U.S. patent application number 11/723546 was filed with the patent office on 2007-09-27 for ni-based super alloy.
This patent application is currently assigned to DAIDO TOKUSHUKO KABUSHIKI KAISHA. Invention is credited to Seiji Kurata, Tetsuya Shimizu, Shigeki Ueta.
Application Number | 20070221298 11/723546 |
Document ID | / |
Family ID | 38169362 |
Filed Date | 2007-09-27 |
United States Patent
Application |
20070221298 |
Kind Code |
A1 |
Kurata; Seiji ; et
al. |
September 27, 2007 |
Ni-based super alloy
Abstract
The present invention provides a Ni-based super alloy including,
by mass %, C: 0.01 to 0.15%; Si: 1% or less; Mn: 1% or less; P:
0.02% or less; S: 0.01% or less; Co: less than 0.10%; Cr: 16 to
22%; Mo: 4 to 10%; W: 5% or less; Al: 1.2 to 2.5%; Ti: 2.4 to 4%;
B: 0.001 to 0.05%; Zr: 0.01 to 0.5%; Fe: 1% or less; and a balance
of Ni and inevitable impurities.
Inventors: |
Kurata; Seiji; (Nagoya-shi,
JP) ; Ueta; Shigeki; (Nagoya-shi, JP) ;
Shimizu; Tetsuya; (Nagoya-shi, JP) |
Correspondence
Address: |
BACON & THOMAS, PLLC
625 SLATERS LANE, FOURTH FLOOR
ALEXANDRIA
VA
22314
US
|
Assignee: |
DAIDO TOKUSHUKO KABUSHIKI
KAISHA
Nagoya-shi
JP
|
Family ID: |
38169362 |
Appl. No.: |
11/723546 |
Filed: |
March 20, 2007 |
Current U.S.
Class: |
148/428 ;
420/443; 420/448; 420/449 |
Current CPC
Class: |
C22C 19/056 20130101;
C22C 19/055 20130101 |
Class at
Publication: |
148/428 ;
420/443; 420/448; 420/449 |
International
Class: |
C22C 19/05 20060101
C22C019/05 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2006 |
JP |
2006-079447 |
Claims
1. A Ni-based super alloy comprising, by mass %: C: 0.01 to 0.15%;
Si: 1% or less; Mn: 1% or less; P: 0.02% or less; S: 0.01% or less;
Co: less than 0.10%; Cr: 16 to 22%; Mo: 4 to 10%; W: 5% or less;
Al: 1.2 to 2.5%; Ti: 2.4 to 4%; B: 0.001 to 0.05%; Zr: 0.01 to
0.5%; Fe: 1% or less; and a balance of Ni and inevitable
impurities.
2. The Ni-based super alloy according to claim 1, wherein Mo+1/2W
is 4 to 10%.
3. The Ni-based super alloy according to claim 1, which further
comprises at least one selected from the group consisting of: Nb:
0.1 to 3%; and Ta: 0.1 to 3%.
4. The Ni-based super alloy according to claim 2, which further
comprises at least one selected from the group consisting of: Nb:
0.1 to 3%; and Ta: 0.1 to 3%.
5. The Ni-based super alloy according to claim 1, which further
comprises at least one selected from the group consisting of: Ca:
0.001 to 0.03%; Mg: 0.001 to 0.03%; and REM: 0.001 to 0.1%.
6. The Ni-based super alloy according to claim 2, which further
comprises at least one selected from the group consisting of: Ca:
0.001 to 0.03%; Mg: 0.001 to 0.03%; and REM: 0.001 to 0.1%.
7. The Ni-based super alloy according to claim 3, which further
comprises at least one selected from the group consisting of: Ca:
0.001 to 0.03%; Mg: 0.001 to 0.03%; and REM: 0.001 to 0.1%.
8. The Ni-based super alloy according to claim 4, which further
comprises at least one selected from the group consisting of: Ca:
0.001 to 0.03%; Mg: 0.001 to 0.03%; and REM: 0.001 to 0.1%.
9. The Ni-based super alloy according to claim 1, which further
comprises: Cu: 0.01 to 2%.
10. The Ni-based super alloy according to claim 2, which further
comprises: Cu: 0.01 to 2%.
11. The Ni-based super alloy according to claim 3, which further
comprises: Cu: 0.01 to 2%.
12. The Ni-based super alloy according to claim 4, which further
comprises: Cu: 0.01 to 2%.
13. The Ni-based super alloy according to claim 5, which further
comprises: Cu: 0.01 to 2%.
14. The Ni-based super alloy according to claim 6, which further
comprises: Cu: 0.01 to 2%.
15. The Ni-based super alloy according to claim 7, which further
comprises: Cu: 0.01 to 2%.
16. The Ni-based super alloy according to claim 8, which further
comprises: Cu: 0.01 to 2%.
17. The Ni-based super alloy according to claim 1, which further
comprises: V: 0.05 to 1%.
18. The Ni-based super alloy according to claim 2, which further
comprises: V: 0.05 to 1%.
19. The Ni-based super alloy according to claim 3, which further
comprises: V: 0.05 to 1%.
20. The Ni-based super alloy according to claim 4, which further
comprises: V: 0.05 to 1%.
21. The Ni-based super alloy according to claim 5, which further
comprises: V: 0.05 to 1%.
22. The Ni-based super alloy according to claim 6, which further
comprises: V: 0.05 to 1%.
23. The Ni-based super alloy according to claim 7, which further
comprises: V: 0.05 to 1%.
24. The Ni-based super alloy according to claim 8, which further
comprises: V: 0.05 to 1%.
25. The Ni-based super alloy according to claim 9, which further
comprises: V: 0.05 to 1%.
26. The Ni-based super alloy according to claim 10, which further
comprises: V: 0.05 to 1%.
27. The Ni-based super alloy according to claim 11, which further
comprises: V: 0.05 to 1%.
28. The Ni-based super alloy according to claim 12, which further
comprises: V: 0.05 to 1%.
29. The Ni-based super alloy according to claim 13, which further
comprises: V: 0.05 to 1%.
30. The Ni-based super alloy according to claim 14, which further
comprises: V: 0.05 to 1%.
31. The Ni-based super alloy according to claim 15, which further
comprises: V: 0.05 to 1%.
32. The Ni-based super alloy according to claim 16, which further
comprises: V: 0.05 to 1%.
Description
FIELD OF THE INVETION
[0001] The present invention relates to a Ni-based super alloy.
BACKGROUND OF THE INVENTION
[0002] Heretofore, as Ni-based super alloys, NCF751, NCF80A, and
the like have been widely known. Such a kind of Ni-based super
alloys have used for exhaust valve of automobile engines and the
like where high-temperature strength is required.
[0003] Furthermore, Reference 1 discloses a Ni-based super alloy
for exhaust valves comprising, by mass %, C: 0.01 to 0.15%, Si:
2.0% or less, Mn: 2.5% or less, Cr: 15 to 25%, Mo+1/2W: 0.5 to
5.0%, Nb+Ta: 0.3 to 3.0%, Ti: 1.5 to 3.5%, Al: 0.5 to 2.5%, B:
0.001 to 0.02%, Fe: 5% or less, and the balance of substantially
Ni.
[0004] In addition, Reference 2 discloses a Ni-based super alloy
for exhaust valves comprising, by mass %, C: 0.16 to 0.54%, Si:
0.5% or less, Mn: 1.0% or less, Co: 2.0 to 8.0%, Fe: 12% or less,
Cr: 17.0 to 23.5%, and one or two of Mo and W in the range of
2.0.ltoreq.Mo+1/2W.ltoreq.5.5, which further containing Al: 1.0 to
2.0%, Ti: 2.5 to 5.0% (provided that
5.0.ltoreq.1.8Al+Ti-4C.ltoreq.6.0), and one or two of B: 0.001 to
0.020% and Zr: 0.005 to 0.15%, and the balance of substantially Ni
excluding impurities.
[0005] [Reference 1] JP-A-61-119640
[0006] [Reference 2] JP-A-5-59472
[0007] However, existing Ni-based super alloys have the following
problems.
[0008] Namely, exhaust gas temperature of the conventional engines
for automobiles are mainly around 800.degree. C.
[0009] However, in recent years, in order to improve fuel costs and
purify exhaust gases, there have been developed engines which
operate near to the stoichiometric ratio. In such a kind of
engines, the exhaust gas temperature reaches 900.degree. C. in some
cases.
[0010] At such a temperature, in the existing Ni-based super
alloys, mechanical properties at high temperature, such as tensile
strength and fatigue strength, decrease in a large extent.
Therefore, even when an exhaust valve is formed using conventional
Ni-based super alloys, there arises a problem that necessary valve
properties cannot be obtained and, as a result, engine performance
cannot be sufficiently enhanced.
[0011] On the other hand, as a Ni-based super alloy which has
excellent high-temperature strength, it is considered to use alloys
containing Co in an amount of 12 to 14%, such as WASPALOY and
UDIMET520.
[0012] However, since these Ni-based super alloys are poor in
grindability, there arise problems that the life of a grindstone
decreases and surface processing accuracy of products lowers.
Furthermore, owing to a high Co content, material costs become very
high.
SUMMARY OF THE INVENTION
[0013] Accordingly, an advantage of some aspects of the invention
is to provide a relatively inexpensive Ni-based super alloy
excellent in high temperature mechanical properties and
grindability.
[0014] The present inventors have made eager investigation to
examine the problem. As a result, it has been found that the
foregoing objects can be achieved by the following Ni-based super
alloys. With this finding, the present invention is
accomplished.
[0015] The present invention is mainly directed to the following
items:
[0016] 1. A Ni-based super alloy comprising, by mass %: C: 0.01 to
0.15%; Si: 1% or less; Mn: 1% or less; P: 0.02% or less; S: 0.01%
or less; Co: less than 0.10%; Cr: 16 to 22%; Mo: 4 to 10%; W: 5% or
less; Al: 1.2 to 2.5%; Ti: 2.4 to 4%; B: 0.001 to 0.05%; Zr: 0.01
to 0.5%; Fe: 1% or less; and a balance of Ni and inevitable
impurities.
[0017] 2. The Ni-based super alloy according to item 1, wherein
Mo+1/2W is 4 to 10%.
[0018] 3. The Ni-based super alloy according to item 1 or 2, which
further comprises at least one selected from the group consisting
of: Nb: 0.1 to 3%; and Ta: 0.1 to 3%.
[0019] 4. The Ni-based super alloy according to any one of items 1
to 3, which further comprises at least one selected from the group
consisting of: Ca: 0.001 to 0.03%; Mg: 0.001 to 0.03%; and REM:
0.001 to 0.1%.
[0020] 5. The Ni-based super alloy according to any one of items 1
to 4, which further comprises: Cu: 0.01 to 2%.
[0021] 6. The Ni-based super alloy according to any one of items 1
to 5, which further comprises: V: 0.05 to 1%.
[0022] The Ni-based super alloy according to the invention has
contents of specific ingredients in specific ranges. Therefore, the
Ni-based super alloy according to the invention is excellent in
mechanical properties such as tensile strength and fatigue strength
even at a high temperature of 900.degree. C.
[0023] In the present invention, the balance is Ni except for
inevitable impurities such as oxide, sulfide, etc.
[0024] Moreover, in the Ni-based super alloy according to the
invention, the content of Co is particularly limited to less than
0.10%. Therefore, it is excellent in grindability and the material
costs become inexpensive as compared with WASPALOY and
UDIMET520.
[0025] Therefore, in the case where the Ni-based super alloy
according to the invention is used as a material for engine valves,
it is easy to improve engine performance. Furthermore, the life of
grindstone to be used at grinding of products is lengthened and
also surface accuracy of the products can be improved.
[0026] In addition, the Ni-based super alloy according to the
invention is also useful for turbine disks, blades, and the like,
for example.
DETAILED DESCRIPTION OF THE INVENTION
[0027] The following will describe one embodiment of the invention
in detail. With regard to the Ni-based super alloy according to the
invention (sometimes referred to as "present alloy"), the contents
of the specific ingredients fall within the ranges defined in the
above and the balance comprises Ni and inevitable impurities. The
reasons for defining the kinds of the specific ingredients and
contents thereof are as follows. In this connection, the unit of
the following contents is mass %.
(1) C: 0.01 to 0.15%:
[0028] C is an element which forms MC carbides in combination with
Ti, Nb, and Ta and M.sub.23C.sub.6 and M.sub.6C carbides in
combination with Cr, Mo, and W, and contributes to prevent
coarsening of grains and strengthening the grain boundary. In order
to obtain the effects, the content of C is suitably 0.01% or more,
preferably 0.03% or more.
[0029] On the other hand, when the content of C increases, the
carbides increases and, for example, it becomes difficult to form a
valve shape and toughness and ductility tend to lower. Therefore,
the content of C is suitably 0.15% or less, preferably 0.10% or
less.
[0030] According to an embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is the
maximum amount used in the examples of the developed alloys as
summarized in Table 1.
(2) Si: 1% or Less:
[0031] Si is an element which acts as a deoxidizer at dissolution
and refining and may be incorporated according to need. Moreover,
Si also contributes to improvement of oxidation resistance.
[0032] When the content of Si increases, toughness and workability
tend to lower. Therefore, the content of Si is suitably 1% or
less.
[0033] According to an embodiment, the minimal amount present in
the alloy is at least 1/10 of the smallest non-zero amount used in
the examples of the developed alloys as summarized in Table 1.
According to a further embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is the
maximum amount used in the examples of the developed alloys as
summarized in Table 1.
(3) Mn: 1% or Less:
[0034] As the case of Si, Mn is an element which mainly acts as a
deoxidizer and may be incorporated according to need.
[0035] When the content of Mn increases, oxidation resistance at
high temperature, workability, and the like tend to lower.
Therefore, the content of Mn is suitably 1% or less.
[0036] According to an embodiment, the minimal amount present in
the alloy is at least 1/10 of the smallest non-zero amount used in
the examples of the developed alloys as summarized in Table 1.
According to a further embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is the
maximum amount used in the examples of the developed alloys as
summarized in Table 1.
(4) P: 0.02% or Less:
[0037] P is an element which lowers hot workability. Since Ni is
lowered in the present alloy, the range of temperature where hot
working is possible is relatively narrow and hence it is desirable
to secure hot workability as far as possible. Therefore, the
content of P is suitably 0.02% or less.
[0038] According to an embodiment, the minimal amount present in
the alloy is at least 1/10 of the smallest non-zero amount used in
the examples of the developed alloys as summarized in Table 1.
According to a further embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is 1.1
times the highest amount used in the examples of the developed
alloys as summarized in Table 1. According to a further embodiment,
the maximum amount present in the alloy is the maximum amount used
in the examples of the developed alloys as summarized in Table
1.
(5) S: 0.01% or Less:
[0039] As the case of P, S is an element which lowers hot
workability. Therefore, the content of S is suitably 0.01% or
less.
[0040] According to an embodiment, the minimal amount present in
the alloy is at least 1/10 of the smallest non-zero amount used in
the examples of the developed alloys as summarized in Table 1.
According to a further embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is 1.1
times the highest amount used in the examples of the developed
alloys as summarized in Table 1. According to a further embodiment,
the maximum amount present in the alloy is the maximum amount used
in the examples of the developed alloys as summarized in Table
1.
(6) Co: Less Than 0.10%:
[0041] Co is a main element which lowers grindability. Moreover, it
is also a main element which increases the material costs.
Therefore, the content of Co is suitably less than 0.10%.
[0042] According to an embodiment, the minimal amount present in
the alloy is at least 1/10 of the smallest non-zero amount used in
the examples of the developed alloys as summarized in Table 1.
According to a further embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is 1.1
times the highest amount used in the examples of the developed
alloys as summarized in Table 1. According to a further embodiment,
the maximum amount present in the alloy is the maximum amount used
in the examples of the developed alloys as summarized in Table
1.
(7) Cr: 16 to 22%:
[0043] Cr is an element which is necessary to improve the high
temperature oxidation resistance and the corrosion resistance. In
order to obtain the effect, the content of Cr is suitably 16% or
more.
[0044] On the other hand, when the content of Cr increases, the
.sigma.-phase precipitates, so that toughness and high-temperature
strength lower. Therefore, the content of Cr is suitably 22% or
less.
[0045] According to an embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is the
maximum amount used in the examples of the developed alloys as
summarized in Table 1.
(8) Mo: 4 to 10%:
[0046] Mo is an element which enhances high-temperature strength
mainly through solid solution strengthening of the matrix. The
content of Mo is suitably 4% or more to enhance strength at
900.degree. C.
[0047] On the other hand, when the content of Mo increases, the
material costs increase and also hot workability and oxidation
resistance tend to lower. Therefore, the content of Mo is suitably
10% or less, preferably 7% or less.
[0048] According to an embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is 1.1
times the highest amount used in the examples of the developed
alloys as summarized in Table 1. According to a further embodiment,
the maximum amount present in the alloy is the maximum amount used
in the examples of the developed alloys as summarized in Table
1.
(9) W: 5% or Less:
[0049] As the case of Mo, W is an element which enhances
high-temperature strength mainly through solid solution
strengthening of the matrix and may be incorporated according to
need.
[0050] When the content of W increases, the material costs increase
and also hot workability and oxidation resistance tend to lower.
Therefore, the content of W is suitably 5% or less, preferably 3%
or less.
[0051] According to an embodiment, the minimal amount present in
the alloy is at least 1/10 of the smallest non-zero amount used in
the examples of the developed alloys as summarized in Table 1.
According to a further embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is the
maximum amount used in the examples of the developed alloys as
summarized in Table 1.
[0052] In the present alloy, the above contents of Mo and W is
preferably selected so that Mo+1/2W falls within the range of 4 to
10%, more preferably within the range of 4 to 7%. This is because
the resulting alloy is excellent in high-temperature strength and
hot workability.
[0053] According to an embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is 1.1
times the highest amount used in the examples of the developed
alloys as summarized in Table 1. According to a further embodiment,
the maximum amount present in the alloy is the maximum amount used
in the examples of the developed alloys as summarized in Table
1.
(10) Al: 1.2 to 2.5%:
[0054] Al is an important element for forming the .gamma.'-phase
which is effective for enhancing high-temperature strength in
combination with Ni. When the content of Al decreases, the
precipitation of the .gamma.'-phase becomes insufficient and
high-temperature strength tends to be hardly secured. Therefore,
the content of Al is suitably 1.2% or more.
[0055] On the other hand, when the content of Al increases, hot
workability tends to lower. Therefore, the content of Al is
suitably 2.5% or less, preferably 2.0% or less.
[0056] According to an embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is the
maximum amount used in the examples of the developed alloys as
summarized in Table 1.
(11) Ti: 2.4 to 4%:
[0057] As the case of Al, Ti is an element for forming the
.gamma.'-phase in combination with Ni. When the content of Ti
decreases, the solid solution temperature of the .gamma.'-phase
lowers and a sufficient high-temperature strength tends to be not
obtained. Therefore, the content of Ti is suitably 2.4% or
more.
[0058] On the other hand, when the content of Ti increases, the
.eta.-phase (Ni.sub.3Ti) is apt to precipitate and thus there is
observed a tendency that high-temperature strength and toughness
deteriorate and hot workability lowers. Therefore, the content of
Ti is suitably 4% or less, preferably 3.5% or less.
[0059] According to an embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is the
maximum amount used in the examples of the developed alloys as
summarized in Table 1.
(12) B: 0.001 to 0.05%:
[0060] B is an element which contributes to the improvement of hot
workability. Moreover, it is an element which segregates at grain
boundary and is effective for strengthening the grain boundary and
improving strength properties. In order to obtain the effects, the
content of B is suitably 0.001% or more.
[0061] On the other hand, when the content of B increases, there is
observed a tendency that the melting point drops and hot
workability lowers. Therefore, the content of B is suitably 0.05%
or less.
[0062] According to an embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is 1.1
times the highest amount used in the examples of the developed
alloys as summarized in Table 1. According to a further embodiment,
the maximum amount present in the alloy is the maximum amount used
in the examples of the developed alloys as summarized in Table
1.
(13) Zr: 0.01 to 0.5%:
[0063] Zr is an element which contributes to the improvement of hot
workability. Moreover, it is an element which segregates at grain
boundary and is effective for strengthening the grain boundary
itself and suppressing the formation of denuded zone of .gamma.' in
the vicinity of grain boundary to enhance strength at high
temperature. In order to obtain the effects, the content of Zr is
suitably 0.01% or more.
[0064] On the other hand, when the content of Zr increases, there
is observed a tendency that toughness lowers. Therefore, the
content of Zr is suitably 0.5% or less.
[0065] According to an embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is the
maximum amount used in the examples of the developed alloys as
summarized in Table 1.
(14) Fe: 1% or Less:
[0066] Fe is an element which lowers high-temperature strength and
thus is desirably reduced as far as possible. Therefore, the
content of Fe is suitably 1% or less.
[0067] According to an embodiment, the minimal amount present in
the alloy is at least 1/10 of the smallest non-zero amount used in
the examples of the developed alloys as summarized in Table 1.
According to a further embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is the
maximum amount used in the examples of the developed alloys as
summarized in Table 1.
[0068] The present alloy may further contain one or more elements
selected from the following elements in addition to the
aforementioned constitutional elements. The reasons for specifying
the contents of these elements are as follows.
<1>At Least One Selected from the Group Consisting of: Nb:
0.1 to 3% and Ta: 0.1 to 3%:
[0069] Nb is an element which strengthens the .gamma.'-phase in
combination with Ni together with Al. In order to obtain the
effect, the content of Nb is suitably 0.1% or more.
[0070] On the other hand, when the content of Nb increases, there
is observed a tendency that hot workability lowers. Therefore, the
content of Nb is suitably 3% or less, preferably 2% or less.
[0071] As the case of Nb, Ta is an element which strengthens the
.gamma.'-phase in combination with Ni together with Al. In order to
obtain the effect, the content of Ta is suitably 0.1% or more.
[0072] On the other hand, when the content of Ta increases, there
is observed a tendency that hot workability lowers. Therefore, the
content of Ta is suitably 3% or less, preferably 2% or less.
[0073] According to an embodiment, the minimal amount present in
the alloy is at least 1/10 of the smallest non-zero amount used in
the examples of the developed alloys as summarized in Table 1.
According to a further embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is 1.1
times the highest amount used in the examples of the developed
alloys as summarized in Table 1. According to a further embodiment,
the maximum amount present in the alloy is the maximum amount used
in the examples of the developed alloys as summarized in Table
1.
<2>At Least One Selected from the Group Consisting of Ca:
0.001 to 0.03%, Mg: 0.001 to 0.03%, and REM: 0.001 to 0.1%:
[0074] Ca, Mg, and REM are elements effective for improving hot
workability. In order to obtain the effect, the contents of Ca, Mg,
and REM are suitably 0.001% or more.
[0075] On the other hand, when the contents of Ca, Mg, and REM
increase, there is observed a tendency that toughness lowers.
Therefore, the content of Ca is suitably 0.03%,or less. The content
of Mg is suitably 0.03% or less. The content of REM is suitably
0.1% or less.
[0076] According to an embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is 1.1
times the highest amount used in the examples of the developed
alloys as summarized in Table 1. According to a further embodiment,
the maximum amount present in the alloy is the maximum amount used
in the examples of the developed alloys as summarized in Table
1.
<3>Cu: 0.01 to 2%:
[0077] Cu is an effective element for improving oxidation
resistance. In order to obtain the effect, the content of Cu is
suitably 0.01% or more.
[0078] On the other hand, when the content of Cu increases, there
is observed a tendency that hot workability lowers. Therefore, the
content of Cu is suitably 2% or less.
[0079] According to an embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is the
maximum amount used in the examples of the developed alloys as
summarized in Table 1.
<4>V: 0.05 to 1%:
[0080] As the cases of Mo and W, V is an element which contributes
to solid solution strengthening of the matrix. Moreover, it has
effects of forming MC carbides and stabilizing the carbides. In
order to obtain the effects, the content of V is suitably 0.05% or
more.
[0081] On the other hand, when the content of V increases, there is
observed a tendency that toughness lower. Therefore, the content of
V is suitably 1% or less.
[0082] According to an embodiment, the minimal amount present in
the alloy is at least 1/10 of the smallest non-zero amount used in
the examples of the developed alloys as summarized in Table 1.
According to a further embodiment, the minimal amount present in
the alloy is the smallest non-zero amount used in the examples of
the developed alloys as summarized in Table 1. According to a
further embodiment, the maximum amount present in the alloy is 1.1
times the highest amount used in the examples of the developed
alloys as summarized in Table 1. According to a further embodiment,
the maximum amount present in the alloy is the maximum amount used
in the examples of the developed alloys as summarized in Table
1.
[0083] The following will describe one example of a process for
producing the present alloy.
[0084] In order to obtain the present alloy, individual raw
materials are weighed so as to obtain the aforementioned chemical
composition and are melted to form an alloy ingot using a melting
furnace such as an induction furnace. Thereafter, the resulting
alloy ingot is subjected to hot forging or hot rolling, or the like
according to need, whereby a desired shape can be obtained.
[0085] Furthermore, the resulting alloy ingot may be subjected to
solution treatment, aging treatment, or the like according to
need.
[0086] As the above solution treatment, there can be specifically
exemplified, for example, a method of heating to a temperature of
950 to 1150.degree. C. and subsequently quenching.
[0087] As the temperature for the above aging treatment, there can
be specifically exemplified, for example, a temperature of 500 to
1000.degree. C., preferably 600 to 900.degree. C.
[0088] The applications of the present alloy as described in the
above are not particularly limited. As applications of the present
alloy, there may be specifically exemplified engine valves, turbine
disks, blades, heat-resistant springs, engine shafts, valves for
ships, volts, and the like.
EXAMPLES
[0089] The present invention is now illustrated in greater detail
with reference to Examples and Comparative Examples, but it should
be understood that the present invention is not to be construed as
being limited thereto.
[0090] First, individual raw materials weighed so as to obtain the
chemical composition shown in Tables 1 and 2 below were melted in
an induction furnace and then cast to 50 kg each. Thereafter, the
resulting each alloy ingot was subjected to hot forging and hot
rolling at 1180.degree. C. to produce a round bar having a diameter
of 16 mm.
[0091] Then, after held at 1050.degree. C. for 1 hour, the
resulting each round bar was water-cooled to perform solution
treatment and, after held at 750.degree. C. for 4 hours, it was
air-cooled to perform aging treatment, thereby each test material
being formed.
[0092] Thereafter, using each test material, a tensile test and a
rotating bending fatigue test were carried out at room temperature
and at 900.degree. C.
[0093] In this connection, the tensile test at room temperature was
carried out in accordance with JIS Z 2241 and the tensile test at
900.degree. C. was carried out in accordance with JIS G 0567.
[0094] In addition, the rotating bending fatigue test was carried
out in accordance with JIS Z 2274 and the test was conducted at a
rotation number of 3500 rpm at room temperature and at 900.degree.
C., respectively. Fatigue strength was obtained as the maximum skin
stress when the number of cycles reached to 10.sup.7 times before
failure.
[0095] Then, a grinding test was carried out on each test material
after aging. In the grinding test, using a test piece having an
outer diameter of 25 mm and a ground part length of 300 mm, the
piece was tested by a method of 5-paths grinding with a grindstone
having an outer diameter of 600 mm at a grinding speed of 700
m/minute, a feeding speed of 30 mm/second, and a radial depth of
0.2 mm per path.
[0096] Then, grindability was evaluated by an abraded amount of the
grindstone after grinding. Namely, the abraded amount of the
grindstone with each test piece was represented by a ratio to the
abraded amount with the test piece according to Comparative Example
1, the amount being assigned as 100. The ratio was regarded as an
index indicating the grindability.
[0097] Tables 1 and 2 shows chemical compositions of the Ni-based
super alloys according to Examples and Comparative Examples and
Table 3 shows test results of the Ni-based super alloys according
to Examples and Comparative Examples.
TABLE-US-00001 TABLE 1 Cu, V, Nb, Ta, Mg, C Si Mn P S Co Cr Mo W Mo
+ 1/2W Al Ti B Zr Fe Ni Ca, REM Example 1 0.04 0.47 0.62 0.005
0.004 0.02 19.7 5.19 -- 5.19 1.64 3.51 0.003 0.02 0.42 Bal. --
Example 2 0.11 0.23 0.44 0.003 0.006 0.07 16.3 4.81 3.16 6.39 1.24
3.68 0.005 0.04 0.38 Bal. -- Example 3 0.06 0.45 0.31 0.002 0.003
0.08 20.5 6.41 -- 6.41 1.74 2.52 0.016 0.23 0.81 Bal. Ta: 1.03
Example 4 0.05 0.21 0.13 0.004 0.007 0.08 19.52 4.28 -- 4.28 1.41
3.24 0.004 0.06 0.31 Bal. Nb: 1.32 Example 5 0.09 0.56 0.27 0.003
0.006 0.01 18.6 4.92 -- 4.92 2.42 3.03 0.026 0.14 0.28 Bal. Ca:
0.003 Example 6 0.01 0.31 0.97 0.008 0.003 0.03 21.3 5.17 1.04 5.69
1.83 3.17 0.007 0.08 0.73 Bal. Cu: 0.05, REM: 0.07 Example 7 0.05
0.64 0.38 0.007 0.002 0.09 20.3 6.83 -- 6.83 1.46 3.97 0.013 0.48
0.52 Bal. -- Example 8 0.03 0.22 0.53 0.013 0.003 0.09 19.1 5.51 --
5.51 1.79 2.54 0.008 0.17 0.94 Bal. Nb: 1.24 Example 9 0.12 0.38
0.14 0.017 0.005 0.04 20.4 4.38 -- 4.38 1.53 3.26 0.005 0.29 0.12
Bal. -- Example 10 0.14 0.41 0.39 0.008 0.008 0.08 17.8 4.12 1.53
4.89 1.26 2.72 0.019 0.07 0.19 Bal. Cu: 0.18, Nb: 1.81 Example 11
0.08 0.96 0.83 0.007 0.002 0.02 21.8 7.91 -- 7.91 2.25 2.43 0.044
0.32 0.32 Bal. V: 0.63, Mg: 0.007 Example 12 0.02 0.19 0.23 0.009
0.006 0.05 20.7 5.23 4.87 7.67 1.62 3.41 0.037 0.12 0.61 Bal. Cu:
1.92 Example 13 0.04 0.21 0.34 0.012 0.008 0.08 19.3 4.16 -- 4.16
1.53 2.76 0.012 0.04 0.03 Bal. -- Example 14 0.08 0.49 0.17 0.007
0.003 0.03 20.6 8.94 -- 8.94 1.76 2.84 0.024 0.21 0.45 Bal. --
Example 15 0.06 0.83 0.78 0.014 0.008 0.07 18.2 5.82 -- 5.82 1.47
3.58 0.008 0.08 0.24 Bal. --
TABLE-US-00002 TABLE 2 Cu, V, Nb, Ta, C Si Mn P S Co Cr Mo W Mo +
1/2W Al Ti B Zr Fe Ni Mg, Ca, REM Comparative 0.05 0.04 0.08 0.007
0.004 13.52 19.72 4.27 -- 4.27 1.42 3.03 0.005 -- 0.52 Bal. --
Example 1 Comparative 0.07 0.08 0.07 0.008 0.003 12.4 19.2 6.03
1.04 6.55 2.02 2.98 0.032 -- 0.03 Bal. -- Example 2 Comparative
0.06 0.14 0.08 0.003 0.006 0.08 20.3 5.24 -- 5.24 1.17 2.31 -- --
0.58 Bal. -- Example 3 Comparative 0.04 0.06 0.07 0.004 0.005 0.04
15.48 0.08 -- 0.08 1.18 2.32 -- -- 7.26 Bal. Nb: 1.03 Example 4
Comparative 0.05 0.08 0.05 0.002 0.003 1.02 19.43 0.06 -- 0.06 1.43
2.26 -- -- 1.53 Bal. -- Example 5
TABLE-US-00003 TABLE 3 Properties Properties at at Room-temperature
900.degree. C. Fatigue Fatigue Tensile strength at Tensile strength
at Grindability strength 10.sup.7 times strength 10.sup.7 times
(abrasion of (MPa) (MPa) (MPa) (MPa) grindstone) Example 1 1346 416
512 257 72 Example 2 1317 403 504 273 63 Example 3 1303 424 508 267
52 Example 4 1321 407 518 261 43 Example 5 1348 414 523 243 68
Example 6 1305 408 531 268 62 Example 7 1343 401 527 281 58 Example
8 1302 426 503 273 48 Example 9 1318 413 508 271 59 Example 10 1301
425 513 276 51 Example 11 1324 403 524 259 48 Example 12 1316 407
519 251 62 Example 13 1323 418 528 273 57 Example 14 1314 406 514
264 49 Example 15 1309 413 516 257 53 Comparative 1314 452 526 306
100 Example 1 Comparative 1468 439 543 316 107 Example 2
Comparative 1008 362 453 121 92 Example 3 Comparative 1310 404 415
107 62 Example 4 Comparative 1179 368 287 82 47 Example 5
[0098] The following are found from Tables 1 to 3. Namely, the
Ni-based super alloys according to Comparative Examples 1 and 2
particularly have an extremely high Co content. Therefore, it is
found that they are poor in grindability. Moreover, since they
contain a large amount of expensive Co, the material costs thereof
are relatively high.
[0099] On the other hand, the Ni-based super alloys according to
Comparative Examples 3 to 5 has a reduced Co content but the
contents of .gamma.'-phase-forming elements such as Al and Ti are
low. Furthermore, the Ni-based super alloys according to
Comparative Examples 4 and 5 has an extremely low contents of solid
solution strengthening elements such as Mo and W and the content of
Fe decreasing high-temperature strength is extremely high. For
these reasons, it is found that the Ni-based super alloys according
to Comparative Examples 3 to 5 are poor in mechanical properties at
high temperature.
[0100] However, in the Ni-based super alloys according to Examples
1 to 15, the contents of the specific ingredients fall within
specific ranges. Therefore, the Ni-based super alloys according to
Examples 1 to 15 are excellent in mechanical properties such as
tensile strength and fatigue strength even at such a high
temperature of 900.degree. C.
[0101] Moreover, in the Ni-based super alloys according to Examples
1 to 15, the content of Co is particularly limited to less than
0.10%. Therefore, they are not only excellent in grindability but
also inexpensive in material costs.
[0102] Therefore, in the case where these Ni-based super alloys are
used as materials for engine valves, it may be easy to improve
engine performance. Furthermore, the life of grindstone to be used
at grinding of products is lengthened and also surface processing
accuracy of the products can be improved.
[0103] While Ni-based super alloys of the present invention has
been described in detail and with reference to specific embodiments
thereof, it will be apparent to one skilled in the art that various
changes and modifications can be made therein without departing
from the spirit and scope thereof.
[0104] The present application is based on Japanese Patent
Application No. 2006-079447 filed on Mar. 22, 2006, and the
contents thereof are incorporated herein by reference.
* * * * *