U.S. patent application number 11/788295 was filed with the patent office on 2007-08-30 for rare earth modified high strength oxidation resistant superalloy with enhanced coating compatibility.
This patent application is currently assigned to Siemens Power Generation, Inc.. Invention is credited to Douglas J. Arrell, Allister W. James.
Application Number | 20070202003 11/788295 |
Document ID | / |
Family ID | 34102111 |
Filed Date | 2007-08-30 |
United States Patent
Application |
20070202003 |
Kind Code |
A1 |
Arrell; Douglas J. ; et
al. |
August 30, 2007 |
Rare earth modified high strength oxidation resistant superalloy
with enhanced coating compatibility
Abstract
The invention concerns a Ni based alloy suitable for single 5
crystalline, directionally solidified or polycrystalline components
to be used at high temperatures. The alloy is a'/ alloy and
consists of different alloying elements within defined ranges.
Among other defined ranges of elements, the alloy contains Pd in a
significant amount sufficient to provide the alloy with an improved
resistance against hydrogen embrittlement. The invention also
concerns a component designed for use as a component in a high
temperature environment. Furthermore, the invention concerns a gas
turbine arrangement. Moreover, the invention concerns the use of Pd
for providing an alloy with improved resistance against hydrogen
embrittlement. The inclusion of two or more rare earth elements in
the alloy provides enhanced bondcoat compatibility.
Inventors: |
Arrell; Douglas J.; (Oviedo,
FL) ; James; Allister W.; (Orlando, FL) |
Correspondence
Address: |
Siemens Corporation;Intellectual Property Department
170 Wood Avenue South
Iselin
NJ
08830
US
|
Assignee: |
Siemens Power Generation,
Inc.
|
Family ID: |
34102111 |
Appl. No.: |
11/788295 |
Filed: |
April 19, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP05/57043 |
Dec 21, 2005 |
|
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|
11788295 |
Apr 19, 2007 |
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Current U.S.
Class: |
420/443 |
Current CPC
Class: |
C22C 19/057 20130101;
C22C 19/055 20130101; C22C 19/056 20130101 |
Class at
Publication: |
420/443 |
International
Class: |
C22C 19/05 20060101
C22C019/05 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] The U.S. Government has a paid-up license in the invention
and the right in limited circumstances to require that patent owner
to license others on reasonable terms as provided for by the terms
of DE-FC26-05NT42644 awarded by the Department of Energy.
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2004 |
SE |
0403162-1 |
Claims
1. A nickel based superalloy consisting essentially of, in weight
percent: 7.0 to 10.0 Cr; 8.5 to 10.0 Co; 0.2 to 2.50 Mo; 6.0 to
12.0 W; 2.0 to 7.0 Ta; 5.0 to 6.0 Al; 0.2 to 1.5 Ti; 0.75 to 2.0
Hf; 0.01 to 0.20 Si; 0.05 to 5.0 Pd; 0 to 0.03 B; 0 to 0.030 Zr; 0
to 0.15 C; 0 to 8.0 Re; 0 to 8.0 Ru; 0.001 to 0.25 of a mixture of
two or more rare earth elements selected from the group of La, Y,
Ce, Nb, Sm, Gd, Pr, and Dy; <30 ppm S; and balance formed from
Ni.
2. A nickel based superalloy of claim 1, wherein, in weight
percents: 7.5 to 8.5 Cr; 9.0 to 9.5 Co; 0.3 to 0.7 Mo; 9.0 to 10.0
W; 3.0 to 3.5 Ta; 5.2 to 5.8 Al; 0.5 to 1.0 Ti; 1.0 to 1.6 Hf; 0.08
to 0.15 Si; 0.05 to 2.0 Pd; 0.005 to 0.025 B; 0.005 to 0.020 Zr;
0.05 to 0.1 C; 1.5 to 2.5 Re; 1.5 to 2.5 Ru; 0.001 to 0.1 of a
mixture of two or more rare earth elements selected from the group
of La, Y, Ce, Nb, Sm, Gd, Pr, and Dy; <8 ppm S; and the balance
formed from Ni.
3. A nickel based superalloy of claim 1, wherein, in weight
percents: 8.0 Cr; 9.3 Co; 0.5 Mo; 9.5 W; 3.2 Ta; 5.55 Al; 0.75 Ti;
1.5 Hf; 0.11 Si; 1.0 Pd; 0.015 B; 0.012 Zr; 0.08 C; 2.0 Re; 2.0 Ru;
0.02 of a mixture of two or more rare earth elements selected from
the group of La, Y, Ce, Nb, Sm, Gd, Pr, and Dy; <2 ppm S; and
the balance formed from Ni.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of international
patent application PCT/EP2005/057043 filed on Dec. 21, 2005, and
claiming priority of Sweden application 0403162-1 filed on Dec. 23,
2004, which international application was published in English as
WO 2006/067189 on Jun. 29, 2006.
FIELD OF THE INVENTION
[0003] A Ni based alloy, a component, a gas turbine arrangement and
use of Pd in connection with such an alloy.
BACKGROUND OF THE INVENTION AND PRIOR ART
[0004] The present invention relates to the field of nickel based
alloys with excellent properties for use at high temperatures. The
alloys according to the invention may for example be used for
components in gas turbines. The invention also relates to
components made from an alloy according to the invention.
Furthermore, the invention relates to a gas turbine arrangement.
Moreover, the invention relates to the use of Pd in alloys.
[0005] Many different alloys for high temperature applications are
known. A group of such alloys are called superalloys. The term
"superalloy" is used to represent complex alloys based on e.g.
nickel, iron, and cobalt, containing additional elements such as
chromium, carbon, aluminium, tungsten, rhenium, titanium, silicon
and molybdenum. The term "based" as used herein means that that
element is the largest weight fraction of the alloy, i.e. that
there is no other element in the alloy that is present in a weight
% that is the same as or higher than the weight % of the base
element. The additives are normally used to impart high values of
mechanical strength and creep resistance at elevated temperatures
and improved oxidation and hot corrosion resistance. For nickel
based superalloys, high hot strength is obtained partly by solid
solution hardening using such elements as tungsten or molybdenum
and partly by precipitation hardening. The precipitates are often
produced by adding aluminium and titanium to form the intermetallic
compound .gamma.' ("gamma prime"), based on Ni.sub.3(Ti,Al), within
the host material (.gamma.).
[0006] The document U.S. Pat. No. 6,177,046 B1 describes
.gamma./.gamma.' superalloys containing Pd. According to this
document, Pd is added in order to provide improved weldability to
the alloy. The document lists quite wide ranges for the contents of
the alloying elements. Concerning Pd, the range 4-32 weight % is
specified in the claims. According to the most preferable ranges of
the alloying elements according to different examples in this
document, the Pd content should be 5-40 weight % (Table 7), 5-45
weight % (Table 8) or 8-27 weight % (the table in column 17). In
the concrete examples in this document, the Pd content is quite
high. It is proposed that up to approximately half of the Ni
content in existing Ni based superalloys should be substituted by
Pd (see column 9).
[0007] The document U.S. Pat. No. 6,007,645 describes
.gamma./.gamma.' Ni based superalloys. The document describes
alloys said to have good hot corrosion resistance, a high
creep-rupture strength and good microstructural stability. The
document stresses that the Cr content should be low. The document
suggests several different alloy compositions. The Cr content is
never above 2.9 weight %. The document mentions that the alloy,
among other alloying elements, can contain 0-10 weight % of one or
more of the elements selected from the group consisting of Ru, Rh,
Pd, Os, Ir and Pt. It is mentioned that such elements are effective
in increasing the creep-rupture strength and oxidation and
corrosion resistance. The document does not seem to mention any
concrete example where Pd is present in the alloy.
[0008] The article "Effect of palladium on the hydrogen
embrittlement of B-doped Ni.sub.3Al" by Liu Yang and Rex B.
McLellan in the Journal of Materials Research, vol. 11, no. 4,
April 1996, pp. 862-864 discusses that hydrogen embrittlement in
B-doped Ni.sub.3Al can be reduced by the addition of Pd.
[0009] It is known that hydrogen may diffuse into alloys and
thereby be the cause of disadvantageous properties of the alloy.
For example, the hydrogen may reduce the ductility of the material,
may be the cause of the occurrence of cracks and may make the
material hard but brittle. The most important mechanism for these
effects is associated with the weakening of grain and particle
boundaries. There may also be a possible disadvantageous synergy
effect between H and S such that hydrogen sulphides are formed at
the grain and particle boundaries. It is also known that S may tend
to segregate preferentially to grain boundaries. Even very low
contents of S may be sufficient to form hydrogen sulphide layers at
these boundaries. Such problems can also occur by the formation of
nickel hydrides in the absence of sulphur. Problems of the
described kinds can be referred to as hydrogen embrittlement
(HE).
[0010] HE can be caused by the presence of hydrogen gas but may
also occur under humid conditions. Alloy elements such as Al may
oxidise in water such that free hydrogen is formed, see the paper
mentioned earlier by Yang & McLellan on gamma prime alloys and
the paper "Environmental effects on tensile and low cycle fatigue
behaviour of single crystal nickel base superalloys" by Nazmy et
al. In Scripta Materialia 48 (2003). This hydrogen can diffuse into
the alloy and cause HE.
[0011] Ni based .gamma./.gamma.' alloys are known to have excellent
properties for use at high temperatures, such as for components in
gas turbines. However, HE has been reported also for these alloys,
see the paper by Nazmy et al mentioned above.
[0012] Ni based .gamma./.gamma.' alloys are quite complex alloys.
These alloys have a matrix of the .gamma. phase, which is Ni with
other elements like Cr, Co, Fe, W, Mo and Re in solution.
Furthermore, such alloys contain particles of the .gamma.' phase,
which normally is Ni.sub.3Al with other elements like Ti, Ta and Nb
in solution. Furthermore, such alloys may contain other elements,
for example in order to strengthen grain boundaries and/or to
stabilise a protective oxide layer. It can also be noted that
different alloying elements tend to be present in different
concentrations in the .gamma. and .gamma.' phases, i.e. a certain
element may tend to be drawn to a certain one of these phases such
that a concentration of the element is higher in this phase than in
the other phase. It has for example been reported that Al tends to
partition favourably to the .gamma.' phase. It has also been
reported that Pd tends to partition favourably to the .gamma.'
phase. Furthermore, the partition of an element between the .gamma.
and .gamma.' phases may change in the presence of further elements.
It has been noted that the addition of Pd can have as an effect
that Al tends to partition more favourably to the .gamma.
phase.
SUMMARY OF THE INVENTION
[0013] Components of Ni based .gamma./.gamma.' alloys usually have
a protective oxide layer that will prevent hydrogen embrittlement.
However, the inventors of the present invention have noticed that
in particular in components that are subject to a variation in
temperature, for example between ambient temperature and a high
service temperature, and in particular if these components are also
exposed to humidity, the microstructure of the oxide scale will
change with time such that the protective oxide layer can loose at
least part of its protective effect or fail mechanically exposing
the parent material. The inventors have found that for such
components, hydrogen embrittlement is likely to occur. Since normal
air contains a certain amount of humidity, humidity can be a
problem in many cases. Furthermore, the inventors have found that
hydrogen embrittlement may be a problem in for example gas turbines
using "wet process" such as fogging and steam cooling. The hydrogen
embrittlement can shorten the time during which such components can
be used. Since for example gas turbines are expensive devices, it
is important that components in such devices can function during a
long time.
[0014] An object of the invention is to provide an improved Ni
based .gamma./.gamma.' alloy suitable to be used for components
exposed to high temperatures. A particular object it thereby that
the alloy should have improved robustness and be resistant to
hydrogen embrittlement. In particular the risk of hydrogen
embrittlement should be reduced when components made from the alloy
are subjected to thermal cycling with humid conditions under at
least parts of the cycle. An object it thereby to provide alloys
for such components which can function without failing during a
long time. A further object of the invention is to provide a
component with advantageous properties, in particular a component
that will resist hydrogen embrittlement. Still an object is to
provide a gas turbine arrangement including one or more components
that have advantageous properties when used at high temperatures.
Another object of the invention is to use Pd in Ni based
.gamma./.gamma.' alloys in order to achieve an advantageous
technical effect.
[0015] The first objects above are achieved by a Ni based alloy
suitable for single crystalline, directionally solidified or
polycrystalline components to be used at high temperatures, the
alloy being a .gamma./.gamma.' alloy and consisting, in weight %,
of: TABLE-US-00001 0.5-25 Cr 0-25 of one or more elements selected
from the group consisting of Co, Fe and Mn 1-25 of one or more
elements selected from the group consisting of Mo, W, Re and Rh
3-25 of one or more elements selected from the group consisting of
Al, Ti, Ta, Nb, and V 0-10 of one or more elements selected from
the group consisting of Ru, Os, Ir and Pt <4.0 Pd 0-3 Hf 0-2 Si
0-2 of one or more elements selected from the group consisting of
B, C, N and Zr 0-1 of one or more elements selected from the group
consisting of Y, La, Sc, the actinides and Ce and the other
lanthanides 0-2 of one or more additional elements selected from
the group consisting of all elements except for Ni and except for
those referred to above in this table balance Ni
[0016] wherein the alloy contains Pd in a significant amount
sufficient to provide the alloy with an improved resistance against
hydrogen embrittlement.
[0017] It should be noted that when in this document a content of a
group of elements is specified (for example: "of one or more
elements selected from the group consisting of . . . ") the content
means the total content of all the elements from the group that are
present in the alloy. Consequently, in case the alloy contains only
one element from the group in question, the specified content is
the content of this element.
[0018] It should also be noted that in this document, if nothing
else is said, the contents of different elements or groups of
elements always concern weight %.
[0019] It can also be noted that when a range of contents begins
with 0, this means that the presence of the element or elements in
question is optional.
[0020] The inventors of the present invention have thus found that
an improved alloy is obtained by selecting the different elements
as defined above. It has thereby been found that in particular an
improved resistance against hydrogen embrittlement is obtained. It
has been found that this improved resistance can be obtained also
with very low concentrations of Pd. Since Pd is an expensive
material, it is an advantageous aspect of the invention that only
small amounts of Pd are needed. The improved resistance against HE
is probably due to the fact that H present at the grain or particle
boundaries is drawn into the .gamma.' phase by Pd. As is mentioned
above, Pd partitions favourably to the .gamma.' phase. Furthermore,
the addition of Pd may have further advantageous effects. It has
for example been reported that Pd may be advantageous in preventing
the formation of TCP (topologically close packed) areas.
Furthermore, since Pd is very similar to Ni, its solubility in Ni
is very high. Moreover, since Pd preferentially partitions to the
.gamma.' phase, also the solubility in Ni.sub.3Al is excellent. As
indicated above, it has also been reported that the addition of Pd
may change the partitioning factors of Ni based .gamma./.gamma.'
alloys such that slightly more Al partitions to the .gamma. phase.
This means, for a given .gamma.' content, that it is possible to
add slightly more Al to the alloy. This would seem to increase the
resistance to oxidation and hot corrosion. Moreover, since it is
sufficient to use a small amount of Pd in order to obtain the
advantageous effects, no significant negative effect of the
addition of Pd has been noted (it has been reported that Pd
potentially could cause problems with heat treatment procedures and
a reduction in creep strength at high temperatures).
[0021] According to an embodiment of the alloy according to the
invention, the content of said additional elements <1.0, or even
only at the level of impurities that are normally accepted in
alloys for components to be used at high temperatures, such as
components used in gas turbines. The properties of the alloy are
easier to control if the alloy only contains a small amount (or no
amount) of such additional elements.
[0022] According to a further embodiment, the content of Pd
>0.05. The content of Pd can be <2.0, preferably <1.0 and
even <0.5. It is an advantageous aspect of the present invention
that the effects aimed at can be achieved also with small amounts
of Pd. This is particularly important since Pd is an expensive
material and since large amounts of Pd possibly could have some
negative effects.
[0023] According to a further embodiment, the content of Cr
>3.0, preferably >6.0. With a fairly large amount of Cr an
excellent corrosion and oxidation resistance is obtained.
[0024] However, according to an alternative embodiment, the content
of Cr .ltoreq.3.0. According to this alternative embodiment, a low
amount of Cr is thus used. This may increase the creep-rupture
strength of the alloy. By a careful selection of the other
elements, a sufficient corrosion and oxidation resistance can be
obtained even if the Cr content is low.
[0025] According to an embodiment, the content of one or more
elements selected from the group consisting of Co, Fe and Mn
>3.0. The content of Co can for example be >6.0. Furthermore,
the content of Co can be >(the content of Fe+the content of Mn).
Co is a material that is known to provide an alloy of this kind
with advantageous properties, in particular a sufficient hardness
at higher temperatures.
[0026] According to still another embodiment, the content of one or
more elements selected from the group consisting of Mo, W, Re and
Rh >3.0. The content of W can, according to a preferred
embodiment, be >content of Mo. Moreover, (the content of Re+the
content of Rh) can be <1.0. With a sufficient amount of for
example W, the strength of the alloy is increased. Furthermore, the
creep resistance is improved.
[0027] According to a further embodiment, the content of Al
>1.0. The content of Al can for example be >3.0 but <10.0.
The molar fraction of Al in the alloy is preferably larger than the
molar fraction of any of the other elements selected from the group
consisting of Al, Ti, Ta, Nb, and V. Al, in particular, is an
advantageous material for the formation of the .gamma.' phase.
Furthermore, Al can increase the oxidation and hot corrosion
resistance.
[0028] According to another embodiment, the content of one or more
elements selected from the group consisting of Ru, Os, Ir and Pt
>0.01 but <5.0. The addition of elements from this group can
be used to control the partition of other elements between the two
phases .gamma. and .gamma.'.
[0029] The content of Hf can, according to an embodiment, be
>0.05.
[0030] According to an embodiment, the content of Si is >0.02.
Hf and/or Si can be used for promoting the formation of a
protective oxide layer.
[0031] The content of one or more elements selected from the group
consisting of B, C, N and Zr can for example be >0.05 but
<0.8. These elements may be used to increase the strength at the
grain boundaries.
[0032] The alloy can, according to an embodiment, have a content of
one or more elements selected from the group consisting of Y, La,
Sc, the actinides and Ce and the other lanthanides >0.005. These
elements can be used to bind S, which can have as an effect that
the risk of the formation of unwanted hydrogen sulphides
decreases.
[0033] Preferably, the content of Ni >35, and, more preferred,
>50. The alloy thus preferably contains a quite large amount of
the base element Ni.
[0034] According to a further embodiment, the volume ratio
.gamma.'/.gamma.>0.4 (40%) or even >0.6 (60%). A quite high
fraction of .gamma.' is advantageous for providing a high hot
strength.
[0035] According to another object of the invention, a component
designed for use as a component in a high temperature environment
is provided in that the component is made from an alloy according
to any of the preceding embodiments. Such a component thus has
advantageous properties as described above in connection with the
embodiments of the alloy. In particular, the component can be used
at high temperatures and still have a good resistance against
hydrogen embrittlement.
[0036] According to an embodiment, the component is a component for
a gas turbine arrangement. The component can for example be a guide
vane or part of a guide vane or a turbine rotor blade or part of a
turbine rotor blade. It has been found to be particularly
advantageous to use the alloy according to the invention for such
components. The components can be used for a very long time without
risking being damaged by for example hydrogen embrittlement.
[0037] A gas turbine arrangement according to the invention
comprises at least one component as defined above. Such a gas
turbine arrangement will thus include components with advantageous
properties as described above.
[0038] A use according to the invention is achieved by using Pd
which forms part of the alloy according to any of the above
embodiments for providing said alloy, according to any of the above
embodiments, with improved resistance against hydrogen
embrittlement. The inventors of the present invention have thus
found a technical effect achieved by a careful use of Pd in alloys
of the above described kind. In particular, it is advantageous that
only a small amount of Pd is sufficient for achieving the
advantageous effects described above.
[0039] According to a preferred embodiment a nickel based
superalloy that displays a superior coating performance of a
thermal barrier coating (TBC) applied to the superalloy via a
bondcoat has in weight percents 7.0 to 10.0 chromium; 8.5 to 10.0
cobalt; 0.2 to 2.50 molybdenum; 6.0 to 12.0 tungsten; 2.0 to 7.0
tantalum; 5.0 to 6.0 aluminum; 0.2 to 1.5 titanium; 0.75 to 2.0
hafnium; 0.01 to 0.20 silicon; 0.05 to 5.0 palladium; 0 to 0.03
boron; 0 to 0.030 zirconium; 0 to 0.15 carbon; 0 to 8.0 rhenium; 0
to 8.0 ruthenium; 0.001 to 0.25 of a mixture of two or more rare
earth elements selected from the group of lanthanum, yttrium,
cerium, niobium, samarium, gadolinium, praseodymium, and
dysprosium; less than 30 ppm sulfur; and the balance formed from
nickel.
[0040] A more preferred nickel based superalloy of this embodiment
has in weight percents: 7.5 to 8.5 chromium; 9.0 to 9.5 cobalt; 0.3
to 0.7 molybdenum; 9.0 to 10.0 tungsten; 3.0 to 3.5 tantalum; 5.2
to 5.8 aluminum; 0.5 to 1.0 titanium; 1.0 to 1.6 hafnium; 0.08 to
0.15 silicon; 0.05 to 2.0 palladium; 0.005 to 0.025 boron; 0.005 to
0.020 zirconium; 0.05 to 0.1 carbon; 1.5 to 2.5 rhenium; 1.5 to 2.5
ruthenium; 0.001 to 0.1 of a mixture of two or more rare earth
elements selected from the group of lanthanum, yttrium, cerium,
niobium, samarium, gadolinium, praseodymium, and dysprosium; less
than 8 ppm sulfur; and the balance formed from nickel.
[0041] A most preferred nickel based superalloy of this embodiment
has in weight percents: 8.0 chromium; 9.3 cobalt; 0.5 molybdenum;
9.5 tungsten; 3.2 tantalum; 5.55 aluminum; 0.75 titanium; 1.5
hafnium; 0.11 silicon; 1.0 palladium; 0.015 boron; 0.012 zirconium;
0.08 carbon; 2.0 rhenium; 2.0 ruthenium; 0.02 of a mixture of two
or more rare earth elements selected from the group of lanthanum,
yttrium, cerium, niobium, samarium, gadolinium, praseodymium, and
dysprosium; less than 2 ppm sulfur; and the balance formed from
nickel.
BRIEF DESCRIPTION OF THE DRAWING
[0042] FIG. 1 shows very schematically a turbine arrangement
according to the invention with a plurality of components according
to the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0043] Below different examples of the composition of alloys
according to the invention are given. The balance is Ni in all the
below examples. In addition to Ni and to the elements specified in
these examples, the alloys, according to these examples, may
contain small amounts of impurities with a concentration which is
normally accepted in alloys of these kinds for use for components
which are intended for use at high temperatures, for example in gas
turbines. Furthermore, all the alloys are Ni based .gamma./.gamma.'
alloys. The ratio .gamma.'/.gamma. can for example be 0.4 (40%) or
>0.6 (60%). This ratio can for example be 0.5 (50%).
[0044] The first example is one concrete example with specified
amounts of the different elements. Each of the examples 2-10
defines small ranges for the different elements. The alloys
according to examples 2-10 can be obtained by slightly changing the
composition of known alloys, i.e. in particular by adding a small
amount of Pd.
[0045] The alloys are suitable for the fabrication of single
crystal or polycrystalline articles.
EXAMPLE 1
[0046] TABLE-US-00002 12.0 Cr 8.0 Co 2.0 Mo 4.0 W 4.0 Al 2.0 Ti 1.5
Ta 1.5 Nb 0.4 Pd 0.1 Hf 0.1 Si 0.01 B 0.05 C
EXAMPLE 2
[0047] TABLE-US-00003 15-17 Cr 8-9 Co 1.5-2.5 Mo 3-4 W 3-4 Al 3-4
Ti 1.5-2.5 Nb 0.1-0.5 Pd 0.05-0.2 C 0.005-0.015 B 0.05-0.015 Zr
EXAMPLE 3
[0048] TABLE-US-00004 12-14 Cr 8-10 Co 1.5-2.5 Mo 3-5 W 3-4 Al
3.5-5 Ti 3-5 Ta 1.5-2.5 Nb 0.1-0.5 Pd 0.1-0.3 C 0.015-0.025 B
0.005-0.015 Zr
EXAMPLE 4
[0049] TABLE-US-00005 12-14 Cr 8-10 Co 1.5-2.5 Mo 3-5 W 3-4 Al
3.5-4.5 Ti 3-5 Ta 0.1-0.5 Pd
EXAMPLE 5
[0050] TABLE-US-00006 7.5-9 Cr 8-11 Co 0.4-0.8 Mo 9-11 W 5-6 Al
0.5-1.5 Ti 2-4 Ta 0.1-0.5 Pd 0.05-0.2 C 0.01-0.02 B 0.005-0.05 Zr
1-2 Hf
EXAMPLE 6
[0051] TABLE-US-00007 21-25 Cr 18-20 Co 1-3 W 1.5-2.5 Al 3-4 Ti 1-2
Ta 0.5-1.5 Nb 0.1-0.5 Pd 0.1-0.2 C 0.005-0.015 B 0.05-0.15 Zr
EXAMPLE 7
[0052] TABLE-US-00008 21-25 Cr 18-20 Co 1-3 W 2-3 Al 3-4 Ti 1-2 Ta
0.5-1.5 Nb 0.1-0.5 Pd 0.1-0.2 C 0.005-0.015 B 0.05-0.15 Zr 0.5-1.5
Hf
EXAMPLE 8
[0053] TABLE-US-00009 8-9 Cr 4-6 Co 1-3 Mo 7-9 w 4.5-5.5 Al 1-2 Ti
5-7 Ta 0.1-0.5 Pd 0.05-0.15 Hf 0.05-0.15 Si 0.005-0.015 C
0.005-0.015 B
EXAMPLE 9
[0054] TABLE-US-00010 6-7 Cr 9-11 Co 0.4-0.8 Mo 5-7 w 2.5-3.5 Re
5-6 Al 0.5-1.5 Ti 5-7 Ta 0.1-0.5 Pd 0.05-0.15 Hf 0.005-0.015 Y
EXAMPLE 10
[0055] TABLE-US-00011 2.2-2.8 Cr 10-14 Co 8-10 W 6-7 Re 1.5-2.5 Ru
5.5-6.5 Al 5-6 Ta 0.1-0.5 Pd 0.05-0.15 Hf 0.05-0.15 Si
[0056] The invention also concerns the use of Pd. According to this
use, Pd, for example in the amounts according to the above
examples, is used in an alloy of the described kind for providing
the alloy within improved resistance against hydrogen
embrittlement.
[0057] In a preferred embodiment, a superalloy that further
promotes superior coating performance of a TBC applied to the
superalloy via a bondcoat may be formed from materials in the
following weight percentages: TABLE-US-00012 7.0-10.0 Cr 8.5-10.0
Co 0.2-2.50 Mo 6.0-12.0 W 2.0-7.0 Ta 5.0-6.0 Al 0.2-1.5 Ti 0.75-2.0
Hf 0.01-0.20 Si 0-0.03 B 0-0.030 Zr 0-0.15 C 0-8.0 Re 0-8.0 Ru
0.05-5.0 Pd
[0058] 0.001-0.25 of a mixture of two or more rare earth elements
selected from the group of La, Y, Ce, Nb, Sm, Gd, Pr, and Dy
[0059] less than 30 ppm S
[0060] and the balance formed from Ni.
[0061] This superalloy of this embodiment contains a relatively
high quantity of Al. Al is known to reinforce the superalloy's
.gamma.' phase as Ni.sub.3Al which improves creep rupture strength
and significantly improve oxidation resistance, although levels of
Al above 4.6 percent are often avoided to avoid excess .gamma.'
precipitate which can lower strength and degrade corrosion
resistance. The level of 5 to 6 percent in the superalloy of the
invention is required to promote the formation of an alumina scale
at the superalloy surface to which the bondcoat is applied.
[0062] The content of Pd in the superalloy of this embodiment can
be low, but in excess of 0.05 weight percent yet provides
significant resistance to hydrogen embrittlement. Although the
content of Pd can be as high as 5.0 weight percent, it is most
preferable that it is less than 2.0 weight percent and is most
preferably about 1.0 weight percent. It is an advantageous aspect
of the present invention that the effects aimed at can be achieved
with small amounts of Pd due to the expense.
[0063] The content of Cr is 7.0 to 10.0 weight percent to achieve a
good corrosion and oxidation resistance. The preferred content is
7.5 to 8.5 weight percent and is most preferably 8.0 weight
percent. To maintain a sufficient hardness at higher temperatures
Co is included at a relatively high level of 8.5 to 10.0 weight
percent. This level also improves the high temperature corrosion
resistance. A preferred Co content is 9.0 to 9.5 weight percent and
9.3 weight percent is the most preferred content. Creep rupture
strength is aided by the inclusion of a relatively high loading of
W of 6.0 to 12.0 weight percent. A preferred weight percent of W is
9.0 to 10.0 and a most preferred alloy has 9.5 weight percent.
[0064] In this embodiment for bond coat compatibility, other
elements of the composition are included at beneficial levels. For
example the levels of Mo is from 0.2 to 2.50 weight percent to and
preferably is 0.3 to 0.7 percent and most preferably 0.5 percent,
and aids in the creep rupture strength without lowering the
oxidation and corrosion resistance that can occur at levels in
excess of 2.5 weight percent. Hf is included at 0.75 to 2.0 weight
percent for corrosion resistance and oxidation resistance with a
minimum level set to permit unidirectional solidification but
maintained below 2.0 to avoid any adverse effect on the melting
point of the alloy. A Ti level of 0.2 to 1.5 weight percent is used
to improve strength but kept below levels where the oxidation
resistance is compromised. A Ta level of 2.0 to 7.0 promotes
.gamma.' strengthening in the inventive alloy. The elements B, C,
and Zr can be included at low levels to increase the strength of
the grain boundaries. Re is included at a level of up to 8.0 weight
percent and preferably at 1.5 to 2.5 weight percent to depress the
overall diffusion rate in the alloy and retard oxide
spallation.
[0065] The bond coating compatible superalloy composition of this
preferred embodiment includes two or more rare earth elements
selected from the group of La, Y, Ce, Nb, Sm, Gd, Pr and Dy. Two or
more of the rare earth elements are provides to enhance coating
performance over that where only a single rare earth metal is
included in the alloy. The combined rare earth elements are used at
or above atomic ratios to S that is sufficient to consume all S
that can be present in the superalloy, which can be up to 30 ppm or
0.003 weight percent. The combined rare earth elements must exceed
152 ppm or 0.0152 weight percent to assure that it is present in
excess of the sulfur. It is most preferred that the superalloy have
a combined rare earth elements content of about 200 ppm or 0.020
weight percent.
[0066] A more preferred superalloy for superior coating performance
comprises in weight percents: TABLE-US-00013 7.5-8.5 Cr 9.0-9.5 Co
0.3-0.7 Mo 9.0-10.0 W 3.0-3.5 Ta 5.2-5.8 Al 0.5-1.0 Ti 1.0-1.6 Hf
0.08-0.15 Si 0.005-0.025 B 0.005-0.020 Zr 0.05-0.1 C 1.5-2.5 Re
1.5-2.5 Ru 0-2.0 Pd
[0067] 0.001-0.1 of a mixture of two or more rare earth elements
selected from the group of La, Y, Ce, Nb, Sm, Gd, Pr and Dy
[0068] less than 8 ppm S
[0069] and the balance formed from Ni.
[0070] A most preferred superalloy comprises in weight percents:
TABLE-US-00014 8.0 Cr 9.3 Co 0.5 Mo 9.5 W 3.2 Ta 5.55 Al 0.75 Ti
1.5 Hf 0.11 Si 0.015 B 0.012 Zr 0.08 C 2.0 Re 2.0 Ru 1.0 Pd
[0071] 0.02 of a mixture of two or more rare earth elements
selected from the group of La, Y, Ce, Nb, Sm, Gd, Pr, and Dy
TABLE-US-00015 <2 ppm S
[0072] and the balance formed from Ni.
[0073] According to the embodiment of the nickel-base superalloys
described above it is possible to provide a high strength oxidation
resistant superalloy with enhanced bond coat compatibility. The
alloy can be used for the fabrication of gas turbine components
that display a superior thermal barrier coating (TBC) performance
which can contribute to an improvement of efficiency of the gas
turbine.
[0074] The alloys according to the invention can be produced in a
manner which is known to a person skilled in the art for producing
Ni based .gamma./.gamma.' superalloys of the prior art. The alloys
can be used for producing single crystal, directionally solidified
or polycrystalline components in a manner known to the person
skilled in the art. The alloy according to the invention can be
used for any component, or part of a component, intended for use at
high temperatures.
[0075] FIG. 1 shows very schematically a sectional view of a part
of a typical gas turbine arrangement according to the invention. In
the embodiment shown in FIG. 1, the gas turbine arrangement has an
annular combustion chamber 11. In FIG. 1 only a lower part of this
combustion chamber 11 is shown. The annular combustion chamber can
be arranged around a symmetry axis marked X-X in FIG. 1. This
symmetry axis X-X can also constitute the axis of rotation of a
rotor that forms part of the gas turbine arrangement. The
combustion chamber 11 is fixed relative to a stator part 14. The
gas turbine arrangement comprises a number of guide vanes 13. In
FIG. 1, two guide vanes 13 are shown. The guide vanes 13 are fixed
relative to the stator 14. The gas turbine arrangement also has a
number of turbine rotor blades 15. Two such rotor blades 15 are
shown in FIG. 1. The rotor blades 15 form part of the rotor that
rotates around the axis of rotation X-X. The gas turbine
arrangement can of course comprise other parts which are known to a
person skilled in the art. The gas turbine arrangement can for
example have one or more compressor stages and also additional
turbine stages. Different components in a gas turbine arrangement
can be made from alloys according to the present invention. For
example, the guide vanes 13 and/or the turbine rotor blades 15 can
be made of alloys according to the present invention. The alloys
according to the invention can also be used for parts of
components, for example for a protective layer on a guide vane 13,
turbine rotor blade 15 or other part of a gas turbine.
[0076] The invention is not limited to the described embodiments
but may be varied and modified within the scoop of the following
claims.
* * * * *