U.S. patent application number 09/496271 was filed with the patent office on 2003-07-24 for high-melting superalloy and method of producing the same.
Invention is credited to Gu, Yuefeng, Harada, Hiroshi, Mitarai, Yoko, Nakazawa, Shizuo, Ro, Yoshikazu, Yu, Xihong.
Application Number | 20030136478 09/496271 |
Document ID | / |
Family ID | 12168841 |
Filed Date | 2003-07-24 |
United States Patent
Application |
20030136478 |
Kind Code |
A1 |
Mitarai, Yoko ; et
al. |
July 24, 2003 |
High-melting superalloy and method of producing the same
Abstract
A high-melting superalloy made of iridium or rhodium or both
thereof as a base and containing at least nickel together with at
least one a metal selected from the metal group consisting of
titanium, zirconium, hafnium, vanadium, niobium, and tantalum,
wherein at least both phases of an fcc phase and an LI.sub.2 phase
are formed in the texture, and an amount of the LI.sub.2 phase from
20 to 80% by volume.
Inventors: |
Mitarai, Yoko; (Ibaraki,
JP) ; Gu, Yuefeng; (Ibaraki, JP) ; Yu,
Xihong; (Ibaraki, JP) ; Ro, Yoshikazu;
(Ibaraki, JP) ; Nakazawa, Shizuo; (Ibaraki,
JP) ; Harada, Hiroshi; (Ibaraki, JP) |
Correspondence
Address: |
Wenderoth, Lind & Ponack
2033 K Street N.W.
Suite 800
Washington
DC
20006
US
|
Family ID: |
12168841 |
Appl. No.: |
09/496271 |
Filed: |
February 1, 2000 |
Current U.S.
Class: |
148/426 ;
148/442; 420/456; 420/461; 420/580 |
Current CPC
Class: |
C22C 19/03 20130101;
C22C 5/04 20130101 |
Class at
Publication: |
148/426 ;
148/442; 420/456; 420/580; 420/461 |
International
Class: |
C22C 005/04; C22C
019/03; C22C 030/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 2, 1999 |
JP |
025540/1999 |
Claims
What is claimed is:
1. A high-melting superalloy comprising (A) from 5 to 65 atomic %
of nickel and (B) from 5 to 20 atomic % of at least one metal
selected from the group consisting of titanium, zirconium, hafnium,
vanadium, niobium, and tantalum, with (C) from 30 to 75 atomic % of
iridium or rhodium, or a mixture thereof, wherein a LI.sub.2 phase
precipitated in a fcc phase of the matrix phase, and an amount of
the LI.sub.2 phase is from 20 to 80% by volume.
2. The high-melting superalloy according to claim 1, wherein an
atomic % of sum of (A) and (B) is from 20 to 70%.
3. The high-melting superalloy according to claim 1 or 2, wherein,
in case that the metal (c) is iridium, an atomic ratio of (A) to
(B) is from 0.3:1 to 8:1.
4. The high-melting superalloy according to claim 1 or 2, wherein,
in case that the metal (c) is rhodium the atomic ratio of (A) to
(B) is from 0.25:1 to 12:1.
5. The high-melting superalloy comprising (A) from 4 to 86 atomic %
of nickel, (B) from 0.5 to 20 atomic % of at least one metal
selected from the group consisting of titanium, Zirconium, hafnium,
vanadium, niobium, and tantalum, and (C) from 4 to 86 atomic % of
iridium or rhodium, or a mixture thereof, with (D) from 0.4 to 20
atomic % of alminum, wherein a LI.sub.2, phase is precipitated in a
fcc phase of the matrix phase, and an amount of the LI.sub.2, phase
is from 20 to 80% by volume.
6. The high-melting superalloy according to claim 5, wherein the
sum of atomic % of (A) and (C), and (B) and (D) are set as
follows,(A)+(C).gtoreq.75 atomic %(B)+(C).ltoreq.25 atomic %
7. A method of producing a high-melting superalloy as set forth in
any of claims 1 to 4, which comprises compounding at least one of
an iridium-base superalloy made of iridium as a base added with at
least one metal selected from the metal group consisting of
titanium, zirconium, hafnium, vanadium, niobium, and tantalum and a
rhodium-base superalloy made of rhodium as a base added with at
least one metal selected from the above-described metal group, with
nickel, followed by ingoting to produce a high-melting
superalloy.
8. A method of producing a high-melting superalloy as set forth in
any of claims 1 to 6, which comprises compounding at least one of
an iridium-base superalloy made of iridium as a base added with at
least one metal selected from the metal group consisting of
titanium, zirconium, hafnium, vanadium, niobium, and tantalum and a
rhodium-base superalloy made of rhodium as a base added with at
least one metal selected from the above-described metal group, with
a nickel-base alloy made of nickel as a base added with at least
one metal selected from the above-described metal group, or
aluminum, followed by ingoting to produce a high-melting
superalloy.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a high-melting superalloy.
More specifically, the invention relates to a new high-melting
superalloy having an excellent high-temperature strength and a good
ductility, which is useful as a material for high-temperature
instruments such as a gas turbine for electric power generation, a
jet engine, a rocket engine, etc.
[0003] 2. Description of the Related Art
[0004] Turbine blades and turbine vanes used for high-temperature
instruments such as a gas turbine for electric power generation, a
jet engine, a rocket engine, etc., are used under high-temperature
and high-stress conditions. Hitherto, for these turbine blades and
turbine vanes, Ni-base superalloys having a high heat resistance
and an excellent high-temperature strength have bee used but the
use temperature have become severe year by year. This is because
the increase of a combustion gas temperature is the most effective
correspondence to further increase the output and the heat
efficiency of high-temperature instruments. Consequently, for the
turbine blades and the turbine vanes, the improvement in the
high-temperature strength has been desired, which means, in other
words, that the improvement in the high-temperature strength of
materials used for turbine blades and turbine vanes is
indispensable. The durable temperature of Ni-base superalloys
capable of having a substantial strength is about 1,100.degree. C.
If a new material, which can be used at a temperature higher than
the temperature and can be realized at a relatively low cost, can
be developed, it is very useful for practical use.
[0005] With respect to Ni-base superalloys having superior
high-temperature strength, various investigations have hitherto
been made in order to improve an acid resistance, a corrosion
resistance, etc. For example, the present inventors have proposed
to improve the high-temperature strength and the high-temperature
corrosion resistance by solid-solution strengthened N-base
superalloys in which from 0.1 to 5 atomic % of iridium (Ir) is
added, whereby iridium is subjected to solid solution in a
.gamma.-phase and a .gamma.'-phase (see Japanese Patent Laid-Open
No. 183281/1998).
[0006] On the other hand, the present inventors have also already
proposed high-melting alloys having two crystal structures, i.e.,
an FCC structure and an LI.sub.2 structure, in which iridium,
rhodium or a mixture thereof is added with niobium, tantalum,
titanium, aluminum, etc., as alloys having excellent
high-temperature strength characteristics and oxidation resistance
characteristics (see Japanese Patent Laid-Open No.
311584/1996).
[0007] However, these Ni-base heat-resistant superalloys are
lowered in ductility with an improvement in the strength and are
troublesome as practically useful heat-resistant materials.
Additionally, the prior above iridium-base alloys or rhodium-base
alloys are high in cost of the raw materials and involve
disadvantages in general-purpose properties. In this sense, the
Ni-base superalloys which are relatively cheap and can be easily
handled are advantageous.
[0008] However, the related art Ni-base heat-resistant superalloys
can not used at the temperature condition of above 1,300.degree. C.
as a melting point.
SUMMARY OF THE INVENTION
[0009] The present invention has been made in view of the
circumstances as described above, and the invention relates to a
new high-melting superalloy which can further improve the output
and the heat efficiency of high-temperature instruments, has the
characteristics better in not only high-temperature strength but
also ductility than the related art Ni-base superalloys, and can be
realized at a relatively low cost.
[0010] As a result of various investigations, the present inventors
have discovered that by compounding or mixing an iridium-base alloy
(melting point: 2,447.degree. C.) or a rhodium-base alloy (melting
point: 1,960.degree. C.) having a high-melting point and a high
strength at a high temperature and being excellent in the oxidation
resistance with nickel or a nickel-base alloy (density: 8.9
g/cm.sup.3 (cf., density of an iridium-base superalloy: 22.4
g/cm.sup.3, density of a rhodium-base superalloy: 12.44
g/cm.sup.3)), which is light-weight, is excellent in ductility, and
is inexpensive as compared with the above-described superalloys,
followed by ingoting, a superalloy wherein both phases of an fcc
phase and an LI.sub.2 phase are formed in the texture, and a
deposit having an LI.sub.2 structure in the matrix phase having an
fcc structure is conformity-deposited is obtained, and that the
obtained superalloy is not only excellent in the high-temperature
strength and the oxidation resistance but also relatively
light-weight and also has a ductility, leading to accomplishment of
the present invention.
[0011] That is, a first aspect of the present invention is to
provide a high-melting superalloy comprising (A) from 5 to 65
atomic % of nickel and (B) from 5 to 20 atomic % of at least one
metal selected from the group consisting of titanium, zirconium,
hafnium, vanadium, niobium, and tantalum, with (C) from 30 to 75
atomic % of iridium or rhodium, or a mixture thereof, wherein a
LI.sub.2 phase is precipitated in a fcc phase of the matrix phase,
and an amount of the LI.sub.2 phase is from 20 to 80% by
volume.
[0012] Also, a second aspect of the invention is to provide the
high-melting superalloy according to the first aspect, wherein an
atomic ratio of sum of (A) and (B) is from 20 to 70%.
[0013] A third aspect of the invention is to provide the
high-melting superalloy according to the first or second aspect,
wherein, in case that the metal (c) is iridium, an atomic ratio of
(A) to (B) is from 0.3:1 to 8:1.
[0014] A fourth aspect of the invention is to provide the
high-melting superalloy according to the first or second aspect,
wherein, in case that the method (C) is rhodium, the atomic ratio
of (A) to (B) is from 0.25:1 to 12:1.
[0015] A fifth aspect of the invention is to provide the
high-melting superalloy conprising (A) from 4 to 86 atomic % of
nickel, (B) from 0.5 to 20 atomic % of at least one metal selected
from the group consisting of titanium, zirconium, habrium,
vanadium, niobium, and tantalum, and (C) from 4 to 86 atomic % of
iridium or rhodium, or a mixture thereof, with (D) from 0.4 to 20
atomic % of alminum, wherein a LI.sub.2 phase is precipitated in a
fcc phase of the matrix phase, and an amount of the LI.sub.2 phase
is from 20 to 80% by volume.
[0016] The sixth aspect of the invention is to provide the
high-melting superalloy according to fifth aspect, wherein the sum
of atomic % of (A) and (C), and (B) and (D) are set as follows;
(A)+(C).gtoreq.75 atomic %
(B)+(D).ltoreq.25 atomic %
[0017] A seventh aspect of the invention is to provide a method of
producing a high-melting superalloy as set forth in any of the
first to fourth aspects, which comprises compounding at least one
of an iridium-base superalloy made of iridium as a base added with
at least one metal selected from the metal group consisting of
titanium, zirconium, hafnium, vanadium, niobium, and tantalum and a
rhodium-base superalloy made of rhodium as a base added with at
least one metal selected from the above-described metal group, with
nickel, followed by ingoting to produce a high-melting
superalloy.
[0018] An eighth aspect of the invention is to provide a method of
producing a high-melting superalloy as set forth in any of the
first to sixth aspects, which comprises compounding at least one of
an iridium-base superalloy made of iridium as a base added with at
least one metal selected from the metal group consisting of
titanium, zirconium, hafnium, vanadium, niobium, and tantalum and a
rhodium-base superalloy made of rhodium as a base added with at
least one metal selected from the above-described metal group, with
a nickel-base alloy made of nickel as a base added with at least
one metal selected from the above-described metal group, or
aluminum, followed by ingoting to produce a high-melting
superalloy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIGS. 1a, 1b, 1c, and 1d each is an optical microphotograph
showing the texture of each sample in Example 1;
[0020] FIG. 2 is a bar graph comparing the compression strength and
the ductile of each sample in Example 1 with those of Ir-15Nb;
[0021] FIGS. 3a, 3b, and 3c each is a secondary electron image
photograph showing the texture of the Ir--Nb--Ni--Al quaternary
alloy in Example 2;
[0022] FIG. 4 is a correlation diagram showing the correlation of
the ratio of an iridium-base superalloy and the compression
strength of the superalloy prepared in Example 2;
[0023] FIG. 5 is a correlation diagram showing the correlation of
the addition amount of niobium or tantalum in an iridium-base
superalloy and the compression strength of the superalloy prepared
in Example 2;
[0024] FIGS. 6a, 6b, 6c, and 6d each is a microphotograph showing
the texture of each sample in Example 3;
[0025] FIG. 7 is a correlation diagram showing the correlation of
the content of nickel in the superalloys prepared in Example 3 to
the compression strength and ductile thereof;
[0026] FIG. 8 is a view showing the compression strengths and the
room-temperature compressive strains of the superalloys of the
invention containing Rh and Ir;
[0027] FIG. 9 is a photograph showing a fracture surface of the
superalloy of the invention; and
[0028] FIG. 10 is a photograph showing the texture of the
superalloy of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0029] Then, the high-melting superalloy of the invention and the
method of producing the same are described in detail.
[0030] The high-melting superalloy according to the invention
comprises (A) from 5 to 73 atomic % of nickel and (B) from 2 to 22
atomic % of at least one metal selected from the group consisting
of titanium, zirconium, hafnium, vanadium, niobium, and tantalum,
with (C) a balance of iridium or rhodium, or a mixture thereof,
wherein an fcc phase and a LI.sub.2 phase are formed in a texture
thereof and the LI.sub.2 phase is precipitated in a fcc phase of
the matrix phase, and an amount of the LI.sub.2 phase is from 20 to
80% by volume.
[0031] Needless to say, it is acceptable that inevitable impurities
mingled in the raw materials during the production or in the
production steps are present in this composition.
[0032] A proportion of the component (C), i.e., iridium or rhodium,
or a mixture thereof, to be contained as a balance is substantially
from 30 to 75 atomic %.
[0033] In the case where, in the high-melting superalloy of the
invention, the components (A), (B) and (C) fall out the
above-described composition range, the requirements which are
indispensable to the composition of the superalloy of the
invention, (1) a LI.sub.2 structure is precipitated in the matrix
phase having an fcc structure; and (2) the precipitation phase
having an LI.sub.2 structure accounts for from 20 to 80% by volume,
cannot be met. Hence, in this case, not only a desired
high-temperature strength but also an improvement in the ductility
cannot be obtained.
[0034] In the invention, in order to attain an excellent
high-temperature strength and an improvement in the ductility, it
is preferred that a sum of atomic % of (A) and (B) is from 20 to
70% and that, in case of iridium as metal (C), an atomic ratio of
the component (A) to the component (B) is from 0.3:1 to 8:1. It is
further preferred that, in case of rhodium as metal (C), the atomic
ratio of the component (A) to the component (B) is from 0.25:1 to
12:1.
[0035] Of titanium, zirconium, hafnium, vanadium, niobium, and
tantalum as the component (C) are particularly preferred niobium,
tantalum and titanium.
[0036] These high-melting superalloys are produced by mixing the
alloy-constituting element materials so as to obtain a specified
composition, followed by ingoting, and more actually, by
compounding at least one of an iridium-base superalloy made of
iridium as a base added with at least one metal selected from the
metal group consisting of titanium, zirconium, hafnium, vanadium,
niobium, and tantalum and a rhodium-base superalloy made of rhodium
as a base added with at least one metal selected from the
above-described metal group, with nickel, followed by ingoting.
[0037] Also, these high-melting superalloys are produced by mixing
at least one of an iridium-base superalloy made of iridium as a
base added with at least one metal selected from the metal group
consisting of titanium, zirconium, hafnium, vanadium, niobium, and
tantalum and a rhodium-base superalloy made of rhodium as a base
added with at least one metal selected from the above-described
metal group, with a nickel-base alloy made of nickel as a base
added with at least one metal selected from the above-described
metal group, followed by ingoting.
[0038] In the invention, aluminum may further be added as the
component. In this case, the high-melting superalloy of the present
invention comprises
[0039] (A) from 4 to 86 atomic % of nickel,
[0040] (B) from 0.5 to 20 atomic % of at least one metal selected
from the group consisting of T.sub.1, Zr, Hf, V, Nb, and Ta,
and
[0041] (C) from 4 to 86 atomic % of Ir or Rh, or a mixture thereof,
with
[0042] (D) from 0.4 to 20 atomic % of Al.
[0043] It is preferred that the sum of atomic % of (A) and (C), and
(B) and (D) are set as follows;
(A)+(C).gtoreq.75 atomic %
(B)+(D).ltoreq.25 atomic %
[0044] In producing the aluminum-containing alloys, nickel-aluminum
(Ni--Al) alloys which are presently used as heat resisting
materials for high-temperature instruments are useful as the
above-described nickel-base alloy.
[0045] With respect to the ingoting in the production method, there
is no particular restriction regarding the system. For example,
there is illustrated a method including an arc-melting of the
mixture and a homogenizing treatment, such as heat-treatment at
high temperature condition of about 1,800.degree. C. and below for
homogenizing the composition carried out thereafter as an
example.
[0046] The high-melting superalloys of this invention produced by
these production methods each has both phase of the fcc phase and
the LI.sub.2 phase in the texture.
[0047] Also, while it is considered that the composition ratio of
the metal components on the superalloy is an important factor, a
two-phase conformity texture wherein a deposit having an LI.sub.2
structure, is conformity-deposited in the matrix phase having an
fcc structure, is formed. In this case, the two-phase conformity
texture means a texture wherein a row of adjacent crystal lattices
is continued without being broken. When the two-phase conformity
texture is formed, the strength is more increased than the
superalloy simply made of two phases of the fcc phase and the
LI.sub.2 phase. This is considered to be caused by that the
conformity interface between the matrix phase and the deposit
disturbs the transfer of the dislocation. Such a two-phase
conformity texture is surely formed in the case where at least one
of the iridium-base superalloy and the rhodium-base superalloy, and
the nickel-base alloy are used as the raw materials in the
above-described production method, and each alloy has a two-phase
conformity texture having an fcc phase and an LI.sub.2 phase.
[0048] It is not always unnecessary that the fcc phase and the
LI.sub.2 phase each exists as one kind regarding the kind of
constituting substances. Because the high-melting superalloy of the
invention is the multi-component alloy as described above, it is
possible that plural kinds of the fcc phases and LI.sub.2 phases
each having a different existing concentration exist together.
[0049] In the texture formed by both phases of the fcc phase and
the LI.sub.2 phase, it is preferred that an amount of the LI.sub.2
phase is from 20 to 80% by volume. When the amount of the LI.sub.2
phase is less than the lower limit, the strength is lowered. On the
other hand, the LI.sub.2 phase may exceeds the upper limit but the
preparation of such a superalloy becomes considerably
difficult.
[0050] Also, in the case where the iridium-base superalloy or the
rhodium-base superalloy, and nickel or the nickel-base alloy are
used as the raw materials, the high-melting superalloy of the
invention can independently show the characteristics of the
iridium-base superalloy or the rhodium-base superalloy and nickel
or the nickel alloy, in the above-described production method. That
is, the high-melting superalloy of the invention shows all the high
melting point, the high-temperature high strength, and the
excellent oxidation resistance of the iridium-base superalloy or
the rhodium-base superalloy and also the right-weight and the
excellent ductility of nickel or the nickel-base alloy. Also, by
the existence of nickel or the nickel-base alloy, the high-melting
superalloy of this invention becomes relatively inexpensive.
[0051] The high-melting superalloy containing 50 atomic % and below
of the iridium-base superalloy or the rhodium-base superalloy of
itself or in terms of them is light-weight and is considered to be
effective as the rotary members of turbine blades, etc., and on the
other hand, when the content of the iridium-base superalloy or the
rhodium-base superalloy is larger than the above-described content,
as 50% and above, the application of the high-melting superalloy of
the invention to the members used at a higher temperature is
expected to be useful.
[0052] Then, the examples of the high-melting superalloy of the
invention and the production method thereof are described.
EXAMPLE 1
[0053] An iridium-15 niobium (Ir-15Nb) alloy was compounded with
nickel (Ni) and the mixture was arc-melted in a vacuum furnace
under an argon atmosphere to produce four kinds of superalloys
(ingots) of A, B, C, and D shown in Table 1 below.
1 TABLE 1 Superalloy Composition (atomic %) Supperalloy Ni Nb Ir A
10 15 Balance B 20 15 Balance C 30 15 Balance D 50 15 Balance
[0054] From each ingot, a test piece having a height of 6 mm and a
diameter of 3 mm was cut and subjected to an aging treatment in a
vacuum furnace of 5.times.10.sup.-7 Torr at 1,300.degree. C. for
one week. Also, the phase formed in each test piece was determined
by an X-ray diffraction analysis (XRD) and an energy dispersion
type X-ray analyzer (EDAX).
[0055] As a result, the superalloys A and B of Table 1 had the
textures composed of only two phases of the fcc phase and the
LI.sub.2 phase. In particular, in the superalloy A, a two-phase
conformity texture that the precipitation having the LI.sub.2
structure was conformity-precipitated in the matrix phase having
the fcc structure was formed. The fcc phase was made of Ir and the
LI.sub.2 phase was made of Ir.sub.3Nb. Also, in each of these
phases, Ni formed a solid solution with the phase. On the other
hand, In the superalloys C and D, in addition to the
above-described two phases, a .delta. phase ((Ir,
Ni).sub.11Nb.sub.9) belonging to a orthorhombic system was
confirmed as a third phase. In addition, in each of the superalloys
shown above, an amount of Ir.sub.3Nb having the LI.sub.2 structure
was within the range of from 20 to 80% by volume.
[0056] FIGS. 1a to 1d each is an optical microphotograph of each
test piece.
[0057] In the superalloy A, a dendrite texture (FIG. 1a) was formed
and in the superalloys B, C, and D, fine textures (FIGS. 1b, 1c,
and 1d) were formed. Also, it was confirmed that with the increase
of the compounding amount of Ni, the texture became thicker and
rougher.
[0058] Also, about the above-described test materials, a
compression test (in the air, stress speed 3.0.times.10.sup.-4/s)
was carried out in the temperature range of from room temperature
to 1,200.degree. C. The results are shown in the graph of FIG.
2.
[0059] As is clear from the graph of FIG. 2, the compression
strength of superalloy A was about 2 times that of Ir-15Nb at room
temperature and was almost same as that of Ir-15Nb at 1,200.degree.
C. The compression strengths of superalloys B, C, and D were lower
than the compression strength of Ir-15Nb at both room temperature
and 1,200.degree. C. However, the compression strengths of each of
the above superalloys are higher than that of an Ni-base superalloy
used for high-temperature instruments.
[0060] Also, in each of the superalloys, the ductility is improved
by the addition of Ni. Particularly, in superalloy B, the ductility
is about 13%, which is far higher than that of Ir-15Nb. Also, it is
admitted that the utility of the superalloys is higher than the
Ir-15Nb alloy. Furthermore, because a part of Ir is replaced with
Ni, the Ir amount of the superalloys can be reduced, which lowers
the cost of the alloys. Thus, in the point, the high utility of the
superalloys is also confirmed.
EXAMPLE 2
[0061] As the iridium-base superalloy, an iridium-20 niobium
(Ir-20Nb) alloy and an iridium-20 tantalum (Ir-20Ta) alloy were
selected and, as the nickel-base alloy, a nickel-16.8 aluminum
(Ni-16.8Al) alloy was selected. The mol fractions of the
iridium-base superalloy and the nickel-base alloy were selected to
be Ir-base superalloy : Ni-base alloy=25:75 (group A), 50:50 (group
B), and 75:25 (group C), sum total 6 kinds of the quaternary alloys
of the compositions shown in Table 2 below were prepared by
arc-melting in an argon atmosphere.
2TABLE 2 Supperalloy Composition (atomic %) Group A
Ir-5Nb-62.4Ni-12.6Al Ir-3.75Ta-62.4Ni-12.6Al Group B
Ir-10Nb-41.6Ni-8.4Al Ir-7.5Ta-41 .6Ni-8.4Al Group C
Ir-15Nb-20.8Ni-4.2Al Ir-11.25Ta-20.8Ni-4.2Al
[0062] About these 6 kinds of the quaternary alloys, the phase
determination and the texture observation as in Example 1 were
carried out.
[0063] As a result, in the 4 kinds of the superalloys of group A
and group C, the two-phase conformity textures composed of the fcc
phase ((Ir, Ni)) and 2 kinds of LI.sub.2 phases ((Ni, Ir).sub.3
(Al, Ir) and (Ir, Ni).sub.3 (Nb, Al), or (Ni, Ir).sub.3 (Ni, Ta)
and (Ir, Ni).sub.3 (Ta, Al)) were formed. On the other hand, in the
2 kinds of the superalloys of group B, the two-phase conformity
textures by the fcc phase and 2 kinds of the LI.sub.2 phases same
as those of the superalloys of group A and group C were formed but
in the cases, B2 phase ((Ir, Ni) (Al, Nb) or (Ir, Ni) (Al, Ta)) was
additionally observed.
[0064] In addition, in the above-described composition formulae,
for example, (Ni, Ir).sub.3 (Al, Nb) means Ni.sub.3Al containing Ir
and Nb, wherein a part of Ni is replaced with Ir and a part of Al
is replaced with Nb. Other composition formulae also employ the
same expression system as above.
[0065] FIGS. 3a, 3b, and 3c are the secondary electron images
showing the textures of Ir--Nb--Ni--Al superalloys belongings to
group A, group B, and group C, respectively.
[0066] In the superalloy A, the fcc phase and the first LI.sub.2
phase of Ni.sub.3Al containing Ir and Nb were observed. In the
superalloys B and C, larger LI.sub.2 phases were deposited. The B2
phase was observed in the superalloy B only as described above. In
three superalloys A to C, together with the first LI.sub.2 phase of
Ni.sub.3Al containing Ir and Nb, a small second LI.sub.2 phase of
Ir.sub.3Nb containing Ni and Al was found in the fcc matrix
phase.
[0067] Then, the alloys prepared were subjected to an aging
treatment in vacuo at 1,300.degree. C. and 1,400.degree. C. for one
week and the textures were observed again.
[0068] In each superalloy subjected to the aging treatment of
1,300.degree. C., 2 kinds of small second LI.sub.2 phases were
precipitated from the fcc matrix phase. As the result of the phase
analysis of the superalloys B and C, it was confirmed that the
second LI.sub.2 phase contained larger amount of Ni than the first
LI.sub.2 phase. In the superalloy A, 23 atomic % Ir was contained
in the first LI.sub.2 phase. The Ir amount in the matrix phase
increased with the increase of the Ir amount of the superalloy. On
the other hand, the Nb amount in the matrix phase is almost the
level of 5 atomic %. After the aging treatment at 1,400.degree. C.,
in addition to a larger first LI.sub.2 phase, a large amount of
second LI.sub.2 phases each having a different form and size were
formed in the fcc phase. Also, in the superalloy B, the B2 phase
was vanished. Thus, it is considered that the melting point of the
B2 phase in the superalloy B is 1,400.degree. C. Also, in each of
the superalloys, an amount of the LI.sub.2 phase was within the
range of from 20 to 80% by volume ratio.
[0069] The above-described texture observation results were the
same as those about the Ir--Ta--Ni--Al quaternary alloy.
[0070] Then, each of the following 6 kinds of the quaternary alloys
was heated to 1,400.degree. C. for one week, and the compression
strength of each of them at 1,200.degree. C. was measured. The
results are shown as the correlation diagrams of FIG. 4 and FIG.
5.
[0071] In theses FIG. 4 and FIG. 5, for comparison, the strengths
of an Ni-base superalloy (Marm 247) and the iridium-base
superalloys of Ir-15Nb and Ir-20Nb are shown together.
[0072] Each of the quaternary alloys shows the high compression
resistance as compared with an Ni-base superalloy applied to
high-temperature instruments. On the other hand, the compression
strengths of these quaternary alloys are lower than that of Ir--Nb.
However, the ductility of each alloy is, by mixing of the
nickel-base alloy, 18% at the lowest and is improved as 89% is
obtained at the highest. Thus, it is admitted that the utility of
the alloys is higher than Ir-15Nb.
[0073] Also, from FIG. 4, it is confirmed that the compression
strength of the quaternary alloy is more improved with the increase
of the addition amount of Nb or Ta which is the addition component
of the indium-base superalloy.
EXAMPLE 3
[0074] Four samples having the compositions of
Rh.sub.85-xNb.sub.15Ni.sub.- x (x=10, 20, 30, and 50) were prepared
by arc-melting and from each ingot, a test piece of a height of 6
mm and a diameter of 3 mm was cut. The test piece was subjected to
an aging treatment in vacuo (<10.sup.-5 Pa) at 1,200.degree. C.
for 100 hours. Also, a compression test (in the air, stress speed
3.0.times.10.sup.-4 s.sup.-1) was carried out at a temperature of
from 20 to 1,200.degree. C. Each test piece was heated to the test
temperature for from 12 to 20 minutes in a furnace so that a
uniform temperature distribution was obtained during the test and
kept at the temperature for 5 minutes before the initiation of
loading. The compression strength was calculated from the change of
the height of each test piece before and after the test.
[0075] Also, the texture of each superalloy was observed by a
scanning electron microscope (SEM) and a transmission electron
microscope (TEM). The test piece observed by the scanning electron
microscope was electron-polished with an ethyl alcohol solution of
5% HCl. The crystal structures and the phase compositions of the
superalloys after the heat treatment were determined by an X-ray
diffraction analysis (XRD) and an energy dispersion type X-ray
analyzer (EDAX).
[0076] Each of the superalloys of Rh.sub.85-xNb.sub.15Ni.sub.x of
x.ltoreq.30 had the texture composed of only 2 phases of the fcc
phase and the LI.sub.2 phase of Rh.sub.3Nb containing Ni.
Particularly, in the Rh.sub.75Nb.sub.15Ni.sub.10 superalloy of
x=10, a two-phase conformity texture that a deposit having the
LI.sub.2 structure was conformity-deposited in the matrix phase
having the fcc structure was formed. On the other hand, in the
Rh.sub.35Nb.sub.15Ni.sub.50 superalloy of x=50, a .gamma." phase
((Ni, Rh).sub.3Nb) belonging to an orthorhombic system was
confirmed. The contents of Ni contained in Rh.sub.3Nb were from 48
atomic % of Rh.sub.75Nb.sub.15Ni.sub.10 (x=10) to 19.6 atomic % of
Rh.sub.35Nb.sub.15Ni.sub.50 (x=50). Also, in each superalloy, an
amount of the LI.sub.2 phase precipitated in fcc matrix phase was
within the range of from 20 to 80% by volume.
[0077] FIG. 6 is the microphotographs of the superalloys
heat-treated for 100 hours at 1,200.degree. C.
[0078] FIGS. 6a to 6d correspond to the compositions of
Rh.sub.85-xNb.sub.15Ni.sub.x (x=10, 20, 30, and 50), respectively,
and, in each of the superalloys, a dendrite texture is formed. From
the comparison of FIGS. 6a to 6d, it is confirmed that with
increase of the compounding amount of Ni, the texture becomes
coarser as in Example 1.
[0079] FIG. 7 is a correlation diagram showing the compression
strength and the ductility of the Rh.sub.85-xNb.sub.15Ni.sub.x
superalloys in the relation of the content of nickel. In FIG. 7,
the data of the Rh-15 atomic % Nb alloy are shown together for
comparison.
[0080] At room temperature, each of the superalloys with Ni added
shows a high compression strength as compared with the Rh--Nb
two-phase alloy. At 1,200.degree. C., the compression strength of
Rh.sub.75Nb.sub.15Ni.sub.10 (x=10) is 473 MPa, which is higher than
the compression strength of the Rh--Nb two-phase alloy but the
compression strength lowers with the increase of the content of Ni.
However, the compression strength of each of the superalloys is
higher than that of Ni-base superalloys which have hitherto been
applied to high-temperature instruments.
[0081] About the ductility at room temperature, the superalloys
with Ni added are equal to that of the Rh--Nb two-phase alloy in
the composition on Rh.sub.55Nb.sub.15Ni.sub.30 (x=30) but the
superalloys having other compositions show lower values. However,
the ductility of the superalloys is 11%
(Rh.sub.75Nb.sub.15Ni.sub.10 (x=10)) at the lowest and have the
room-temperature ductility higher than those of the In-base
superalloys shown in Example 1.
EXAMPLE 4
[0082] By following the same procedure as Example 2 except that
rhodium was used as the component of constituting the superalloys
in place of iridium, superalloys were prepared. The compression
strength and the ductility of each superalloy were measured
together with the determination of each phase and the observation
of each texture. Each of the superalloys obtained shows a high
compression strength and an improved ductility almost the same as
those of Example 2 using iridium, as compared with the Ni-base
superalloys which have hitherto been used for high-temperature
instruments.
EXAMPLE 5
[0083] By following the same procedure as in Example 1, the alloys
of the following 2 kinds of compositions (atomic %) were
produced.
Rh.sub.50Ir.sub.25Nb.sub.15Ni.sub.10
Rh.sub.25Ir.sub.50Nb.sub.15Ni.sub.10
[0084] About the 2 kinds of the alloys, the compression strengths
(at room temperature and at 1,200.degree. C.) and the
room-temperature compressive strain were measured, they were
compared with those of the high-temperature superalloys of
Rh.sub.75Nb.sub.15Ni.sub.10 and Ir.sub.75Nb.sub.15Ni.sub.10 and
also those of the alloy of Ir--Nb.sub.15 of related art, and the
results are shown in FIG. 8.
[0085] From FIG. 8, it can be seen that in the superalloys of this
invention containing both Rh and Ir, at room temperature, the
compression strength is about 2 times that of the binary alloy of
Ir--Nb.sub.15, at 1,200.degree. C., the compression strength is
almost same as that of the binary alloy, that is, the
high-temperature compression strength is not lowered. Also, it can
be seen that the room-temperature compressive strain is more
improved as the amount of Rh becomes larger.
[0086] FIG. 9 and FIG. 10 are the photographs observing the rupture
cross-sections of the alloys and the photographs showing the alloy
textures of them, and the alloys are as follows:
[0087] a: Rh.sub.75Nb.sub.15Ni.sub.10
[0088] b: Rh.sub.50Ir.sub.25Nb.sub.15Ni.sub.10
[0089] c: Rh.sub.25Ir.sub.50Nb.sub.15Ni.sub.10
[0090] d: Ir.sub.75Nb.sub.15Ni.sub.10
[0091] From FIG. 9, it was confirmed that each alloy showed a
transgranular rupture and improved the brittle property of the
Ir--Nb binary alloy caused by an intergranular rupture.
[0092] From FIG. 10, it was confirmed that in each case, a third
phase was not formed and the texture of each alloy was a two-phase
texture of fcc+LI.sub.2.
[0093] As a matter of course, the invention is not limited to the
above-described examples. That is, about the compositions, the
compounding ratios, the preparation methods, etc., of the
superalloys, various modifications are possible.
[0094] As described above in detail, according to the present
invention, new high-melting superalloys which have the
characteristics better than Ni-base superalloys in related art and
can be realized at a relatively low cost are provided. Also. by the
invention, the more improvements in the output and the heat
efficiency of high-temperature instruments can be realized.
* * * * *