U.S. patent application number 15/723819 was filed with the patent office on 2018-02-15 for method of facilitating visual detection of a crack in a component of a gas turbine engine.
The applicant listed for this patent is PRATT & WHITNEY CANADA CORP.. Invention is credited to Kin-Leung CHEUNG.
Application Number | 20180045608 15/723819 |
Document ID | / |
Family ID | 53881930 |
Filed Date | 2018-02-15 |
United States Patent
Application |
20180045608 |
Kind Code |
A1 |
CHEUNG; Kin-Leung |
February 15, 2018 |
METHOD OF FACILITATING VISUAL DETECTION OF A CRACK IN A COMPONENT
OF A GAS TURBINE ENGINE
Abstract
A component of a gas turbine engine comprises a substrate, a
corrosion resistant top layer, and an intermediate corrodible layer
disposed between the corrosion resistant top layer and the
substrate. When corroding, the intermediate layer has a color
contrasting with a color of the top layer. A method of detecting a
crack when it penetrated the top layer in a component of a gas
turbine engine having a corrosion resistant top layer and an
intermediate corrodible layer comprises, in sequence, observing
that at least one area of the component has a color contrasting
with that of the top layer; determining that the color of the at
least one area is a result of corrosion of the intermediate
corrodible layer; and determining that the top layer has a crack as
a result of determining corrosion of the intermediate layer. A
method of facilitating crack detection in a component is also
presented.
Inventors: |
CHEUNG; Kin-Leung; (Toronto,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PRATT & WHITNEY CANADA CORP. |
Longueuil |
|
CA |
|
|
Family ID: |
53881930 |
Appl. No.: |
15/723819 |
Filed: |
October 3, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14191689 |
Feb 27, 2014 |
9804058 |
|
|
15723819 |
|
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|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 28/022 20130101;
C23C 28/30 20130101; F01D 5/288 20130101; F01D 5/286 20130101; C23C
28/44 20130101; C23C 28/021 20130101; C23C 4/073 20160101; C23C
28/00 20130101; F01D 5/282 20130101; F01D 5/284 20130101; F05D
2260/80 20130101; G01M 15/14 20130101; C23C 28/3215 20130101; F01D
5/28 20130101; C23C 28/042 20130101; C23C 28/32 20130101 |
International
Class: |
G01M 15/14 20060101
G01M015/14; C23C 4/073 20060101 C23C004/073; C23C 28/04 20060101
C23C028/04; C23C 28/02 20060101 C23C028/02; F01D 5/28 20060101
F01D005/28; C23C 28/00 20060101 C23C028/00 |
Claims
1. A component of a gas turbine engine, the component comprising: a
substrate; a corrosion resistant top layer; and an intermediate
corrodible layer disposed between the corrosion resistant top layer
and the substrate, when corroding, the corroded intermediate layer
having a color contrasting with a color of the top layer.
2. The component as defined in claim 1, wherein the top layer is
metal.
3. The component as defined in claim 2, wherein the top layer is
cobalt.
4. The component as defined in claim 1, wherein the intermediate
layer is a ferrous alloy.
5. The component as defined in claim 1, wherein when corroding, the
corroded intermediate layer expands on corrosion.
6. The component as defined in claim 1, wherein the substrate is an
aluminum alloy.
7. The component as defined in claim 1, wherein the intermediate
layer stiffens and strengthens the component.
8. The component as defined in claim 1, wherein the top layer is
not galvanic compatible with the substrate.
9. The component as defined in claim 1, wherein the top layer is
generally gray in color and when corroding, the corroded
intermediate layer is generally red in color.
10. The component as defined in claim 1, wherein the top layer is
plated.
11. The component as defined in claim 1, wherein the top layer
includes a crack therethrough and the intermediate layer has a
corroded portion expanding through the crack.
12. A method of detecting a crack in a component of a gas turbine
engine having a corrosion resistant top layer and an intermediate
corrodible layer, the method comprising, in sequence: observing
that at least one area of the component has a color contrasting
with that of the top layer; determining that the color of the at
least one area is a result of corrosion of the intermediate
corrodible layer; and determining that the top layer has a crack
therethrough as a result of determining corrosion of the
intermediate corrodible layer.
13. The method as defined in claim 12, wherein observing that at
least one area of the component has a color contrasting with that
of the top layer comprises observing red color stains over a gray
color background.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a divisional application of U.S.
patent application Ser. No. 14/191,689 filed on Feb. 27, 2014,
incorporated herewith by reference.
TECHNICAL FIELD
[0002] The application relates generally to components of gas
turbine engines and more specifically to detection of cracks in
those components.
BACKGROUND OF THE ART
[0003] Parts of a gas turbine engine can become scratched or
cracked by normal wear, stress loading, or by incident such as
foreign object impact at high velocity. Some of the parts of the
gas turbine engine are made of a substrate and of at least one
coating over the substrate. Cracks in the coating can expose the
substrate, which in turn can leave the component vulnerable to
stress fractures, such as stress corrosion cracks whereby in the
presence of stress and corrosion the component would crack and
fracture at a stress level below the tensile strength of the
substrate.
SUMMARY
[0004] In one aspect is provided a component of a gas turbine
engine, the component comprising: a substrate; a corrosion
resistant top layer; and an intermediate corrodible layer disposed
between the corrosion resistant top layer and the substrate, when
corroding, the intermediate layer having a color contrasting with a
color of the top layer.
[0005] In another aspect is provided method of detecting a crack in
a component of a gas turbine engine having a corrosion resistant
top layer and an intermediate corrodible layer, the method
comprising, in sequence: observing that at least one area of the
component has a color contrasting with that of the top layer;
determining that the color of the at least one area is a result of
corrosion of the intermediate corrodible layer; and determining
that the top layer has a crack therethrough as a result of
determining corrosion of the intermediate corrodible layer.
[0006] In yet another aspect, there is provided a method of
facilitating crack detection in a component of a gas turbine
engine, the method comprising: obtaining a substrate of the
component; depositing an intermediate corrodible layer onto the
substrate; and depositing a corrosion resistant top layer onto the
intermediate corrodible layer, wherein when a crack in the top
layer exposes the intermediate corrodible layer, the corroded
intermediate layer corroding in a color contrasting with a color of
the top layer.
DESCRIPTION OF THE DRAWINGS
[0007] Reference is now made to the accompanying figures in
which:
[0008] FIG. 1 is a schematic cross-sectional view of a gas turbine
engine;
[0009] FIG. 2 is a schematic cross-section view of a component of
the gas turbine engine of FIG. 1 having a substrate, a corrosion
resistant top layer and an intermediate corrodible layer;
[0010] FIG. 3 is a schematic cross-section view of the component of
FIG. 2 showing a crack penetrated through the top layer;
[0011] FIG. 4 is a schematic cross-section view of the component of
FIG. 3 showing the corroded intermediate layer expanded through the
crack in the top layer and partially covering a surface of the
component; and
[0012] FIG. 5 is a flow chart of a method of detecting a crack such
as the crack in the component of FIG. 3.
DETAILED DESCRIPTION
[0013] FIG. 1 illustrates a gas turbine engine 10 of a type
preferably provided for use in subsonic flight, generally
comprising in serial flow communication a fan 12 through which
ambient air is propelled, a compressor section 14 for pressurizing
the air, a combustor 16 in which the compressed air is mixed with
fuel and ignited for generating an annular stream of hot combustion
gases, and a turbine section 18 for extracting energy from the
combustion gases.
[0014] Referring to FIG. 2, a component 20 of the gas turbine
engine 10 includes a corrosion resistant top layer 22 and a
substrate 26. An intermediate corrodible layer 24 is disposed
between the substrate 26 and the top layer 22 and allows detecting
cracks in the top layer 22 before the substrate 26 becomes
exposed.
[0015] The component 20 can be used in various parts of a gas
turbine engine. In one embodiment, the substrate 26 is an aluminum
alloy, the intermediate layer 24 a ferrous alloy and the top layer
22 a metal plating of cobalt. The component 20 may be coated,
plated, or the like. The substrate 26, the intermediate layer 24,
and the top layer 22 may be various materials depending of the
intended use of the component 20. Examples of materials for the top
layer 22 include non-exhaustively a metal alloy, and a non-metal.
Yet, for any choice of the top layer 22, intermediate layer 24 and
substrate 26, the top layer 22 is chosen to be corrosion resistant
and the intermediate layer 24 to be corrodible. The substrate 26,
however, may or may not be corrosion resistant. In addition, the
intermediate layer 24 is selected to have a corroded color
contrasting with that of the top layer 22 for allowing visual
detection of cracks of the top layer 22, as will be described
below. By "contrasting", it should be understood any color
difference which would be detectable without confusion by a normal
healthy human eye. Examples of color contrasting include a dark
color over a light background, a vivid color over a pastel
background. Colors that could not be easily dateable such as green
over red for daltonians are preferably avoided. In one embodiment
where the top layer 22 is cobalt and the substrate 26 is aluminum,
the top layer 22 has a generally light grey color and the substrate
26 has a generally silver to dull grey color, and a crack in the
top layer 22 may be difficult to detect during visual inspection.
The presence of the intermediate layer 24 having a corroded color
contrasting with that of the top layer 22 facilitates visual
detection of cracks in the top layer 22. Cracks are undesirable
because they may lead to fracture of the component 20. For example,
the substrate 26 and the top layer 22 may not be galvanic
compatible, and if the top layer 22 is scratched and the substrate
26 exposed, a fluid could involuntary connect the substrate 26 to
the top layer 22 and cause galvanic corrosion. It is therefore
undesirable to leave the component 20 with a portion of the
substrate 26 exposed. Exposing involuntarily a portion of the
substrate 26 could also cause stress corrosion cracking thereby
inducing potentially cracking and fracture of the component 20 at a
lower stress level than it otherwise would.
[0016] In the embodiment described herein, the top layer 22 and the
intermediate layer 24 may be formed by a specific electrolytic
deposition to deposit metal to a grain size in the nanometer range,
for example 10 to 15 nanometers. However, the top layer 22 and the
intermediate layer 24 may be formed using plating techniques other
than the above described electrolytic deposition process, and the
cobalt grain size of the top layer 22 and/or the ferrous grain size
of the intermediate layer 24 used in the electrolytic process may
have a grain size other than in the nanometer size range. The top
layer 22 and/or intermediate layer 24 may also not be plated.
[0017] The top layer 22 has a thickness 23, the intermediate layer
24 has a thickness 25 and the substrate 26 has a thickness 27. FIG.
2 is schematic and the top layer 22, intermediate layer 24 and
substrate 26 may have dimensions relative to each other different
than the ones shown in FIG. 2. For example, the intermediate layer
24 may be thicker than the top layer 22.
[0018] FIG. 3 schematically shows the component 20 having a crack
30 in the top layer 22. The crack 30 could originate from various
events, including normal wear, stress loading, or foreign object
impact at high velocity. The crack 30 extends through the thickness
23 of the top layer 22 and exposes the intermediate layer 24. FIG.
3 is schematic, and the crack 30 may have other shapes and
dimensions as the ones shown in FIG. 3. For example, the crack 30
could be linear shaped or non linear shaped. The crack 30 may also
extend through a portion of the intermediate layer 24 before
exposing the substrate 26.
[0019] The intermediate layer 24 is a corrodible material selected
to have a corrosion color contrasting with that of the top layer 22
in order to enhance visual detection of the crack 30. In the
example described herein, the intermediate layer 24 is a ferrous
alloy and corrodes in a generally red color. One example of a
ferrous alloy is an alloy of 75 to 80% iron by weight. When
corroding, the ferrous alloy turns into a red color, while the top
layer 22 remains grey. As a consequence, a user inspecting the
component 20 would visually detect the red areas. Knowing that the
red areas are a consequence of corrosion of the intermediate layer
24 (as opposed to areas of different color not related to the crack
detection described herein), the user can deduce that these areas
or stains are locations where a crack is present and that the crack
30 had penetrated through the thickness of the top layer 22 which
may cause the component 20 to be subject to retirement from the
engine 10. In one embodiment, the thickness 25 of the intermediate
layer 24 is selected so that the crack 30 would not propagate
through the thickness 25 of the intermediate layer 24 of the
component 20 and would not reach the substrate 26 for at least two
scheduled inspection intervals. This could correspond to 1,500 to
3,000 hours of engine operation. The component 20 could then be
able to have a margin of safety to operate to the second scheduled
inspection knowing the crack 30 would not be able to reach and
expose the substrate 26 to corrosion and stress corrosion if the
crack 30 misses detection at the first scheduled inspection. The
thickness 25 of the intermediate layer 24 could be determined by
crack propagation methodology. If the user detects no stains
related to corrosion of the intermediate layer 24, the user deduces
that no crack 30 is present or that the crack 30 is at an early
stage and yet not penetrated through the thickness 23 of the top
layer 22 that would otherwise makes the crack visually visible.
[0020] Depending on the choices of the top layer 22, intermediate
layer 24 and substrate 26, the intermediate layer 24 can also act
as a stiffener and supports structural loads for the component 20.
In the example described herein, the ferrous alloy of the
intermediate layer 24 is a stiffener and a structural load
supporting element for the component 20 made of a cobalt top layer
22 and an aluminum alloy of the substrate 26. The intermediate
layer 24 may not only serves to aid crack detection but also
support the structural loads at the top layer 22 and the substrate
26 and provides stiffening to the component 20. A ferrous
intermediate layer 24 tensile modulus and tensile strength may be
respectively three times and over two times that of a high strength
aluminum alloy of the substrate 26. It is contemplated that the
intermediate layer 24 also acts to stiffen and strengthen the
component 20.
[0021] Turning to FIG. 4, the corroded intermediate layer 24 may
expand in the crack 30 through the top layer 22 which could further
enhance visual detection of the crack 30. FIG. 4 is schematic, and
the corroded intermediate layer 24 may expand more or less than
shown in FIG. 4. For example, the corroded intermediate layer 24
may expand only partially in the crack 30 at onset of corrosion in
the intermediate layer 24. In the schematic of FIG. 4, the corroded
intermediate layer 24 is shown to completely fill crack 30 in the
top layer 22 and onto a surface 21 of the component 20, but it
contemplated that the corroded intermediate layer 24 could be
contained within the crack 30 at the onset of corrosion in the
intermediate layer 24.
[0022] Turning to FIG. 5, a method 40 of detecting the crack 30
that had penetrated the thickness 23 of the top layer 22 in the
component 20 starts at step 42 with observing that at least one
area of the component 20 has a color different from a rest of the
top layer 22. In the example described herein, one may observe red
color stains over a gray color background. From step 42, the method
goes to step 44, where it is determined that the color is a result
of corrosion of the intermediate layer 24. This can be achieved by
knowing that the color is a typical color of corrosion of the
intermediate layer or by sampling the corrosion residue and
determining that it is indeed a product of the corrosion. From step
44, the method goes to step 46 where it is determined that the
crack 30 had penetrated the top layer 22 as a result of determining
corrosion of the intermediate corrodible layer 24.
[0023] A manufacturer of the component 20 of the gas turbine engine
10 may perform a method of facilitating crack detection by
obtaining the substrate 26 of the component 20; depositing the
intermediate corrodible layer 24 onto the substrate 26; and
depositing the corrosion resistant top layer 22 onto the
intermediate corrodible layer 26. When the crack 30 in the top
layer 22 exposes the intermediate corrodible layer 24, the corroded
intermediate layer 26 corrodes in the color contrasting with a
color of the top layer 22.
[0024] The above described layered component and method allow
detecting cracks that penetrated the top layer before the substrate
becomes exposed by using an intermediate layer of corrodible
material that has a corrosion color contrasting with that of the
top layer. The intermediate layer corrodes at an accelerated rate
from galvanic corrosion with the top layer thereby provides earlier
crack warnings than it otherwise would. The substrate being
susceptible to stress corrosion cracking, i.e. at the presence of
both stress and corrosion, it may fail at a stress corrosion crack
stress level below its ultimate tensile strength. Earlier crack
detection is thus enabled which is desired since crack tip stress
is lower for smaller cracks and cracks grows over time from
repeated cyclic stressing. The above detection method does not
require detection tools, and relies only on the visual detection of
the stains which can be done during the routine checks. The better
the contrast between the top layer and the corroded intermediate
layer, the easier the visual detection. In addition, the
intermediate layer may not be parasitic, but rather enhances the
stiffness, strength, and fatigue endurance life of the
component.
[0025] The above description is meant to be exemplary only, and one
skilled in the art will recognize that changes may be made to the
embodiments described without departing from the scope of the
invention disclosed. Still other modifications which fall within
the scope of the present invention will be apparent to those
skilled in the art, in light of a review of this disclosure, and
such modifications are intended to fall within the appended
claims.
* * * * *