U.S. patent application number 14/272979 was filed with the patent office on 2014-08-28 for high temperature thermal barrier coating.
The applicant listed for this patent is ALSTOM Technology Ltd, Eidgenossische Technische Hochschule Zurich. Invention is credited to Anup BHATTACHARYA, Hans-Peter BOSSMANN, Valery SHKLOVER, Gregoire Etienne WITZ.
Application Number | 20140242411 14/272979 |
Document ID | / |
Family ID | 47137723 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140242411 |
Kind Code |
A1 |
WITZ; Gregoire Etienne ; et
al. |
August 28, 2014 |
HIGH TEMPERATURE THERMAL BARRIER COATING
Abstract
A high temperature thermal barrier coating which consists of a
stabilized ZrO.sub.2 composition for the protection of thermally
loaded components (10, 10') of a thermal machine, especially a gas
turbine, is disclosed. The thermal barrier coating is stabilized
with at least 15 mol % Y.sub.1+v Ta.sub.1-vO.sub.4-v, the ZrO.sub.2
is partially substituted by at least 10 mol % HfO.sub.2 and the
composition is established according to the formula
(Y.sub.1+vTa.sub.1-vO.sub.4-v).sub.z(Zr.sub.1-xHf.sub.xO.sub.2).sub.1-z,
with x ranging from 0.1 to 0.5, v ranging from -0.1 to 0.2 and z
ranging from 0.15 to 0.25.
Inventors: |
WITZ; Gregoire Etienne;
(Birmenstorf, CH) ; BOSSMANN; Hans-Peter;
(Lauchringen, DE) ; BHATTACHARYA; Anup; (Mumbai,
IN) ; SHKLOVER; Valery; (Zurich, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALSTOM Technology Ltd
Eidgenossische Technische Hochschule Zurich |
Baden
Zurich |
|
CH
CH |
|
|
Family ID: |
47137723 |
Appl. No.: |
14/272979 |
Filed: |
May 8, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2012/071839 |
Nov 5, 2012 |
|
|
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14272979 |
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Current U.S.
Class: |
428/623 ;
427/453; 428/457; 428/472; 428/633 |
Current CPC
Class: |
C23C 28/3215 20130101;
C23C 4/11 20160101; F01D 5/288 20130101; C23C 4/02 20130101; Y10T
428/12549 20150115; C04B 2235/3225 20130101; F05D 2230/80 20130101;
F05D 2300/135 20130101; C04B 2235/3251 20130101; C04B 2235/765
20130101; Y10T 428/12618 20150115; C04B 35/486 20130101; C23C
28/3455 20130101; F05D 2300/2118 20130101; Y10T 428/31678
20150401 |
Class at
Publication: |
428/623 ;
428/472; 428/633; 428/457; 427/453 |
International
Class: |
F01D 5/28 20060101
F01D005/28; C23C 4/10 20060101 C23C004/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 10, 2011 |
CH |
01800/11 |
Claims
1. A high temperature thermal barrier coating for the protection of
thermally loaded components of a thermal machine, especially a gas
turbine, said thermal barrier coating comprising a stabilized
ZrO.sub.2 composition, wherein said composition is stabilized with
at least 15 mol % Y.sub.1+vTa.sub.1-vO.sub.4-v, the ZrO.sub.2 is
partially substituted by at least 10 mol % HfO.sub.2 and the
composition is established according to the formula
(Y.sub.1+vTa.sub.1-vO.sub.4-v).sub.z(Zr.sub.1-xHf.sub.xO.sub.2).sub.1-z,
with x ranging from 0.1 to 0.5, v ranging from -0.1 to 0.2 and z
ranging from 0.15 to 0.25.
2. The high temperature thermal barrier coating according to claim
1, wherein x will range from 0.15 to 0.25, v will range from 0 to
0.1 and z will range from 0.18 to 0.23.
3. The high temperature thermal barrier coating according to claim
1, wherein the high temperature thermal barrier coating covers a
component made of a base alloy.
4. The high temperature thermal barrier coating according to claim
3, further comprising a bondcoat provided between the base alloy of
the component and the high temperature thermal barrier coating.
5. The high temperature thermal barrier coating according to claim
4, wherein the bondcoat consists of MCrAlYX, where M.dbd.Ni, Co or
Fe or a mixture thereof and X.dbd.Si, Ta, B, Ca or Mg or a mixture
thereof, and said bondcoat is deposited by a thermal spray
process.
6. The high temperature thermal barrier coating according to claim
4, further comprising an intermediate layer provided between the
bondcoat and the high temperature thermal barrier coating.
7. The high temperature thermal barrier coating according to claim
6, wherein the intermediate layer consists of 7YSZ deposited by a
thermal spray process.
8. The high temperature thermal barrier coating according claim 1,
wherein the high temperature thermal barrier coating is deposited
by a thermal spray process.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to PCT/EP2012/071839 filed
Nov. 5, 2012, which claims priority to Swiss application 01800/11
filed Nov. 10, 2011, both of which are hereby incorporated in their
entireties.
TECHNICAL FIELD
[0002] The present invention relates to the technology of
high-temperature components for thermal machines, especially for
gas turbines. It refers to a high temperature thermal barrier
coating according to the preamble of claim 1.
BACKGROUND
[0003] Advancements in the technology of gas turbines depend mainly
on the development of advanced materials for its components,
especially blades, vanes, heat shields or combustor liners. On the
other hand, a growth in the gas turbine market can be made
compatible with the goals of the Kyoto Protocol by increasing the
efficiency of gas turbine plants and working towards CO.sub.2
caption and storage (which will reduce the overall plant
efficiency). Increase of efficiency can be achieved either by
reduction of cooling for turbine blades and combustor liners or by
increasing firing temperature.
[0004] In the past, it has been shown that Thermal Barrier Coatings
(TBCs) of the blades or other components prepared with Yttria
Stabilized Zirconia (YSZ) reached the intrinsic limits of the
material. An increase of operating temperature can be obtained by
either incorporating new stabilizing elements to zirconia or by
using new protection materials. The goal is a new generation of gas
turbines which require TBCs being able to withstand temperatures
around 1400 .degree. C. during more than 20'000 hours. These high
operating temperatures require new coating solutions.
[0005] In the prior art, an increase of the high temperature
stability of zirconia by stabilizing it with two or more oxides has
been proposed (see for example documents U.S. Pat. No. 7,087,266,
U.S. Pat. No. 7,060,365, U.S. Pat. No. 6,960,395, U.S. Pat. No.
6,890,668 and US 2006/0046090), or entrapping stabilizing carbon or
a carbon containing gas in the pores (see documents U.S. Pat. No.
6,998,172 or US 2005/0126494), or providing an alumina containing
environmental barrier in the upper layer (see documents U.S. Pat.
No. 7,008,674 and U.S. Pat. No. 6,893,750), or compounds having a
rhombohedral phase (see documents US 2006/0121294 and US
2006/0121293) or a cubic zirconia phase (see documents U.S. Pat.
No. 6,887,595 and US 2005/0170200).
[0006] Others are working on improving the thermal stability of
zirconia by incorporating high amounts of ytterbia or yttria (see
document U.S. Pat. No. 6,946,208 or U.S. Pat. No. 6,930,066), or on
alumina containing top layer providing an environmental barrier
(see document U.S. Pat. No. 6,929,852), or on new oxides having a
pyrochlore structure (see documents U.S. Pat. No. 6,835,465, U.S.
Pat. No. 6,387,539, U.S. Pat. No. 6,387,526, U.S. Pat. No.
6,365,281, US 2006/0286401 and US 2006/0245984).
[0007] Further work is done on increasing the stability of zirconia
by mixing it with Er203 (see document U.S. Pat. No. 6,916,551), on
Re.sub.xZr.sub.1-x,C.sub.y, (see documents U.S. Pat. No. 7,041,383
and U.S. Pat. No. 6,803,135). Document U.S. Pat. No. 7,001,859
relates to work on zirconia stabilized with a primary stabilizer
together with two cluster-forming dopants.
[0008] Since YSZ stabilized with 6-8 weight percent of yttria
decomposition kinetic becomes significant at temperatures
>1200.degree. C. it cannot operate for extended operating
intervals with surface temperatures above 1200.degree. C. There are
numerous materials that can theoretically withstand surface
temperatures up to 1400.degree. C. But up to now no one has been
fully proven to be suited for use in TBC, mostly because their
chemical stability in combustion environment, therm-mechanical
compatibility and chemical stability with other TBC constituents
are only partially understood.
SUMMARY
[0009] It is an object of the present invention to provide a
high-temperature thermal barrier coating (HT-TBC), especially for
gas turbine blades, capable to withstand the operation at around
1400.degree. C. during 20'000 h and having a thermal conductivity
(TC) .kappa.<2 W/mK for the temperature range 1000.degree.
C.-1400.degree. C. of the TBC system.
[0010] It is another object of the invention to provide a component
for a thermal machine being protected by such a HT-TBC.
[0011] This and other objects are obtained by a coating according
to claim 1.
[0012] The high temperature thermal barrier coating for the
protection of thermally loaded components of a thermal machine,
especially a gas turbine, consists of a stabilized ZrO.sub.2
composition. It is characterized in that said composition is
stabilized with at least 15 mol % Y.sub.1+vTa.sub.1-vO.sub.4-v, the
ZrO.sub.2 is partially substituted by at least 10 mol % HfO.sub.2
and the composition is established according to the formula
(Y.sub.1+vTa.sub.1-vO.sub.4-v).sub.z(Zr.sub.1-xHf.sub.xO.sub.2).sub.1-z,
with x ranging from 0.1 to 0.5, v ranging from -0.1 to 0.2 and z
ranging from 0.15 to 0.25.
[0013] Especially, x will range from 0.15 to 0.25, v will range
from 0 to 0.1 and z will range from 0.18 to 0.23.
[0014] According to another embodiment of the invention the high
temperature thermal barrier coating covers a component made of a
base alloy.
[0015] According to another embodiment of the invention a bondcoat
is provided between the base alloy of the component and the high
temperature thermal barrier coating.
[0016] Especially, the bondcoat consists of MCrAlYX, where
M.dbd.Ni, Co or Fe or a mixture thereof and X.dbd.Si, Ta, B, Ca or
Mg or a mixture thereof, and said bondcoat is deposited by a
thermal spray process.
[0017] According to another embodiment of the invention an
intermediate layer is provided between the bondcoat and the high
temperature thermal barrier coating.
[0018] Especially, the intermediate layer consists of 7YSZ
deposited by a thermal spray process.
[0019] According to another embodiment of the invention the high
temperature thermal barrier coating is deposited by a thermal spray
process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The present invention is now to be explained more closely by
means of different embodiments and with reference to the attached
drawings.
[0021] FIG. 1 shows X-ray diffraction curves (intensity dependant
on diffraction angle 2.theta.) for
(YTaO.sub.4).sub.0.2(Zr.sub.1-xHf.sub.x).sub.0.8 treated at
1500.degree. C. for 4 h with different x-values;
[0022] FIG. 2 shows a section of a thermally protected component
according to an embodiment of the invention; and
[0023] FIG. 3 shows a section of a thermally protected component
according to another embodiment of the invention.
DETAILED DESCRIPTION
[0024] The invention is intended at providing a thermal barrier
coating material and system thermodynamically stable at
temperatures up to >1400.degree. C. The material is a tetragonal
stabilized material which is stable at high temperature and has a
high toughness value. Most of the high temperature stable zirconia
have a cubic structure not allowing them to have a high toughness
due to the absence of ferroelasticity in the cubic system.
[0025] Thermal barrier coating systems made of 6-8 wt %
Y.sub.2O.sub.3 stabilized ZrO.sub.2 (7YSZ) are not suited for use
at temperatures above 1300.degree. C. due to the decomposition of
the metastable tetragonal phase into cubic, and low Y.sub.2O.sub.3
content zirconia which transforms into monoclinic upon cooling. The
monoclinic to tetragonal transformation leads to a volume change
and will thus reduce the life of the coating. Fully stabilized
zirconia systems have been considered as TBC material, but they
have not the high toughness that has tetragonal 7YSZ, due to the
absence of a ferroelastic mechanism. For this reason a stable
tetragonal zirconia composition is highly desirable.
[0026] ZrO.sub.2 stabilized with YTaO.sub.4 has been proposed as a
TBC material having a tetragonal unit cell and being stable at high
temperature. The present invention proposes a ZrO.sub.2 composition
stabilized with YTaO.sub.4 where ZrO.sub.2 is partially substituted
by HfO.sub.2, bringing two advantages: [0027] 1. increased
tetragonality leading to an increase of fracture toughness; and
[0028] 2. an increased density of scattering centres for phonon
diffusion, leading to a reduction of thermal conductivity.
[0029] The HT-TBC of the invention can be applied as a single layer
ceramic layer directly on the bondcoat (see FIG. 2), or as a dual
layer system where 7YSZ is deposited as an intermediate layer on
the bondcoat and the new HT-TBC material is deposited on the 7YSZ
layer (see FIG. 3). High temperature annealing of the proposed
material composition shows no decomposition at 1500.degree. C.
after 4 hours of annealing, a condition where a 7YSZ system will be
fully decomposed.
[0030] FIG. 2 shows a section of a component according to an
embodiment of the invention, the component 10 being made of a base
alloy 11, which is covered by a bondcoat 12, the bondcoat 12 being
directly covered by a HT-TBC 13 according to the invention.
[0031] FIG. 3 shows a section of a component according to another
embodiment of the invention, the component 10' being made of a base
alloy 11, which is covered by a bondcoat 12, the bondcoat 12 being
covered by a HT-TBC 13 according to the invention with an
intermediate layer 14 being provided between the bondcoat 12 and
the HT-TBC 13.
[0032] An embodiment of the thermal barrier coating according to
the invention comprises an MCrAlYX bondcoat (with M.dbd.Ni, Co or
Fe or a mixture thereof and X.dbd.Si, Ta, B, Ca or Mg or a mixture
thereof) deposited by a thermal spray process, a HT-TBC layer
deposited by a thermal spray process composed of
(Zr.sub.1-xHf.sub.x)O.sub.2 doped with 15-25 mol % of YTaO.sub.4, x
ranging from 0.1 to 0.5, and possibly an intermediate layer of 7YSZ
deposited by thermal spray separating the bondcoat from the HT-TBC
layer.
[0033] The TaYSZH system has the following compositions: [0034] 1.
20 mol % YTaO.sub.4 in (Zr.sub.1-xHf.sub.x)O.sub.2 with x=10% to
25% [0035] 2. 20 mol % YTaO.sub.4 in (Zr.sub.1-xHf.sub.x)O.sub.2
with x=50%
[0036] Synthesis is done by reverse co-precipitation with
NH.sub.4OH as precipitating agent.
[0037] The results are: [0038] 1. Single tetragonal phase from
composition 1. [0039] 2. Single tetragonal phase +0.48 mol %
m-ZrO.sub.2 from composition 2 [0040] 3. Single tetragonal phase
was stable at 1500.degree. C. for 4 h [0041] 4. Tetragonality
increases with increasing Hf content
[0042] FIG. 1 shows X-ray diffraction curves (intensity dependant
on diffraction angle 2.theta.) for a 20 mol %
YTaO.sub.4(Zr.sub.1-xHf.sub.x) treated at 1500.degree. C. for 4 h
with x-values of x=0 (curve A), x=0.1 (curve B), x=0.25 (curve C)
and x=0.5 (curve D).
[0043] The general composition of the new coating material is
(Y.sub.1+vTa.sub.1-vO.sub.4-v).sub.z(Zr.sub.1-xHf.sub.xO.sub.2).sub.1-z,
with x ranging from 0.1 to 0.5, v ranging from -0.1 to 0.2 and z
ranging from 0.15 to 0.25. Preferably, x will range from 0.15 to
0.25, v will range from 0 to 0.1 and z will range from 0.18 to
0.23.
[0044] The thermal barrier coating according to the invention is
intended to be used for providing a thermal protection to hot parts
of thermal machines, especially gas turbines, like blades, vanes,
heat shields, burners or combustor liners. It gives the advantage
of increasing the temperature capability of current thermal barrier
coating systems by: [0045] 1. reduced decomposition kinetic
compared to currently Yttria Stabilized Zirconia YSZ, which
decomposes into a cubic and monoclinic phase upon long term
exposure at high temperatures; the proposed compositions show very
little decomposition at temperatures up to at least 1500.degree.
C., whereas current TBC are already significantly decomposed after
few hundred hours at temperatures as low as 1200.degree. C. [0046]
2. the increased tetragonality of the system brings an improvement
in fracture toughness of the material; this allows to reduce crack
growth in the ceramic upon thermal cycling.
* * * * *