INCO Shaw Alloys of nickel, chromium and cobalt (IN939) 1978
US4108647A
Publication
Number: US4108647A
Publication
Date: 1978-08-22
Priority
Number: GB197530043A |
US1976703563A
Application
Date: 1976-07-08
Title:
Alloys of nickel, chromium and cobalt
Inventor
- w/address: Shaw Stuart Walter
Ker,Sutton Coldfield,GB
Assignee/Applicant:
The International Nickel Company Inc.,New
York,NY,US
Abstract:
The high temperature properties of a nickel-base alloy
containing correlated percentages of chromium, cobalt, tungsten, molybdenum,
titanium, aluminium, carbon, tantalum, niobium, zirconium, hafnium, boron,
yttrium and lanthanum are substantially maintainedor improved by further
correlation of the percentages of chromium, carbon and boron in the alloy.
First Claim:
1. In combination with
a nickel-base alloy adapted for use at elevated temperature consisting
essentially of, by weight, about 20% to 25% chromium, about 5% to 25% cobalt,
up to 3.5% molybdenum, up to 5% tungsten, the tungsten and molybdenum being
correlated such that the %W + 0.5(%Mo) is from 0.5% to 5%, about 1.7% to 5%
titanium and about 1% to 4% aluminum, the sum of the titanium and aluminum being
about 4% to 6.5% with the ratio there between being from 0.75:1 to 4:1, from
0.02% to 0.25% carbon, from 0.5% to 3% tantalum, up to 3% niobium, 0.005% to 1%
zirconium and up to 2% hafnium, the value of % Zr + 0.5(%Hf) being from 0.01%
to 1%, about 0.001% to 0.05% boron, up to about 0.2% in total of yttrium and/or
lanthanum, and balance essentially nickel in an amount at least 30%, the
improvement comprising a chromium content of more than 22% and carbon and boron
contents in ranges of 0.001% to 0.25% carbon and 0.05% to 1% boron provided
that when the carbon content is in the range of from 0.02% to 0.25%, the boron
content is greater than 0.05% up to 1%.
Description w/Pub Language: This invention relates to improved castable
nickel-chromium-cobalt base alloys.
In the Specification
of my Application No. 536,173 filed Dec. 24, 1974, (now U.S. Pat. No.
4,039,330) which is a continuation-in-part of Ser. No. 241 443 filed Apr. 5,
1972, abandoned I have described and claimed a nickel-base alloy adapted for use
at elevated temperature and characterised by high stress-rupture strength and
good corrosion resistance in sulphur-and chloride-containing environments while
concomitantly exhibiting extended resistance to embrittlement for long periods
upon prolonged exposure to temperatures at least as high as 870. degree. C.,
said alloy having about 20% to 25% chromium, about 5% to 25% cobalt, up to 5%
tungsten, up to 3.5% molybdenum, the tungsten and molybdenum being correlated
such that the %W + 0.5 (%Mo) is from 0.5% to 5%, about 1.7% to 5% titanium and
about 1% to 4% aluminium, the sum of the titanium and aluminium being about 4%
to 6.5% with the ratio therebetween being from 0.75:1 to 4:1, from 0.02% to
0.25% carbon, from 0. 5% to 3% tantalum, up to 3% niobium, 0.005% to 1%
zirconium, and up to 2% hafnium, the value of %Zr + 0.5 (%Hf) being from about
0.01% to 1%, about 0.001% to 0.05% boron, up to about 0.2% in total of yttrium
and/or lanthanum, and the balance being essentially nickel in an amount of at
least 30%.
It is said that carbon
contents below 0.02% lead to a reduction in stress-rupture strength, that the
chromium content must be a minimum of about 20% for good corrosion resistance,
and that amounts of boron in excess of 0.05% lead to inadequate impact resistance.
I have now found that
provided the chromium content is a certain minimum, the carbon content can be
reduced and/or the boron content can be increased, and yet the expected
deterioration of high temperature properties is minimised or does not occur,
and in some instances the properties may even be further improved.
Generally speaking and
in accordance herewith, the present invention contemplates alloys having, by
weight, about 5 to 25% cobalt, up to 3.5% molybdenum, up to 5% tungsten, the
tungsten and molybdenum being correlated such that the %W + 0.5 (%Mo) is from
0.5 to 5, about 1. 7 to 5% titanium and about 1 to 4% aluminum, the sum of the
titanium and aluminum being about 4 to 6.5% with the ratio there between being
from 0. 75:1 to 4:1, from 0.5 to 3% tantalum, up to 3% niobium, 0.005 to 1%
zirconium and up to 2% hafnium, the value of %Zr + 0.5 (%Hf) being from 0. 01
to 1, up to about 0.2% in total of yttrium and/or lanthanum, and having
chromium, carbon, and boron, the balance being essentially nickel in an amount
of at least 30%, the improvement that the chromium content is at least 22 to
25% and the carbon and boron contents are such that when the carbon content is
less than 0.02 down to 0.001% the boron content is in the range of from 0.001
to 1% and when the carbon content is in the range of from 0.02 to 0.25% the
boron content is greater than 0. 05 up to 1%.
All percentages and
ratios in this specification are by weight.
The alloys must
contain at least 22 up to 25% chromium and from 0. 001 to 1% boron when the
carbon content is less than 0.02 down to 0. 001%, or from 0.05 up to 1% boron
when the carbon content is in the range of from 0.02 to 0.25%, as outside these
ranges the desired high temperature properties are impaired.
Preferably, if the
carbon content is below 0.02%, the boron content is at least 0.05%, and
advantageously at least 0.15%. Preferably, if the carbon content is above
0.02%, the carbon content is in the range of from 0.04 to 0.16% and the boron
content is in the range of from 0.06 to 0.5%. An advantageous combination of
properties is exhibited by a preferred group of alloys containing from 0.049 to
0.245% carbon, more than 22.0, preferably from 22.5, to 23.3% chromium, from 18
to 20% cobalt, preferably from 18.6 to 19.1% cobalt, from 1.87 to 2.21%
tungsten, from 3. 5 to 4.0, preferably from 3.63 to 3.80% titanium, from 1.7 to
2.3, preferably from 1.92 to 2.0% aluminium, from 1.2 to 1.6, preferably from
1.34 to 1.40% tantalum, from 0.8 to 1.2, preferably from 0.93 to 0.98% niobium,
from 0.07 to 0.13, preferably from 0.10 to 0.11% zirconium, from 0.07 to 0.5%
boron, balance nickel.
Even more
advantageously the boron content should be in excess of 0.3% and a particularly
advantageous combination of properties is exhibited by a preferred group of
alloys containing from 0.01 to 0.02% carbon, from more than 22 to not more than
23% chromium, from 18.5 to 19. 5% cobalt, from 1.5 to 2.5% tungsten, from 3 to
4% titanium, from 1.5 to 2.5% aluminium, from 1 to 2% tantalum, from 0.5 to
1.5% niobium, from 0. 05 to 0.15% zirconium and from 0.3 to 0.85% boron, the
balance, apart from impurities, being nickel. Preferably niobium is present in
alloys of the invention in the range of from 0.2 to 3%.
To develop the full
stress-rupture properties of the alloys of the present invention, they should
be subjected to a heat treatment involving solution heating and subsequent
ageing. Suitable heat treatments are those disclosed in the Specification of
Application No. 536,173 with the modification that the solution heating
treatment advantageously comprises heating for a time in the range of from 1 to
20 hours at a temperature in the range 1100° C to 1250° C and subsequent ageing
for from 1 to 48 hours at a temperature in the range 600° to 950° C. A
preferable heat treatment comprises solution heating at a temperature in the
range 1,120° to 1200. degree. C for a time in the range 2 to 16 hours, followed
by heating at a temperature in the range 970° to 1030° C for a time in the
range 2 to 10 hours, followed by heating at a temperature in the range 870° to
930° C for a time in the range 8 to 48 hours, then ageing at a temperature in
the range 600° to 800° C for a time in the range 8 to 48 hours. A particularly
advantageous heat treatment is to solution heat at 1150. degree. C for 4 hours,
air cool, heat at 1000° C for 6 hours, air cool, heat at 900° C for 24 hours,
air cool, and finally age at 700° C for 16 hours and again air cool.
The stress-rupture
properties exhibited by alloys of the present invention are illustrated in the
following Example I.
EXAMPLE I
Alloys with
compositions as shown in Table I were vacuum-melted and cast in vacuum to
tapered test bar blanks, from which test pieces were machined. Prior to the
machining of the test pieces, the blanks were heat treated by solution heating
at 1150° C for 4 hours, air cooling, heating at 1000° C for 6 hours, air
cooling, heating at 900° C for 24 hours, air cooling, and ageing at 700° C for
16 hours and air cooling. The heat treated test pieces were then subjected to
various stress-rupture tests with the results shown in Table II. In Tables I
and II, Alloys 1 to 9 are according to the present invention and Alloy A is a
typical alloy according to claim 1 of Application No. 536173 for comparison
purposes.
TABLE I (See PDF)
TABLE II (See PDF)
It can be seen from
Tables I and II that Alloy 1 with 0.015% carbon and 0.018% boron and Alloy 2
with 0.013% carbon and 0.07% boron had similar but slightly inferior
stress-rupture life and elongation properties at 600 N/mm.sup.2 and 732° C, at
330 N/mm.sup.2 and 816. degree. C, and at 120 N/mm.sup.2 and 927° C to those of
Alloy A, but had slightly better stress-rupture life properties at 550 N/mm.
sup.2 and 760° C. Alloys 3 and 4 with 0.013% carbon and with 0. 12% and 0.15%
boron, respectively, had, as can be seen from the results of Table II, better
stress-rupture life properties at 600 N/mm.sup.2 and 732. degree. C, and at 550
N/mm.sup.2 and 760° C than Alloy A, with similar elongation values, and
stress-rupture life and elongation properties at 330 N/mm.sup.2 and 816° C and
at 120 N/mm.sup.2 and 927° C similar to those of Alloy A. A comparison of the
property values for Alloys 1 to 4 and A shows that for better properties alloys
containing less than 0.02% carbon preferably should contain at least 0. 05%
boron and more preferably at least 0.1% boron.
The effect of
increasing the boron content still further with alloys containing less than
0.02% carbon can be seen from the results for Alloys 4 to 8 in Table II.
The property
improvements shown by Alloy 4 with 0.15% boron are even more marked with Alloys
5 to 8 which contained in excess of 0.3% boron. Thus, advantageously, alloys
according to the invention containing less than 0.02% carbon should contain
more than 0.3% boron. As can be seen from the results of Table II, Alloys 5 to
8 with more than 0.3% boron had better stress rupture life properties than
Alloy A at 732° C, 760. degree. C, 816° C and 927° C with similar ductility as
shown by the elongation results.
Hence a preferred
group of alloys according to the present invention contains from 0.01 to 0.02%
carbon, from more than 22 to not more than 23% chromium, from 18.5 to 19.5%
cobalt, from 1.5 to 2.5% tungsten, from 3 to 4% titanium, from 1.5 to 2.5%
aluminium, from 1 to 2% tantalum, from 0.5 to 1.5% niobium, from 0.05 to 0.15%
zirconium, from 0. 3 to 0.85% boron, balance nickel.
The test results for
Alloy 9 in Table II show that even with 0. 144% carbon and a boron content of
0.28% better stress-rupture properties are obtained in comparison with Allloy A
at 732° C, 760° C and 816° C with a slight fall off in properties at 927° C.
With the exception of
Alloys 1 to 9 and the comparative Alloy A, Alloys 2 to 8 of Example I had
carbon contents of less than 0.02% boron contents in excess of 0.05%. The
following Example 2 illustrates properties illustrated by alloys of the
invention having carbon contents in excess of 0.02% and boron contents in
excess of 0.05%.
EXAMPLE 2
Alloys with
compositions as shown in the following Table III were prepared as detailed in
Example 1. In Table III Alloys 10 to 22 are according to the invention and
Alloys A and B are typical alloys according to claim 1 of Application No.
536,173 for comparison purposes.
Test pieces from the
Alloys of Table III were made and heat treated according to the procedure of
Example 1 and then subjected to various stress-rupture tests with the results
shown in Table IV and to impact resistance tests with the results shown in
Table V.
TABLE III (See PDF)
TABLE IV (See PDF)
TABLE V (See PDF)
It can be seen from
Tables III and IV that in all instances increasing the boron content above the
0.015% of comparison Alloy A for carbon contents between 0.049 and 0.245% resulted
in improved stress-rupture life properties at 550 N/mm.sup.2 and 760° C with
the best improvement being achieved at boron contents in excess of 0.3%. Creep
ductility properties at 550 N/mm.sup.2 and 760° C are in many cases similar but
in general slightly inferior to those of Alloy A when the boron content is
increased above the 0.015% of Alloy A.
At 330 N/mm.sup.2 and
816° C, with the exception of Alloys 20, 21 and 22 with carbon contents
nominally of 0.24%, the stress rupture life properties are also improved in
comparison with those of Alloy A for boron contents in excess of 0.015% for
carbon contents between 0.049 and 0.154%. Again the creep ductility properties
of Alloys 10 to 19 are similar to those of Alloy A and in the case of Alloys
20, 21 and 22 are better than those of Alloy A.
For an optimum balance
of stress rupture life and creep ductility properties it is preferred that
alloys according to the invention when containing more than 0.02% carbon should
preferably contain carbon in the range of from 0.04 to 0.16% and boron in the
range of from 0.06 to 0. 5%. Advantageously the boron content should be in the
range of from 0.3 to 0. 5%.
A preferred group of
alloys according to the invention contains from 0. 049 to 0.245% carbon, more
than 22.0, preferably from 22.5, to 23. 3% chromium, from 18 to 20% cobalt,
preferably from 18.6 to 19.1% cobalt, from 1.87 to 2.21% tungsten, from 3.5 to
4.0, preferably from 3.63 to 3. 80% titanium, from 1.7 to 2.3, preferably from
1.92 to 2.0% aluminium, from 1.2 to 1.6, preferably from 1.34 to 1.40%
tantalum, from 0.8 to 1.2, preferably from 0.93 to 0.98% niobium, from 0.07 to
0.13, preferably from 0.10 to 0.11% zirconium, from 0.07 to 0.5% boron, balance
nickel.
Specimens 11.4
millimeter in diameter produced from the Alloys 10 to 22 and B, were Charpy
impact tested after soaking for 1,000 hours at 816. degree. C. As can be seen
from Table III and V, apart from Alloy 22 containing 0.24% carbon and 0.46%
boron, the specimens from the remaining Alloys 10 to 21 all had impact
resistance properties, at least comparable to and in most cases better than
those of the comparative Alloy B. For optimum impact resistance properties
alloys according to the invention when containing more than 0.02% carbon should
preferably contain carbon in the range of from 0.04 to 0.16% and boron in the
range of from 0.06 to 0.50%. Excellent impact resistance properties were
achieved with a boron content in the range of from 0.10 to 0.30% for a nominal
carbon content of 0.05%.
Alloys according to
the present invention when containing more than 0. 3% boron would have a
minimum stress-rupture life of 60 hours under a stress of 550 N/mm.sup.2 at
760° C, a minimum stress-rupture life of 130 hours under a stress of 600
N/mm.sup.2 at 732° C and a minimum stress-rupture life of 270 hours under a
stress of 330 N/mm.sup.2 at 816° C.
Alloys according to
the invention are suitable for use in cast or wrought form in applications
requiring a high level of stress rupture strength at high temperatures such as
for gas turbine rotor blades.
Although the present
invention has been described in conjunction with preferred embodiments, it is
to be understood that modifications and variations may be resorted to without
departing from the spirit and scope of the invention as those skilled in the
art will readily understand. Such modifications and variations are considered
to be within the purview and scope of the invention and appended claims.
Claims:
I claim:
1. In combination with
a nickel-base alloy adapted for use at elevated temperature consisting
essentially of, by weight, about 20% to 25% chromium, about 5% to 25% cobalt,
up to 3.5% molybdenum, up to 5% tungsten, the tungsten and molybdenum being
correlated such that the %W + 0.5(%Mo) is from 0.5% to 5%, about 1.7% to 5%
titanium and about 1% to 4% aluminum, the sum of the titanium and aluminum
being about 4% to 6.5% with the ratio there between being from 0.75:1 to 4:1,
from 0.02% to 0.25% carbon, from 0.5% to 3% tantalum, up to 3% niobium, 0.005%
to 1% zirconium and up to 2% hafnium, the value of % Zr + 0.5(%Hf) being from
0.01% to 1%, about 0.001% to 0.05% boron, up to about 0.2% in total of yttrium
and/or lanthanum, and balance essentially nickel in an amount at least 30%, the
improvement comprising a chromium content of more than 22% and carbon and boron
contents in ranges of 0.001% to 0.25% carbon and 0.05% to 1% boron provided
that when the carbon content is in the range of from 0.02% to 0.25%, the boron
content is greater than 0.05% up to 1%.
2. An alloy in
accordance with claim 1, containing at least 0.3% boron.
3. An alloy in
accordance with claim 1, containing from more than 22 to not more than 23%
chromium, from 18.5 to 19.5% cobalt, from 1.5 to 2.5% tungsten, from 3 to 4%
titanium, from 1.5 to 2.5% aluminium, from 1 to 2% tantalum, from 0.5 to 1.5%
niobium, from 0.05 to 0.15% zirconium, from 0.3 to 0.85% boron and from 0.01 to
0.02% carbon.
4. An alloy in
accordance with claim 1, containing from 0.04 to 0.16% carbon and from 0.06 to
0.5% boron.
5. An alloy in
accordance with claim 1, containing more than 22.0 up to 23.3% chromium, from
18 to 20% cobalt, from 1.87 to 2.21% tungsten, from 3.5 to 4.0% titanium, from
1.7 to 2.3% aluminium, from 1.2 to 1.6% tantalum, from 0.8 to 1.2% niobium,
from 0.07 to 0.13% zirconium, from 0.07 to 0.5% boron and from 0.049 to 0.245%
carbon.
6. An alloy in
accordance with claim 1, containing from 22.5 to 23.3% chromium, from 18 to 20%
cobalt, from 1.87 to 2.21% tungsten, from 3.63 to 3.80% titanium, from 1.92 to
2.0% aluminium, from 1.34 to 1.40% tantalum, from 0.93 to 0.98% niobium, from
0.10 to 0.11% zirconium, from 0.07 to 0.5% boron and from 0.049 to 0.245%
carbon.
7. An alloy as set
forth in claim 1 wherein the carbon content is below 0.02% and the boron
content is at least 0.15%.
8. An alloy as set
forth in claim 1 wherein the carbon content is below 0.02% and the boron
content is 0.36% to 0.79%.