U.S. patent application number 12/684176 was filed with the patent office on 2010-05-13 for production of alloys based on titanium aluminides.
This patent application is currently assigned to GKSS-FORSCHUNGSZENTRUM GEESTHACHT GMBH. Invention is credited to Fritz APPEL, Michael OEHRING, Jonathan PAUL.
Application Number | 20100119402 12/684176 |
Document ID | / |
Family ID | 39768203 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100119402 |
Kind Code |
A1 |
PAUL; Jonathan ; et
al. |
May 13, 2010 |
PRODUCTION OF ALLOYS BASED ON TITANIUM ALUMINIDES
Abstract
In an alloy based on titanium aluminides, metal droplets are
obtained from a titanium aluminide metal melt. The metal droplets
are enriched with halogens resulting in halogen-enriched titanium
aluminide metal droplets. The alloy is molded from the
halogen-enriched titanium aluminide metal droplets by, preferably
hot isostatic, pressing. Titanium aluminide powder can be heated in
a container, for a predetermined period of time, wherein an
atmosphere, enriched with halogens, is or will be provided in the
container, so that a halogen-enriched titanium aluminide metal
powder is formed, or metal droplets are formed from a titanium
aluminide metal melt. The metal droplets are enriched with halogens
so that halogen-enriched titanium aluminide metal droplets result.
Subsequently, the alloy is molded from the halogen-enriched
titanium aluminide metal droplets.
Inventors: |
PAUL; Jonathan; (Hamburg,
DE) ; APPEL; Fritz; (Geesthacht, DE) ;
OEHRING; Michael; (Geesthacht, DE) |
Correspondence
Address: |
MICHAUD-Kinney Group LLP
306 INDUSTRIAL PARK ROAD, SUITE 206
MIDDLETOWN
CT
06457
US
|
Assignee: |
GKSS-FORSCHUNGSZENTRUM GEESTHACHT
GMBH
Geesthacht
DE
|
Family ID: |
39768203 |
Appl. No.: |
12/684176 |
Filed: |
January 8, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2008/003173 |
Apr 21, 2008 |
|
|
|
12684176 |
|
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Current U.S.
Class: |
419/33 |
Current CPC
Class: |
C22C 14/00 20130101;
B22F 2998/10 20130101; B22F 2998/10 20130101; C22C 1/0458 20130101;
C22C 30/00 20130101; B22F 2201/00 20130101; C22C 1/0416 20130101;
B22F 9/082 20130101; B22F 9/04 20130101; B22F 3/15 20130101; B22F
2201/00 20130101; B22F 2998/10 20130101; B22F 3/15 20130101; C22C
21/003 20130101 |
Class at
Publication: |
419/33 |
International
Class: |
B22F 3/15 20060101
B22F003/15; B22F 1/00 20060101 B22F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2007 |
DE |
10 2007 032 406.7 |
Claims
1. A method for producing an alloy based on titanium aluminides,
wherein metal droplets are obtained from a titanium aluminide metal
melt using the gas atomization method, the metal droplets being
enriched with halogens by exposure to a halogen-containing gas, so
that halogen-enriched titanium aluminide metal droplets are formed
and subsequently the alloy is molded from the halogen-enriched
titanium aluminide metal droplets by, preferably hot isostatic,
pressing.
2. The method of claim 1, wherein at least one of the metal melt
and the metal droplets is treated with a carrier gas, and wherein
the carrier gas will be or is mixed with the halogen-containing
gas.
3. The method of claim 1, wherein a titanium aluminide metal powder
is formed from the halogen-enriched metal droplets and molded into
the alloy.
4. The method of one of claim 1, wherein a component is produced
from the alloy.
5. A method for producing an alloy on the basis of titanium
aluminides, wherein titanium-containing powder and
aluminum-containing powder or powdery titanium aluminide, is milled
wherein a halogen enriched atmosphere is provided during the
milling process in the mill, so that a halogen enriched titanium
aluminide metal powder is formed during the milling process and
subsequently the powdery titanium aluminide, enriched with
halogens, is molded into an alloy by, hot isostatic, pressing.
6. The method of claim 5, wherein the atmosphere, enriched with
halogens, is supplied as one of a gaseous and liquid
atmosphere.
7. The method of claim 5, wherein the atmosphere, enriched with
halogens, is supplied with at least one inert gas.
8. The method of claim 5, wherein a component is produced from the
alloy.
9. A method for producing an alloy based on titanium aluminides,
wherein titanium aluminide powder, is heated for a predetermined
time in a container, wherein an atmosphere, enriched with halogens
is provided in the container, so that halogen-enriched titanium
aluminide metal powder is formed during the heating time and
subsequently the titanium aluminide metal powder, enriched with
halogens, is molded into an alloy by, hot isostatic, pressing.
10. The method of claim 9, wherein before the container is heated,
the titanium aluminide powder is exposed to a vacuum in the
container.
11. The method of claim 9, wherein an atmosphere, enriched with
halogens, is supplied with at least one inert gas, after evacuation
of the container.
12. The method of claim 9, wherein at least one of the container
and the titanium aluminide powder is heated for a predetermined
period of about 15 minutes to about 24 hours.
13. The method of claim 9, wherein at least one of the container
and the titanium aluminide powder is heated to a predetermined
temperature between about 300.degree. C. and about 1300.degree.
C.
14. The method of claim 9, wherein after the container is heated,
the titanium aluminide powder, is exposed to a vacuum.
15. The method of claim 9, wherein a component is produced from the
alloy.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of and claims priority to
International Patent Application No. PCT/EP2008/003173 filed on
Apr. 21, 2008, which claims priority to German Patent Application
No. 10 2007 032 406.7 filed on Jul. 10, 2007, subject matter of
these patent documents is incorporated by reference herein in its
entirety.
FIELD OF THE INVENTION
[0002] The invention relates to a method for the production of an
alloy based on titanium aluminides.
BACKGROUND OF THE INVENTION
[0003] Alloys, based on titanium aluminides, prepared using melt
metallurgical and powder metallurgical techniques, with a specified
alloy composition of titanium and aluminum and, optionally, further
components such as niobium, boron, chromium, molybdenum, manganese
and vanadium etc., as well as carbon in different compositions are
known in the prior art.
[0004] Titanium aluminide alloys have properties, which are
particularly advantageous for use as a light-weight construction
material, in particular for high temperature applications. Because
of their strength and creep properties at high temperatures, these
light-weight construction materials based on titanium aluminides
open up possibilities for manufacturing mechanically stressed
components in high temperature technology, such as turbine blades
in aircraft construction, final stage impellers, engine valves,
etc. Moreover, because of their low density (approximately 3.8 to
4.3 g/cm.sup.3), their use as a replacement for nickel-based super
alloys, which typically have a density of 8.5 g/cm.sup.3, suggests
itself.
[0005] The formulation of titanium aluminide alloys is limited by
their limited resistance to oxidation to temperatures below about
750.degree. C. Moreover, it is known that the oxidation behavior is
improved clearly by a slight amount of halogens in the surface of
the titanium aluminide material because of the so-called halogen
effect, by means of which the areas of use of the materials can be
extended to temperatures above about 1000.degree. C.
[0006] For example, the DE-A-103 51 946 discloses a method for the
treatment of the surface of a component, consisting of a titanium
aluminide alloy, for improving its oxidation resistance.
Furthermore, the DE-C-196 27 605 discloses a method for increasing
the corrosion resistance of alloys based on titanium aluminide,
wherein halogens are transferred by the process of ion implantation
into the surface of the material.
[0007] Furthermore, products of an intermetallic compound of a
Ti--Al system with a high resistance to oxidation and wear, and a
method for the production of these products are described in
DE-T-693 09 167.
[0008] It is an object of the present invention to provide titanium
aluminide alloys with a high oxidation resistance, wherein, when
the alloys are used or employed, any damage to the alloy in the
surface will not have an effect on the oxidation resistance.
Moreover, it is an object of the invention to provide a component
of a corresponding titanium aluminide alloy.
SUMMARY OF THE INVENTION
[0009] The present invention resides in one aspect in a method for
producing an alloy based on titanium aluminides, wherein metal
droplets are obtained from a titanium aluminide metal melt, in
particular by using the gas atomization method, the metal droplets
being enriched with halogen by exposure to a halogen-containing
gas, so that halogen-enriched titanium aluminide metal droplets or
halogen-enriched TiAl metal powder are formed and subsequently the
alloy is molded from the halogen-enriched titanium aluminide metal
droplets or the TiAl metal powder by, preferably hot isostatic,
pressing.
[0010] Halogens were alloyed with the titanium aluminide alloy, by
using the halogen-containing gas in order to enrich the metal
droplets with halogens, whereby a fine or homogeneous distribution
of the halogens in the material and in each partial volume of the
material or of the alloy and not only at the surface of the
material or the alloy is achieved.
[0011] According to the invention, halogens are present also in
layers, which are lower than the previously known oxidation layers
of titanium aluminide alloys and which are larger or lie deeper,
for example, at depths of more than about 100, 200, 300, 400, 500
.mu.m and more below the surface of the alloy or in the whole of
the alloy, whereby the resistance to oxidation is present and
retained even after the surface of a component, produced from the
titanium aluminide alloy, is damaged, since the resistance to
oxidation of the whole of the alloy is maintained even at a great
depth by the halogens, introduced and, in particular, distributed
particularly homogeneously or randomly uniformly in the alloy or in
the material.
[0012] The metal powder or the metal droplets are passivated by the
intensive contact of the halogens with the titanium aluminide metal
droplets.
[0013] Preferably, chlorine and/or fluorine are introduced as
halogen into the bulk material produced from titanium aluminide.
Within the scope of the invention, the use of other halogens, such
as iodine and/or bromine is also possible.
[0014] Moreover, by the hot isostatic pressing (HIP), an alloy with
a high isotropy and a uniform consolidation of the material is
achieved. Typically, the process of hot isostatic pressing takes
place at very high pressures, such as 100 Mpa, and at high
temperatures, for example, at temperatures between 1000.degree. C.
and 2000.degree. C.
[0015] Moreover, provisions are made so that the metal melt and/or
the metal droplets are treated with a carrier gas, preferably with
an inert gas, wherein in particular the carrier gas will be or is
mixed with the halogen-containing gas.
[0016] Argon or helium or other inert gases have proven their value
as a carrier gas, so that, by mixing with a halogen-containing gas,
the metal melt is treated selectively in order to obtain metal
droplets, which are enriched with halogens.
[0017] Furthermore, in an embodiment of the invention, a titanium
aluminide metal powder is formed from the halogen-enriched metal
droplets and molded into the alloy. Usually, this takes place by
hot isostatic pressing. In particular, a component, which has a
high resistance to oxidation even when the surface of the component
is damaged, is produced from the molded alloy. The component may,
for example, be from the automobile, space, aircraft and industrial
machine tool sector.
[0018] Moreover, the object of the invention is solved by a method
for producing an alloy based on titanium aluminides, wherein
titanium-containing powder and aluminum-containing powder or
titanium powder and aluminum powder and/or powdery titanium
aluminide, particularly titanium aluminide metal powder is milled
by means of or in a mill, preferably by means of or in a ball mill,
wherein a halogen enriched atmosphere will be or is provided during
the milling process in the mill, particularly the ball mill, so
that a halogen enriched titanium aluminide metal powder is formed
during the milling process and subsequently the powdery titanium
aluminide, enriched with halogens, is molded into an alloy by,
preferably hot isostatic, pressing.
[0019] Owing to the fact that the metal powder, while being milled
in the ball mill and with the introduction of gases into the ball
mill, has intensive contact, a particularly homogeneous, enrichment
of powdery titanium aluminide is also achieved, as a result of
which the halogens are distributed in the whole of the alloy
produced or molded. The distribution of the halogens in the alloy
is such that the (relative) content of halogens (per volume) is or
will be kept almost constant or constant in any specified volume or
partial volume or also in small partial volumes of the finished
alloy.
[0020] Instead of pre-alloyed metal powder, that is, titanium
aluminides in powder form, or in addition to the pre-alloyed metal
powder, it is possible, according to the invention in this second
method to use or provide also elementary powdery titanium and
elementary powdery aluminum, so that a TiAl alloy in powder form
arises from milling the titanium powder and the aluminum powder,
the halogen content of which is or will be enriched in the ball
mill as a result of the presence of the halogen-containing gas at a
high pressure in the ball mill.
[0021] The implementation of the aforementioned steps of the method
achieves the same, preferably uniform, distribution of the halogens
at the surface as well as at a depth below the surface of an alloy
as is achieved with the method described above for treating the
metal melt with halogen gases. In this respect, the realizations of
the first method apply in the same way as the steps of the method
for producing the alloy described here.
[0022] Moreover, the atmosphere, enriched with halogens, is
supplied as a gaseous and/or liquid atmosphere in a further step of
the method, by means of which an intensive exchange or an intensive
enrichment of the powder is carried out in the gaseous or in the
liquid halogen-containing atmosphere, for example, in liquid carbon
tetrachloride (CCl.sub.4).
[0023] Preferably, the atmosphere, in particular the gaseous
atmosphere, which is enriched with halogen, is supplied with at
least one inert gas, such as argon or helium. Furthermore, a
component is produced from the alloy having a constant (relative)
proportion of halogens in each volume or partial volume or spatial
volume of the alloy.
[0024] The present invention further resides in a method for
producing an alloy based on titanium aluminides is provided,
wherein powdery titanium aluminide, in particular titanium
aluminide metal powder, will be or is heated for a predetermined
time in a, preferably closed, container, wherein an atmosphere,
enriched with halogens, is or will be provided in the container, so
that halogen-enriched titanium aluminide metal powder is formed
during the heating time and subsequently the titanium aluminide
metal powder, enriched with halogens, is molded into an alloy by,
preferably hot isostatic, pressing.
[0025] For this third method also, an alloy is provided, which in
the same way has the advantages of the alloys produced by the
method described above. In carrying out the steps of the method,
titanium aluminide alloys are also produced, for which halogens are
alloyed with the whole of the material, the (relative) proportion
of halogen (per volume) in the alloy remaining constant over the
whole volume or in a (small) partial volume of the component or of
the alloy, wherein it is entirely possible that the proportion of
halogens may vary typically over a range of about .+-.15%,
preferably of about .+-.10%, and particularly of about .+-.5%,
since the proportion of halogens in the alloy typically may
fluctuate between about 0.005 atom percent and about 1.5 atom
percent, preferably between about 0.005 atom percent or about 0.01
atom percent and about 0.9 atom percent. Aside from fluorine and/or
chlorine, which are distributed in an alloy, further halogens, such
as bromine and/or iodine may also be used.
[0026] In order to make the alloy, produced according to all three
of the method introduced, resistant to oxidation at the surface, a
desired surface of an object or component, which is produced from
the alloy and for which oxidation resistance is desired, is
oxidized.
[0027] Moreover, within the scope of the invention, it is
conceivable that halogen-like compounds, such as silicon
halogen-containing compounds or silicon halogen mixtures, which
also have a positive effect on the oxidation resistance of the
alloy, are used for the three methods named.
[0028] Furthermore, a halogen-containing gas is understood to be a
gas which, aside from other gases, preferably inert gases, also
contains a halogen element or also a mixture of several halogen
elements.
[0029] In a further step of the method, the powdery titanium
aluminide, in particular a titanium aluminide metal powder, is
exposed to a vacuum in the container, before the container is
heated. Moreover, a further step of the method is distinguished in
that, for the gassing of the metal powder, the atmosphere, enriched
with halogen, is supplied with at least one inert gas, in
particular after an evacuation of the container.
[0030] In order to achieve a good and homogeneous enrichment of the
titanium aluminide metal powder in the container, the container
and/or the powdery titanium aluminide is heated for a period of 15
minutes to 25 hours, preferably of 30 minutes to 10 hours. By these
means, a sufficiently high, uniform enrichment of titanium
aluminides in accordance with the desired degree of halogen
enrichment in the molded titanium alloy is attained.
[0031] Moreover, the container and/or the powdery titanium
aluminide are/is heated to a temperature between 300.degree. C. and
1300.degree. C. and preferably between 500.degree. C. and
1000.degree. C. By these means, a good enrichment of the metal
powder with halogens or halogen-like compounds is achieved.
[0032] The evacuating, gassing and heating steps of the method can
also be carried out several times consecutively, in order to
achieve higher halogen enrichment.
[0033] In addition, in a further step of the method after the
container is heated, the powdery titanium aluminide, in particular
titanium aluminide metal powder, is exposed to a reduced pressure
or a vacuum.
[0034] Finally, a component is produced from the alloy molded by
hot isostatic pressing.
[0035] Moreover, the object is solved by a component, which is or
will be produced from an alloy, which is produced according to one
of the aforementioned methods or method steps.
[0036] Titanium aluminide alloys are produced preferably using
casting metallurgical or powder metallurgical techniques. For
carrying out the methods, the titanium aluminide alloys usually are
present in the form of a powder, in order to enrich the metal
powder according to the invention with halogens. Components of
titanium aluminides usually are produced appropriately with known
molding methods and atomization methods.
[0037] For example, for the mentioned methods, the TiAl-based
intermetallic compounds may be alloys with a general composition of
titanium and aluminum corresponding to the desired and specified
requirements for the alloy.
[0038] Titanium aluminide alloys, which are produced according to
the inventive method introduced, generally may have, for example,
between about 30 atom percent and about 70 atom percent aluminum,
wherein in addition further materials or elements, which are
mentioned further below, may be taken up in accordance with the
desired requirements, which are to be met by the alloy or the
material.
[0039] In technically important areas of alloys, in which the TiAl
alloys may be used, for example, as a light-weight construction
material, the alloys may contain between about 44 atom percent and
about 49 atom percent aluminum. In addition, further components,
such as chromium (Cr), niobium (Nb), manganese (Mn), vanadium (V),
tantalum (Ta), molybdenum (Mo), zirconium (Zr), tungsten (W),
silicon (Si) and optionally additions of carbon (C) and/or boron
(B) may be contained, these additional materials being present in
an amount of about 0.1 atom percent to about 10 atom percent.
[0040] For industrial practice, in particular alloys, which are
based on the intermetallic phase .gamma.(TiAl) of a tetragonal
structure, are also of interest. These .gamma. titanium aluminide
alloys are distinguished by such properties as a low density (about
3.85 to 4.3 g/cm.sup.3), a high modulus of elasticity and a high
strength as well as creep resistance up to about 700.degree. C.
[0041] In particular, a preferred alloy has a composition
comprising Ti--(about 45 atom percent to about 49 atom percent)
Al--(about 5 atom percent to about 10 atom percent) X, wherein
X=Cr, Nb, Mn, V, Ta, Mo, Zr, W, Si and is formed optionally with
additions of carbon and/or boron.
[0042] A titanium aluminide alloy of a particularly high strength
has a composition comprising titanium, aluminide and niobium, to
which optionally components of boron and/or carbon may still be
added, the proportion of boron and/or carbon in the alloy being
less than about 0.5 atom percent. Typically, the titanium aluminide
alloy has a composition of Ti--45 atom percent Al--x Nb with 5 atom
percent .ltoreq.x.ltoreq.10 atom percent and optionally up to 0.5
atom percent B (boron) and/or up to 0.5 atom percent C
(carbon).
[0043] Moreover, titanium aluminide alloys with a fine and
homogeneous structure morphology may also be provided by the
inventive methods, the titanium aluminides having an alloy
composition of Ti--z Al--y Nb with 44.5 atom percent
.ltoreq.z.ltoreq.47 atom percent, in particular with 44.5 atom
percent .ltoreq.z.ltoreq.45.5 atom percent, and 5 atom percent
.ltoreq.y.ltoreq.10 atom percent, wherein this composition contains
molybdenum (Mo) ranging in amounts from about 0.1 atom percent to
about 3.0 atom percent. The remainder of the alloy consists of Ti
(titanium).
[0044] Especially for Ti--(44.5 atom percent to 45.5 atom percent)
Al--(5 atom percent to 10 atom percent) Nb, the addition of about
1.0 atom percent to about 3.0 atom percent of molybdenum has led to
good microstructures with a high degree of structural
homogeneity.
[0045] In accordance with a further advantageous development, the
aforementioned alloy also contains boron, preferably in an amount
in the alloy ranging from about 0.05 atom percent to about 0.8 atom
percent. The addition of boron advantageously leads to the
formation of stable precipitates, which contribute to the
mechanical hardening of the inventive alloy and to the
stabilization of the structure of the alloy.
[0046] Moreover, it is advantageous if the alloy contains carbon,
preferably in an amount of about 0.05 atom percent to about 0.8
atom percent. The addition of carbon, preferably in combination
with the aforementioned additive, boron, leads to the formation of
stable precipitates, which also contributes to the mechanical
hardening of the alloy and to the stabilization of the
structure.
[0047] A titanium aluminide alloy with a fine and homogeneous
structure morphology with formation of a stable .beta. phase at
high temperatures above 700.degree. C. is also provided by an alloy
based on titanium aluminide, produced by using melt metallurgy and
powder metallurgy techniques, with an alloy composition of Ti--z
Al--y Nb--x B with 44.5 atom percent .ltoreq.z.ltoreq.47 atom
percent, in particular with 44.5 atom percent .ltoreq.z.ltoreq.45.5
atom percent, 5 atom percent .ltoreq.y.ltoreq.10 atom percent and
0.05 atom percent .ltoreq.x.ltoreq.0.8 atom percent, this alloy
containing 0.1 atom percent to 3 atom percent molybdenum (Mo).
[0048] Moreover, an alloy composition of Ti--z Al--y Nb--w C with
44.5 atom percent .ltoreq.z.ltoreq.47 atom percent and in
particular with 44.5 atom percent .ltoreq.z.ltoreq.45.5 atom
percent, 5 atom percent .ltoreq.y.ltoreq.10 atom percent and 0.05
atom percent .ltoreq.w.ltoreq.0.8 atom percent, containing about
0.5 atom percent to about 3 atom percent of molybdenum (Mo), has a
fine and homogeneous structure morphology, the .beta. phase formed
being stable up to temperatures of 1320.degree. C.
[0049] The .beta. phase, which is stable up to temperatures of
1320.degree. C., is also formed with an alloy composition of Ti--z
Al--y Nb--x B--w C with 44.5 atom percent .ltoreq.z.ltoreq.47 atom
percent, in particular with 44.5 atom percent .ltoreq.z.ltoreq.45.5
atom percent, 5 atom percent .ltoreq.y.ltoreq.10 atom percent, 0.05
atom percent .ltoreq.x.ltoreq.0.8 atom percent and 0.05 atom
percent .ltoreq.w.ltoreq.0.8 atom percent, containing between about
0.1 atom percent and 3 atom percent molybdenum (Mo).
[0050] An appropriate TiAl alloy, given above, is provided within
the scope of the invention in accordance with the requirements
desired, as a metal powder or in powder form for the implementation
of one of the methods named, in order to obtain, as a result of the
inventive halogenation or halogen enrichment of the TiAl metal
powder, a TiAl alloy, which has an almost constant relative
proportion of halogens in a small partial volume at the surface and
at a depth away from the surface, as a result of which the
oxidation resistance of the material or of the whole alloy is
improved.
[0051] Preferably, in one embodiment, silicon-containing halogens
or combinations of silicon and halogens furthermore are used for
the implementation of the method, as a result of which the
oxidation resistance of the titanium aluminide alloys produced is
improved, owing to the fact that the elements or compounds,
increasing the oxidation resistance, are contained distributed
entirely homogeneously or randomly at the surface as well as in the
material.
[0052] In this respect, it is furthermore possible within the scope
of the invention to use, aside from halogens, also further
materials or mixtures, which increase the oxidation resistance of
titanium aluminide alloys.
* * * * *