U.S. patent application number 11/446168 was filed with the patent office on 2007-03-15 for nickel based superalloy.
Invention is credited to Robert W. Broomfield, Kenneth C. Grubb, Colin N. Jones, Catherine M.F Rae.
Application Number | 20070059550 11/446168 |
Document ID | / |
Family ID | 35248772 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070059550 |
Kind Code |
A1 |
Jones; Colin N. ; et
al. |
March 15, 2007 |
Nickel based superalloy
Abstract
A nickel based single crystal superalloy comprising 7-9 wt %
cobalt, 3.5-4.5 wt % chromium, 0-2.4 wt % molybdenum, 4-8 wt %
tungsten, 3.5-6 wt % rhenium, 5-6.5 wt % aluminium, 6.5-8.5 wt %
tantalum, 0-0.2 wt % hafnium and the balance nickel plus incidental
impurities. The nickel based single crystal superalloy is suitable
for use as a gas turbine engine turbine blade or turbine vane. It
is of particular us on cooled turbine blades and turbine vanes
which have ceramic thermal barrier coatings, because the superalloy
is compatible with the ceramic thermal barrier coating to minimise
spalling. The superalloy has better mechanical properties than
other second-generation single crystal superalloys and has better
creep strength and oxidation resistance.
Inventors: |
Jones; Colin N.;
(Nottingham, GB) ; Broomfield; Robert W.;
(Bristol, GB) ; Rae; Catherine M.F; (Cambridge,
GB) ; Grubb; Kenneth C.; (Bristol, GB) |
Correspondence
Address: |
MANELLI DENISON & SELTER
2000 M STREET NW SUITE 700
WASHINGTON
DC
20036-3307
US
|
Family ID: |
35248772 |
Appl. No.: |
11/446168 |
Filed: |
June 5, 2006 |
Current U.S.
Class: |
428/632 ;
148/428; 420/444; 428/670; 428/680 |
Current CPC
Class: |
C22C 19/00 20130101;
Y10T 428/12611 20150115; F23M 2900/05004 20130101; C22C 19/057
20130101; F23R 3/007 20130101; Y10T 428/12875 20150115; C30B 21/02
20130101; Y10T 428/12944 20150115; C21D 2201/04 20130101; C30B
29/52 20130101; C22F 1/10 20130101 |
Class at
Publication: |
428/632 ;
428/670; 428/680; 148/428; 420/444 |
International
Class: |
C22C 19/05 20060101
C22C019/05 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2005 |
GB |
0513121.4 |
Claims
1. A nickel based single crystal superalloy comprising 7-9 wt %
cobalt, 3.5-4.5 wt % chromium, 0-2.4 wt % molybdenum, 4-8 wt %
tungsten, 3.5-6 wt % rhenium, 5-6.5 wt % aluminium, 6.5-8.5 wt %
tantalum, 0-0.2 wt % hafnium and the balance nickel plus incidental
impurities.
2. A nickel based single crystal superalloy as claimed in claim 1
comprising 7.5-8.5 wt % cobalt, 3.5-4.5 wt % chromium, 0-2.4 wt %
molybdenum, 4-7.5 wt % tungsten, 3.5-5.8 wt % rhenium, 5.3-6.3 wt %
aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
3. A nickel based single crystal superalloy as claimed in claim 1
comprising 7-9 wt % cobalt, 3.5-4.5 wt % chromium, 2-2.4 wt %
molybdenum, 4-5 wt % tungsten, 3.5-4.5 wt % rhenium, 5-6.5 wt %
aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
4. A nickel based single crystal superalloy as claimed in claim 3
comprising 7.5-8.5 wt % cobalt, 3.5-4.5 wt % chromium, 2-2.4 wt %
molybdenum, 4-5 wt % tungsten, 3.5-4.5 wt % rhenium, 5.3-6.3 wt %
aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
5. A nickel based single crystal superalloy as claimed in claim 4
comprising 7.7-8.3 wt % cobalt, 3.7-4.3 wt % chromium, 2-2.4 wt %
molybdenum, 4.3-4.9 wt % tungsten, 3.8-4.4 wt % rhenium, 5.5-6.1 wt
% aluminium, 7.2-7.8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
6. A nickel based single crystal superalloy as claimed in claim 5
comprising 8 wt % cobalt, 4 wt % chromium, 2.2 wt % molybdenum, 4.6
wt % tungsten, 4.1 wt % rhenium, 5.8 wt % aluminium, 7.5 wt %
tantalum, 0.1 wt % hafnium and the balance nickel plus incidental
impurities.
7. A nickel based single crystal superalloy as claimed in claim 1
comprising 7-9 wt % cobalt, 3.5-4.5 wt % chromium, 6-8 wt %
tungsten, 4.8-5.8 wt % rhenium, 5-6.5 wt % aluminium, 7-8 wt %
tantalum, 0.05-0.15 wt % hafnium and the balance nickel plus
incidental impurities.
8. A nickel based single crystal superalloy as claimed in claim 7
comprising 7.5-8.5 wt % cobalt, 3.5-4.5 wt % chromium, 6-8 wt %
tungsten, 4.8-5.8 wt % rhenium, 5.3-6.3 wt % aluminium, 7-8 wt %
tantalum, 0.05-0.15 wt % hafnium and the balance nickel plus
incidental impurities.
9. A nickel based single crystal superalloy as claimed in claim 8
comprising 7.7-8.3 wt % cobalt, 3.7-4.3 wt % chromium, 6.5-7.5 wt %
tungsten, 5.0-5.6 wt % rhenium, 5.5-6.1 wt % aluminium, 7.0-8.0 wt
% tantalum, 0.05-0.15 wt % hafnium and the balance nickel plus
incidental impurities.
10. A nickel based single crystal superalloy as claimed in claim 9
comprising 8 wt % cobalt, 4 wt % chromium, 7 wt % tungsten, 5.3 wt
% rhenium, 5.8 wt % aluminium, 7.5 wt % tantalum, 0.1 wt % hafnium
and the balance nickel plus incidental impurities.
11. A cast single crystal nickel based superalloy article
comprising 7-9 wt % cobalt, 3.5-4.5 wt % chromium, 0-2.4 wt %
molybdenum, 4-8 wt % tungsten, 3.5-6 wt % rhenium, 5-6.5 wt %
aluminium, 6.5-8.5 wt % tantalum, 0-0.2 wt % hafnium and the
balance nickel plus incidental impurities.
12. A cast single crystal nickel based superalloy article as claim
in claim 11 comprising 7.5-8.5 wt % cobalt, 3.5-4.5 wt % chromium,
0-2.4 wt % molybdenum, 4-7.5 wt % tungsten, 3.5-5.8 wt % rhenium,
5.3-6.3 wt % aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium
and the balance nickel plus incidental impurities.
13. A cast single crystal nickel based superalloy article as
claimed in claim 11 comprising 7-9 wt % cobalt, 3.5-4.5 wt %
chromium, 2-2.4 wt % molybdenum, 4-5 wt % tungsten, 3.5-4.5 wt %
rhenium, 5-6.5 wt % aluminium, 7-8 wt % tantalum, 0.05-0.15 wt %
hafnium and the balance nickel plus incidental impurities.
14. A cast single crystal nickel based superalloy article as
claimed in claim 13 comprising 7.5-8.5 wt % cobalt, 3.5-4.5 wt %
chromium, 2-2.4 wt % molybdenum, 4-5 wt % tungsten, 3.5-4.5 wt %
rhenium, 5.3-6.3 wt % aluminium, 7-8 wt % tantalum, 0.05-0.15 wt %
hafnium and the balance nickel plus incidental impurities.
15. A cast single crystal nickel based superalloy article as
claimed in claim 14 comprising 7.7-8.3 wt % cobalt, 3.7-4.3 wt %
chromium, 2-2.4 wt % molybdenum, 4.3-4.9 wt % tungsten, 3.8-4.4 wt
% rhenium, 5.5-6.1 wt % aluminium, 7.2-7.8 wt % tantalum, 0.05-0.15
wt % hafnium and the balance nickel plus incidental impurities.
16. A cast single crystal nickel based superalloy article as
claimed in claim 15 comprising 8 wt % cobalt, 4 wt % chromium, 2.2
wt % molybdenum, 4.6 wt % tungsten, 4.1 wt % rhenium, 5.8 wt %
aluminium, 7.5 wt % tantalum, 0.1 wt % hafnium and the balance
nickel plus incidental impurities.
17. A cast single crystal nickel based superalloy article as
claimed in claim 11 comprising 7-9 wt % cobalt, 3.5-4.5 wt %
chromium, 6-8 wt % tungsten, 4.8-5.8 wt % rhenium, 5-6.5 wt %
aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
18. A cast single crystal nickel based superalloy article as
claimed in claim 17 comprising 7.5-8.5 wt % cobalt, 3.5-4.5 wt %
chromium, 6-8 wt % tungsten, 4.8-5.8 wt % rhenium, 5.3-6.3 wt %
aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
19. A cast single crystal nickel based superalloy article as
claimed in claim 18 comprising 7.7-8.3 wt % cobalt, 3.7-4.3 wt %
chromium, 6.5-7.5 wt % tungsten, 5.0-5.6 wt % rhenium, 5.5-6.1 wt %
aluminium, 7.0-8.0 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
20. A cast single crystal nickel based superalloy article as
claimed in claim 19 comprising 8 wt % cobalt, 4 wt % chromium, 7 wt
% tungsten, 5.3 wt % rhenium, 5.8 wt % aluminium, 7.5 wt %
tantalum, 0.1 wt % hafnium, and the balance nickel plus incidental
impurities.
21. A cast single crystal nickel based superalloy article as
claimed in claim 11 wherein the article comprises a turbine blade,
a turbine vane or a combustor component.
22. A cast single crystal nickel based superalloy article as
claimed in claim 21 wherein the article comprises at least one
internal passage for the flow of cooling fluid.
23. A cast single crystal nickel based superalloy article as
claimed in claim 21 wherein the article comprises a bond coating on
the article and a ceramic thermal barrier coating on the bond
coating.
24. A cast single crystal nickel based superalloy article as
claimed in claim 23 wherein the bond coating comprises a layer of
alumina.
25. A cast single crystal nickel based superalloy article as
claimed in claim 23 wherein the bond coating comprises a layer
comprising platinum enriched gamma prime phase and platinum
enriched gamma phase.
26. A nickel based single crystal superalloy comprising 7.8-8.2 wt
% cobalt, 3.8-4.2 wt % chromium, 6.8-7.2 wt % tungsten, 5.1-5.5 wt
% rhenium, 5.6-6.0 wt % aluminium, 7.7-7.9 wt % tantalum, 0.05-0.15
wt % hafnium and the balance nickel plus incidental impurities.
27. A cast single crystal nickel based superalloy article
comprising 7.8-8.2 wt % cobalt, 3.8-4.2 wt % chromium, 6.8-7.2 wt %
tungsten, 5.1-5.5 wt % rhenium, 5.6-6.0 wt % aluminium, 7.7-7.9 wt
% tantalum, 0.05-0.15 wt % hafnium and the balance nickel plus
incidental impurities.
Description
[0001] The present invention relates to nickel based superalloys,
particularly to nickel based single crystal superalloys, or
particularly nicked based single crystal superalloys for use as
turbine blades, turbine vanes, turbine seals and combustor
components of gas turbine engines, but they may be used in internal
combustion engines etc.
[0002] Nickel based single crystal superalloys have been developed
to provide improved high temperature mechanical properties such as
creep strength. However, there are many other important properties,
which need to be optimised to a high level in order for a nickel
based single crystal superalloy to be acceptable for use in a gas
turbine engine. Other properties, which need to be optimised, are
density, resistance to oxidation, resistance to corrosion,
compatibility with protective coatings, heat treatment response and
castability.
[0003] There are three generations of nickel based single crystal
superalloys which differ by the amount of the key element rhenium.
The first generation of nickel based single crystal superalloys
contained no rhenium, examples of these are disclosed in published
UK patent application nos. GB2039296A, GB2073774A, GB2105369A,
GB2106138A and GB2151659A. The first generation of nickel based
single crystal superalloys have densities of 7.9 to 8.7 gm per
cm.sup.3. The second generation of nickel based single crystal
superalloys contained about 3 wt % rhenium, examples of these are
disclosed in published European patent application nos. EP0155827A
and EP0208645A. The second generation of nickel based single
crystal superalloys have densities of 8.7 to 8.9 gm per cm.sup.3.
The second generation of nickel based single crystal superalloys
have a benefit in creep strength capability of about 30.degree. C.
over the first generation of nickel based single crystal
superalloys. The third generation of nickel based single crystal
superalloys contained about 6 wt % rhenium, examples of these are
disclosed in U.S. Pat. Nos. 5,366,695 and 5,270,123 and published
European patent application no. EP0848071A. The third generation of
nickel based single crystal superalloys have densities of 8.9 to
9.1 gm per cm.sup.3. The third generation of nickel based single
crystal superalloys have a benefit in creep strength capability of
about 30.degree. C. over the second generation of nickel based
single crystal superalloys. However, the third generation of nickel
based single crystal superalloys may also have narrow heat
treatment ranges, which incur manufacturing costs. The high levels
of strengthening elements, such as rhenium and tungsten, that are
added also have a detrimental effect on the metallurgical stability
of the third generation of nickel based single crystal
superalloys.
[0004] Thus it is seen that the increase in creep strength is to
the detriment of the density and the cost of the superalloy. An
increase in density of the turbine blades and turbine vanes makes
the gas turbine engine heavier and also results in a requirement to
make the turbine rotor disc stronger to carry the heavier turbine
blades, which also results in an increase in the weight of the
turbine rotor disc.
[0005] The metal temperature of the investment cast turbine blades,
or turbine vanes, is frequently reduced by air cooling of the
turbine blades, or turbine vanes. It is often the case that cooled
turbine blades, or turbine vanes, are protected by ceramic thermal
barrier coatings. A major concern with a ceramic thermal barrier
coating is that the ceramic thermal barrier coating will spall
prematurely during engine service. The adherence of a ceramic
thermal barrier coating is influenced by many factors, but a major
factor is the composition of the superalloy substrate on which the
ceramic thermal barrier coating is deposited.
[0006] The present invention seeks to provide a novel nickel based
single crystal superalloy, which has a capability greater than the
second generation of nickel based single crystal superalloys, but
which is metallurgically stable without excessive costs.
[0007] Accordingly the present invention provides a nickel based
single crystal superalloy comprising 7-9 wt % cobalt, 3.5-4.5 wt %
chromium, 0-2.4 wt % molybdenum, 4-8 wt % tungsten, 3.5-6 wt %
rhenium, 5-6.5 wt % aluminium, 6.5-8.5 wt % tantalum, 0-0.2 wt %
hafnium and the balance nickel plus incidental impurities.
[0008] Preferably the nickel based single crystal superalloy
comprises 7.5-8.5 wt % cobalt, 3.5-4.5 wt % chromium, 0-2.4 wt %
molybdenum, 4-7.5 wt % tungsten, 3.5-5.8 wt % rhenium, 5.3-6.3 wt %
aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
[0009] Preferably the nickel based single crystal superalloy
comprises 7-9 wt % cobalt, 3.5-4.5 wt % chromium, 2-2.4 wt %
molybdenum, 4-5 wt % tungsten, 3.5-4.5 wt % rhenium, 5-6.5 wt %
aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
[0010] Preferably the nickel based single crystal superalloy
comprises 7.5-8.5 wt % cobalt, 3.5-4.5 wt % chromium, 2-2.4 wt %
molybdenum, 4-5 wt % tungsten, 3.5-4.5 wt % rhenium, 5.3-6.3 wt %
aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
[0011] Preferably the nickel based single crystal superalloy
comprises 7.7-8.3 wt % cobalt, 3.7-4.3 wt % chromium, 2-2.4 wt %
molybdenum, 4.3-4.9 wt % tungsten, 3.8-4.4 wt % rhenium, 5.5-6.1 wt
% aluminium, 7.2-7.8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
[0012] The nickel based single crystal superalloy may comprise 8 wt
% cobalt, 4 wt % chromium, 2.2 wt % molybdenum, 4.6 wt % tungsten,
4.1 wt % rhenium, 5.8 wt % aluminium, 7.5 wt % tantalum, 0.1 wt %
hafnium and the balance nickel plus incidental impurities.
[0013] Alternatively the nickel based single crystal superalloy
comprises 7-9 wt % cobalt, 3.5-4.5 wt % chromium, 6-8 wt %
tungsten, 4.8-5.8 wt % rhenium, 5-6.5 wt % aluminium, 7-8 wt %
tantalum, 0.05-0.15 wt % hafnium and the balance nickel plus
incidental impurities.
[0014] The nickel based single crystal superalloy may comprise
7.5-8.5 wt % cobalt, 3.5-4.5 wt % chromium, 6-8 wt % tungsten,
4.8-5.8 wt % rhenium, 5.3-6.3 wt % aluminium, 7-8 wt % tantalum,
0.05-0.15 wt % hafnium and the balance nickel plus incidental
impurities.
[0015] The nickel based single crystal superalloy may comprise
7.7-8.3 wt % cobalt, 3.7-4.3 wt % chromium, 6.5-7.5 wt % tungsten,
5.0-5.6 wt % rhenium, 5.5-6.1 wt % aluminium, 7.0-8.0 wt %
tantalum, 0.05-0.15 wt % hafnium and the balance nickel plus
incidental impurities.
[0016] The nickel based single crystal superalloy may comprise 8 wt
% cobalt, 4 wt % chromium, 7 wt % tungsten, 5.3 wt % rhenium, 5.8
wt % aluminium, 7.5 wt % tantalum, 0.1 wt % hafnium and the balance
nickel plus incidental impurities.
[0017] The present invention also provides a cast single crystal
nickel based superalloy article comprising 7-9 wt % cobalt, 3.5-4.5
wt % chromium, 0-2.4 wt % molybdenum, 4-8 wt % tungsten, 3.5-6 wt %
rhenium, 5-6.5 wt % aluminium, 6.5-8.5 wt % tantalum, 0-0.2 wt %
hafnium and the balance nickel plus incidental impurities.
[0018] Preferably the cast single crystal nickel based superalloy
article comprises 7.5-8.5 wt % cobalt, 3.5-4.5 wt % chromium, 0.2.4
wt % molybdenum, 4-7.5 wt % tungsten, 3.5-5.8 wt % rhenium, 5.3-6.3
wt % aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
[0019] Preferably the cast single crystal nickel based superalloy
article comprises 7-9 wt % cobalt, 3.5-4.5 wt % chromium, 2-2.4 wt
% molybdenum, 4-5 wt % tungsten, 3.5-4.5 wt % rhenium, 5-6.5 wt %
aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
[0020] Preferably the cast single crystal nickel based superalloy
article comprises 7.5-8.5 wt % cobalt, 3.5-4.5 wt % chromium, 2-2.4
wt % molybdenum, 4-5 wt % tungsten, 3.5-4.5 wt % rhenium, 5.3-6.3
wt % aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
[0021] Preferably the cast single crystal nickel based superalloy
article comprises 7.7-8.3 wt % cobalt, 3.7-4.3 wt % chromium, 2-2.4
wt % molybdenum, 4.3-4.9 wt % tungsten, 3.8-4.4 wt % rhenium,
5.5-6.1 wt % aluminium, 7.2-7.8 wt % tantalum, 0.05-0.15 wt %
hafnium and the balance nickel plus incidental impurities.
[0022] The cast single crystal nickel based superalloy article may
comprise 8 wt % cobalt, 4 wt % chromium, 2.2 wt % molybdenum, 4.6
wt % tungsten, 4.1 wt % rhenium, 5.8 wt % aluminium, 7.5 wt %
tantalum, 0.1 wt % hafnium and the balance nickel plus incidental
impurities.
[0023] Alternatively the cast single crystal nickel based
superalloy article comprises 7-9 wt % cobalt, 3.5-4.5 wt %
chromium, 6-8 wt % tungsten, 4.8-5.8 wt % rhenium, 5-6.5 wt %
aluminium, 7-8 wt % tantalum, 0.05-0.15 wt % hafnium and the
balance nickel plus incidental impurities.
[0024] The cast single crystal nickel based superalloy article may
comprise 7.5-8.5 wt % cobalt, 3.5-4.5 wt % chromium, 6-8 wt %
tungsten, 4.8-5.8 wt % rhenium, 5.3-6.3 wt % aluminium, 7-8 wt %
tantalum, 0.05-0.15 wt % hafnium and the balance nickel plus
incidental impurities.
[0025] The cast single crystal nickel based superalloy article may
comprise 7.7-8.3 wt % cobalt, 3.7-4.3 wt % chromium, 6.5-7.5 wt %
tungsten, 5.0-5.6 wt % rhenium, 5.5-6.1 wt % aluminium, 7.0-8.0 wt
% tantalum, 0.05-0.15 wt % hafnium and the balance nickel plus
incidental impurities.
[0026] The cast single crystal nickel based superalloy article may
comprise 8 wt % cobalt, 4 wt % chromium, 7 wt % tungsten, 5.3 wt %
rhenium, 5.8 wt % aluminium, 7.5 wt % tantalum, 0.1 wt % hafnium
and the balance nickel plus incidental impurities.
[0027] Preferably the cast single crystal article comprises a
turbine blade, a turbine vane or a combustor component.
[0028] Preferably the cast single crystal article comprises at
least one internal passage for the flow of cooling fluid.
[0029] Preferably the cast single crystal article comprises a bond
coating on the article and a ceramic thermal barrier coating on the
bond coating.
[0030] Preferably the bond coating comprises a layer of
alumina.
[0031] Preferably the bond coating comprises a layer comprising
platinum enriched gamma prime phase and platinum enriched gamma
phase.
[0032] The present invention will be more fully described by way of
example with reference to the accompanying drawings, in which:
[0033] FIG. 1 is a bar chart comparing high temperature oxidation
resistance at 1100.degree. C. for two nickel based single crystal
superalloys according to the present invention and a prior art
nickel based single crystal superalloy.
[0034] FIG. 2 is a bar chart showing the average thermal barrier
coating spallation time against temperature for two nickel based
single crystal superalloys according to the present invention and a
prior art nickel based single crystal superalloy.
[0035] FIG. 3 is a graph showing the ratio of time to 1% creep
strain for two nickel based single crystal superalloys according to
the present invention and a prior art nickel based single crystal
superalloy against temperature.
[0036] FIG. 4 is a graph showing the ratio of creep rupture lives
for two nickel based single crystal superalloys according to the
present invention and a prior art nickel based single crystal
superalloy against temperature.
[0037] A nickel based single crystal superalloy with high
temperature mechanical properties, high temperature oxidation
resistance and metallurgical stability better than
second-generation nickel based single crystal superalloys but which
has compatibility with ceramic thermal barrier coatings.
[0038] The compositions of the nickel based single crystal
superalloys of the present invention were defined to give an
increase in mechanical strength over the second generation nickel
based single crystal superalloy CMSX4, in particular by increasing
the level of rhenium relative to CMSX4, e.g. to above 3 wt %. The
chromium level was decreased relative to CMSX4 to ensure
metallurgical stability against formation of the undesirable
topologically close packed (TCP) phases whilst retaining sufficient
resistance against low temperature oxidation. The titanium level
was set to zero because this element degrades the oxidation
resistance of cast nickel based single crystal superalloys, in
particular it promotes spalling of ceramic thermal barrier
coatings. The rhenium level was set at a maximum of 5.3 wt % to
avoid excessive raw material costs. The density of the nickel based
single crystal superalloy was maintained below 9 gm per cm.sup.3 to
avoid excessive stresses on the turbine discs and increases in
weight in the gas turbine engine.
[0039] Materials modelling capability was used to assess melting
temperature and the gamma prime solvus temperature to ensure a
sufficient heat treatment window for cost effective practical
production of the nickel based single crystal superalloy
components, e.g. turbine blades, turbine vanes etc. Materials
modelling capability was used to assess the propensity for
formation of the damaging topologically close packed (TCP) phases
to ensure that the nickel based single crystal superalloys has
sufficient metallurgical stability for application as turbine
blades, turbine vanes etc in gas turbine engines.
[0040] A number of alloys were prepared as shown in Table 1, and
Table 1 also includes known superalloy CMSX4 and CMSX10 of
Cannon-Muskegon Corporation, of 2875 Lincoln Street, Muskegon,
Mich., USA and described in European patent application EP0155827A
and U.S. Pat. No. 5,366,695 respectively. TABLE-US-00001 TABLE 1
Element (wt %) Alloy Co Cr Mo W Re Al Ti Ta Nb Hf Ni A 8.0 4.0 2.2
4.6 4.1 5.8 0 7.5 0 0.1 bal B 8.0 4.0 2.2 4.6 5.3 5.8 0 7.5 0 0.1
bal C 8.0 4.0 2.2 5.8 4.1 5.8 0 7.5 0 0.1 bal D 8.0 4.0 2.2 5.2 4.7
5.8 0 7.5 0 0.1 bal E 8.0 4.0 2.2 5.2 4.7 5.8 0 6.5 0.6 0.1 bal F
8.0 4.0 2.2 5.2 4.7 5.8 0 5.2 1.2 0.1 bal G 8.0 4.0 3.5 4.0 4.0 5.8
0 6.5 0.6 0.1 bal H 8.0 4.0 0.0 7.0 5.3 5.8 0 7.5 0 0.1 bal I 8.0
5.5 2.0 4.0 5.3 5.8 0 7.5 0 0.1 bal J 2.0 4.0 2.2 5.2 4.7 5.8 0 7.5
0 0.1 bal K 12.0 4.0 2.2 5.2 4.7 5.8 0 7.5 0 0.1 bal L 8.0 2.5 2.2
4.6 5.3 6.0 0 7.5 0 0.1 bal CMSX4 9.5 6.5 0.6 6.4 3.0 5.6 1.0 6.5 0
0.1 bal CMSX10 2.7 2.0 0.4 5.3 6.3 5.65 0.2 5.8 7.9 0.04 bal
[0041] The nickel based single crystal superalloys in Table 1,
except for CMSX10, were subjected to a series of tests. The tests
comprised testing to establish a heat treatment cycle, creep
testing, oxidation testing, thermal barrier coating spallation
testing, thermal exposure to study formation of topologically close
packed (TCP) phases and detailed metallurgical examination.
[0042] The tests showed that superalloys A and H in particular have
advantages over the prior art alloy CMSX4. Both superalloys A and H
can be heat treated and homogenised at high temperatures to
dissolve the gamma prime eutectic phase and this helps optimise the
properties of the superalloys.
[0043] The superalloys in Table 1 were initially tested for
oxidation resistance. Cyclic oxidation testing was performed on a
burner rig, the cycling rate was 4 cycles per hour and 0.25 ppm of
simulated sea salt was added to the gas flow to simulate operation
in marine environment. The measure of amount of attack on the
superalloy samples is by metal loss per surface and the data is
shown in FIG. 1 for testing at a temperature of 1100.degree. C. for
superalloys A, H and CMSX4. After 400 cycles of testing the
superalloy samples were sectioned and the metal loss measured using
a travelling microscope. It can be seen that superalloys A and H
have better oxidation resistance to CMSX4.
[0044] The superalloys in Table 1 were tested for compatibility
with a known thermal barrier coating system by depositing about 8
.mu.m of platinum onto the samples of the superalloy substrate and
heat treating at 1150.degree. C. to form a layer comprising
platinum enriched gamma phase and platinum enriched gamma prime
phase. This layer together with a layer of alumina which forms on
the layer becomes a bond coating for a ceramic thermal barrier
coating deposited by electron beam physical vapour deposition.
[0045] Samples of each superalloy were exposed in a still air
furnace at temperatures of 1170.degree. C., 1190.degree. C.,
1210.degree. C., 1230.degree. C. and 1250.degree. C. until
spallation of the ceramic thermal barrier coating occurred over
more than 50% of the surface of the sample. The compatibility of
the superalloys with the thermal barrier coating is shown in FIG.
2, this shows that superalloy H has significantly better
compatibility with thermal barrier coatings than both superalloy A
and CMXS4 across the temperature range tested. This also shows that
superalloy A has a compatibility with thermal barrier coatings that
is intermediate that of superalloy H and CMSX4 and superalloy A has
a compatibility better than CMSX4 at some temperatures.
[0046] The creep performance can be expressed as the time to 1%
creep strain under various conditions of stress and temperature.
The ratio of the creep lives for 1% strain to the lives of CMSX4
across the temperature range are shown in FIG. 3 and this shows
that both superalloys A and H are superior to CMSX4 across the
temperature range and that superalloy H is superior to superalloy
A, especially at 950.degree. C.
[0047] The ratio of the creep rupture lives of superalloys A and H
as a function of the creep rupture life of CMSX4 are shown in FIG.
4 and this shows that both of superalloys A and H are superior to
CMSX4 across the temperature range and superalloy H is superior to
superalloy A.
[0048] The metallurgical stability of the superalloys was assessed
by detailed metallurgical examination of samples of the superalloy
exposed in a furnace together with examination of the samples of
the superalloys exposed to the creep tests. The examinations showed
that both superalloys A and H were extremely stable. In particular
superalloy A showed no evidence of topologically close packed (TCP)
phase formation. Superalloy H showed very limited topologically
close packed (TCP) phase formation after 240 hours exposure at
1100.degree. C.
[0049] The present invention has shown that superalloys A and H are
metallurgically stable, have superior properties to CMSX4 and are
suitable for use as turbine blades and turbine vanes in aero gas
turbine engines, marine gas turbine engines or for industrial gas
turbine engines. Superalloy H has the advantage of better overall
properties compared to superalloy A. However, superalloy A has the
advantage of slightly improved metallurgical stability, lower
rhenium content and hence lower cost and slightly lower density.
Superalloy A has a density of 8.85 gm per cm.sup.3 and superalloy H
has a density of 9.0 gm per cm.sup.3. The superalloys of the
present invention also allow operation at a temperature of
15.degree. C. to 25.degree. C. higher relative to CMSX4.
[0050] Other suitable bond coatings may be used on the nickel based
single crystal superalloy article, for example MCrAlY, aluminide,
platinum aluminide, etc. The ceramic thermal barrier coatings may
be deposited by other suitable methods for example sputtering,
vacuum plasma spraying, air plasma spraying, chemical vapour
deposition, etc. The ceramic thermal barrier coatings may comprise
yttria-stabilised zirconia, ceria stabilised zirconia or other
suitable ceramics.
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