Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
TiAl-BASED INTERMETALLIC SINTERED COMPACT AND METHOD FOR
PRODUCING TiAl-BASED INTERMETALLIC SINTERED COMPACT
Field
[0001] The present invention relates to a TiAl-based
intermetallic sintered compact and a method for producing a
TiAl-based intermetallic sintered compact.
Background
[0002] A TiAl-based intermetallic compound is an
intermetallic compound (alloy) in which Ti (titanium) and
Al (aluminum) are bonded and is applied to structures for
high-temperature use, such as engines and aerospace
instruments, because of its light weight and high strength
at high temperatures. The TiAl-based intermetallic
compound is difficult to be shaped by forging or casting
for its low ductility and other reasons and is sometimes
shaped by sintering. A sintered compact of a TiAl-based
intermetallic compound is formed by sintering a TiAl-based
intermetallic compound powder, for example, as described in
Patent Literature 1.
Citation List
Patent Literature
[0003] Patent Literature 1: Japanese Patent Application
Laid-open No. 3-243741
Summary
Technical Problem
[0004] The strength of a sintered compact of a TiAl-
based intermetallic compound can be increased by increasing
the sintered density in sintering. There is therefore a
demand for increasing the sintered density.
[0005] The present invention is then aimed to provide a
TiAl-based intermetallic sintered compact with high
sintered density and high strength and a method for
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producing a TiAl-based intermetallic sintered compact with
high sintered density and high strength.
Solution to Problem
[0006] To solve the problem described above and achieve
the object, a method for producing a TiAl-based
intermetallic sintered compact of the present disclosure
includes sintering TiAl-based powder to produce a TiAl-
based intermetallic sintered compact, the TiAl-based powder
containing a TiAl-based intermetallic compound in which Ti
and Al are bonded and an additional metal. The additional
metal is Ni, or Ni and Fe. This method for producing a
TiAl-based intermetallic sintered compact allows the TiAl-
based intermetallic sintered compact to exhibit a metal
structure in which the additional metal phase exists at the
grain boundary between adjacent TiAl phases. Accordingly,
this method for producing a TiAl-based intermetallic
sintered compact can increase the sintered density and
increase the strength.
[0007] It is preferable that the method for producing a
TiAl-based intermetallic sintered compact includes a mixing
step of mixing the TiAl-based powder with a binder to yield
a mixture; an injection molding step of molding the mixture
into a molded product with a metal-powder injection molder;
a degreasing step of degreasing the molded product to
produce a degreased product; and a sintering step of
sintering the degreased product to produce the TiAl-based
intermetallic sintered compact. This method for producing
a TiAl-based intermetallic sintered compact uses a metal-
powder injection molding method and therefore can improve
the shape accuracy while improving the sintered density.
[0008] It is preferable that in the method for producing
a TiAl-based intermetallic sintered compact, the TiAl-based
powder has a Ni content of 0.01% by weight to 1% by weight.
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This method for producing a TiAl-based intermetallic
sintered compact allows the additional metal phase to exist
appropriately at the grain boundary between adjacent TiAl
phases, thereby appropriately improving the sintered
density.
[0009] It is preferable that in the method for producing
a TiAl-based intermetallic sintered compact, the TiAl-based
powder has a total amount of Ni and Fe of 0.01% by weight
to 2% by weight. This method for producing a TiAl-based
intermetallic sintered compact allows the additional metal
phase to exist appropriately at the grain boundary between
adjacent TiAl phases, thereby appropriately improving the
sintered density.
[0010] It is preferable that in the method for producing
a TiAl-based intermetallic sintered compact, the TiAl-based
powder is formed by mixing a plurality of TiAl-based solid-
solution powder particles containing the TiAl-based
intermetallic compound and the additional metal. This
method for producing a TiAl-based intermetallic sintered
compact allows the additional metal phase to exist
appropriately at the grain boundary between adjacent TiAl
phases, thereby appropriately improving the sintered
density.
[0011] It is preferable that in the method for producing
a TiAl-based intermetallic sintered compact, the TiAl-based
powder is formed by mixing a plurality of TiAl-based powder
particles and a plurality of additional metal powder
particles, the TiAl-based powder particles being powder
particles of the TiAl-based intermetallic compound, the
additional metal powder particles containing the additional
metal. This method for producing a TiAl-based
intermetallic sintered compact allows the additional metal
phase to exist appropriately at the grain boundary between
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adjacent TiAl phases, thereby appropriately improving the
sintered density.
[0012] To solve the problem described above and achieve
the object, a TiAl-based intermetallic sintered compact of
the present disclosure contains a TiAl-based intermetallic
compound in which Ti and Al are bonded and an additional
metal that is Ni. A Ni content is 0.01% by weight to 1% by
weight of total content. Since this TiAl-based
intermetallic sintered compact contains Ni in this
proportion with respect to the TiAl-based intermetallic
compound, the Ni phase can exist at the grain boundary of
TiAl phases of the sintered compact. Accordingly, this
TiAl-based intermetallic sintered compact improves in
sintered density.
[0013] To solve the problem described above and achieve
the object, a TiAl-based intermetallic sintered compact of
the present disclosure contains a TiAl-based intermetallic
compound in which Ti and Al are bonded and an additional
metal that is Ni and Fe. A total content of Ni and Fe is
0.01% by weight to 2% by weight of total content. Since
this TiAl-based intermetallic sintered compact contains Ni
and Fe in this proportion with respect to the TiAl-based
intermetallic compound, the NiFe phase can exist at the
grain boundary of TiAl phases of the sintered compact.
Accordingly, this TiAl-based intermetallic sintered compact
improves in sintered density.
[0014] It is preferable that in the TiAl-based
intermetallic sintered compact, the TiAl-based
intermetallic compound contains 20 to 80% by weight of Ti,
20 to 80% by weight of Al, and 0 to 30% by weight of mixed
metal, and the mixed metal contains at least one of Nb, Cr,
and Mn. This TiAl-based intermetallic sintered compact
contains the TiAl-based intermetallic compound in this
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proportion and therefore improves in strength.
[0015] It is preferable that in the TiAl-based intermetallic
sintered compact, a plurality of TiAl-based sintered powder
particles containing the TiAl-based intermetallic compound and
the additional metal are bonded, and an additional metal phase
that is a metal phase of the additional metal exists between
the TiAl-based sintered powder particles adjacent to each
other. The TiAl-based intermetallic sintered compact improves
in sintered density more appropriately because the additional
metal phase exists at the grain boundary of TiAl phases of the
sintered compact.
[0015a] In one exemplary embodiment, there is further
provided a method for producing a TiAl-based intermetallic
sintered compact, comprising: a mixing step of mixing TiAl-
based powder with a binder to yield a mixture, the TiAl-based
powder containing a TiAl-based intermetallic compound in which
Ti and Al are bonded, additional metals, and a mixed metal; an
injection molding step of molding the mixture into a molded
product with a metal-powder injection molder; a degreasing step
of degreasing the molded product to produce a degreased
product; and a sintering step of sintering the degreased
product to produce the TiAl-based intermetallic sintered
compact, wherein the additional metals are Ni and Fe, and the
mixed metal contains at least one of Nb and Mn.
Advantageous Effects of Invention
[0016] The present invention can increase the sintered
density of a TiAl-based intermetallic sintered compact and
increase the strength.
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Brief Description of Drawings
[0017] FIG. 1 is a block diagram illustrating a
configuration of a sintered compact production system
according to a first embodiment.
FIG. 2 is a diagram schematically illustrating a
configuration of a powder production apparatus according to
the first embodiment.
FIG. 3 is a schematic diagram illustrating phases of a
TiAl-based intermetallic sintered compact according to the
first embodiment.
FIG. 4 is a flowchart illustrating the production flow
of the TiAl-based intermetallic sintered compact with the
sintered compact production system according to the first
embodiment.
FIG. 5 is a diagram illustrating the metal structure of
the TiAl-based intermetallic sintered compact in a comparative
example.
FIG.6 is a diagram illustrating the metal structure of the
TiAl-based intermetallic sintered compact in a comparative
example.
FIG.7 is a diagram of the metal structure of the TiAl-
based intermetallic sintered compact in an example.
FIG. 8 is a diagram of the metal structure of the TiAl-
based intermetallic sintered compact in an example.
FIG. 9 is a graph illustrating the relation between the Ni
content and the sintered density.
FIG. 10 is a diagram of the metal structure of the TiAl-
based intermetallic sintered compact in a comparative example.
FIG. 11 is a diagram of the metal structure of the TiAl-
based intermetallic sintered compact in an example.
Date Recue/Date Received 2021-02-05
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6a
FIG. 12 is a diagram of the metal structure of the TiAl-
based intermetallic sintered compact in an example.
FIG. 13 is a graph illustrating the relation between the
Ni and the Fe content and the sintered density.
FIG. 14 is a diagram of the metal structure of the TiAl-
based intermetallic sintered compact in a comparative example.
FIG. 15 is a diagram of the metal structure of the TiAl-
based intermetallic sintered compact in an example.
Description of Embodiments
[0018] Preferred embodiments of the present invention will
be described in detail below with reference to the accompanying
drawings. It should be noted that the present
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invention is not limited by those embodiments and when a
plurality of embodiments are provided, the embodiments may
be combined.
[0019] First Embodiment
FIG. 1 is a block diagram illustrating a configuration
of a sintered compact production system according to a
first embodiment. The sintered compact production system 1
according to the first embodiment is a system for
performing a method for producing a sintered compact of a
TiAl-based intermetallic compound. The TiAl-based
intermetallic sintered compact refers to a sintered compact
mainly composed of a TiAl-based intermetallic compound
(TiAl-based alloy). The TiAl-based intermetallic compound
in the present embodiment is a compound (TiAl, Ti3A1, A13Ti,
and the like) in which Ti (titanium) and Al (aluminum) are
bonded. However, the TiAl-based intermetallic compound may
be a solid-solution of a mixed metal M as described later
in a TiAl phase, which is a phase in which Ti and Al are
bonded.
[0020] As illustrated in FIG. 1, the sintered compact
production system 1 includes a powder production apparatus
10, a metal-powder injection molding apparatus 20, a
degreasing apparatus 30, and a sintering apparatus 40. The
sintered compact production system 1 produces a sintered
compact of a TiAl-based intermetallic compound (TiAl-based
intermetallic sintered compact) by producing powder
particles of a TiAl-based intermetallic compound with the
powder production apparatus 10, injection-molding the
powder particles together with a binder with the metal-
powder injection molding apparatus 20, and sintering the
molded product subjected to metal-powder injection molding
with the sintering apparatus 40.
[0021] The powder production apparatus 10 produces TiAl-
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based solid-solution powder particles B1 from a TiAl-based
ingot Al. The TiAl-based ingot Al is an ingot of the
above-noted TiAl-based intermetallic compound. The TiAl-
based ingot Al in the present embodiment is a solid-
solution of an additional metal in the TiAl phase of the
TiAl-based intermetallic compound. The additional metal in
the first embodiment is Ni (nickel). The TiAl-based ingot
Al contains 99% by weight to 99.99% by weight of the TiAl-
based intermetallic compound and 0.01% by weight to 1% by
weight of Ni as an additional metal. More preferably, the
Ni content as an additional metal is 0.2% by weight to 0.6%
by weight.
[0022] The TiAl-based intermetallic compound in the
TiAl-based ingot Al contains 20 to 80% by weight of Ti, 20
to 80% by weight of Al, and 0 to 30% by weight of a mixed
metal M. That is, in terms of all components including the
additional metal, the TiAl-based ingot Al contains 19.8% by
weight to 79.992% by weight of Ti, 19.8% by weight to
79.992% by weight of Al, and 0% by weight to 29.997% by
weight of a mixed metal M. When the TiAl-based
intermetallic compound in the TiAl-based ingot Al contains
a mixed metal M, the mixed metal M is in a solid-solution
state in the TiAl phase. The mixed metal M is a metal
other than Ti and Al and contains, for example, at least
one of Nb (niobium), Cr (chromium), and Mn (manganese).
[0023] As described above, the TiAl-based ingot Al is a
mass of an alloy that is a solid solution of Ni as an
additional metal and the mixed metal M in the TiAl phase of
the TiAl-based intermetallic compound. The TiAl-based
ingot Al is produced by melting and mixing pure metals of
the components (Ti, Al, Ni, mixed metal M), followed by
cooling.
[0024] FIG. 2 is a diagram schematically illustrating a
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configuration of the powder production apparatus according
to the first embodiment. As illustrated in FIG. 2, the
powder production apparatus 10 includes a heater 12 and a
gas injector 14. The heater 12 is a heating wire wound
around the TiAl-based ingot Al into a coil shape. Current
is fed through the heater 12 to generate heat, which melts
the TiAl-based ingot Al. The melted TiAl-based ingot Ai
drops as liquid TiAl-based melt A2 vertically downward of
the TiAl-based ingot Ai.
[0025] The gas injector 14 is an injection pipe into
which an inert gas G (in the present embodiment, argon) is
introduced and jetted from an opening. The opening of the
gas injector 14 is positioned vertically below the TiAl-
based ingot Al and jets the inert gas G toward the TiAl-
based melt A2 dropped vertically downward of the TiAl-based
ingot Al. The TiAl-based melt A2 to which the inert gas G
is jetted is split and cooled to be solidified into a
plurality of TiAl-based solid-solution powder particles Bl.
In the present embodiment, a plurality of gas injectors 14
are provided. However, one gas injector 14 may be provided
or more than one gas injector 14 may be provided.
[0026] The TiAl-based solid-solution powder particles Bl
are produced by melting the TiAl-based ingot Al and
thereafter solidifying the melt and therefore contain the
same metal components as the TiAl-based ingot Al. That is,
the TiAl-based solid-solution powder particles Bl are
powder (particles) of an alloy that is a solid-solution of
Ni as an additional metal and a mixed metal M in the TiAl
phase of the TiAl-based intermetallic compound. The ratio
of each metal component contained in the TiAl-based solid-
solution powder particle B1 is the same as the TiAl-based
ingot Al. The particle size of the TiAl-based solid-
solution powder particle Bl is 1 pm to 50 pm, more
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preferably 1 pm to 20 pm. In the description of the
present embodiment, one particle of powder is referred to
as powder particle, and an aggregate of powder particles is
referred to as powder. The TiAl-based solid-solution
5 powder particle Bl is one particle, and an aggregate of
TiAl-based solid-solution powder particles Bl is referred
to as TiAl-based powder B2-
[0027] The metal-powder injection molding apparatus 20
illustrated in FIG. 1 is an apparatus that performs metal-
10 powder injection molding (MIM). The metal-powder injection
molding apparatus 20 produces a molded product D from a
mixture C. The mixture C is a mixture of TiAl-based powder
B2 produced by the powder production apparatus 10 and a
binder. The binder bonds the TiAl-based solid-solution
powder particles BI in the TiAl-based powder B2 and is a
resin having flowability. The addition of a binder imparts
flowability and moldability to the mixture C.
[0028] The metal-powder injection molding apparatus 20
injects the mixture C into a mold. The mixture C injected
into the mold forms a molded product D. The molded product
D has flowability because of the addition of a binder and
is kept in a shape defined by the mold even after being
released from the mold.
[0029] The degreasing apparatus 30 is an apparatus that
degreases the molded product D. Specifically, the
degreasing apparatus 30 accommodates the molded product D
released from the mold and heats the inside to a degreasing
temperature to remove (degrease) the binder from the molded
product D, thereby producing a degreased product E. The
degreasing temperature is a temperature equal to or higher
than the temperature at which the binder is thermally
decomposed.
[0030] The sintering apparatus 40 accommodates the
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degreased product E and heats the inside to a sintering
temperature to sinter the degreased product E (sinter the
TiAl-based solid-solution powder particles Bl in the
degreased product E), thereby producing a TiAl-based
intermetallic sintered compact F. The sintering
temperature is a temperature that allows the TiAl-based
solid-solution powder particles Bl to be sintered and, for
example, is in a range from 1400 C to 1500 C. The
sintering apparatus 40 keeps the inside at a sintering
temperature for a predetermined time (for example, one
hour) to accelerate sintering. The sintering apparatus 40
may be an apparatus independent of the degreasing apparatus
30 or may be the same apparatus as the degreasing apparatus
30. When the sintering apparatus 40 is the same apparatus
as the degreasing apparatus 30, the temperature is not
lowered from the degreasing temperature and is continuously
increased to the sintering temperature.
[0031] The TiAl-based intermetallic sintered compact F
is formed by sintering the TiAl-based solid-solution powder
particles Bl in the degreased product E and therefore has
the same components as the TiAl-based solid-solution powder
particles Bl in the same ratios. That is, the TiAl-based
intermetallic sintered compact F contains 99% by weight to
99.99% by weight of the TiAl-based intermetallic compound
and contains 0.01% by weight to 1% by weight of Ni as an
additional metal. More preferably, the Ni content as an
additional metal is 0.2% by weight to 0.6% by weight. The
TiAl-based intermetallic compound in the TiAl-based
intermetallic sintered compact F contains 20 to 80% by
weight of Ti, 20 to 80% by weight of Al, and 0 to 30% by
weight of the mixed metal M. That is, in terms of all
components including the additional metal, the TiAl-based
intermetallic sintered compact F contains 19.8% by weight
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to 79.992% by weight of Ti, 19.8% by weight to 79.992% by
weight of Al, and 0% by weight to 29.997% by weight of the
mixed metal M.
[0032] Here, the TiAl-based solid-solution powder
particles B1 bonded by sintering are referred to as TiAl-
based sintered powder particles Fl. The TiAl-based
intermetallic sintered compact F is formed such that a
plurality of TiAl-based sintered powder particles Fl form
necks to be bonded (fused). The TiAl-based solid-solution
powder particles B1 are a solid solution of Ni as an
additional metal in the TiAl-based intermetallic compound
(in the TiAl phase). On the other hand, the TiAl-based
sintered powder particles Fl are not a solid solution of Ni
as an additional metal in the TiAl-based intermetallic
compound (in the TiAl phase) but the TiAl phase is separate
from the additional metal phase (Ni phase). In other words,
the TiAl-based intermetallic compound (TiAl phase) in the
TiAl-based intermetallic sintered compact F contains Ti, Al,
and the mixed metal M and does not contain Ni.
[0033] FIG. 3 is a schematic diagram illustrating the
phases of the TiAl-based intermetallic sintered compact
according to the first embodiment. In the following, the
TiAl phase in the TiAl-based sintered powder particle Fl is
referred to as TiAl phase F2 and the additional metal phase
(Ni phase) is referred to as additional metal phase F3. As
illustrated in FIG. 3, the Ni phase (additional metal phase
F3) is present between adjacent TiAl-based sintered powder
particles Fl (grain boundary), that is, between the TiAl
phase F2 of one TiAl-based sintered powder particle Fl and
the TiAl phase F2 of the adjacent TiAl-based sintered
powder particle Fl. To put it another way, the Ni phase
(additional metal phase F3) is present on the periphery of
each of a plurality of TiAl-based intermetallic compounds
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(TiAl phase F2).
[0034] The TiAl-based intermetallic sintered compact F
improves in sintered density because the additional metal
phase F3 is present at the grain boundary between adjacent
TiAl phases F2.
[0035] The production flow of the TiAl-based
intermetallic sintered compact F with the sintered compact
production system 1 will be described below. FIG. 4 is a
flowchart illustrating the production flow of the TiAl-
based intermetallic sintered compact with the sintered
compact production system according to the first embodiment.
As illustrated in FIG. 4, first of all, the sintered
compact production system 1 generates a plurality of TiAl-
based solid-solution powder particles B1 (TiAl-based powder
B2) from the TiAl-based ingot Al with the powder production
apparatus 10 (step S10). After generating the TiAl-based
solid-solution powder particles B1, the sintered compact
production system 1 mixes the TiAl-based powder B2 with a
binder to produce a mixture C (step S12) and injection-
molds the mixture C with the metal-powder injection molding
apparatus 20 to mold a molded product D (step S14). After
molding the molded product D, the sintered compact
production system 1 degreases the molded product D with the
degreasing apparatus 30 to produce a degreased product E
(step S16) and sinters the degreased product E with the
sintering apparatus 40 to produce a TiAl-based
intermetallic sintered compact F (step S18). At step S18,
the production method for the TiAl-based intermetallic
sintered compact is finished.
[0036] As described above, the method for producing the
TiAl-based intermetallic sintered compact F by the sintered
compact production system 1 in the present embodiment
sinters the TiAl-based powder 22 to produce the TiAl-based
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intermetallic sintered compact F. The TiAl-based powder B2
contains a TiAl-based intermetallic compound in which Ti
and Al are bonded and an additional metal. The additional
metal is Ni in the first embodiment. Since this method for
producing the TiAl-based intermetallic sintered compact F
sinters the TiAl-based powder B2 containing a TiAl-based
intermetallic compound and an additional metal, the TiAl-
based intermetallic sintered compact F exhibits a metal
structure in which the additional metal phase F3 exists at
the grain boundary between adjacent TiAl phases F2.
Therefore, this method for producing the TiAl-based
intermetallic sintered compact F can increase the sintered
density and increase the strength.
[0037] The method for producing the TiAl-based
intermetallic sintered compact F by the sintered compact
production system 1 includes a mixing step, an injection
molding step, a degreasing step, and a sintering step. The
mixing step mixes the TiAl-based powder B2 with a binder to
yield a mixture C. The injection molding step molds the
mixture C into a molded product D with a metal-powder
injection molder (metal-powder injection molding apparatus
20). The degreasing step degreases the molded product D to
produce a degreased product E. The sintering step sinters
the degreased product E to produce a TiAl-based
intermetallic sintered compact F. This method for
producing the TiAl-based intermetallic sintered compact F
produces the TiAl-based intermetallic sintered compact F
using a metal-powder injection molding method. When a
metal-powder injection molding method is used, it is
necessary to perform sintering with the molded shape being
kept. In particular, when a sintered compact of a TiAl-
based intermetallic compound is produced by a metal-powder
injection molding method, the sintering condition for
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sintering while keeping the molded shape is strict, such as
a narrow range of sintering temperatures. For this reason,
when a sintered compact of a TiAl-based intermetallic
compound is produced by a metal-powder injection molding
5 method, it may be difficult to improve the sintered density
while keeping the molded shape because of a failure to set
the sintering condition appropriately. However, according
to the present embodiment, the TiAl-based intermetallic
sintered compact F has a metal structure in which the
10 additional metal phase F3 exists at the grain boundary
between adjacent TiAl phases F2. Thus, this method for
producing the TiAl-based intermetallic sintered compact F
can improve the shape accuracy with the metal-powder
injection molding method while keeping the sintered density
15 high.
[0038] The TiAl-based powder B2 has a Ni content of
0.01% by weight to 1% by weight. Thus, the sintering
apparatus 40 allows the additional metal phase F3 to exist
appropriately at the grain boundary between adjacent TiAl
phases F2. Accordingly, this method for producing the
TiAl-based intermetallic sintered compact F can improve the
sintered density more appropriately.
[0039] The TiAl-based powder B2 is a mixture of a
plurality of TiAl-based solid-solution powder particles B1
containing a TiAl-based intermetallic compound and an
additional metal. In this method for producing the TiAl-
based intermetallic sintered compact F, since the TiAl-
based solid-solution powder particle Bl used in sintering
is a particle containing a TiAl-based intermetallic
compound and an additional metal, the additional metal
phase F3 can exist appropriately at the grain boundary
between the TiAl phases F2 of the sintered compact.
Therefore, this method for producing the TiAl-based
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intermetallic sintered compact F can improve the sintered
density more appropriately.
[0040] The TiAl-based intermetallic sintered compact F
according to the present embodiment contains a TiAl-based
intermetallic compound in which Ti and Al are bonded and an
additional metal that is Ni, and the Ni content is 0.01% by
weight to 1% by weight of the total content. Since this
TiAl-based intermetallic sintered compact F contains Ni in
this proportion with respect to the TiAl-based
intermetallic compound, the additional metal phase F3 can
exist at the grain boundary of the TiAl phase F2 of the
sintered compact. Therefore, the sintered density of this
TiAl-based intermetallic sintered compact F can be improved
more appropriately.
[0041] In the TiAl-based intermetallic sintered compact
F, the TiAl-based intermetallic compound contains 20 to 80%
by weight of Ti, 20 to 80% by weight of Al, and 0 to 30% by
weight of a mixed metal M, and the mixed metal M contains
at least one of Nb, Cr, and Mn. This TiAl-based
intermetallic sintered compact F improves in strength
because the TiAl-based intermetallic compound has such a
proportion.
[0042] In the TiAl-based intermetallic sintered compact
F, a plurality of TiAl-based sintered powder particles Fl
containing a TiAl-based intermetallic compound and an
additional metal are bonded to each other, and the
additional metal phase, which is the metal phase of the
additional metal, exists between the adjacent TiAl-based
sintered powder particles Fl. In this TiAl-based
intermetallic sintered compact F, since the additional
metal phase F3 exists at the grain boundary of the TiAl
phase F2 of the sintered compact, the sintered density can
be improved more appropriately.
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[0043] Second Embodiment
A second embodiment will now be described. The second
embodiment differs from the first embodiment in that Ni and
Fe (iron) are used as additional metal. In the second
embodiment, the parts having a configuration common to that
of the first embodiment are not further elaborated.
[0044] The additional metal according to the second
embodiment is Ni and Fe. A TiAl-based ingot Al according
to the second embodiment contains 98% by weight to 99.99%
by weight of a TiAl-based intermetallic compound and
contains 0.01% by weight to 2% by weight of Ni and Fe in
total as the additional metal. The Ni content is equal to
or greater than 0.01% by weight and less than 2% by weight
with respect to the total amount of Ni and Fe, more
preferably 0.01% by weight to 1% by weight.
[0045] In the second embodiment, a TiAl-based
intermetallic sintered compact F is produced using the
TiAl-based ingot Al containing Ni and Fe as additional
metal by a method similar as in the first embodiment. The
TiAl-based intermetallic sintered compact F according to
the second embodiment contains 98% by weight to 99.99% by
weight of a TiAl-based intermetallic compound and 0.01% by
weight to 2% by weight of Ni and Fe in total.
[0046] The TiAl-based intermetallic sintered compact F
according to the second embodiment forms phases similar as
in the first embodiment. That is, in the TiAl-based
intermetallic sintered compact F according to the second
embodiment, the alloy phase of Ni and Fe (additional metal
phase F3) exists between adjacent TiAl-based sintered
powder particles Fl (grain boundary), that is, between the
TiAl phase F2 of one TiAl-based sintered powder particle Fl
and the TiAl phase F2 of the adjacent TiAl-based sintered
powder particle Fl. Thus, the TiAl-based intermetallic
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sintered compact F according to the second embodiment also
improves in sintered density, because the additional metal
phase F3 is present at the grain boundary between adjacent
TiAl phases F2.
[0047] The TiAl-based powder B2 according to the second
embodiment contains 0.01% by weight to 2% by weight of Ni
and Fe in total. Thus, the sintering apparatus 40 allows
the additional metal phase F3 to exist at the grain
boundary between adjacent TiAl phases F2 appropriately.
The method for producing the TiAl-based intermetallic
sintered compact F according to the second embodiment
therefore also can improve the sintered density more
appropriately.
[0048] The TiAl-based intermetallic sintered compact F
according to the second embodiment contains a TiAl-based
intermetallic compound in which Ti and Al are bonded and
additional metal that is Fe and Ni, and the total content
of Fe and Ni is 0.01% by weight to 2% by weight of the
total content. Since this TiAl-based intermetallic
sintered compact F contains Fe and Ni in this proportion
with respect to the TiAl-based intermetallic compound, the
additional metal phase F3 can exist at the grain boundary
of the TiAl phase F2 of the sintered compact. Therefore,
the sintered density of this TiAl-based intermetallic
sintered compact F can be improved more appropriately.
[0049] As illustrated in the first embodiment and the
second embodiment, the use of Ni, or Ni and Fe as the
additional metal can improve the sintered density of the
TiAl-based intermetallic sintered compact F more
appropriately.
[0050] Third Embodiment
A third embodiment will now be described. The third
embodiment differs from the first embodiment in that a
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mixture of a plurality of TiAl-based powder particles that
are powder particles of a TiAl-based intermetallic compound
and a plurality of additional metal powder particles
containing Ni as an additional metal is used as a TiAl-
based powder. In the third embodiment, the parts having a
configuration common to that in the first embodiment are
not further elaborated.
[0051] The powder production apparatus 10 according to
the third embodiment produces TiAl-based powder particles
Bia from a TiAl-based ingot Ala. The TiAl-based ingot Ala
does not contain Ni as an additional metal and contains a
TiAl-based intermetallic compound alone. The TiAl-based
intermetallic compound here contains Ti, Al and a mixed
metal M similar to the first embodiment, and the proportion
is also the same as in the first embodiment. The TiAl-
based powder particle Bla is a powder particle containing
Ti, Al, and a mixed metal M and has the same content ratios
as the TiAl-based ingot Ala. The particle size of the
TiAl-based powder particle Bia is the same as the TiAl-
based solid-solution powder particle B, of the first
embodiment.
[0052] In the third embodiment, a plurality of TiAl-
based powder particles Bia and a plurality of additional
metal powder particles B3a are mixed to produce a TiAl-
based powder B2a. The additional metal powder particles
B3a are powder particles of Ni. That is, the TiAl-based
powder B2a includes powder particles of different two
components, namely, powder particles of a TiAl-based
intermetallic compound and powder particles of Ni that are
additional metal powder particles. The content ratio
between the TiAl-based intermetallic compound and Ni in the
TiAl-based powder B2a is the same as the TiAl-based powder
B2 according to the first embodiment.
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[0053] The particle size of the additional metal powder
particle B3a is in the same range as the TiAl-based powder
particle Bla, more preferably smaller than the TiAl-based
powder particle Bia. For example, the particle size of the
5 additional metal powder particle B3a is preferably 0.01
time to 0.2 time the TiAl-based powder particle Bia.
[0054] The sintered compact production system 1
according to the third embodiment mixes this TiAl-based
powder B2a with a binder to produce a mixture C, and the
10 subsequent process of the sintered compact production
system 1 according to the third embodiment is similar as in
the first embodiment and produces the same TiAl-based
intermetallic sintered compact F as in the first embodiment.
[0055] In this way, the TiAl-based powder B2a according
15 to the third embodiment is a mixture of TiAl-based powder
particles Bia that are powder particles of a TiAl-based
intermetallic compound and additional metal powder
particles B3a containing Ni as an additional metal. Also
in such a case, the TiAl-based intermetallic sintered
20 compact F similar to the first embodiment can be produced,
and the sintered compact production system 1 according to
the third embodiment can improve the sintered density
appropriately as in the first embodiment.
[0056] The production method according to the third
embodiment is applicable to the second embodiment. That is,
the additional metal powder particles B3a may be powder
particles of Ni and Fe. In this case, the additional metal
powder particles B3a may be powder particles of Ni and
powder particles of Fe or may be powder particles of the
alloy of Ni and Fe. In this case, the content ratio
between the TiAl-based intermetallic compound and Ni and Fe
in the TiAl-based powder 82a is similar to that of the
TiAl-based powder B2 according to the second embodiment.
84549528
21
The content ratio between Ni and Fe in the additional metal
powder B2a is also the same as in the first embodiment.
[0057] In the foregoing description, the additional metal is
Ni, or Ni and Fe. However, the additional metal of Fe alone can
increase the sintered density similarly if the Fe content is
equal to or greater than 2% by weight. In this case, it is
preferable that the Fe content is equal to or less than 5% by
weight of the total content in order to suppress reduction in
strength of the sintered compact (creep strength) and to
suppress reduction in oxidation resistance.
[0058] Examples
Examples will now be described. Table 1 (below)
illustrates the sintered density in examples and comparative
examples. FIG. 5 and FIG. 6 are diagrams illustrating the metal
structure of the TiAl-based intermetallic sintered compact in a
comparative example. FIG. 7 and FIG. 8 are diagrams of the
metal structure of the TiAl-based intermetallic sintered
compact in an example. FIG. 9 is a graph illustrating the
relation between the Ni content and the sintered density. In
examples described below, the molded product molded with a
metal-powder injection molder is degreased and then sintered at
a sintering temperature of 1450 C for two hours to produce a
TiAl-based intermetallic sintered compact F. In comparative
examples described below, the molded product molded with a
metal-powder injection molder is degreased and then sintered at
a sintering temperature of 1450 C for two hours in the same
manner as in the examples to produce a TiAl-based intermetallic
sintered compact Fx. The TiAl-based intermetallic sintered
compact F in the examples contains 30% by weight of Al, 14% by
Date Recue/Date Received 2021-02-05
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22
weight of Nb as a mixed metal M, and 0.7% by weight of Cr as a
mixed metal M.
This is the same in the TiAl-based intermetallic sintered
compact Fx in the comparative examples.
TABLE 1
AMOUNT AMOUNT SNTERED TPHASEOF
OF Fe OF Ni DENSITY
GRAIN
01&%) (lvt%) (3/0) BOUNDARY
COMPARATIVE
.0105 <0.01 91
EXAMPLE1
COMPARATIVE <0.05 1.05 97 PRESENT
EXAMPLE2
EXAMPLE1 <0.05 0.2 98 ABSENT
EXAMPUE2 <0.05 0.6 97 ABSENT
[0059] The
TiAl-based intermetallic sintered compact Fx
according to Comparative Example 1 contains neither Fe nor Ni.
More specifically, the TiAl-based intermetallic sintered
compact Fx according to Comparative Example 1 has a Fe content
less than 0.05% by weight and a Ni content less than 0.01% by
weight. As illustrated in Table 1, the TiAl-based intermetallic
sintered compact Fx according to Comparative Example 2 has a Fe
content of less than 0.05% by weight and a Ni content of 1.05%
by weight. As illustrated in Table 1, the TiAl-based
intermetallic sintered compact F according to Example 1
contains Ni alone as an additional metal, in which the Ni
content is 0.2% by weight of the total content, and the Fe
content is less than 0.05% by weight of the total content. The
TiAl-based intermetallic sintered compact F according to
Example 2 contains Ni alone as an additional metal, in which
the Ni content is 0.6% by weight of the total content, and the
Fe content is equal to or less than 0.05% by weight of the
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total content. In Comparative Example 1 and Examples 1 and 2,
the method in the third embodiment, that is, the production
method of mixing the TiAl-based powder particles Bia and the
additional metal powder particles B3a was employed.
[0060] The TiAl-based intermetallic sintered compact Fx
according to Comparative Example 1 has a sintered density of
91% as illustrated in Table 1 and has many pores V as
illustrated in FIG. 5. The TiAl-based intermetallic sintered
compact Fx according to Comparative Example 2 has a sintered
density of 97% as illustrated in Table 1 and has many pores V
as illustrated in FIG. 6, and a y-phase colony occurs at the
grain boundary. The y-phase colony is a mass of single y-phase
and deteriorates the performance of the TiAl-based
intermetallic sintered compact having a lamellar structure.
[0061] On the other hand, the TiAl-based intermetallic
sintered compact F according to Example 1 has a sintered
density of 98% as illustrated in Table 1 and has fewer pores V
as illustrated in FIG. 7, and a y-phase colony does not occur.
The TiAl-based intermetallic sintered compact F according to
the Example 2 has a sintered density of 97% as illustrated in
Table 1 and has fewer pores V as illustrated in FIG. 8, and a
y-phase colony does not occur.
[0062] The horizontal axis in FIG. 9 represents the Ni
content and the vertical axis represents the sintered density.
FIG. 9 is a plot of results of Comparative Examples 1 and 2 and
Examples 1 and 2. As illustrated in FIG. 9, when the TiAl-based
intermetallic sintered compact F containing Ni alone as an
additional metal has a Ni content of 0.1% by weight to 1% by
weight of the total content, the sintered density is high and
occurrence of a y-phase colony is suppressed.
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[0063]
Table 2 (below) illustrates the sintered density in
examples and a comparative example. FIG. 10 is a diagram of the
metal structure of the TiAl-based intermetallic sintered
compact in a comparative example. FIG. 11 and FIG. 12 are
diagrams of the metal structure of the TiAl-based intermetallic
sintered compact in an example. FIG. 13 is a graph illustrating
the relation between the Ni and Fe content and the sintered
density.
TABLE 2
AMOUNT AMOUNT PRODUCTION SNTERED r PHASE OF Ni OF Fe PROCESS DENSITY
OF GRAIN
(vt%) (wtA) (%) BOUNDARY
COMPARATIVE
EXAMPLE3 0.34 139 EMBODIMENT
PRESENT
97
FIRST
EXAMPLE3 OAT 0.92 99
ARSFNT
EMBODIMENT
THIRD EXAMPLE4 0.17 092 EMBODIMENT
97
ABSENT
[0064] As illustrated in Table 2, the TiAl-based
intermetallic sintered compact Fx according to Comparative
Example 3 has a Ni content of 0.34% by weight and a Fe content
of 1.79% by weight. That is, the TiAl-based intermetallic
sintered compact Fx according to Comparative Example 3 has a
total content of Ni and Fe of 2.13% by weight. The TiAl-based
intermetallic sintered compact F according to Examples 3 and 4
has a Ni content of 0.17% by weight and a Fe content of 0.92%
by weight. That is, the TiAl-based intermetallic sintered
compact F according to Examples 3 and 4 has a total content of
Ni and Fe of 1.09% by weight. For the TiAl-based intermetallic
sintered compact Fx according to Comparative Example 3, a
similar method as in the third embodiment was employed, and in
Example 4, the method in the third embodiment, that is, the
production method of mixing the TiAl-based powder particles Bia
Date Recue/Date Received 2021-02-05
84549528
and the additional metal powder particles B3a was employed. On
the other hand, in the Example 3, the method in the first
embodiment, that is, the production method using the TiAl-based
solid-solution powder particles 131 containing a TiAl-based
5 intermetallic compound and an additional metal was employed.
[0065] The TiAl-based intermetallic sintered compact Fx
according to Comparative Example 3 has a sintered density of
97% as illustrated in Table 2 and has many pores V as
illustrated in FIG. 10, and a y-phase colony occurs at the
10 grain boundary. On the other hand, the TiAl-based intermetallic
sintered compact F according to Example 3 has a sintered
density of 99% as illustrated in Table 2 and has fewer pores V
as illustrated in FIG. 11, and a y-phase colony does not occur.
The TiAl-based intermetallic sintered compact F according to
15 Example 4 has a sintered density of 97% as illustrated in Table
2 and has fewer pores V as illustrated in FIG. 12, and a y-
phase colony does not occur.
[0066] The horizontal axis in FIG. 13 represents the total
content of Ni and Fe and the vertical axis represents the
20 sintered density. FIG. 13 is a plot of the results of
Comparative Examples 1 and 3 and Examples 3 and 4. As
illustrated in FIG. 13, when the TiAl-based intermetallic
sintered compact F containing Ni and Fe as additional metal has
a total content of Ni and Fe of 0.1% by weight to 2% by weight
25 of the total content, the sintered density is high and
occurrence of a y-phase colony is suppressed. Referring to
Example 3 and Example 4, it is understood that the sintered
density can be increased either by the method in the third
embodiment, that is, the production method of mixing the TiAl-
based powder particles Bla and the additional metal powder
particles B3a or by the method in the first embodiment, that
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is, the production method using the TiAl-based solid-solution
powder particles B1 containing a TiAl-based intermetallic
compound and an additional metal.
[0067] Table 3 (below) illustrates the sintered density in
an example and a comparative example. FIG. 14 is a diagram of
the metal structure of the TiAl-based intermetallic sintered
compact in a comparative example. FIG. 15 is a diagram of the
metal structure of the TiAl-based intermetallic sintered
compact in an example. As illustrated in Table 3, the TiAl-
based intermetallic sintered compact Fx according to
Comparative Example 4 has a Fe content of 1.08% by weight and a
Ni content of less than 0.1% by weight. The TiAl-based
intermetallic sintered compact F according to Example 5 has a
Fe content of 2.13% by weight and a Ni content of less than
0.01% by weight. In Comparative Example 4 and Example 5, the
sintering temperature is 1420 C. The other conditions are the
same in Comparative Example 4 and Comparative Example 1 and are
the same in Example 5 and Example 1.
TABLE 3
AMOUNT AMOUNT SINTERED
OF Fe OF Ni DENSITY
(wt%) (wt%) (%)
COMPARATIVE
1.08 <0.01 93
EXAMPLE 4
EXAMPLE 5 2.13 <0.01 98
[0068] The TiAl-based intermetallic sintered compact Fx
according to Comparative Example 4 has a sintered density of
93% as illustrated in Table 3 and has many pores V as
illustrated in FIG. 14. On the other hand, the TiAl-based
intermetallic sintered compact F according to Example 5 has a
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sintered density of 98% as illustrated in Table 3 and has fewer
pores V as illustrated in FIG. 15, and a y-phase colony does
not occur.
[0069] In this way, the TiAl-based intermetallic sintered
compact F achieves a high sintered density when Fe alone is an
additional metal and the Fe content is equal to or greater than
2% by weight.
[0070] Although embodiments of the present invention have
been described above, embodiments are not intended to be
limited by the specifics of these embodiments. The components
above include those easily conceived by those skilled in the
art, those substantially identical, and equivalents.
Furthermore, the components above can be combined as
appropriate. The components can be omitted, replaced, or
modified in various ways without departing from the spirit of
the foregoing embodiments.
Reference Signs List
[0071] 1 Sintered compact production system
10 Powder production apparatus
20 Metal-powder injection molding apparatus
Degreasing apparatus
Sintering apparatus
Ai TiAl-based ingot
A2 TiAl-based melt
25 Bl TiAl-based solid-solution powder particle
Bla TiAl-based powder particle
B2 TiAl-based powder
B3a Additional metal powder particle
C Mixture
30 D Molded product
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E Degreased product
F TiAl-based intermetallic sintered compact
Fl TiAl-based sintered powder particle
F2 TiAl phase
F3 Additional metal phase
