U.S. patent application number 11/059263 was filed with the patent office on 2006-08-17 for high strength oxidation resistant superalloy with enhanced coating compatibility.
This patent application is currently assigned to Siemens Westinghouse Power Corp.. Invention is credited to Allister William James, Michael Tamaddoni.
Application Number | 20060182649 11/059263 |
Document ID | / |
Family ID | 36815839 |
Filed Date | 2006-08-17 |
United States Patent
Application |
20060182649 |
Kind Code |
A1 |
Tamaddoni; Michael ; et
al. |
August 17, 2006 |
High strength oxidation resistant superalloy with enhanced coating
compatibility
Abstract
A superalloy with enhanced coating compatibility. The alloy is a
nickel-based alloy and may be used in various applications, such as
the production of gas turbine components, due to its high strength.
The alloys are highly oxidation resistant and have enhanced coating
compatibility. The alloys may be used as an underlying substrate
with a variety of different coatings, including thermal and
environmental barrier coatings. The alloys may be produced using
known casting and or alloy mastering techniques.
Inventors: |
Tamaddoni; Michael;
(Orlando, FL) ; James; Allister William; (Orlando,
FL) |
Correspondence
Address: |
Siemens Corporation;Intellectual Property Department
170 Wood Avenue South
Iselin
NJ
08830
US
|
Assignee: |
Siemens Westinghouse Power
Corp.
|
Family ID: |
36815839 |
Appl. No.: |
11/059263 |
Filed: |
February 16, 2005 |
Current U.S.
Class: |
420/443 ;
420/455 |
Current CPC
Class: |
Y02T 50/60 20130101;
C22C 19/03 20130101; C23C 30/00 20130101; C22C 19/057 20130101 |
Class at
Publication: |
420/443 ;
420/455 |
International
Class: |
C22C 19/03 20060101
C22C019/03; C22C 19/05 20060101 C22C019/05 |
Claims
1. A composition comprising: from about 55 to about 70 percent, by
weight, nickel; from about 1.0 to about 2.0 percent, by weight, of
hafnium; from about 5.0 to about 6.0 percent, by weight, of
aluminum; from about 8.8 to about 10.2 percent, by weight, of
tungsten; and from about 0.001 to about 0.12 percent, by weight, of
at least one rare earth element.
2. The composition of claim 1, wherein the at least one rare earth
element is selected from lanthanum, yttrium, cerium, or a
combination thereof.
3. The composition of claim 1, wherein the at least one rare earth
element comprises two rare earth elements selected from lanthanum,
yttrium, or cerium.
4. The composition of claim 1, wherein the at least one rare earth
element comprises a combination of lanthanum, yttrium, and
cerium.
5. The composition of claim 1, wherein the composition further
comprises: from about 7.2 to about 9.3 percent, by weight, of
chromium; from about 8.5 to about 10.0 percent, by weight, of
cobalt; from about 0.2 to about 0.8 percent, by weight, of
molybdenum; from about 2.8 to about 3.7 percent, by weight, of
tantalum; from about 0.4 to about 1.2 percent, by weight, of
titanium; from about 0.005 to about 0.03 percent, by weight, of
boron; from about 0.003 to about 0.03 percent, by weight, of
zirconium; and from about 0.03 to about 0.13 percent, by weight, of
carbon.
6. The composition of claim 1, wherein the composition comprises:
from about 55 to about 70 percent, by weight, nickel; from about
7.6 to about 8.5 percent, by weight, of chromium; from about 8.8 to
about 9.7 percent, by weight, of cobalt; from about 0.3 to about
0.7 percent, by weight, of molybdenum; from about 9.2 to about 9.8
percent, by weight, of tungsten; from about 3.0 to about 3.5
percent, by weight, of tantalum; from about 5.2 to about 5.8
percent, by weight, of aluminum; from about 0.6 to about 0.9
percent, by weight, of titanium; from about 0.008 to about 0.025
percent, by weight, of boron; from about 0.006 to about 0.025
percent, by weight, of zirconium; from about 0.05 to about 0.11
percent, by weight, of carbon; from about 1.2 to about 1.8 percent,
by weight, of hafnium; and from about 0.005 to about 0.05 percent,
by weight, of at least one rare earth element.
7. The composition of claim 6, wherein the at least one rare earth
element is selected from lanthanum, yttrium, cerium, or a
combination thereof.
8. The composition of claim 6, wherein the at least one rare earth
element comprises two rare earth elements selected from lanthanum,
yttrium, or cerium.
9. The composition of claim 6, wherein the at least one rare earth
element comprises a combination of lanthanum, yttrium, and
cerium.
10. The composition of claim 1, wherein the composition comprises:
from about 55 to about 70 percent, by weight, nickel; from about
7.8 to about 8.3 percent, by weight, of chromium; from about 9.1 to
about 9.5 percent, by weight, of cobalt; from about 0.4 to about
0.6 percent, by weight, of molybdenum; from about 9.4 to about 9.6
percent, by weight, of tungsten; from about 3.1 to about 3.3
percent, by weight, of tantalum; from about 5.5 to about 5.6
percent, by weight, of aluminum; from about 0.7 to about 0.8
percent, by weight, of titanium; from about 0.01 to about 0.02
percent, by weight, of boron; from about 0.01 to about 0.02
percent, by weight, of zirconium; from about 0.07 to about 0.09
percent, by weight, of carbon; from about 1.4 to about 1.6 percent,
by weight, of hafnium; and from about 0.015 to about 0.025 percent,
by weight, of at least one rare earth element.
11. The composition of claim 10, wherein the at least one rare
earth element is selected from lanthanum, yttrium, cerium, or a
combination thereof.
12. The composition of claim 10, wherein the at least one rare
earth element comprises two rare earth elements selected from
lanthanum, yttrium, or cerium.
13. The composition of claim 10, wherein the at least one rare
earth element comprises a combination of lanthanum, yttrium, and
cerium.
14. A composition comprising: from about 55 to about 70 percent, by
weight, nickel; from about 7.2 to about 9.3 percent, by weight, of
chromium; from about 8.5 to about 10.0 percent, by weight, of
cobalt; from about 0.2 to about 0.8 percent, by weight, of
molybdenum; from about 8.8 to about 10.2 percent, by weight, of
tungsten; from about 2.8 to about 3.7 percent, by weight, of
tantalum; from about 5.0 to about 6.0 percent, by weight, of
aluminum; from about 0.4 to about 1.2 percent, by weight, of
titanium; from about 0.005 to about 0.03 percent, by weight, of
boron; from about 0.003 to about 0.03 percent, by weight, of
zirconium; from about 0.03 to about 0.13 percent, by weight, of
carbon; from about 1.0 to about 2.0 percent, by weight, of hafnium;
and from about 0.001 to about 0.12 percent, by weight, of at least
one rare earth element; wherein the at least one rare earth element
is selected from lanthanum, yttrium, cerium, or a combination
thereof.
15. The composition of claim 14, wherein the composition comprises:
from about 55 to about 70 percent, by weight, nickel; from about
7.6 to about 8.5 percent, by weight, of chromium; from about 8.8 to
about 9.7 percent, by weight, of cobalt; from about 0.3 to about
0.7 percent, by weight, of molybdenum; from about 9.2 to about 9.8
percent, by weight, of tungsten; from about 3.0 to about 3.5
percent, by weight, of tantalum; from about 5.2 to about 5.8
percent, by weight, of aluminum; from about 0.6 to about 0.9
percent, by weight, of titanium; from about 0.008 to about 0.025
percent, by weight, of boron; from about 0.006 to about 0.025
percent, by weight, of zirconium; from about 0.05 to about 0.11
percent, by weight, of carbon; from about 1.2 to about 1.8 percent,
by weight, of hafnium; and from about 0.005 to about 0.05 percent,
by weight, of at least one rare earth element.
16. The composition of claim 15, wherein the composition comprises:
from about 55 to about 70 percent, by weight, nickel; from about
7.8 to about 8.3 percent, by weight, of chromium; from about 9.1 to
about 9.5 percent, by weight, of cobalt; from about 0.4 to about
0.6 percent, by weight, of molybdenum; from about 9.4 to about 9.6
percent, by weight, of tungsten; from about 3.1 to about 3.3
percent, by weight, of tantalum; from about 5.5 to about 5.6
percent, by weight, of aluminum; from about 0.7 to about 0.8
percent, by weight, of titanium; from about 0.01 to about 0.02
percent, by weight, of boron; from about 0.01 to about 0.02
percent, by weight, of zirconium; from about 0.07 to about 0.09
percent, by weight, of carbon; from about 1.4 to about 1.6 percent,
by weight, of hafnium; and from about 0.015 to about 0.025 percent,
by weight, of at least one rare earth element.
17. The composition of claim 14, wherein the at least one rare
earth element comprises two rare earth elements selected from
lanthanum, yttrium, or cerium.
18. The composition of claim 14, wherein the at least one rare
earth element comprises a combination of lanthanum, yttrium, and
cerium.
Description
FIELD OF THE INVENTION
[0001] This invention is directed generally to alloys, and more
particularly to alloys with enhanced coating compatibility.
BACKGROUND
[0002] Nickel-base superalloys are alloys having more nickel than
any other element, and contain a group of elements that provide
solid solution or gamma-prime strengthening. The gamma prime phase
forms during cooling from the solution treatment temperature. Other
secondary phases may form during heat treatment or during service.
Nickel-base superalloys are the currently preferred alloy choice
for making the components of aircraft and industrial-gas turbine
engines that are exposed to the highest temperatures. Examples
include turbine blades, turbine vanes, turbine blade rings,
combustion system components, discs, some shafts, some rotors, and
interstage seals.
[0003] A nickel-base alloy and an article of manufacture containing
a substrate formed of such a nickel-base alloy is may be seen in
the book "Superalloys II", edited by C. T. Sims, N. S. Stoloff and
W. C. Hagel (editors), John Wiley & Sons, New York 1987. Of
particular relevance in this context are chapter 4 "Nickel-base
alloys", pages 97-134, chapter 7 "Directionally Solidified
Superalloys", pages 189-214, and chapter 20 "Future of
Superalloys", pages 549-562. The book discloses particular
embodiments of such nickel-base alloys, termed as "superalloys".
These superalloys are characterized by their superior mechanical
properties and their ability to retain these properties to
temperatures amounting up to 90% of the respective melting
temperatures.
[0004] A nickel-base superalloy may be characterized in general
terms as set out above. In several instances, a nickel-base
superalloy contains a continuous matrix composed of a solid
solution of chromium in nickel and a precipitate granularly
dispersed in and coherent with the matrix and composed of an
intermetallic nickel compound. To specify the precipitate as
coherent with the matrix means that crystalline structures of the
matrix are continued into the precipitate. Thus, there are, in
general, no physical boundaries between the matrix and the grains
of the precipitate. Instead, an interface between the matrix and
the precipitate will be characterized by a local change in chemical
composition through a continuous, however strained, crystal
lattice.
[0005] It is beneficial for nickel-base superalloys to exhibit
acceptable mechanical properties at both low and high temperatures,
such as good strength, good fatigue resistance, low creep rates,
sufficient ductility, and acceptable density. It is also beneficial
for the alloys to have good corrosion and oxidation resistance in a
harsh combustion-gas environment. Further, it is beneficial for the
superalloys to have good stability in both extended exposure at
elevated temperature and during cyclic heating and cooling
patterns. These properties may be achieved through the careful
selection of the alloying elements and the processing of the
material. A number of superalloy compositions have been developed
to supply the appropriate combinations of these properties for
various applications in the gas turbine environment.
[0006] Nickel-based superalloys are widely used for hot section
components in both aero and industrial gas turbines as they retain
their excellent mechanical properties to high temperatures.
However, to operate at increasingly higher temperatures it is
sometimes necessary to apply a coating to the superalloy for
thermal protection. The thermal protection system typically
includes a bondcoat and a thermal barrier coating (TBC). The
bondcoat provides an interfacial layer between the superalloy and
the TBC. During prolonged high temperature exposure the bondcoat
degrades and this degradation eventually leads to the spallation of
the TBC and loss of thermal protection of the coating. The rate at
which the bondcoat degrades depends greatly on the composition of
the superalloy substrate. The alumina forming superalloys generally
exhibit better bondcoat compatibility and consequently longer
coating lives than the chromia forming superalloys.
[0007] Accordingly, what is needed is an alloy having better
coating compatibility. Also what is needed is an alloy having
enhanced coating compatibility that may be formed using
conventional alloy forming methods. Also what is needed is an alloy
that may be used in a variety of different applications, such as
those in gas turbine engine components.
SUMMARY OF THE INVENTION
[0008] This present invention provides an alloy having enhanced
coating compatibility. The alloys of the present invention are
nickel-based alloys and may be used in various applications, such
as the production of gas turbine components, due to the high
strength and/or oxidation resistance of the alloys. The alloys of
the present invention include large quantities of aluminum which
promotes the formation of a stable alumina scale when exposed to
high temperatures in an oxidizing environment. The alloys of the
present invention also include one or more rare earth elements
selected from lanthanum, yttrium, cerium, or a combination thereof.
The rare earth element improves oxidation resistance and/or
enhances the compatibility of the alloy with various coatings. The
alloys of the present invention may be used as an underlying
substrate with a variety of different coatings, including thermal
and environmental barrier coatings. The alloys may be produced
using known vacuum or inert environment casting and or alloy
mastering techniques. The alloys may be used in investment cast
components produced by conventional casting, directional
solidification, or single crystal casting techniques.
[0009] These and other embodiments are described in more detail
below.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The present invention is more particularly described in the
following description and examples that are intended to be
illustrative only since numerous modifications and variations
therein will be apparent to those skilled in the art. As used in
the specification and in the claims, the singular form "a," "an,"
and "the" may include plural referents unless the context clearly
dictates otherwise. Also, as used in the specification and in the
claims, the term "comprising" may include the embodiments
"consisting of" and "consisting essentially of."
[0011] The present invention provides an alloy. The alloy is
designed to have enhanced coating compatibility, especially for
thermal barrier coatings (TBC). In addition, the alloys of the
present invention may be designed to have excellent oxidation
resistance. The base superalloy, the TBC, and any bondcoat may be
considered as a system wherein each part of the system may be
matched for optimum performance and/or life of the system.
Traditionally, coatings have been developed to match existing
superalloy compositions and little work has been undertaken to
optimize the superalloy composition for coating compatibility
and/or optimum system performance.
[0012] The alloys of the present invention contain relatively large
amounts of aluminum that promotes the formation of a stable alumina
scale when exposed to a high temperature an oxidizing environment.
The alloys of the present invention also contain small amounts of
one or more rare earth elements in combined amounts of up to about
0.12% by weight of the alloy.
[0013] The addition of small amounts of rare earth elements
lanthanum (La), yttrium (Y), and/or cerium (Ce) in small amounts
has been found to dramatically improve the oxidation resistance
and/or enhance the compatibility of the alloy with various
coatings. The increase in coating life, though the addition of one
or more rare earth elements, is attributed to the ability of these
elements to form sulfides and oxi-sulfides that reduce the residual
sulfur content and that help to prevent the diffusion of sulfur
atoms to the alumina scale. Sulfur has been cited as being one of
the elements most detrimental to the protective alumina scale. One
reason for this is that sulfur reduces the adherence of the alumina
scale by weakening the Van der Waal's bond between the scale the
superalloy base material.
[0014] Accordingly, in one embodiment of the present invention, the
alloys include small amounts lanthanum, yttrium, cerium, or a
combination thereof. The alloys may include one or more rare earth
elements. Accordingly, based upon the alloy, the amounts of the
other components, and/or the selected characteristics of the final
alloy, the alloy may include only one of lanthanum, yttrium or
cerium. In alternative embodiments, the alloy may include only two
of lanthanum, yttrium or cerium. In other alternative embodiments,
the alloy may include all three of lanthanum, yttrium and
cerium.
[0015] The amounts of the at least one rare earth elements included
in the alloy may vary depending on one or more factors including,
but not limited to, the alloy, the amounts of the other components,
and/or the selected characteristics of the final alloy. In one
embodiment, the total amount of lanthanum, yttrium, cerium, or a
combination thereof in the alloy is from about 0.001 to about 0.12
percent, by weight, of the alloy. In another embodiment, the total
amount of lanthanum, yttrium, cerium, or a combination thereof in
the alloy is from about 0.005 to about 0.05 percent, by weight, of
the alloy. In yet another embodiment, the total amount of
lanthanum, yttrium, cerium, or a combination thereof in the alloy
is from about 0.015 to about 0.025 percent, by weight, of the
alloy.
[0016] In addition to the at least one rare earth element, the
alloys of the present invention include various other elements. The
amounts of each element are selected to achieve an alloy having
enhanced compatibility to coatings. The alloys of the present
invention, in various embodiments, include varying amounts of
chromium (Cr), cobalt (Co), molybdenum (Mo), tungsten (W), tantalum
(Ta), aluminum (Al), titanium (Ti), boron (B), zirconium (Zr),
carbon (C), hafnium (Hf), and nickel (Ni).
[0017] In one aspect, the alloys of the present invention include
chromium. In one embodiment, the amount of chromium in the alloy is
from about 7.2 to about 9.3 percent, by weight, of the alloy. In
another embodiment, the amount of chromium in the alloy is from
about 7.6 to about 8.5 percent, by weight, of the alloy. In yet
another embodiment, the amount of chromium in the alloy is from
about 7.8 to about 8.3 percent, by weight, of the alloy.
[0018] In another aspect, the alloys of the present invention
include cobalt. In one embodiment, the amount of cobalt in the
alloy is from about 8.5 to about 10.0 percent, by weight, of the
alloy. In another embodiment, the amount of cobalt in the alloy is
from about 8.8 to about 9.7 percent, by weight, of the alloy. In
yet another embodiment, the amount of cobalt in the alloy is from
about 9.1 to about 9.5 percent, by weight, of the alloy.
[0019] In still another aspect, the alloys of the present invention
include molybdenum. In one embodiment, the amount of molybdenum in
the alloy is from about 0.2 to about 0.8 percent, by weight, of the
alloy. In another embodiment, the amount of molybdenum in the alloy
is from about 0.3 to about 0.7 percent, by weight, of the alloy. In
yet another embodiment, the amount of molybdenum in the alloy is
from about 0.4 to about 0.6 percent, by weight, of the alloy.
[0020] In yet another aspect, the alloys of the present invention
include tungsten. In one embodiment, the amount of tungsten in the
alloy is from about 8.8 to about 10.2 percent, by weight, of the
alloy. In another embodiment, the amount of tungsten in the alloy
is from about 9.2 to about 9.8 percent, by weight, of the alloy. In
yet another embodiment, the amount of tungsten in the alloy is from
about 9.4 to about 9.6 percent, by weight, of the alloy.
[0021] In still another aspect, the alloys of the present invention
include tantalum. In one embodiment, the amount of tantalum in the
alloy is from about 2.8 to about 3.7 percent, by weight, of the
alloy. In another embodiment, the amount of tantalum in the alloy
is from about 3.0 to about 3.5 percent, by weight, of the alloy. In
yet another embodiment, the amount of tantalum in the alloy is from
about 3.1 to about 3.3 percent, by weight, of the alloy.
[0022] In yet another aspect, the alloys of the present invention
include aluminum. In one embodiment, the amount of aluminum in the
alloy is from about 5.0 to about 6.0 percent, by weight, of the
alloy. In another embodiment, the amount of aluminum in the alloy
is from about 5.2 to about 5.8 percent, by weight, of the alloy. In
yet another embodiment, the amount of aluminum in the alloy is from
about 5.5 to about 5.6 percent, by weight, of the alloy.
[0023] In still another aspect, the alloys of the present invention
include titanium. In one embodiment, the amount of titanium in the
alloy is from about 0.4 to about 1.2 percent, by weight, of the
alloy. In another embodiment, the amount of titanium in the alloy
is from about 0.6 to about 0.9 percent, by weight, of the alloy. In
yet another embodiment, the amount of titanium in the alloy is from
about 0.7 to about 0.8 percent, by weight, of the alloy.
[0024] In yet another aspect, the alloys of the present invention
include boron. In one embodiment, the amount of boron in the alloy
is from about 0.005 to about 0.03 percent, by weight, of the alloy.
In another embodiment, the amount of boron in the alloy is from
about 0.008 to about 0.025 percent, by weight, of the alloy. In yet
another embodiment, the amount of boron in the alloy is from about
0.01 to about 0.02 percent, by weight, of the alloy.
[0025] In still another aspect, the alloys of the present invention
include zirconium. In one embodiment, the amount of zirconium in
the alloy is from about 0.003 to about 0.03 percent, by weight, of
the alloy. In another embodiment, the amount of zirconium in the
alloy is from about 0.006 to about 0.025 percent, by weight, of the
alloy. In yet another embodiment, the amount of zirconium in the
alloy is from about 0.01 to about 0.02 percent, by weight, of the
alloy.
[0026] In yet another aspect, the alloys of the present invention
include carbon. In one embodiment, the amount of carbon in the
alloy is from about 0.03 to about 0.13 percent, by weight, of the
alloy. In another embodiment, the amount of carbon in the alloy is
from about 0.05 to about 0.11 percent, by weight, of the alloy. In
yet another embodiment, the amount of carbon in the alloy is from
about 0.07 to about 0.09 percent, by weight, of the alloy.
[0027] In still another aspect, the alloys of the present invention
include hafnium. In one embodiment, the amount of hafnium in the
alloy is from about 1.0 to about 2.0 percent, by weight, of the
alloy. In another embodiment, the amount of hafnium in the alloy is
from about 1.2 to about 1.8 percent, by weight, of the alloy. In
yet another embodiment, the amount of hafnium in the alloy is from
about 1.4 to about 1.6 percent, by weight, of the alloy.
[0028] The balance of the alloy, i.e. from about 55 to about 70
percent, by weight, is nickel.
[0029] The alloys of the present invention may be produced by known
vacuum or inert environment casting and or alloy mastering
techniques. The alloys may be used in investment cast components
produced by conventional casting, directional solidification or
single crystal casting techniques.
[0030] One example of a conventional casting technique is equiaxed
investment casting in which there is a thin-shell ceramic mold
comprised of a pour cup, sprue, runners, gates and component
patterns. The alloy is pre-melted in a crucible and subsequently
poured into the ceramic mold where is solidifies with an equiaxed
grain structure. Upon completion of alloy solidification, the
ceramic shell is broken away from the cast components. The cast
components are cut away from the gating system and finished into a
final casting.
[0031] One example of a directional solidification casting method
is directionally solidified investment casting in which there is a
thin-shell ceramic mold comprised of a pour cup, sprue, runners,
gates, starter blocks and component patterns arranged such that the
bottom of the mold is open at the starter blocks. The alloy is
pre-melted in a crucible and subsequently poured into the ceramic
mold which sits on a `chill plate`. Solidification of the molten
alloy initiates at the starter blocks and is subsequently
controlled by the removal of heat from the bottom of the mold to
the top, resulting in a `directionally solidified` grain structure.
Upon completion of alloy solidification, the ceramic shell is
broken away from the cast components. The cast components are cut
away from the gating system and starter blocks and finished into a
final casting.
[0032] The superalloys of the present invention may be used in the
formation of a wide variety of different articles. Examples of
articles that may be made by the present invention include, but are
not limited to, gas turbine components such as turbine blades,
turbine vanes, turbine blade rings, combustion system components,
heat shield elements, or a combination thereof.
[0033] The alloys of the present invention have enhanced coating
compatibilities. As such, coatings may be applied either directly
to the alloy, or onto a bondcoat that has been applied to the
alloy. The coating that may be applied may be any coating capable
of being applied to an alloy. Examples of coatings that may be
applied include, but are not limited to, bondcoats, overlay
coatings, environmental barrier coatings, thermal barrier coatings,
or a combination thereof.
[0034] The foregoing is provided for purposes of illustrating,
explaining, and describing embodiments of this invention.
Modifications and adaptations to these embodiments will be apparent
to those skilled in the art and may be made without departing from
the scope or spirit of this invention.
* * * * *