U.S. patent application number 12/749785 was filed with the patent office on 2011-10-06 for metallic coating for non-line of sight areas.
Invention is credited to Kevin W. Schlichting, Brian S. Tryon.
Application Number | 20110244138 12/749785 |
Document ID | / |
Family ID | 44140800 |
Filed Date | 2011-10-06 |
United States Patent
Application |
20110244138 |
Kind Code |
A1 |
Schlichting; Kevin W. ; et
al. |
October 6, 2011 |
METALLIC COATING FOR NON-LINE OF SIGHT AREAS
Abstract
A disclosed process for coating a turbine vane includes the
steps of applying a coating to line of sight surfaces with a
thermal spraying process and applying a slurry coating to non-line
of sight surfaces to provide oxidative protection and desired
thermal protection. Moreover, the applied coating on both the line
of sight and non-line of sight surfaces provides a bond layer for
the application of a ceramic coating.
Inventors: |
Schlichting; Kevin W.;
(South Glastonbury, CT) ; Tryon; Brian S.;
(Glastonbury, CT) |
Family ID: |
44140800 |
Appl. No.: |
12/749785 |
Filed: |
March 30, 2010 |
Current U.S.
Class: |
427/448 |
Current CPC
Class: |
Y02T 50/6765 20180501;
C23C 28/325 20130101; F05D 2260/95 20130101; C23C 4/06 20130101;
C23C 28/3215 20130101; F01D 5/286 20130101; C23C 28/345 20130101;
C23C 28/3455 20130101; F05D 2230/90 20130101; F01D 5/288 20130101;
Y02T 50/60 20130101; C23C 10/18 20130101; C23C 10/60 20130101; C23C
4/073 20160101; C23C 4/18 20130101 |
Class at
Publication: |
427/448 |
International
Class: |
C23C 4/06 20060101
C23C004/06 |
Claims
1. A process of coating a component comprising the steps of:
applying a spray coating to at least one first surface of a
component reachable by a thermal spraying process; applying a
slurry coating to at least one second surface of the component,
wherein the second surface is not reachable by the spray coating
process utilized to coat the first surface; and heat-treating the
component to release undesired portions of the slurry from the
component.
2. The process as recited in claim 1, including the step of
diffusing the applied spray coating and the slurry coating into the
first and second surface of the component.
3. The process as recited in claim 2, wherein the spray coating on
the at least one first surface and the slurry coating on the at
least one second surface comprise a metallic coating that provides
oxidative resistance and creates a bonding layer onto which a
subsequently applied ceramic coating bonds.
4. The process as recited in claim 3, including the step of
applying a ceramic coating to the component after diffusion of the
spray coating and the slurry coating.
5. The process as recited in claim 1, wherein the application of
the spray coating comprises a thermal spraying operation.
6. The process as recited in claim 1, wherein the slurry coating
comprises a suspension including one of nickel based alloy
particles and MCrAlY based alloy particles.
7. The process as recited in claim 6, wherein the one of the nickel
based alloy particles and the MCrAlY based alloy particles are
smaller than 25 microns and are suspended in an organic binder.
8. The process as recited in claim 1, wherein the component
comprises a turbine vane assembly.
9. The process as recited in claim 1, including the step of
mechanically treating at least one surface of the component.
10. A process of surface treating a turbine vane comprising the
steps of: applying a metallic coating with thermal spraying process
to surfaces of the turbine vane accessible by the thermal spraying
process; preparing a slurry coating including metallic particles
suspended in an organic binder; applying the slurry coating to at
least some of the surfaces of the component that are not accessible
by the thermal spraying process; and heat-treating the component to
diffusion bond the metallic particles to the component.
11. The process as recited in claim 10, wherein the step of
preparing a slurry coating comprise preparing a oxidation resistant
composition capable of bonding with a subsequently applied ceramic
coating.
12. The process as recited in claim 11, wherein the slurry coating
comprises a material that produces a thermally grown oxide that
provides for bonding to the subsequently applied ceramic
coating.
13. The process as recited in claim 10, including the step of
applying a ceramic coating to the turbine vane to the surfaces
coated with the metallic coating and the slurry coating on both the
surfaces accessible from an exterior of the turbine vane and the
surfaces not accessible from the exterior of the turbine vane after
heat-treating.
14. The process as recited in claim 10, wherein the heat-treating
step includes diffusing the slurry coating and the metallic coating
applied with the thermal spraying process onto the surface of the
turbine vane.
15. The process as recited in claim 13, wherein the metallic
coating applied with the thermal spraying process and the coating
applied with the slurry coating form a bond layer to which the
ceramic coating bonds.
16. The process as recited in claim 10, wherein the thermal
spraying process includes the step of propelling coating material
heated with a plasma torch onto the surface of the turbine
vane.
17. The process as recited in claim 10, wherein the turbine vane
includes at least one airfoil and at least one surface on which a
coating cannot be applied using the thermal spraying process, and
coating the at least one surface on which a coating cannot be
applied using the thermal spraying process with the slurry
coating.
18. The process as recited in claim 10, wherein the step of
preparing a slurry coating comprises preparing a suspension of
nickel based alloy particles within the organic binder.
19. The process as recited in claim 18, wherein the step of
preparing the slurry comprises suspending nickel based alloy
particles no larger than 25 microns in the organic binder.
20. The process as recited in claim 10, wherein the heat-treating
of the turbine vane comprises removing the organic binder from the
turbine vane.
Description
BACKGROUND
[0001] This disclosure generally relates to a process of applying a
thermal and oxidative resistant coating. More particularly, this
disclosure relates to a process of applying a thermal and oxidative
resistant coating to non-line of sight regions of a component.
[0002] Components that operate in high temperature environments
such as turbine vanes are coated to provide thermal and oxidative
protection. Such coatings are often applied using a thermal
spraying technique. Thermal spraying techniques use melted
materials that are sprayed onto a desired surface. The coating
material is heated by a plasma or arc torch and propelled onto the
surfaces of the component part.
SUMMARY
[0003] A disclosed process for coating an aircraft component
includes the steps of applying a coating to line of sight surfaces
with a thermal spraying process and applying a slurry coating to
non-line of sight surfaces to provide oxidative protection and a
surface to which a ceramic material is bonded.
[0004] An example disclosed component is a turbine vane configured
as a doublet. Turbine vanes operate in a high temperature
environment and therefore are coated to provide oxidative
resistance and to create a thermal barrier. The example process
utilizes a thermal spraying process to apply a coating on line of
sight surfaces and a slurry coating for applying a coating to
surfaces not reachable with the thermal spraying process referred
to as non-line of sight surfaces. The applied coating on both the
line of sight and non-line of sight surfaces provides a bond layer
for the application of a ceramic coating.
[0005] These and other features disclosed herein can be best
understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic representation of example process for
coating a component.
[0007] FIG. 2 is a schematic representation of example layers of
coating applied to the component.
DETAILED DESCRIPTION
[0008] Referring to FIG. 1, an example turbine vane 10 is
configured as a doublet that includes two airfoils attached to
common upper and lower platforms. Turbine vanes operate in a high
temperature environment and therefore are coated to provide
oxidative resistance and to create a thermal barrier. Moreover,
turbine vanes The example process utilizes one process for applying
a coating to surfaces reachable utilizing a thermal spraying
process, referred to in this disclosure as line of sight surfaces,
and a second process for applying a coating to surfaces not
reachable with the thermal spraying process, referred to as
non-line of sight surfaces in this disclosure. The coatings applied
by thermal spraying and slurry application provide a bond layer for
a ceramic layer. Although a turbine vane doublet 10 is disclosed by
example, the disclosed process will benefit other components that
require coatings to provide oxidation protection for the component
improving the thermal durability.
[0009] The example coating process utilizes a line of sight thermal
spraying process as indicated at 12. The example thermal spraying
process utilizes a plasma torch 14 that directs heated materials 16
onto a surface of the turbine vane 10. The example thermal spraying
process is a low-pressure plasma spraying process that utilizes
heat generated by the plasma torch 14 to melt and propel materials
on to line of sight surfaces 18. The example line of sight surfaces
18 are those surfaces that are reachable with the thermal spraying
process such that desired coating coverages and thicknesses can be
accomplished. As appreciated, there are some surfaces that are not
feasibly reachable with the thermal spraying process where desired
coating coverages and thicknesses cannot be reliable created.
Although some material may be deposited in such non-line of sight
surfaces schematically indicated at 20, the microstructure, coating
thickness and physical properties achieved by thermal spraying may
not be as desired.
[0010] The example process begins with the application of a coating
15 by the thermal spraying process 12. The disclosed example
spraying process utilizes a plasma torch 14 to both melt and propel
the coating material on to the line of sight surfaces 18. As
appreciated, other thermal spaying processes may be utilized as
desired to meet the final process parameters.
[0011] The example material that is coated onto the turbine vane 10
can include compounds of Nickel, Cobalt, Aluminum, Iron and any
mixture of such materials that provide the desired thermal
capability and oxidative protection. Moreover, the example material
can also include compounds known in the art as MCrAlYs where the M
denotes one of Nickel (Ni), Cobalt (Co) or NiCo materials and Cr,
Al, and Y represent the elemental designations for Chromium,
Aluminum, and Yttrium, respectively. The example material is also
selected such that it serves as a bond coat for ceramic material
applied subsequent to the metal coating.
[0012] Once the line of sight surfaces 18 have been coated using
the thermal spraying process 12, the non-line of sight surfaces 20
may still require a coating. The non-line of sight surfaces include
those surfaces of the turbine vane 10 that the thermal spraying
process 12 cannot reliably deposit material required to form the
bond coat for the ceramic material. Prior to any additional
processing actions, the surfaces 18 and 20 are treated to remove
any loose materials and to remove any oxidation that may have
developed. The treatment of these surfaces is accomplished using a
grit blast process, vapor blasting process, application of emery
paper, or any other process known for removing an undesired
oxidative coating. Moreover, the treatment of these surfaces may be
bypassed depending on the amount, or lack of oxidation build up on
the metallic coatings applied during the initial thermal spraying
process.
[0013] The disclosed process includes the step of applying a slurry
coating as is schematically indicated at 22. The example slurry
coating indicated schematically at 24 is a suspension of Nickel or
MCrAlY based alloy particles in an organic binder. The example
particle sizes are less than about 25 microns. The prepared slurry
is applied to the non-line of sight areas 20 through a process
capable of applying the slurry 24 on to difficult to reach non-line
of sight locations on the turbine vane 10.
[0014] In this example, the slurry coating 24 is brushed on.
Different processes and methods can be utilized within the
contemplation of the disclosed method for, filling cavities or
spreading the slurry, such as other manual application processes
utilizing various spreading and application tools including for
example brushing, dipping and spraying processes. The viscosity of
the slurry within the organic binder maintains the slurry coating
on the non-line of sight surfaces 20. In other words, the slurry
coating compositions provides a desired viscosity that temporarily
adheres the slurry to the surface 20 of the turbine vane 10 until
heat a heat treat diffusion process.
[0015] Once the slurry coating 24 is applied to the non-line of
sight surfaces 20 of the turbine vane 10, a heat treat step
indicated at 26 is performed. The heat treat step 26 provides for
the elimination of the organic binder portion of the slurry coating
24. The heat treat step 26 also provides for the diffusion bonding
of both the slurry coating 24 and the thermally sprayed coating 15.
Diffusion bonding of the coatings 15 and 24 create the oxidative
resistant layer as well as provides a layer onto which a thermal
barrier, such as a ceramic coating, can adhere. This enables the
desired operation in the high temperature environments in which the
turbine vane 10 operates.
[0016] The example heat treat process 26 is accomplished by
applying heat 28 to the turbine vane 10 to attain a temperature
sufficient to burn out the organic binder of the slurry and to
diffuse both the thermally sprayed coating 15 and the slurry
coating 24 into the substrate of the turbine vane 10. The
temperature and duration that the turbine vane 10 is maintained is
dependent on the substrate, and the specific material composition
of the coatings 15, 24. In the disclosed example, the coated
turbine vane 10 is heat treated for 1 to 4 hours at a temperature
range between 1600.degree. F. and 2000.degree. F. (871.degree. C.
and 1093.degree. C.). Other durations and temperatures would be
utilized depending on the material composition of the coatings.
Diffusion bonding of the coatings 15 and 24 create an oxidative
resistant layer that enables desired operation in the high
temperature environment in which the example turbine vane 10
operates.
[0017] Once the turbine vane 10 is heat treated, the surface is
mechanically treated and or prepared. The surface treatment as is
schematically indicated at 30 comprises a cold working process such
as peening or other surface blast processes that improve mechanical
properties of the coating on the turbine vane 10. The example
surface treatment process includes propelling shot 32 at the
surface of the turbine vane 10. The mechanical working of the
surface induces compressive stresses while reducing tensile
stresses to provide an increased resistance to fatigue and
corrosion. The surface treatment process also prepares the surface
of the turbine vane 10 for the application of a ceramic coating 36
as is schematically indicated at 34. The preparation process
smoothes the surface for ceramic coating and closes up pores in the
coating on the turbine vane 10.
[0018] Referring to FIG. 2 with continued reference to FIG. 1, the
turbine vane 10 includes the substrate 38 onto which the metallic
coating layer 40 is applied. The layer 40 comprises the thermally
sprayed coating 15 and the slurry coating 24. The layer 40 is heat
treated such that it diffuses into the substrate 38. Surface
treatment of the layer 40 improves the mechanical properties of the
layer 40. Following surface heat treatment, turbine vane 10, which
includes layer 40, is typically heat treated prior to application
of the ceramic coating. This heat treatment forms a thermally grown
oxide on the surface of the layer 40. In this example, the
thermally grown oxide includes primarily aluminum oxide. Other
thermally grown oxide compositions can form depending on the
chemical composition of layer 40.
[0019] The ceramic layer 42 is then applied and bonds to the
thermally grown oxide on layer 40. The ceramic layer 42 is applied
using ceramic application techniques such as thermal spraying and
vapor depositions processes. The layer 40 is present on both the
line of sight 18 and non-line of sight 20 surfaces of the turbine
vane 10 that form the gas path surfaces of the turbine vane 10.
Therefore, the ceramic layer 42 can be applied and bonded to the
gas path surfaces of the turbine vane 10. The ceramic layer 40
provides improved durability and thermal protection characteristics
when applied not only to the line of sight surfaces 18, but also to
the non-line of sight surfaces 20.
[0020] The example process enables ceramic coating of all gas path
surfaces for components with difficult to coat geometries and
configurations such as the example doublet turbine vane 10 because
metal bond layer coatings can be applied, and controlled as desired
on all gas path surfaces. Moreover, the example process provides a
bond coat to which ceramic coatings can be applied on both line of
sight and non-line of sight surfaces.
[0021] Although an example embodiment has been disclosed, a worker
of ordinary skill in this art would recognize that certain
modifications would come within the scope of this disclosure. For
that reason, the following claims should be studied to determine
the scope and content of this invention.
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