A microstructurally stable, high strength cobalt based alloy for use at elevated temperatures to 2125 F was developed. The alloys are particularly directed for use in stators and other low stress components in advanced gas turbines

Dreshfield, R. L.

Freche, J. C.

Sandrock, G. D.

English

NASA Technical Reports Server

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
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OCT 1 8 1973
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Patent Matters
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United States Patent
Dreshfield et al.
[in 3,762,918
[45] Oct. 2, 1973
[54] COB ALT-BASE ALLOY
[75] Inventors: Robert L. Dreshfield, Middleburg
Heights, Ohio; Gary D. Sandrock,
Ringwood, N.J.; John C. Freche,
Fairview Park, Ohio
[73] Assignee: The United States of America as
represented by the Administrator of
the National Aeronautics and Space
Administration, Washington, D.C.
[22] Filed: Jan. 26, 1972
[21] Appl. No.: 221,093
[52] U.S. Cl 75/170, 75/171
[51 ] Int. Cl C22c 19/00
[58] Field of Search -. 75/170, 171
[56] References Cited
UNITED STATES PATENTS
3,276,865 10/1966 Freche et ai 75/170
3,383,205 5/1968 Sims et al 75/171
3,403,021 9/1968 Wlodek 75/171
2,974,037 3/1961 Thielemann 75/171
3,582,320 6/1971 Herchenroeder 75/171
3,432,294 3/1969 Wheaton 75/171
Primary Examiner—G. T. Ozaki
Attorney—N. T. Musial et al.
[57] ABSTRACT
Cobalt-tungsten alloys containing titanium, zirconium,
carbon, chromium, rhenium, iron and nickel in pre-
ferred weight percentage ranges have superior
strengths at elevated temperatures.
5 Claims, No Drawings
f(NASA-Case-LEW-10ii36-1)
(Patent (NASA) 3 p
COBALT-BASE ALLOY
CSCL 11F
N73-32415
Unclas
00/17 18178
COBALT-BASE ALLOY
ORIGIN OF THE INVENTION
3,762,918
Cobalt Balance
The invention described herein was made by employ-
ees of the United States Government and may be man-
ufactured and used by or for the Government for gov-
ernmental purposes without the payment of any royal-
ties thereon or therefor.
BACKGROUND OF THE INVENTION
This invention is concerned with microstructurally
stable, high-strength cobalt base alloys for use at ele-
vated temperatures. The invention is particularly di-
rected to cobalt-tungsten alloys for components in ad-
vanced gas turbines.
Nickel base alloys have been proposed for the hot
components of gas turbine engines. However, many of
the materials drop off sharply in strength above 1900°
to 2000° F. Higher turbine inlet temperatures above
2000° F are necessary to meet the increased perfor-
mance requirements of advanced gas turbines. This
creates a need for materials that have improved
strength at high temperatures.
While high temperature strength is of primary impor-
tance in gas turbines, ductility is also important at all
temperatures to the maximum use temperature. The
ductility must not be substantially decreased upon long
time exposure at any temperature. A cobalt base alloy
described in U.S. Pat. No. 3,276,865 has been consid-
ered for use in advanced gas turbines. However, this
alloy is subject to embrittlement upon exposure to tem-
peratures between 1200° F and 1600° F.
SUMMARY OF THE INVENTION
These requirements have been met by the cobalt-
tungsten alloys of the present invention. The nominal
compositions, in weight percentages, of these alloys are
10-25 percent tungsten, .5-1 percent titanium, .25-5
percent zirconium, .1-1 percent carbon, 0-5 percent
chromium, 0-3 percent rhenium, 1-10 percent iron,
1-10 percent nickel, and the balance cobalt.
OBJECTS OF THE INVENTION
It is, therefore, an object of the present invention to
provide cobalt-tungsten alloys having improved
strengths at elevated temperatures up to 2125° F.
Another object of the invention is to provide micros-
tructurally stable alloys having properties pertinent to
long time engine applications.
A further object of the invention is to provide a co-
balt-tungsten alloy having adequate ductility at all tem-
peratures to the maximum use temperature wherein the
ductility is not substantially decreased upon long time
exposure at any temperature.
These and other objects of the invention will be ap-
parent from the specification that follows.
A preferred embodiment of the invention includes
alloys having the following nominal composition range
, in weight percent:
Tungsten
Titanium
Zirconium
Carbon
10 Chromium
Rhenium
Iron
Nickel
Cobalt
Percent
From 15 to 20
From 0.5 to 1.0
From 0.25 to 0.5
From 0.4 to 0.6
From 1 to 3
From 2 to 3
From 4 to 6
From 1 to 7.5
Balance
15 The alloys are prepared by conventional melting
methods used for the preparation of either nickel-base
or cobalt-base superalloys. Vacuum induction melting
and investment castings are preferred for preparing
cast parts.
20 Specimens of several known cobalt' alloys and pre-
ferred compositions of the present invention were
tested. A comparison of some mechanical properties of
these specimens is shown in Table 1.
25 TABLE I
30
35
Alloy
VM 103
VM 105
VM 106
VM 107
VM 108
VM 109
Average Stress
Rupture Life
In
Helium, Hours
2125°F
8.000 Ib
in1
133
97
52
74
49
73
2000°F
4.000 Ib 10.000 Ib
in* in*
>2000 157
156.0
>2000 170
164.2
Average room temp.
Elongation after
%
192 hrs
I600T
0.5
1.4
2.0
1.2
500 hrs
I400°F
1.0
3.0
2.0
DESCRIPTION OF THE PREFERRED
EMBODIMENT
These test specimens were prepared by vacuum in-
duction melting in stabilized zirconia crucibles. Before
each melt was poured, the chamber was backfilled to
300 torr of argon. The pour temperature was deter-
mined by an optical pyrometer to be 3100° F. Zircon
shell molds imbedded in fire-clay grog and held at
1600° F by a resistance mold heater were used.
Each casting consisted of a cluster of tensile test bars.
After casting, the molds were allowed to remain in the
vacuum chamber for 15 minutes. They were then re-
moved and permitted to cool to room temperature in
about 6 hours before knock out and cutoff. Before test-
ing all specimens were vapor-blasted and inspected by
radiographic and fluorescent penetrant techniques.
An alloy described in U.S. Pat. No. 3,276,865 was
vacuum melted and designated as VM 103. The nomi-
nal compositions of VM 103 and the other test speci-
mens in weight percents are listed in Table II.
TABLE if
45
50
The present invention is embodied in alloys having
the following composition range, the amount of each
alloying element being listed as a percentage by weight:
Tungsten
Titanium
Zirconium
Carbon
Chromium
Rhenium
Iron
Nickel
Percent
From about 10 to about 25
From about 0.5 to about 1
From about 0.25 to about 0.5
From about 0.1 to about 1
From about 0 to about 5
From about 0 to about 3
From about 1 to about 10
From about 1 to about 10
65
Alloy
VM
VM
VM
VM
VM
VM
103
105
106
107
108
109
Co
Bal
Bal
Bal
Bal
Bal
Bal
W
25.0
20.0
17.5
20.0
17.5
17.5
Ti
1.0
1.0
0.75
1.0
0.75
0.75
Zr
0.5
0.5
0.37
0.5
0.37
0.37
Fe
0
5.0
5.0
S.O
5.0
5.0
Re
0
3.0
3.0
3.0
3.0
3.0
Ni
0
0
1.0
0
5.0
7.5
Cr
3.0
3.0
3.0
3.0
3.0
C
0.4
0.5
0.5
0.6
0.5
0.5
The incipient melting temperature of VM 108, one of
the preferred alloys, is between 2475° F and 2500° F.
3,762,918
3 4
This is 100° F higher than that of the highest melting to 20 percent tungsten, from 0.5 percent to 1 percent
point cast nickel base alloys. This is desirable for poten- titanium, from 0.4 percent to 0.6 percent carbon, from
tial stator vane applications of advanced engines. These 0.25 percent to 0.5 percent zirconium, from 1 percent
stator vanes must often withstand localized tempera- to 3 percent chromium, from 2 percent to 3 percent
tures of 200° F or more higher than the average gas 5 rhenium, from 4 percent to 6 percent iron, from 1 per-
temperatures because of the uneven combustion gas
 cent to 7.5 percent nickel, and the balance cobalt,
profiles. 3. \ cobalt-tungsten alloy as claimed in claim 1 con-
While several preferred alloys have been described,
 sisting essentially of in weight percents from 17.5 per-
various modifications may be made to the alloy compo-
 cent to 20 percent tungsten, from 0.75 percent to 1
sitions without departing from the spirit of the mven- 10
 percent titanium> .5 percent carbon, from 0.37 percent
tion or the scope of the subjoined claims. It is contem-
 tQ Q 5 m zirconium 3 nt chromjunl) 3 per.
plated that the average electron vacancy concentration
 cem rhenium 5 nt ; from , m to 7 5
,s controlled by suitable alloying adjustments to pre-
 M ^ ^ ^ ^ ^^ ^^
vent formation of the intermetalhe compound Co,W •*
 cobalt.t ten allo as claimed in claim i con.
which embrittles these alloys if it forms during expo- 15 .. .. ,, , . . , , _ ,
sure to temperatures between 1200° F and 1600° F slstin« e^entially of ,n weight percents 17.5 percent
What is claimed is- tungsten, 0.75 percent titanium, 0.5 percent carbon,
1. A cobalt-tungsten alloy consisting essentially of in °'37 Percent ^rconium, 3.0 percent chromium, 3 per-
weight percents from 10 percent to 25 percent tung- cent rhenium, 5 percent iron, from 5 percent to 7.5
sten, from 0.5 percent to 1 percent titanium, from 0.1 20 Percent nickel, and the balance cobalt.
percent to 1 percent carbon, from .25 percent to 0.5 5- A cobalt-tungsten alloy as claimed in claim 1 con-
percent, zirconium, from 0 percent to 5 percent chro- sisting essentially of in weight percents 17.5 percent
mium, from 0 percent to 3 percent rhenium, from 1 tungsten, 0.75 percent titanium, 0.5 percent carbon,
percent to 10 percent iron, from 1 percent to 10 per- 0.37 percent zirconium, 3.0 percent chromium, 3 per-
cent nickel, and the balance cobalt. 25 cent rhenium, 5 percent iron, 5 percent nickel, and the
2. A cobalt-tungsten alloy as claimed in claim 1 con- balance cobalt.
sisting essentially of in weight percents from 15 percent * * * * *
30
35
40
45
50
1
I
55
60
65


Cobalt-base alloy

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