the combustion chamber 110, a cooling system is provided for the
heat shield elements 155 and/or for their holding elements.
[0065] The combustion chamber 110 is designed in particular to
detect losses in 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.
* * * * *