U.S. patent application number 12/971370 was filed with the patent office on 2011-04-14 for thermal barrier coating with a plasma spray top layer.
This patent application is currently assigned to UNITED TECHNOLOGIES CORPORATION. Invention is credited to Melvin Freling, David A. Litton, Michael J. Maloney, Kevin W. Schlichting, John G. Smeggil, David Snow.
Application Number | 20110086179 12/971370 |
Document ID | / |
Family ID | 38952020 |
Filed Date | 2011-04-14 |
United States Patent
Application |
20110086179 |
Kind Code |
A1 |
Schlichting; Kevin W. ; et
al. |
April 14, 2011 |
THERMAL BARRIER COATING WITH A PLASMA SPRAY TOP LAYER
Abstract
A turbine engine component has a substrate, a thermal barrier
coating deposited onto the substrate, and a sealing layer of
ceramic material on an outer surface of the thermal barrier coating
for limiting molten sand penetration.
Inventors: |
Schlichting; Kevin W.;
(South Glastonbury, CT) ; Maloney; Michael J.;
(Marlborough, CT) ; Litton; David A.; (West
Hartford, CT) ; Freling; Melvin; (West Hartford,
CT) ; Smeggil; John G.; (Simsbury, CT) ; Snow;
David; (Glastonbury, CT) |
Assignee: |
UNITED TECHNOLOGIES
CORPORATION
Hartford
CT
|
Family ID: |
38952020 |
Appl. No.: |
12/971370 |
Filed: |
December 17, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11506376 |
Aug 18, 2006 |
7875370 |
|
|
12971370 |
|
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Current U.S.
Class: |
427/454 ;
427/446; 427/455 |
Current CPC
Class: |
C23C 4/02 20130101; Y02T
50/6765 20180501; Y02T 50/60 20130101; C23C 4/18 20130101; C23C
28/3215 20130101; C23C 28/321 20130101; C23C 28/3455 20130101 |
Class at
Publication: |
427/454 ;
427/446; 427/455 |
International
Class: |
C23C 4/12 20060101
C23C004/12; C23C 4/10 20060101 C23C004/10; C23C 4/08 20060101
C23C004/08 |
Claims
1-14. (canceled)
15. A method for forming a coating on a turbine engine component
comprising the steps of: forming a thermal barrier coating on a
surface of said turbine engine component; and plasma spraying a
sealing layer onto said thermal barrier coating.
16. The method of claim 15, wherein said plasma spraying step
comprises plasma spraying a ceramic material onto said thermal
barrier coating.
17. The method of claim 15, wherein said plasma spraying step
comprises plasma spraying a yttria stabilized zirconia layer onto
said thermal barrier coating.
18. The method of claim 15, wherein said plasma spraying step
comprises depositing said sealing layer using a plasma spray gun
operating at from 30 to 70 volts and from 300 to 900 amps and a
ceramic powder flow rate of from 30 to 70 grams per minute.
19. The method of claim 15, wherein said thermal barrier coating
step comprises depositing at least one layer of yttria stabilized
zirconia onto said surface.
20. The method of claim 15, wherein said thermal barrier coating
step comprises depositing at least one layer of gadolinia
stabilized zirconia onto said surface.
21. The method of claim 15, wherein said thermal barrier coating
step comprises depositing a ceramic material at a temperature of
from 1700 to 2000.degree. F., a pressure of from 0.05 to 2.0
millitors, and a feed rate of from 0.3 to 2.0 inches per hour.
22. The method of claim 15, further comprising applying a bond coat
to said surface of said turbine engine component prior to said
thermal barrier coating forming step.
23. The method according to claim 22, wherein said bond coat
applying step comprises applying a material selected from the group
of a MCrAlY coating, an aluminide coating, a platinum aluminide
coating, a ceramic based material, and a silica based material.
24-33. (canceled)
Description
BACKGROUND
[0001] (1) Field of the Invention
[0002] The present invention relates to the use of a plasma sprayed
outer layer on top of a thermal barrier coating to block the
penetration of molten sands into the thermal barrier coating.
[0003] (2) Prior Art
[0004] Turbine engine airfoils used in desert environments may
degrade due to sand related distress of thermal barrier coatings.
The mechanism for such distress is believed to be caused by the
penetration of fluid sand deposits into 7YSZ ceramic thermal
barrier coatings that leads to spallation and then accelerated
oxidation of exposed metal. It has been observed that gadolinia
stabilized zirconia coatings react with fluid sand deposits and a
reaction product forms that inhibits fluid sand penetration into
the coating. The reaction product has been identified as being a
silicate oxyapatite/garnet containing primarily gadolinia, calcia,
zirconia, and silica.
[0005] There remains a need however for a coating system which
effectively deals with sand related distress.
SUMMARY OF THE INVENTION
[0006] A turbine engine component is provided which uses an air
plasma sprayed outer layer on top of a thermal barrier coating to
block the penetration of molten sands into the thermal barrier
coating.
[0007] In accordance with the present invention, there is provided
a turbine engine component which broadly comprises a substrate, a
thermal barrier coating deposited onto the substrate, and means for
sealing an outer surface of the thermal barrier coating and thereby
limiting molten sand penetration into the thermal barrier
coating.
[0008] Further in accordance with the present invention, there is
provided a method for forming a coating on a turbine engine
component broadly comprising the steps of forming a thermal barrier
coating on a surface of the turbine engine component, and plasma
spraying a sealing layer onto the thermal barrier coating.
[0009] Other details of the thermal barrier coating with a
plasma-spray top layer of the present invention, as well as other
objects and advantages attendant thereto, are set forth in the
following detailed description and the accompanying drawings
wherein like reference numerals depict like elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The FIGURE is a schematic representation of a thermal
barrier coating system in accordance with the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0011] Referring now to the FIGURE, there is shown a turbine engine
component 10, such as a blade, a vane, a combustor panel, or a seal
having a substrate 12, such as an airfoil portion or a platform
portion of a blade or vane or a portion of a combustor panel or a
portion of a seal, and a thermal barrier coating 14 on at least one
surface of the substrate 12. The substrate 12 may be formed from
any suitable material known in the art such as a nickel based
superalloy, a cobalt based superalloy, molybdenum, or niobium.
Alternatively, the substrate 12 may be a ceramic based substrate or
a ceramic matrix composite substrate.
[0012] The thermal barrier coating 14 may comprise one or more
layers of a ceramic material such as a yttria stabilized zirconia
material or a gadolinia stabilized zirconia material. The yttria
stabilized zirconia material may contain from 1.0 to 25 wt % yttria
and the balance zirconia. The gadolinia stabilized zirconia
material may contain from 5.0 to 99 wt % gadolinia, more preferably
30 to 70 wt %, and the balance zirconia. The ceramic material
layer(s) may be deposited using any suitable method known in the
art.
[0013] The thermal barrier coating 14 may be applied using any
suitable technique known in the art such as electron beam physical
vapor deposition, thermal spray, sol-gel, slurry, chemical vapor
deposition, and sputtering. The use of different spray parameters
will create distinctly different microstructures which would
differentiate between the layers, i.e. a dense top sealing layer
with a porous bottom layer. A preferred method for depositing the
thermal barrier coating is by electron bean physical vapor
deposition (EB-PVD). The deposition may occur in a chamber with a
temperature of from 1700 to 2000.degree. F. and a pressure of from
0.05 to 2.0 millitors. The ceramic feedstock may be feed at a rate
of 0.3 to 2.0 inches per hour with a coating time from 20 to 120
minutes.
[0014] If desired a bond coated may be deposited on the substrate
prior to the application of the thermal barrier coating 14. The
bond coat may be either a MCrAly coating where M is nickel and/or
cobalt, an aluminide coating, a platinum aluminide coating, a
ceramic based bond coat, or a silica based bond coat. The bond coat
may be applied using any suitable technique known in the art.
[0015] After the thermal barrier coating 14 has been applied to the
substrate 12, a plasma-sprayed layer 16 is applied on top of the
thermal barrier coating. The plasma-sprayed layer 16 is preferably
formed from a ceramic material such as yttria stabilized zirconia.
The layer 16 may be formed using a plasma-spray gun operating at
from 30 to 70 volts and from 300 to 900 amps. A mixture of argon
and helium or argon and hydrogen may be used as the carrier gas.
The gun may have a standoff distance from 2 to 8 inches and a
ceramic powder flow rate of from 30 to 70 grams per minute. The
resulting structure is a two-layer ceramic where the plasma-sprayed
layer 16 is preferably on the outer surface. The two layers 14 and
16 may not have a defined interface, but they may rather blend
together.
[0016] Plasma-sprayed coatings are formed by injecting powder,
either metallic or ceramic, into a plasma plume where the material
is heated and accelerated toward the substrate to be coated. The
molten or semi-molten particles impact the substrate and form a
splat or pancake type structure. The coating thickness is built up
as additional molten particles impact the substrate and form
splats. As these splats build up, defects are incorporated into the
coating such as porosity (both micro and macro), cracks, and splat
boundaries. Spray parameters can be adjusted to yield a very dense
or porous coating depending on the application. The resulting
structure of the outer plasma-sprayed layer acts as a barrier to
prevent the penetration of molten sand into the thermal barrier
coating below due to its lower porosity and more tortuous path. The
average porosity for the EB-PVD coating layer 14 can be anywhere
from 10 to 20%, while the porosity of the plasma-sprayed coating
layer 16 can be from 2.0 to 30% depending on the parameters
used.
[0017] The benefit of the present invention is a thermal barrier
coating system that resists penetration of molten silicate material
and provides enhanced durability in environments where sand induced
distress of turbine airfoils occurs. The outer plasma sprayed layer
seals the surface of the thermal barrier coating to limit molten
sand from penetrating therein.
[0018] It is apparent that there has been provided in accordance
with the present invention a thermal barrier coating with a
plasma-spray top layer which fully satisfies the objects, means,
and advantages set forth hereinbefore. While the present invention
has been described in the context of specific embodiments thereof,
other unforseeable alternatives, modifications and variations may
become apparent to those skilled in the art having read the
foregoing description. Accordingly, it is intended to embrace those
alternatives, modifications, and variations as fall within the
broad scope of the appended claims.
* * * * *