U.S. patent application number 10/922510 was filed with the patent office on 2006-02-23 for stable, high-temperature nickel-base superalloy and single-crystal articles utilizing the superalloy.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Ramgopal Darolia, Christine Govern, Kevin Swayne O'Hara, William Scott Walston.
Application Number | 20060039820 10/922510 |
Document ID | / |
Family ID | 35429334 |
Filed Date | 2006-02-23 |
United States Patent
Application |
20060039820 |
Kind Code |
A1 |
Darolia; Ramgopal ; et
al. |
February 23, 2006 |
Stable, high-temperature nickel-base superalloy and single-crystal
articles utilizing the superalloy
Abstract
An article includes a substantially single crystal piece having
a composition consisting essentially of, in weight percent, from
0.4 to 6.5 percent ruthenium, from 3 to 8 percent rhenium, from 5.8
to 10.7 percent tantalum, from 4.25 to 17.0 percent cobalt, from
0.1 to 2.0 percent hafnium, from 0.02 to 0.4 percent carbon, from
0.001 to 0.005 percent boron, from 0 to 0.02 percent yttrium, from
1 to 4 percent molybdenum, from 1.25 to 10 percent chromium, from
0.5 to 2.0 percent niobium, from 0.05 to 0.5 percent zirconium,
from 5.0 to 6.6 percent aluminum, from 0 to 2.0 percent titanium,
from 3.0 to 7.5 percent tungsten, and from 0.1 to 6 percent of
platinum, iridium, rhodium, and palladium, and combinations
thereof, balance nickel and incidental impurities.
Inventors: |
Darolia; Ramgopal; (West
Chester, OH) ; Walston; William Scott; (Cincinnati,
OH) ; O'Hara; Kevin Swayne; (Boxford, MA) ;
Govern; Christine; (Cincinnati, OH) |
Correspondence
Address: |
MCNEES WALLACE & NURICK LLC
100 PINE STREET
P.O. BOX 1166
HARRISBURG
PA
17108-1166
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
35429334 |
Appl. No.: |
10/922510 |
Filed: |
August 20, 2004 |
Current U.S.
Class: |
420/444 |
Current CPC
Class: |
F01D 25/005 20130101;
F05D 2300/607 20130101; Y02T 50/60 20130101; C22C 19/057 20130101;
C23C 28/3455 20130101; Y02T 50/671 20130101; F01D 5/28 20130101;
Y02T 50/67 20130101; C23C 28/322 20130101 |
Class at
Publication: |
420/444 |
International
Class: |
C22C 19/05 20060101
C22C019/05 |
Claims
1. A composition of matter consisting essentially of, in weight
percent, from about 0.4 to about 6.5 percent ruthenium, from about
3 to about 8 percent rhenium, from about 5.8 to about 10.7 percent
tantalum, from about 4.25 to about 17.0 percent cobalt, from 0.1 to
about 2.0 percent hafnium, from about 0.02 to about 0.4 percent
carbon, from about 0.001 to about 0.005 percent boron, from 0 to
about 0.02 percent yttrium, from about 1 to about 4 percent
molybdenum, from about 1.25 to about 10 percent chromium, from
about 0.5 to about 2.0 percent niobium, from about 0.05 to about
0.5 percent zirconium, from about 5.0 to about 6.6 percent
aluminum, from 0 to about 2.0 percent titanium, from about 3.0 to
about 7.5 percent tungsten, and from about 0.1 to about 6 percent
of an element selected from the group consisting of platinum,
iridium, rhodium, and palladium, and combinations thereof, balance
nickel and incidental impurities.
2. The composition of matter of claim 1, wherein the composition
has a nominal composition, in weight percent, of about 3 percent
ruthenium, about 5.5 percent rhenium, about 8.25 percent tantalum,
about 16.5 percent cobalt, from 0.5 to about 2.0 percent hafnium,
about 0.03 percent carbon, about 0.004 percent boron, about 0.01
percent yttrium, about 2.0 percent molybdenum, about 2 percent
chromium, from about 1 to about 2 percent niobium, from about 0.1
to about 0.5 percent zirconium, about 5.5 percent aluminum, from 0
to about 2.0 percent titanium, about 6 percent tungsten, and from
about 0.5 to about 2.0 percent of the element selected from the
group consisting of platinum, iridium, rhodium, and palladium, and
combinations thereof.
3. The composition of matter of claim 1, wherein the composition
has from about 0.5 to about 2.0 percent of the element selected
from the group consisting of platinum, iridium, rhodium, and
palladium, and combinations thereof.
4. An article comprising: a substantially single crystal piece
having a composition consisting essentially of, in weight percent,
from about 0.4 to about 6.5 percent ruthenium, from about 3 to
about 8 percent rhenium, from about 5.8 to about 10.7 percent
tantalum, from about 4.25 to about 17.0 percent cobalt, from 0.1 to
about 2.0 percent hafnium, from about 0.02 to about 0.4 percent
carbon, from about 0.001 to about 0.005 percent boron, from 0 to
about 0.02 percent yttrium, from about 1 to about 4 percent
molybdenum, from about 1.25 to about 10 percent chromium, from
about 0.5 to about 2.0 percent niobium, from about 0.05 to about
0.5 percent zirconium, from about 5.0 to about 6.6 percent
aluminum, from 0 to about 2.0 percent titanium, from about 3.0 to
about 7.5 percent tungsten, and from about 0.1 to about 6 percent
of an element selected from the group consisting of platinum,
iridium, rhodium, and palladium, and combinations thereof, balance
nickel and incidental impurities.
5. The article of claim 4, wherein the single crystal piece is
substantially free of TCP phase.
6. The article of claim 4, wherein the article has a nominal
composition, in weight percent, of about 3 percent ruthenium, about
5.5 percent rhenium, about 8.25 percent tantalum, about 16.5
percent cobalt, from 0.5 to about 2.0 percent hafnium, about 0.03
percent carbon, about 0.004 percent boron, about 0.01 percent
yttrium, about 2.0 percent molybdenum, about 2 percent chromium,
from about 1 to about 2 percent niobium, from about 0.1 to about
0.5 percent zirconium, about 5.5 percent aluminum, from 0 to about
2.0 percent titanium, about 6 percent tungsten, and from about 0.5
to about 2.0 percent of the element selected from the group
consisting of platinum, iridium, rhodium, and palladium, and
combinations thereof.
7. The article of claim 4, wherein the article has a nominal
composition including from about 0.5 to about 2.0 percent of the
element selected from the group consisting of platinum, iridium,
rhodium, and palladium, and combinations thereof.
8. The article of claim 4, wherein the article is a component of a
gas turbine engine.
9. The article of claim 4, wherein the article is a gas turbine
blade or a gas turbine vane.
10. The article of claim 4, further including a protective coating
overlying the substantially single-crystal piece.
11. The article of claim 4, wherein the single crystal piece is
substantially free of TCP phase.
Description
[0001] This invention relates to a nickel-base superalloy such as
that used in aircraft gas turbine engines, and in particular to a
single-crystal nickel-base superalloy such as that used in gas
turbine blades and vanes.
BACKGROUND OF THE INVENTION
[0002] In an aircraft gas turbine (jet) engine, air is drawn into
the front of the engine, compressed by a shaft-mounted compressor,
and mixed with fuel. The mixture is combusted, and the resulting
hot combustion gases are passed through a turbine mounted on the
same shaft. The flow of hot combustion gas turns the turbine by
contacting an airfoil portion of the turbine blade, which turns the
shaft and provides power to the compressor. The hot exhaust gases
flow from the back of the engine, driving it and the aircraft
forward. There may additionally be a bypass fan that forces air
around the center core of the engine, driven by a shaft extending
from the turbine section.
[0003] The higher the temperature of the hot combustion gas, the
greater the efficiency of the engine. There is therefore an
incentive to operate the materials of the engine at ever-higher
temperatures and loadings. A variety of techniques and structures
have been used to achieve higher temperatures, including, for
example, improved alloy compositions, oriented and single crystal
turbine blades, thermal barrier coatings that provide environmental
protection and act as insulation applied to the turbine blades, and
physical cooling techniques. Nickel-based superalloys are widely
used as the materials of construction of gas turbine blades and
vanes.
[0004] Advanced nickel-base superalloys include substantial amounts
of refractory alloying elements, such as rhenium, tungsten,
tantalum, and molybdenum, that inhibit atomic diffusion of other
elements and consequently improve the high-temperature mechanical
properties such as creep. The presence of the large amounts of
refractory alloying elements may also lead to various types of
microstructural instabilities in the articles made from the
superalloys. One such microstructural instability is the formation
of topologically close-packed (TCP) phases after prolonged exposure
of the superalloy to temperatures above about 1800.degree. F. TCP
phases are brittle and also cause partitioning of
solid-solution-strengthening elements to the TCP phases, resulting
in a loss of high-temperature strength.
[0005] There is a need for an approach that allows the refractory
elements to be present to perform their function of reducing
diffusion of other elements and improving elevated temperature
mechanical properties, while reducing or ideally avoiding
instabilities such as TCP phase formation, and while retaining or
improving high-temperature mechanical properties. The present
invention fulfills this need, and further provides related
advantages.
SUMMARY OF THE INVENTION
[0006] The present invention provides a nickel-base superalloy with
high levels of refractory metals but reduced tendency toward
microstructural instability. High-temperature mechanical properties
are also improved. Castability and heat treatability are not
sacrificed in the nickel-base superalloy.
[0007] A composition of matter consists essentially of, in weight
percent, from about 0.4 to about 6.5 percent ruthenium, from about
3 to about 8 percent rhenium, from about 5.8 to about 10.7 percent
tantalum, from about 4.25 to about 17.0 percent cobalt, from 0.1 to
about 2.0 percent hafnium, from about 0.02 to about 0.4 percent
carbon, from about 0.001 to about 0.005 percent boron, from 0 to
about 0.02 percent yttrium, from about 1 to about 4 percent
molybdenum, from about 1.25 to about 10 percent chromium, from
about 0.5 to about 2.0 percent niobium, from about 0.05 to about
0.5 percent zirconium, from about 5.0 to about 6.6 percent
aluminum, from 0 to about 2.0 percent titanium, from about 3.0 to
about 7.5 percent tungsten, and from about 0.1 to about 6 percent
of an element selected from the group consisting of platinum,
iridium, rhodium, and palladium, and combinations thereof. The
balance of the composition of matter is nickel and incidental
impurities.
[0008] A preferred composition of matter within this broad range
has a nominal composition, in weight percent, of about 3 percent
ruthenium, about 5.5 percent rhenium, about 8.25 percent tantalum,
about 16.5 percent cobalt, from 0.5 to about 2.0 percent hafnium,
about 0.03 percent carbon, about 0.004 percent boron, about 0.01
percent yttrium, about 2.0 percent molybdenum, about 2 percent
chromium, from about 1 to about 2 percent niobium, from about 0.1
to about 0.5 percent zirconium, about 5.5 percent aluminum, from 0
to about 2.0 percent titanium, about 6 percent tungsten and the
balance nickel and incidental impurities. It is preferred that this
composition has from about 0.5 to about 2.0 percent of the element
selected from the group consisting of platinum, iridium, rhodium,
and palladium, and combinations thereof.
[0009] An article comprises a substantially single crystal piece
having a composition as set forth above and elsewhere herein. The
single crystal piece is desirably substantially free of TCP phase.
The article may be a component of a gas turbine engine such as a
gas turbine blade or a gas turbine vane. In some applications,
there may be a protective coating overlying the substantially
single-crystal piece, such as an aluminide protective coating and
optionally a ceramic thermal barrier coating.
[0010] The present approach achieves mechanical properties in the
superalloy that equal or exceed those of conventional superalloys,
while minimizing, delaying, or, ideally, completely avoiding the
formation of microstructural instabilities such as TCP phases. The
presence of an elevated level of iridium, rhodium, palladium,
and/or platinum improves mechanical properties. The hafnium and
zirconium contribute to improved strength and environmental
resistance, both in the case of an uncoated article as well as a
coated article with an aluminide protective coating. Good
castability and heat treatability are retained.
[0011] Other features and advantages of the present invention will
be apparent from the following more detailed description of the
preferred embodiment, taken in conjunction with the accompanying
drawings, which illustrate, by way of example, the principles of
the invention. The scope of the invention is not, however, limited
to this preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view of a turbine blade; and
[0013] FIG. 2 is a sectional view through the turbine blade of FIG.
1, taken on line 2-2.
DETAILED DESCRIPTION OF THE INVENTION
[0014] FIG. 1 depicts a component article of a gas turbine engine
such as a turbine blade or turbine vane, and in this illustration a
turbine blade 20. The turbine blade 20 includes an airfoil 22
against which the flow of hot exhaust gas is directed. (The turbine
vane has a similar appearance in respect to the pertinent airfoil
portion.) At least the airfoil 22, and preferably the entire
turbine blade 20, is substantially single crystal. That is, there
are substantially no grain boundaries in the single crystal
portion, and the crystallographic orientation is the same
throughout. The term "substantially single crystal" means that
virtually the entire article, preferably at least 90 percent of its
volume, is a single crystal, although there may be some incidental
small regions having other crystalline orientations present. Even a
substantially single crystal article typically has a number of
low-angle grain boundaries present, and these are permitted within
the scope of the term "substantially single crystal" as is known in
the art.
[0015] The article must be substantially a single crystal (i.e.,
single grain). It may not be a polycrystal, either a random
polycrystal or an oriented polycrystal such as produced by
directional solidification. In the polycrystalline alloys, it has
been conventional to add higher levels of elements that are known
to strengthen grain boundaries, such as carbon, boron, hafnium, and
zirconium. Zirconium and hafnium are chemically reactive, modify
the morphologies of precipitate phases, and may adversely affect
the heat treatment of the alloys. Because these elements are not
needed to strength high-angle grain boundaries, which are not
present in substantially single-crystal articles, it has therefore
been the general industry practice to omit them from single-crystal
articles except in very minor amounts to strengthen the low-angle
grain boundaries that may be present. The present alloy departs
from that approach and adds substantial amounts of hafnium and
zirconium even to a substantially single-crystal alloy.
[0016] The turbine blade 20 is mounted to a turbine disk (not
shown) by a dovetail 24 which extends downwardly from the airfoil
22 and engages a slot on the turbine disk. A platform 26 extends
longitudinally outwardly from the area where the airfoil 22 is
joined to the dovetail 24. In some articles, a number of optional
cooling channels extend through the interior of the airfoil 22,
ending in openings 28 in the surface of the airfoil 22. A flow of
cooling air is directed through the cooling channels, to reduce the
temperature of the airfoil 22.
[0017] The substantially single-crystal article is preferably
manufactured by the directional solidification of a melt of the
alloy composition as discussed next. Directional solidification
techniques to produce substantially single-crystal pieces of other
materials and compositions are known in the art, and the same
techniques may be used here.
[0018] The article is formed of a nickel-base superalloy. As used
herein, "nickel-base" means that the composition has more nickel
present than any other element. The nickel-base superalloys are
typically of a composition that is strengthened by the
precipitation of gamma-prime phase or a related phase.
[0019] The article and nickel-base superalloy preferably have a
composition consisting essentially of, in weight percent, from 0.4
to 6.5 percent ruthenium, from 3 to 8 percent rhenium, from 5.8 to
10.7 percent tantalum, from 4.25 to 17.0 percent cobalt, from 0.1
to 2.0 percent hafnium, from 0.02 to 0.4 percent carbon, from 0.001
to 0.005 percent boron, from 0 to 0.02 percent yttrium, from 1 to 4
percent molybdenum, from 1.25 to 10 percent chromium, from 0.5 to
2.0 percent niobium, from 0.05 to 0.5 percent zirconium, from 5.0
to 6.6 percent aluminum, from 0 to 2.0 percent titanium, from 3.0
to 7.5 percent tungsten, and from 0.1 to 6 percent of an element
selected from the group consisting of platinum, iridium, rhodium,
and palladium, and combinations thereof. The balance of the
composition is nickel and incidental impurities.
[0020] More preferably, within this broad range the article has
specific elemental limitations, in weight percent, of 3 percent
ruthenium, 5.5 percent rhenium, 8.25 percent tantalum, 16.5 percent
cobalt, from 0.5 to 2.0 percent hafnium, 0.03 percent carbon, 0.004
percent boron, 0.01 percent yttrium, 2.0 percent molybdenum, 2
percent chromium, from 1 to 2 percent niobium, from 0.1 to 0.5
percent zirconium, 5.5 percent aluminum, from 0 to 2.0 percent
titanium, 6 percent tungsten and the balance nickel and incidental
impurities. It is preferred that this composition has from 0.5 to
2.0 percent of the element selected from the group consisting of
platinum, iridium, rhodium, and palladium, and combinations
thereof.
[0021] The amount of ruthenium may not be below about 0.4 percent
by weight because smaller amounts of ruthenium would not
effectively stabilize the microstructure against detrimental TCP
formation. The amount of ruthenium may not be above about 8 percent
by weight because the stability benefits of larger amounts of
ruthenium do not outweigh the cost and density increases to the
alloy.
[0022] The amount of rhenium may not be below about 3 percent by
weight because smaller amounts would not provide sufficient creep
rupture strength through solid solution strengthening. The amount
of rhenium may not be above about 8 percent by weight because
larger amounts lead to microstructural instability, increased cost,
and increased density of the material.
[0023] The amount of tantalum may not be below about 5.8 percent by
weight because smaller amounts would not provide sufficient creep
rupture strength through precipitation strengthening. The amount of
tantalum may not be above about 10.7 percent by weight because the
strength benefits above this level do not outweigh the cost and
density increases to the alloy.
[0024] The amount of cobalt may not be below about 4.25 percent by
weight because smaller amounts would not effectively act to
stabilize the microstructure against detrimental TCP formation. The
amount of cobalt may not be above about 17.0 percent by weight
because larger amounts are detrimental to high-temperature strength
by reducing the temperature of the gamma prime solvus.
[0025] The amount of hafnium may not be below about 0.1 percent by
weight because lower amounts would not provide sufficient low angle
grain boundary strengthening, precipitation strengthening, and
environmental resistance. The amount of hafnium may not be above
about 2.0 percent by weight because larger amounts cause difficulty
in properly heat treating the alloy to obtain the optimum
strength.
[0026] The amount of carbon may not be below about 0.02 percent by
weight because smaller amounts would not effectively serve to clean
the alloy melt of detrimental inclusions. The amount of carbon may
not be above about 0.4 percent by weight because larger amounts
cause excessive carbide formation that may reduce fatigue
properties.
[0027] The amount of boron may not be below about 0.001 percent by
weight because smaller amounts would not provide sufficient
low-angle grain boundary strength. The amount of boron may not be
above about 0.006 percent by weight because larger amounts cause
excessive incipient melting.
[0028] The amount of yttrium may not be above 0.02 percent by
weight because larger amounts cause excessive incipient
melting.
[0029] The amount of molybdenum may not be below about 1 percent by
weight because smaller amounts do not provide sufficient creep
rupture strength through solid solution strengthening. The amount
of molybdenum may not be above 4 percent by weight because larger
amounts degrade environmental resistance.
[0030] The amount of chromium may not be below about 1.25 percent
by weight because smaller amounts would not provide sufficient
environmental resistance. The amount of chromium may not be above
about 10 percent by weight because larger amounts cause
microstructural instability.
[0031] The amount of niobium may not be below about 0.5 percent by
weight because smaller amounts would not provide sufficient creep
rupture strength through precipitation strengthening. The amount of
niobium may not be above about 2 percent by weight because larger
amounts degrade environmental resistance
[0032] The amount of zirconium may not be below about 0.05 percent
by weight because smaller amounts do not provide sufficient
low-angle grain-boundary strengthening, precipitation hardening,
and environmental resistance. The amount of zirconium may not be
above about 0.5 percent by weight because larger amounts cause
excessive incipient melting.
[0033] The amount of aluminum may not be below about 5.0 percent by
weight because smaller amounts do not provide sufficient
environmental resistance. The amount of aluminum may not be above
6.6 percent by weight because larger amounts cause microstructural
instability.
[0034] The amount of titanium may not be above about 2.0 percent by
weight because larger amounts degrade environmental resistance.
[0035] The amount of tungsten may not be below about 3.0 percent by
weight because smaller amounts do not provide sufficient creep
rupture strength through solid solution strengthening. The amount
of tungsten may not be above about 7.5 percent by weight because
larger amounts cause microstructural instability.
[0036] The amount of platinum, iridium, rhodium, or palladium, or
combinations thereof, may not be less than about 0.1 percent by
weight because smaller amounts do not provide sufficient creep
strength. The amount of platinum, iridium, rhodium, or palladium,
or combinations thereof, may not be greater than about 6 percent by
weight because the strength benefits of larger amounts do not
outweigh the cost and density increase to the alloy.
[0037] FIG. 2 is a sectional view through the airfoil 22 of the
turbine blade 20. In the sectional view, the body of the airfoil 22
is made of the nickel-base superalloy discussed above. The body is
substantially a single-crystal piece 40, which is preferably
substantially free of TCP phases, both as fabricated and after
exposure for extended times at elevated temperatures, such as
exposure for more than 400 hours at a temperature above about
1800.degree. F.
[0038] The single-crystal piece 40 may be used with bare surfaces.
However, at the elevated service temperatures in a combustion gas
environment, the bare surfaces are rapidly oxidized with
significant metal loss. Optionally but preferably, a protective
coating 42 is applied overlying the surfaces 44 of the
substantially single-crystal piece 40. The protective coating 42
reduces oxidation and hot-gas damage to the surfaces 44. FIG. 2
shows two embodiments of the optional protective coating 42. In
one, the protective coating 42 includes only an environmental
coating 46 contacting the surface 44, such as a diffusional or
overlay aluminum-containing coating of the types disclosed in U.S.
Pat. No. 6,607,611, whose disclosure is incorporated by reference
in its entirety. In the other, the protective coating 42 includes
the environmental coating 46 contacting the surface 44, and
additionally a thermal barrier coating 48 of a ceramic material
such as yttria-stabilized zirconia overlying and contacting the
environmental coating 46. The thermal barrier coating 48 and its
deposition are also described in U.S. Pat. No. 6,607,611.
[0039] Although a particular embodiment of the invention has been
described in detail for purposes of illustration, various
modifications and enhancements may be made without departing from
the spirit and scope of the invention. Accordingly, the invention
is not to be limited except as by the appended claims.
* * * * *