U.S. patent application number 11/792629 was filed with the patent office on 2007-11-15 for method of protecting a component against hot corrosion.
Invention is credited to Paul Box, Mick Whitehurst.
Application Number | 20070264126 11/792629 |
Document ID | / |
Family ID | 34073550 |
Filed Date | 2007-11-15 |
United States Patent
Application |
20070264126 |
Kind Code |
A1 |
Box; Paul ; et al. |
November 15, 2007 |
Method of Protecting a Component Against Hot Corrosion
Abstract
A method of protecting a component against hot corrosion
comprising the steps: (a) applying a chromium diffusion coating to
the component; and (b) applying a further coating to selected
regions of the chromium diffusion coating, the selected regions
being chosen dependent on subsequent use of the component.
Inventors: |
Box; Paul; (Lincoln, GB)
; Whitehurst; Mick; (Lincoln, GB) |
Correspondence
Address: |
SIEMENS CORPORATION;INTELLECTUAL PROPERTY DEPARTMENT
170 WOOD AVENUE SOUTH
ISELIN
NJ
08830
US
|
Family ID: |
34073550 |
Appl. No.: |
11/792629 |
Filed: |
December 9, 2005 |
PCT Filed: |
December 9, 2005 |
PCT NO: |
PCT/EP05/56643 |
371 Date: |
June 8, 2007 |
Current U.S.
Class: |
416/241R |
Current CPC
Class: |
F05D 2300/611 20130101;
C23C 10/56 20130101; F05D 2230/90 20130101; F01D 5/288 20130101;
C23C 10/16 20130101; C23C 10/60 20130101; C23C 10/04 20130101; C23C
10/58 20130101; F01D 25/007 20130101 |
Class at
Publication: |
416/241.00R |
International
Class: |
C23C 28/02 20060101
C23C028/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 2004 |
GB |
0427155.7 |
Claims
1-20. (canceled)
21. A turbine blade comprising: an aerofoil; a shroud arranged at a
first end of the aerofoil; a platform arranged at a second end of
the aerofoil; a root arranged adjacent the platform; and a
protective coating system for protecting the turbine blade against
hot corrosion, wherein the coating system has: a first layer with a
chromium diffusion coating applied to the turbine blade, and a
second layer arranged on top of the first layer having an aluminium
diffusion coating applied to the aerofoil, the shroud, the platform
and the root, wherein the second layer covers the root only in
part.
22. The turbine blade according to claim 21, wherein the first
layer covers the entire turbine blade.
23. The turbine blade according to claim 21, wherein the chromium
diffusion coating comprises 15 to 30 weight % chromium and is 5 to
25 microns thick.
24. The turbine blade according to claim 21, wherein the turbine
blade is a nickel based superalloy turbine blade.
25. A turbine blade comprising: an aerofoil; a shroud arranged at a
first end of the aerofoil; a platform arranged at a second end of
the aerofoil, the platform comprising a top face arranged adjacent
the aerofoil; a protective coating system for protecting the
turbine blade against hot corrosion, wherein the coating system
comprises: a first layer, the first layer comprising a chromium
diffusion coating applied to the turbine blade, and a second layer,
the second layer arranged on top of the first layer and comprising
a MCrAlY overlay coating, wherein M is selected from the group
consisting of Ni, Co and a combination of Ni and Co, and the
overlay coating is applied only to the aerofoil, the shroud and the
top face of the platform.
26. The turbine blade according to claim 25, wherein the first
layer covers the entire turbine blade.
27. A turbine blade according to claim 25, wherein the turbine
blade comprises a third layer, wherein the third layer is an
aluminium diffusion coating, arranged on top of the second
layer.
28. The turbine blade according to claim 25, wherein the MCrAlY
overlay coating comprises: 30 to 70 weight % Nickel, 30 to 50
weight % Cobalt, 15 to 25 weight % Chromium, 5 to 15 weight %
Aluminium, and up to 1 weight % Yttrium.
29. The turbine blade according to claim 25, wherein the MCrAlY
overlay coating additionally includes at least one element selected
from the group consisting of rhenium, silicon and hafnium.
30. The turbine blade according to claim 25, wherein the chromium
diffusion coating comprises 15 to 30 weight % chromium and is 5 to
25 microns thick.
31. The turbine blade according to claim 25, wherein the turbine
blade is a nickel based superalloy turbine blade.
32. A method of protecting a turbine blade against hot corrosion,
comprising: providing the turbine blade comprising: an aerofoil, a
shroud arranged at a first end of the aerofoil, a platform arranged
at a second end of the aerofoil, and a root arranged adjacent the
platform; applying a first layer comprising a chromium diffusion
coating to the turbine blade; and applying a second layer
comprising an aluminium diffusion coating to the aerofoil, the
shroud, the platform and the root, wherein the second layer covers
the root only in part.
33. The method according to claim 32, wherein the chromium
diffusion coating comprises 15 to 30 weight % chromium and is 5 to
25 microns thick.
34. The method according to claim 32, wherein the turbine blade is
a nickel based superalloy turbine blade.
35. A method of protecting a turbine blade against hot corrosion,
comprising: providing the turbine blade, wherein the turbine blade
comprises: an aerofoil, a shroud arranged at a first end of the
aerofoil, and a platform arranged at a second end of the aerofoil,
the platform comprising a top face arranged adjacent the aerofoil;
applying a first coating layer including a chromium diffusion
coating to the turbine blade; and applying a second coating layer
on top of the first coating layer to the aerofoil, the shroud and
the top face of the platform, wherein the second layer is an MCrAlY
overlay coating, and wherein M is selected from the group
consisting of Ni, Co and a combination of Ni and Co.
36. The method according to claim 35, further comprising applying a
third coating layer on top of the MCrAlY coating, wherein the third
coating is an aluminium diffusion coating.
37. The method according to claim 35, wherein the MCrAlY coating
comprises: 30 to 70 weight % Nickel; 30 to 50 weight % Cobalt; 15
to 25 weight % Chromium; 5 to 15 weight % Aluminium; and up to 1
weight % Yttrium.
38. The method according to claim 35, wherein the MCrAlY overlay
coating includes at least one element selected from the group
consisting of rhenium, silicon and hafnium.
39. A method according to claim 35, wherein the chromium diffusion
coating comprises 15 to 30 weight % chromium and is 5 to 25 microns
thick.
40. A method according to claim 35, wherein the turbine blade is a
nickel based superalloy turbine blade.
Description
[0001] This invention relates to a method of protecting a component
against hot corrosion.
[0002] The invention finds particular application in the protection
against hot corrosion of a gas turbine engine rotor blade.
[0003] It is known that chromium provides excellent protection
against so called Type I and Type II hot corrosion. In this regard,
diffusion coatings produced by the diffusion of chromium and
aluminium into the alloy substrate have long been used to provide
this protection. MCrAlY overlay coatings (where M is Ni or Co or a
combination of the two) have been used as an alternative to
diffusion coatings at higher temperatures to protect against
oxidation. The use of diffused chromium alone (chromising) is known
to provide excellent protection against relatively low temperature
Type II hot corrosion, and further to be strain tolerant (to have
no effect on the fatigue properties of the substrate).
[0004] According to the present invention there is provided a
method of protecting a component against hot corrosion comprising
the steps: (a) applying a chromium diffusion coating to the
component; and (b) applying a further coating to selected regions
of the chromium diffusion coating, the selected regions being
chosen dependent on subsequent use of the component.
[0005] Preferably, the selected regions are regions not subject to
higher physical stress in the subsequent use of the component.
[0006] In a first method according to the present invention
described below, the further coating comprises an aluminium
diffusion coating.
[0007] In a second method according to the present invention
described below, the further coating comprises an MCrAlY overlay
coating, where M is Ni or Co or a combination of the two.
[0008] In a third method according to the present invention
described below, the further coating comprises an MCrAlY overlay
coating, where M is Ni or Co or a combination of the two, and the
method further comprises the step (c) applying an aluminium
diffusion coating to the selected regions coated with the MCrAlY
overlay coating.
[0009] In the second and third methods the MCrAlY overlay coating
applied in step (b) suitably comprises: 30 to 70 weight % Nickel;
30 to 50 weight % Cobalt; 15 to 25 weight % Chromium; 5 to 15
weight % Aluminium; and up to 1 weight % Yttrium.
[0010] In the second and third methods the MCrAlY overlay coating
applied in step (b) may additionally include one or more elements
selected from the group consisting of rhenium, silicon and
hafnium.
[0011] The chromium diffusion coating applied in step (a) suitably
comprises 15 to 30 weight % chromium and is 5 to 25 microns
thick.
[0012] Methods according to the present invention find particular
application in the protection against hot corrosion of nickel based
superalloy components.
[0013] Methods according to the present invention find particular
application in the protection against hot corrosion of gas turbine
engine rotor blades.
[0014] The present invention also extends to components protected
against hot corrosion by means of a method according to the present
invention.
[0015] The invention will now be described, by way of example, with
reference to the accompanying drawings, in which:
[0016] FIG. 1 shows a gas turbine engine rotor blade and the
coating of this blade using a first method in accordance with the
present invention;
[0017] FIG. 2 is a view of a side of the rotor blade of FIG. 1
hidden in FIG. 1 but to be seen when looking from the right in FIG.
1;
[0018] FIG. 3 shows a gas turbine engine rotor blade and the
coating of this blade using a second method in accordance with the
present invention;
[0019] FIG. 4 is a view of a side of the rotor blade of FIG. 3
hidden in FIG. 3 but to be seen when looking from the right in FIG.
3;
[0020] FIG. 5 shows a gas turbine engine rotor blade and the
coating of this blade using a third method in accordance with the
present invention; and
[0021] FIG. 6 is a view of a side of the rotor blade of FIG. 5
hidden in FIG. 5 but to be seen when looking from the right in FIG.
5.
[0022] In each of the first to third methods the rotor blade coated
is a nickel based superalloy rotor blade. The rotor blade may be
produced by conventional or directionally solidified (including
single crystal) casting techniques. Typical alloys are MarM247,
IN6203 and CMSX-4.
[0023] Referring to FIGS. 1 and 2, the blade coated comprises an
outer shroud part 1 (above dotted line A), an aerofoil part 3
(between dotted lines A and B), a platform part 5 (between dotted
lines B and C), and a root part 7 (below dotted line C). The blade
includes an internal cooling passage 9 which commences as shown in
FIG. 1, loops within the blade, and exits (exit not shown) via the
top side of shroud part 1.
[0024] In a first stage of the first method, all surfaces of all
parts of the blade, including internal cooling passage 9, are
chromised, i.e. chromium is diffused into the surfaces. This
diffusion is achieved by any suitable method, e.g. pack cementation
or chemical vapour deposition (CVD). This results in a surface
layer rich in chromium. The layer should typically contain 15 to 30
weight % chromium and be 5 to 25 microns thick.
[0025] In a second stage of the first method, an aluminium
diffusion coating is applied to all external surfaces of the blade
above dotted line M. This diffusion is again achieved by any
suitable method, e.g. pack cementation or CVD. Masking is employed
below dotted line M to prevent stray aluminium depositing below
this line. If such stray depositing does occur, this is acceptable
between dotted lines M and S, but not below dotted line S, i.e. not
on the so called fir tree root of root part 7. Thus, a chromium
modified aluminide coating results on all external surfaces of the
blade above dotted line M. The so called outer beta layer of the
chromium modified aluminide coating should typically contain 15 to
30 weight % aluminium and 5 to 15 weight % chromium. The total
thickness of the chromium modified aluminide coating, including
inter-diffusion zone, should typically be 25 to 100 microns.
[0026] Finally, the blade is heat treated to ensure that it
maintains its optimum mechanical properties.
[0027] It is to be noted that in the final blade, all external
surfaces above dotted line M are chromised plus aluminised, whereas
all external surfaces below dotted line M and internal cooling
passage 9 are chromised only.
[0028] Referring to FIGS. 3 and 4, the blade coated comprises an
outer shroud part 1 (above dotted line A), an aerofoil part 3
(between dotted lines A and B), a platform part 5 (between dotted
lines B and C), and a root part 7 (below dotted line C). The blade
includes an internal cooling passage 9 which commences as shown in
FIG. 3, loops within the blade, and exits (exit not shown) via the
top side of shroud part 1.
[0029] In a first stage of the second method, all surfaces of all
parts of the blade, including internal cooling passage 9, are
chromised, i.e. chromium is diffused into the surfaces. This
diffusion is achieved by any suitable method, e.g. pack cementation
or CVD. This results in a surface layer rich in chromium. The layer
should typically contain 15 to 30 weight % chromium and be 5 to 25
microns thick.
[0030] In a second stage of the second method, an MCrAlY overlay
coating (where M is Ni or Co or a combination of the two) is
applied to the following parts of the blade: outer shroud part 1,
aerofoil part 3, and the top face 11 of platform part 5. The
coating suitably comprises 30 to 70 weight % Nickel, 30 to 50
weight % Cobalt, 15 to 25 weight % Chromium, 5 to 15 weight %
Aluminium, and up to 1 weight % Yttrium. The coating may
additionally include one or more elements selected from the group
consisting of rhenium, silicon and hafnium. The coating is applied
by any suitable method, e.g. by thermal spray techniques such as
vacuum plasma spraying (VPS), low pressure plasma spraying (LPPS),
and high velocity ox-fuel spraying (HVOF), or by electroplating.
Masking is employed to ensure that MCrAlY is not deposited on the
remainder of platform part 5 below top face 11, and on root part
7.
[0031] Finally, the blade is heat treated to ensure that it
maintains its optimum mechanical properties.
[0032] It is to be noted that in the final blade, outer shroud part
1, aerofoil part 3, and the top face 11 of platform part 5 are
chromised plus have an overlay coating of MCrAlY, whereas the
remainder of platform part 5 below top face 11, root part 7, and
internal cooling passage 9 are chromised only.
[0033] Referring to FIGS. 5 and 6, the blade coated comprises an
outer shroud part 1 (above dotted line A), an aerofoil part 3
(between dotted lines A and B), a platform part 5 (between dotted
lines B and C), and a root part 7 (below dotted line C). The blade
includes an internal cooling passage 9 which commences as shown in
FIG. 5, loops within the blade, and exits (exit not shown) via the
top side of shroud part 1.
[0034] In a first stage of the third method, all surfaces of all
parts of the blade, including internal cooling passage 9, are
chromised, i.e. chromium is diffused into the surfaces. This
diffusion is achieved by any suitable method, e.g. pack cementation
or CVD. This results in a surface layer rich in chromium. The layer
should typically contain 15 to 30 weight % chromium and be 5 to 25
microns thick.
[0035] In a second stage of the third method, an MCrAlY overlay
coating (where M is Ni or Co or a combination of the two) is
applied to the following parts of the blade: outer shroud part 1,
aerofoil part 3, and the top face 11 of platform part 5. The
coating suitably comprises 30 to 70 weight % Nickel, 30 to 50
weight % Cobalt, 15 to 25 weight % Chromium, 5 to 15 weight %
Aluminium, and up to 1 weight % Yttrium. The coating may
additionally include one or more elements selected from the group
consisting of rhenium, silicon and hafnium. The coating is applied
by any suitable method, e.g. by thermal spray techniques such as
VPS, LPPS, and HVOF, or by electroplating. Masking is employed to
ensure that MCrAlY is not deposited on the remainder of platform
part 5 below top face 11, and on root part 7.
[0036] In a third stage of the third method, those parts of the
blade to which the MCrAlY overlay coating was applied (outer shroud
part 1, aerofoil part 3, and the top face 11 of platform part 5)
are over-aluminised, i.e. an aluminium diffusion coating is applied
to these parts. The diffusion is achieved by any suitable method,
e.g. pack cementation or CVD. Masking is employed to ensure that
stray aluminium is not deposited on the remainder of platform part
5 below top face 11, and on root part 7. The result of the
over-aluminisation should be that the outer surface of the MCrAlY
overlay coating has an aluminium content of typically 15 to 30
weight %. The total thickness of the over-aluminised MCrAlY
coating, including inter-diffusion zone, should typically be 100 to
200 microns.
[0037] Finally, the blade is heat treated to ensure that it
maintains its optimum mechanical properties.
[0038] It is to be noted that in the final blade, outer shroud part
1, aerofoil part 3, and the top face 11 of platform part 5 are
chromised plus have an overlay coating of MCrAlY, which MCrAlY
overlay coating has been over-aluminised, whereas the remainder of
platform part 5 below top face 11, root part 7, and internal
cooling passage 9 are chromised only.
[0039] It is to be appreciated that in the above described first to
third methods the application of further coating(s) in addition to
the initial chromium diffusion coating is restricted to regions of
the rotor blade not subject to higher physical stress in use of the
blade. In the first method, the diffused aluminium coating is
restricted to all external surfaces above dotted line M. In the
second method, the MCrAlY overlay coating is restricted to outer
shroud part 1, aerofoil part 3, and the top face 11 of platform
part 5. In the third method, the MCrAlY overlay coating plus
over-aluminisation is restricted to outer shroud part 1, aerofoil
part 3, and the top face 11 of platform part 5. This restriction
ensures that those regions of the blade that are subject to higher
physical stress are coated with a chromium diffusion coating alone
which is strain tolerant, and that the strain tolerance of this
coating is not degraded by the application of further coating(s).
The purpose of the application of the further coating(s) is to
provide additional protection against hot corrosion. The approach
taken therefore with regard to the application of the further
coating(s) is as follows. It is first determined where on the blade
there will be a region of relatively high temperature. Further
coating(s) are then applied to this region provided it is not also
a region that will experience higher physical stress.
* * * * *