U.S. patent application number 13/100441 was filed with the patent office on 2012-11-08 for nickel-base alloy.
This patent application is currently assigned to General Electric Company. Invention is credited to Sundar Amancherla, Stephen Joseph Balsone, Ganjiang Feng, Gitahi Charles Mukira, Jon Conrad Schaeffer, Hariharan Sundaram.
Application Number | 20120282086 13/100441 |
Document ID | / |
Family ID | 46084846 |
Filed Date | 2012-11-08 |
United States Patent
Application |
20120282086 |
Kind Code |
A1 |
Feng; Ganjiang ; et
al. |
November 8, 2012 |
NICKEL-BASE ALLOY
Abstract
The invention is a class of nickel-base alloys for gas turbine
applications, comprising, by weight, about 13.7 to about 14.3
percent chromium, about 5.0 to about 10.0 percent cobalt, about 3.5
to about 5.2 percent tungsten, about 2.8 to about 5.2 percent
titanium, about 2.8 to about 4.6 percent aluminum, about 0.0 to
about 3.5 percent tantalum, about 1.0 to about 1.7 percent
molybdenum, about 0.08 to about 0.13 percent carbon, about 0.005 to
about 0.02 percent boron, about 0.0 to about 1.5 percent niobium,
about 0.0 to about 2.5 percent hafnium, about 0.0 to about 0.04
percent zirconium, and the balance substantially nickel. The
nickel-base alloys may be provided in the form of useful articles
of manufacture, and which possess a unique combination of
mechanical properties, microstructural stability, resistance to
localized pitting and hot corrosion in high temperature corrosive
environments, and high yields during the initial forming process as
well as post-forming manufacturing and repair processes.
Inventors: |
Feng; Ganjiang; (Greenville,
SC) ; Schaeffer; Jon Conrad; (Simpsonville, SC)
; Balsone; Stephen Joseph; (Simpsonville, SC) ;
Sundaram; Hariharan; (Bangalore, IN) ; Amancherla;
Sundar; (Bangalore, IN) ; Mukira; Gitahi Charles;
(Simpsonville, SC) |
Assignee: |
General Electric Company
|
Family ID: |
46084846 |
Appl. No.: |
13/100441 |
Filed: |
May 4, 2011 |
Current U.S.
Class: |
415/200 ;
420/448; 420/449; 420/450 |
Current CPC
Class: |
C22C 19/05 20130101;
F05D 2300/607 20130101; C22C 19/056 20130101; F01D 5/28
20130101 |
Class at
Publication: |
415/200 ;
420/448; 420/449; 420/450 |
International
Class: |
F01D 9/02 20060101
F01D009/02; C22C 19/05 20060101 C22C019/05 |
Claims
1. An alloy comprising the following elements, by weight: a. about
13.7 to about 14.3 percent chromium, b. about 5.0 to about 10.0
percent cobalt, c. about 3.5 to about 5.2 percent tungsten, d.
about 2.8 to about 5.2 percent titanium, e. about 2.8 to about 4.6
percent aluminum, f. about 0.0 to about 3.5 percent tantalum, g.
about 1.0 to about 1.7 percent molybdenum, h. about 0.08 to about
0.13 percent carbon, i. about 0.005 to about 0.02 percent boron, j.
about 0.0 to about 1.5 percent niobium, k. about 0.0 to about 2.5
percent hafnium, l. about 0.0 to about 0.04 percent zirconium, m.
the balance substantially nickel.
2. The alloy of claim 1, comprising about 4.0 to about 4.6 percent
tungsten.
3. The alloy of claim 1, comprising about 3.6 to about 4.3 percent
titanium.
4. The alloy of claim 1, comprising about 3.5 to about 3.9 percent
aluminum.
5. The alloy of claim 1, comprising about 3.1 to about 3.5 percent
tantalum.
6. The alloy of claim 1, comprising about 0.0 to about 1.5 percent
niobium or about 0.0 to about 3.5 percent tantalum.
7. The alloy of claim 1, wherein the ratio of percent aluminum to
percent titanium is about 0.8 to about 1.0, by weight.
8. An alloy comprising the following elements, by weight, and
having about zero Eta phase (Ni.sub.3Ti) and segregated titanium:
a. about 13.7 to about 14.3 percent chromium, b. about 5.0 to about
10.0 percent cobalt, c. about 3.5 to about 5.2 percent tungsten, d.
about 2.8 to about 5.2 percent titanium, e. about 2.8 to about 4.6
percent aluminum, f. about 0.0 to about 3.5 percent tantalum, g.
about 1.0 to about 1.7 percent molybdenum, h. about 0.08 to about
0.13 percent carbon, i. about 0.005 to about 0.02 percent boron, j.
about 0.0 to about 1.5 percent niobium, k. about 0.0 to about 2.5
percent hafnium, l. about 0.0 to about 0.04 percent zirconium, m.
the balance substantially nickel.
9. The alloy of claim 8, comprising about 4.0 to about 4.6 percent
tungsten.
10. The alloy of claim 8, comprising about 3.6 to about 4.3 percent
titanium.
11. The alloy of claim 8, comprising about 3.5 to about 3.9 percent
aluminum.
12. The alloy of claim 8, comprising about 3.1 to about 3.5 percent
tantalum.
13. The alloy of claim 8, comprising about 0.0 to about 1.5 percent
niobium or about 0.0 to about 3.5 percent tantalum.
14. The alloy of claim 8, wherein the ratio of percent aluminum to
percent titanium is about 0.8 to about 1.0, by weight.
15. An alloy comprising the following elements, by weight: a. about
13.9 percent chromium, b. about 9.5 percent cobalt, c. about 4.5
percent tungsten, d. about 4.2 percent titanium, e. about 3.7
percent aluminum, f. about 3.4 percent tantalum, g. about 1.6
percent molybdenum, h. about 0.1 percent carbon, i. about 0.01
percent boron, j. less than 0.01 percent zirconium, k. the balance
substantially nickel.
16. An alloy comprising the following elements, by weight: a. about
13.9 percent chromium, b. about 9.5 percent cobalt, c. about 4.2
percent tungsten, d. about 3.7 percent titanium, e. about 3.7
percent aluminum, f. about 3.2 percent tantalum, g. about 1.5
percent molybdenum, h. about 0.1 percent carbon, i. about 0.01
percent boron, j. about 0.002 percent zirconium, k. the balance
substantially nickel.
17. An article of manufacture that may be used in a gas turbine and
is formed from an alloy comprising the following elements, by
weight: a. about 13.7 to about 14.3 percent chromium, b. about 5.0
to about 10.0 percent cobalt, c. about 3.5 to about 5.2 percent
tungsten, d. about 2.8 to about 5.2 percent titanium, e. about 2.8
to about 4.6 percent aluminum, f. about 0.0 to about 3.5 percent
tantalum, g. about 1.0 to about 1.7 percent molybdenum, h. about
0.08 to about 0.13 percent carbon, i. about 0.005 to about 0.02
percent boron, j. about 0.0 to about 1.5 percent niobium, k. about
0.0 to about 2.5 percent hafnium, l. about 0.0 to about 0.04
percent zirconium, m. the balance substantially nickel.
18. The alloy of claim 17, comprising about 4.0 to about 4.6
percent tungsten.
19. The alloy of claim 17, comprising about 3.6 to about 4.3
percent titanium.
20. The alloy of claim 17, comprising about 3.5 to about 3.9
percent aluminum.
21. The alloy of claim 17, comprising about 3.1 to about 3.5
percent tantalum.
22. The alloy of claim 17, comprising about 0.0 to about 1.5
percent niobium or about 0.0 to about 3.5 percent tantalum.
23. The alloy of claim 17, wherein the ratio of percent aluminum to
percent titanium is about 0.8 to about 1.0, by weight.
24. The article of claim 17, wherein the method of forming is
casting.
25. The article of claim 24, wherein the method of forming is
casting performed in such a manner as to produce an equiaxed grain
structure.
26. The article of claim 24, wherein the method of forming is
casting performed in such a manner as to produce a directionally
solidified grain structure.
27. The article of claim 24, wherein the method of forming is
casting performed in such a manner as to produce a single crystal
grain structure.
28. The article of claim 17, wherein that article is a gas turbine
bucket or other form of rotating airfoil located in the turbine hot
section.
29. The article of claim 17, wherein that article is a gas turbine
nozzle or other form of stationary airfoil located in the turbine
hot section.
30. An article that may be used in a gas turbine and is formed from
an alloy comprising the following elements, by weight: a. about
13.9 percent chromium, b. about 9.5 percent cobalt, c. about 4.5
percent tungsten, d. about 4.2 percent titanium, e. about 3.7
percent aluminum, f. about 3.4 percent tantalum, g. about 1.6
percent molybdenum, h. about 0.1 percent carbon, i. about 0.01
percent boron, j. less than 0.01 percent zirconium, k. the balance
substantially nickel.
31. The article of claim 30, wherein the method of forming is
casting.
32. The article of claim 31, wherein the method of forming is
casting performed in such a manner as to produce an equiaxed grain
structure.
33. The article of claim 30, wherein that article is a gas turbine
bucket or other form of rotating airfoil located in the turbine hot
section.
34. The article of claim 30, wherein that article is a gas turbine
nozzle or other form of stationary airfoil located in the turbine
hot section.
35. An article that may be used in a gas turbine and is formed from
an alloy comprising the following elements, by weight: a. about
13.9 percent chromium, b. about 9.5 percent cobalt, c. about 4.2
percent tungsten, d. about 3.7 percent titanium, e. about 3.7
percent aluminum, f. about 3.2 percent tantalum, g. about 1.5
percent molybdenum, h. about 0.1 percent carbon, i. about 0.01
percent boron, j. about 0.002 percent zirconium, k. the balance
substantially nickel.
36. The article of claim 35, wherein the method of forming is
casting.
37. The article of claim 36, wherein the method of forming is
casting performed in such a manner as to produce a directionally
solidified grain structure.
38. The article of claim 35, wherein that article is a gas turbine
bucket or other form of rotating airfoil located in the turbine hot
section.
39. The article of claim 35, wherein that article is a gas turbine
nozzle or other form of stationary airfoil located in the turbine
hot section.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to nickel-base
alloys for gas turbine applications, which possess a unique
combination of mechanical properties, microstructural stability,
and resistance to localized pitting and hot corrosion. More
specifically, the invention relates to a class of nickel-base
alloys having very low fractions of Eta phase and segregated
titanium; resulting in improved yield, manufacturability, and
repairability of articles formed therefrom.
[0002] The present invention is an improvement to the class of
alloys disclosed and claimed in U.S. Pat. No. 6,416,596 B1, issued
Jul. 9, 2002 to John H. Wood et al.; which was an improvement to
the class of alloys disclosed and claimed in U.S. Pat. No.
3,615,376, issued Oct. 26, 1971 to Earl W. Ross. Both patents are
assigned to the assignee hereof. The invention retains the
advantageous attributes of those alloys; including high strength
and ductility, high resistance to creep and fatigue, excellent
microstructural stability, and high resistance to localized pitting
and hot corrosion in high temperature corrosive environments. This
unique combination of properties makes those alloys attractive for
use in gas turbines.
[0003] However, an attribute of the alloys disclosed and claimed in
U.S. Pat. No. 6,416,596 (hereinafter referred to as the "reference
alloys") is the presence of "Eta" phase, a hexagonal close-packed
form of the intermetallic Ni.sub.3Ti, as well as segregated
titanium metal in the solidified alloy. During alloy
solidification, titanium has a strong tendency to be rejected from
the liquid side of the solid/liquid interface, resulting in the
segregation (local enrichment) of titanium in the solidification
front and promoting the formation of Eta in the last solidified
liquid. The segregation of titanium also reduces the solidus
temperature, increasing the fraction of .gamma./ .gamma.' eutectic
phases and resulting micro-shrinkages in the solidified alloy. The
Eta phase, in particular, may cause certain articles formed from
those alloys to be rejected during the initial forming process, as
well as post-forming manufacturing and repair processes. In
addition, the presence of Eta phase may result in degradation of
the alloy's mechanical properties during service exposure.
[0004] It was learned from experimental evaluations that the
fractions of both Eta phase and segregated titanium in the
solidified alloy are reduced by changing the alloy composition in
such a manner that the content of titanium is reduced, and the
ratio of aluminum to titanium is increased, relative to the
composition of the reference alloys. This results from atom
partitioning in the solid/liquid interface during alloy
solidification, causing a reduction in the fraction of the .gamma./
.gamma.' eutectic phase in the solidified alloy. It was also
learned in these evaluations that the Eta phase is further reduced
by changing the alloy composition in such a manner that the content
of tantalum is increased, and the ratio of aluminum to tantalum is
reduced, relative to the composition of the reference alloys.
Tantalum was known to stabilize the gamma prime (.gamma.') phase
(Ni.sub.3Al), further reducing the availability of titanium in the
alloy.
[0005] It was also known that advantageous amounts of gamma prime
(.gamma.') phase are retained when the content of tantalum is
reduced and the content of niobium is increased, such that niobium
may be entirely substituted for tantalum if desired, as taught in
U.S. Pat. No. 6,902,633 B2, issued Jun. 7, 2005 to Warren T. King
et al. and assigned to the assignee hereof; and U.S. Pat. Appl.
Publ. No. 2007/0095441 A1, published May 3, 2007 by Liang Jiang et
al. and assigned to the assignee hereof.
[0006] It was also known that increasing the contents of tantalum
and tungsten relative to the reference alloys result in improved
mechanical properties through a combination of solid solution and
precipitation strengthening. These changes produced alloys having
tensile strength, yield strength, ductility, and Low Cycle Fatigue
(LCF) strength generally comparable to the reference alloys; as
well as improved creep strength and lower machining energy relative
to the reference alloys for certain embodiments of the present
invention.
[0007] The totality of these changes produced additional benefits.
For example, the alloys exhibit a narrow solidification range
(defined as the difference in temperature between the liquidus and
solidus of the alloy) and the microstructures of the solidified
alloys exhibit a finer .gamma./.gamma.' eutectic and carbide
structure than the microstructures of the reference alloys.
BRIEF DESCRIPTION OF THE INVENTION
[0008] The present invention provides a class of nickel-base alloys
for gas turbine applications, and useful articles of manufacture
formed therefrom, which possess a unique combination of mechanical
properties, microstructural stability, resistance to localized
pitting and hot corrosion in high temperature corrosive
environments, and high yields during the initial forming process as
well as post-forming manufacturing and repair processes. The
invention is further characterized by having very low fractions of
Eta phase and segregated Titanium in the solidified nickel-base
alloys.
[0009] According to a particular embodiment of the present
invention, the nickel-base alloy comprises, by weight, about 13.7
to about 14.3 percent chromium, about 5.0 to about 10.0 percent
cobalt, about 3.5 to about 5.2 percent tungsten, about 2.8 to about
5.2 percent titanium, about 2.8 to about 4.6 percent aluminum,
about 0.0 to about 3.5 percent tantalum, about 1.0 to about 1.7
percent molybdenum, about 0.08 to about 0.13 percent carbon, about
0.005 to about 0.02 percent boron, about 0.0 to about 1.5 percent
niobium, about 0.0 to about 2.5 percent hafnium, about 0.0 to about
0.04 percent zirconium, and the balance substantially nickel.
[0010] According to another embodiment of the present invention,
wherein the form of the invention is an article of manufacture; the
nickel-base alloy comprises, by weight, about 13.7 to about 14.3
percent chromium, about 5.0 to about 10.0 percent cobalt, about 3.5
to about 5.2 percent tungsten, about 2.8 to about 5.2 percent
titanium, about 2.8 to about 4.6 percent aluminum, about 0.0 to
about 3.5 percent tantalum, about 1.0 to about 1.7 percent
molybdenum, about 0.08 to about 0.13 percent carbon, about 0.005 to
about 0.02 percent boron, about 0.0 to about 1.5 percent niobium,
about 0.0 to about 2.5 percent hafnium, about 0.0 to about 0.04
percent zirconium, and the balance substantially nickel.
[0011] Other objects and advantages of the present invention will
be better appreciated from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Non-limiting and non-exhaustive embodiments are described
with reference to the following drawings.
[0013] FIG. 1 is a photomicrograph of Alloy 1, as embodied by the
invention.
[0014] FIG. 2 is a photomicrograph of Alloy 2, as embodied by the
invention.
[0015] FIG. 3 is a photomicrograph of Alloy 3, as embodied by the
invention.
[0016] FIG. 4 is a photomicrograph of Alloy 4, as embodied by the
invention.
[0017] FIG. 5 is a photomicrograph of Alloy 5, as embodied by the
invention.
[0018] FIG. 6 is a photomicrograph of Alloy 6, as embodied by the
invention.
[0019] FIG. 7 is a photomicrograph of Alloy 7, as embodied by the
invention.
[0020] FIG. 8 is a plot showing normalized tensile strength of
Alloys 1 to 4, measured at 20.degree. C. (68.degree. F.) and
760.degree. C. (1400.degree. F.), shown as the fraction of the
average tensile strength of the reference alloys at those
temperatures.
[0021] FIG. 9 is a plot showing normalized creep life of Alloys 1
to 4, in terms of the times to 1.0% strain at 732.degree. C.
(1350.degree. F.), shown as the fraction of the average creep life
of the reference alloys at the same strain and temperature.
[0022] FIG. 10 is a plot showing the machining energy (in Joules)
required for Alloys 1 and 2 during a milling operation.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The present invention was the result of an investigation to
develop a class of nickel-base alloys for gas turbine applications,
and useful articles of manufacture formed therefrom, which possess
a unique combination of mechanical properties, microstructural
stability, resistance to localized pitting and hot corrosion in
high temperature corrosive environments, and high yields during the
initial forming process as well as post-forming manufacturing and
repair processes. The invention is further characterized by having
very low fractions of Eta phase and segregated Titanium in the
solidified nickel-base alloys.
[0024] According to a particular embodiment of the present
invention, the nickel-base alloy comprises, by weight, about 13.7
to about 14.3 percent chromium, about 5.0 to about 10.0 percent
cobalt, about 3.5 to about 5.2 percent tungsten, about 2.8 to about
5.2 percent titanium, about 2.8 to about 4.6 percent aluminum,
about 0.0 to about 3.5 percent tantalum, about 1.0 to about 1.7
percent molybdenum, about 0.08 to about 0.13 percent carbon, about
0.005 to about 0.02 percent boron, about 0.0 to about 1.5 percent
niobium, about 0.0 to about 2.5 percent hafnium, about 0.0 to about
0.04 percent zirconium, and the balance substantially nickel.
[0025] According to another embodiment of the present invention,
the nickel-base alloy is characterized by having very low fractions
of Eta phase and segregated Titanium; and comprises, by weight,
about 13.7 to about 14.3 percent chromium, about 5.0 to about 10.0
percent cobalt, about 3.5 to about 5.2 percent tungsten, about 2.8
to about 5.2 percent titanium, about 2.8 to about 4.6 percent
aluminum, about 0.0 to about 3.5 percent tantalum, about 1.0 to
about 1.7 percent molybdenum, about 0.08 to about 0.13 percent
carbon, about 0.005 to about 0.02 percent boron, about 0.0 to about
1.5 percent niobium, about 0.0 to about 2.5 percent hafnium, about
0.0 to about 0.04 percent zirconium, and the balance substantially
nickel.
[0026] According to another embodiment of the present invention,
the nickel-base alloy comprises, by weight, about 13.9 percent
chromium, about 9.5 percent cobalt, about 4.5 percent tungsten,
about 4.2 percent titanium, about 3.7 percent aluminum, about 3.4
percent tantalum, about 1.6 percent molybdenum, about 0.1 percent
carbon, about 0.01 percent boron, less than 0.01 percent zirconium,
and the balance substantially nickel.
[0027] According to yet another embodiment of the present
invention, the nickel-base alloy comprises, by weight, about 13.9
percent chromium, about 9.5 percent cobalt, about 4.2 percent
tungsten, about 3.7 percent titanium, about 3.7 percent aluminum,
about 3.2 percent tantalum, about 1.5 percent molybdenum, about 0.1
percent carbon, about 0.01 percent boron, about 0.002 percent
zirconium, and the balance substantially nickel.
[0028] According to embodiments of the present invention, wherein
the form of the invention is an article of manufacture, the article
may be formed by a casting method comprising the following steps:
(1) preparing an ingot of the composition in the amounts stated
above, (2) remelting the ingot and casting it to a form of the size
and shape of the desired article, (3) heat treating the article in
a suitable atmosphere and in accordance with a suitable time and
temperature schedule, and (4) coating the article, if desired, with
a suitable material for thermal or environmental protection. The
grain structure of the cast articles may be either equiaxed (having
no preferred orientation), directionally solidified (having a
preferred orientation), or single crystal (having no grain
boundaries). The article may be a gas turbine bucket or other form
of rotating airfoil, or a gas turbine nozzle or other form of
stationary airfoil, or another gas turbine component, that is
located in the gas turbine hot section and designed in such a
manner as to take advantage of the beneficial properties of the
alloy.
[0029] According to a particular embodiment of the present
invention, wherein the form of the invention is an article of
manufacture, the nickel-base alloy comprises, by weight, about 13.7
to about 14.3 percent chromium, about 5.0 to about 10.0 percent
cobalt, about 3.5 to about 5.2 percent tungsten, about 2.8 to about
5.2 percent titanium, about 2.8 to about 4.6 percent aluminum,
about 0.0 to about 3.5 percent tantalum, about 1.0 to about 1.7
percent molybdenum, about 0.08 to about 0.13 percent carbon, about
0.005 to about 0.02 percent boron, about 0.0 to about 1.5 percent
niobium, about 0.0 to about 2.5 percent hafnium, about 0.0 to about
0.04 percent zirconium, and the balance substantially nickel; and
the article may be formed by a casting method that produces gas
turbine airfoils or other components having either an equiaxed,
directionally solidified, or single crystal grain structure.
[0030] According to another embodiment of the present invention,
wherein the form of the invention is an article of manufacture, the
nickel-base alloy comprises, by weight, about 13.9 percent
chromium, about 9.5 percent cobalt, about 4.5 percent tungsten,
about 4.2 percent titanium, about 3.7 percent aluminum, about 3.4
percent tantalum, about 1.6 percent molybdenum, about 0.1 percent
carbon, about 0.01 percent boron, less than 0.01 percent zirconium,
and the balance substantially nickel; and the article may be formed
by a casting method that produces gas turbine airfoils or other
components having an equiaxed grain structure.
[0031] According to yet another embodiment of the present
invention, wherein the form of the invention is an article of
manufacture, the nickel-base alloy comprises, by weight, about 13.9
percent chromium, about 9.5 percent cobalt, about 4.2 percent
tungsten, about 3.7 percent titanium, about 3.7 percent aluminum,
about 3.2 percent tantalum, about 1.5 percent molybdenum, about 0.1
percent carbon, about 0.01 percent boron, about 0.002 percent
zirconium, and the balance substantially nickel; and the article
may be formed by a casting method that produces gas turbine
airfoils or other components having a directionally solidified
grain structure.
[0032] A feature of embodiments of the present invention is that
the contents of aluminum and titanium and their relative ratios may
be adjusted in such a manner that reduces the fractions of the
.gamma./.gamma.' eutectic phase, Eta phase, and segregated titanium
that form during alloy solidification. For example, the solidified
alloys are substantially free of Eta phase when the ratio of
aluminum to titanium is between about 0.8 and about 1.0, by weight.
A further benefit is a strengthening effect that may be due to an
increase in .gamma.' phase in the .gamma. matrix.
[0033] Another feature of embodiments of the present invention is
that the contents of aluminum and tantalum and their relative
ratios may be adjusted in such a manner that further reduces the
formation of Eta phase, while maintaining the fraction of .gamma.'
phase, in the solidified alloy. For example, the solidified alloys
are substantially free of Eta phase when the ratio of aluminum to
tantalum is between about 0.9 and about 1.3, by weight.
[0034] Another feature of embodiments of the present invention is
that the content of tantalum may be reduced and the content of
niobium may be increased, such that niobium may be entirely
substituted for tantalum if desired.
[0035] Another feature of embodiments of the present invention is
that the contents of tantalum and tungsten may be adjusted in such
a manner that results in a combination of precipitation and solid
solution strengthening.
[0036] Four experimental alloys having equiaxed grain structures
were formed into test articles using a casting method and
comprising the compositions given in Table 1 (in percent weight).
Alloys 2 and 3 are variations of the reference alloys, having
ratios of aluminum to titanium near the upper limit (Alloy 2) and
lower limit (Alloy 3) of the ranges specified for the reference
alloys. Alloys 1 and 4 are derivations of the reference alloys,
having higher ratios of aluminum to titanium, as well as higher
contents of tantalum and tungsten, than the ranges specified for
the reference alloys.
TABLE-US-00001 TABLE 1 Alloy 1 Alloy 2 Alloy 3 Alloy 4 Chromium
(Cr) 13.9 13.9 13.9 14.0 Cobalt (Co) 9.5 9.5 9.5 9.5 Tungsten (W)
4.5 3.7 3.8 3.9 Titanium (Ti) 4.2 5.0 5.2 3.8 Aluminum (Al) 3.7 3.3
3.0 3.8 Tantalum (Ta) 3.4 2.9 2.8 3.4 Molybdenum (Mo) 1.6 1.5 1.5
1.5 Carbon (C) 0.1 0.1 0.1 0.1 Boron (B) 0.01 0.01 0.01 0.01
Niobium (Nb) 0.02 0.03 0.03 0.03 Hafnium (Hf) 0.02 0.01 0.02 0.02
Zirconium (Zr) <0.01 <0.01 <0.01 <0.01 Nickel (Ni)
Balance Balance Balance Balance
[0037] The microstructures of the four experimental alloys from
Table 1 are shown in FIGS. 1 to 4, respectively. The
microstructural evaluations showed that Alloy 1 had no visible Eta
phase, a low fraction of eutectic phase, and a low fraction of
carbides (FIG. 1); Alloy 2 had no visible Eta phase, an expected
fraction of eutectic phase, and an expected fraction of carbides
(FIG. 2); Alloy 3 had visible Eta phase, an expected fraction of
eutectic phase, and an expected fraction of carbides (FIG. 3); and
Alloy 4 had no visible Eta phase, a low fraction of eutectic phase,
and a low fraction of carbides (FIG. 4).
[0038] Three other experimental alloys having directionally
solidified grain structures were formed into test articles using a
casting method and comprising the compositions given in Table 2 (in
percent weight). Alloy 5 is a derivation of the reference alloys,
having a higher ratio of aluminum to titanium, as well as higher
contents of tantalum and tungsten, than the ranges specified for
the reference alloys; while Alloys 6 and 7 are variations of the
reference alloys.
TABLE-US-00002 TABLE 2 Alloy 5 Alloy 6 Alloy 7 Chromium (Cr) 13.9
13.9 13.9 Cobalt (Co) 9.5 9.5 9.5 Tungsten (W) 4.2 3.7 3.7 Titanium
(Ti) 3.7 4.8 5.0 Aluminum (Al) 3.7 3.3 2.9 Tantalum (Ta) 3.2 2.6
2.6 Molybdenum (Mo) 1.5 1.5 1.5 Carbon (C) 0.1 0.1 0.1 Boron (B)
0.01 0.01 0.01 Niobium (Nb) 0.02 0.02 0.02 Hafnium (Hf) 0.01 0.01
0.01 Zirconium (Zr) 0.002 0.002 0.002 Nickel (Ni) Balance Balance
Balance
[0039] The microstructures of the three experimental alloys from
Table 2 are shown in FIGS. 5 to 7, respectively. The
microstructural evaluations showed that Alloy 5 had no visible Eta
phase and a low fraction of eutectic phase (FIG. 5); Alloy 6 had no
visible Eta phase and an expected fraction of eutectic phase (FIG.
6); and Alloy 7 had visible Eta phase and an expected fraction of
eutectic phase (FIG. 7).
[0040] The results of representative mechanical and manufacturing
evaluations performed on the test articles prepared from the four
experimental alloys from Table 1 are shown in FIGS. 8 to 10,
respectively. These results show that all four experimental alloys
have tensile strength that is above 90% of the tensile strength of
the reference alloys at both 20.degree. C. and 760.degree. C. (FIG.
8). The results also showed that the creep life of Alloy 1 at
732.degree. C. is generally equal to or greater than the creep life
of the reference alloys at 1.0% strain (FIG. 9), and that Alloy 1
required less machining energy than Alloy 2 (a variation of the
reference alloys) during milling (FIG. 12).
[0041] Summarizing, the present invention contemplates the use in a
class of nickel-base alloys of the elements aluminum, titanium,
tantalum, and tungsten in a novel manner that advantageously
improves both manufacturing yield and mechanical properties of
alloys having superior microstructural stability and resistance to
localized pitting and hot corrosion in high temperature corrosive
environments. The broad, preferred, and nominal compositions (by
weight) of this class of nickel-base alloys are summarized in Table
3.
TABLE-US-00003 TABLE 3 Broad Preferred Nominal 1 Nominal 2 Chromium
(Cr) 13.7 to 14.3 13.7 to 14.3 13.9 13.9 Cobalt (Co) 5.0 to 10.0
5.0 to 10.0 9.5 9.5 Tungsten (W) 3.5 to 5.2 4.0 to 4.6 4.5 4.2
Titanium (Ti) 2.8 to 5.2 3.6 to 4.3 4.2 3.7 Aluminum (Al) 2.8 to
4.6 3.5 to 3.9 3.7 3.7 Tantalum (Ta) 0.0 to 3.5 3.1 to 3.5 3.4 3.2
Molybdenum 1.0 to 1.7 1.0 to 1.7 1.6 1.5 (Mo) Carbon (C) 0.08 to
0.13 0.08 to 0.13 0.1 0.1 Boron (B) 0.005 to 0.02 0.005 to 0.02
0.01 0.01 Niobium (Nb) 0.0 to 1.5 0.0 to 1.5 0.02 0.02 Hafnium (Hf)
0.0 to 2.5 0.0 to 2.5 0.02 0.01 Zirconium (Zr) 0.0 to 0.04 0.0 to
0.04 <0.01 0.002 Nickel (Ni) Balance Balance Balance Balance
[0042] As used herein, an element or step recited in the singular
and proceeded with the word "a" or "an" should be understood as not
excluding plural elements or steps, unless such exclusion is
explicitly recited. Furthermore, references to "one embodiment" of
the present invention are not intended to be interpreted as
excluding the existence of additional embodiments that also
incorporate the recited features.
[0043] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
* * * * *