Note: Descriptions are shown in the official language in which they were submitted.
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Method for manufacturing components with a nickel base alloy
as well as components manufactured therewith
The invention relates to a method for manufacturing components
with a nickel base alloy as well as to components manufactured
with this method. With this solution, manufacturing the most
differently shaped components in various three-dimensional
geometries is possible. The components, thus manufactured, may
also represent porous structures or may comprise such porous
structures.
With the nickel base alloys which are known per se, different
components are allowed to be manufactured of course, wherein
this can be primarily achieved with the known shaping methods.
Thus, such components are allowed to be manufactured as cast
parts which can be subsequently cold-worked or warm-worked
again, as the case may be.
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In particular during such a cutting shaping treatment, however, problems arise
due to
the mechanical properties of such nickel base alloys.
Furthermore, it has been proposed to modify components made of nickel by means
of sintering methods, wherein the formation of solid solution or the formation
of
intermetallic phases (preferentially of NiAl) should be achieved by sintering
in order to
achieve an improvement of the properties of such components. However,
particularly
in this form, the thermal properties of such components could be merely
improved,
and as a result the mechanical properties have not been improved in the
desired
form.
Therefore, it is an object of the invention to predetermine ways by means of
which
most differently shaped components are producible with nickel base alloys
which
comprise improved mechanical properties.
According to one aspect of the present invention, there is a provided method
for
manufacturing a component coated with a nickel base alloy, comprising:
depositing a
surface coating comprising a binding agent and a metal powder on a substrate
core
to form a coated substrate, the substrate core made of nickel, or of a nickel
base
alloy with a nickel content of at least 20 wt%, and the metal powder
comprising nickel
in an amount of at least 20 wt% and at least one alloy forming element other
than
nickel; and subjecting said coated substrate core to a stepped thermal
treatment
comprising: (i) expelling the binding agent, and (ii) subsequently sintering
the metal
powder to develop a graduated alloy composition from the surface of the nickel
substrate core and/or to form a solid nickel base alloy surface coating;
wherein the
substrate core is a porous foam body; the foam body is coated with the binding
agent, and the coated foam body is pressed to remove the binding agent from
pores
of the foam body, the metal powder is deposited on the foam body wetted with
said
binding agent, the foam body is deformed and subsequently the stepped thermal
treatment is carried out; and the foam body is fixed in a vibration device and
vibrated
during and/or after depositing said metal powder.
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Also provided are components manufactured according to the method described
herein.
Advantageous embodiments and improvements of the invention can be achieved
with
the features described herein.
According to one aspect of the present invention, there is provided the method
described herein, wherein the content of the nickel in the metal powder is
smaller
than the content of the nickel in the substrate core formed of the nickel base
alloy.
According to another aspect of the present invention, there is provided the
method
described herein, wherein the at least one alloy forming element of the metal
powder
comprise carbon, chromium, molybdenum, iron, cobalt, niobium, titanium,
aluminium,
boron, zircon, manganese, silicon, or lanthanum or two or more thereof.
According to yet another aspect of the present invention, there is provided
the
method described herein, wherein the coated substrate core or the coated
porous
foam body is deformed before the stepped thermal treatment.
According to still a further aspect of the present invention, there is
provided the
method described herein, wherein the binding agent and the metal powder are
combined to form a suspension/dispersion and the foam body is coated with the
suspension/dispersion before the stepped thermal treatment is carried out.
According to another aspect of the present invention, there is provided the
method
described herein, wherein the coated foam body is pressed to remove the
suspension/dispersion from pores of the foam body.
According to yet another aspect of the present invention, there is provided
the
method described herein, wherein the substrate core comprises at least a first
and a
second substrate core and a surface of at least the first substrate core is
coated with
the suspension/dispersion to form a coated surface, the coated surface is
brought
into touching contact with a surface of at least the second substrate core,
the stepped
thermal treatment is applied thereto, and an adhesive force type connection of
the at
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least the first and the second substrate core is developed by means of the
stepped
thermal treatment.
According to another aspect of the present invention, there is provided the
method
described herein, wherein the foam body comprises at least a first and a
second
foam body and the at least the first and the second foam body are coated with
the
binding agent.
According to another aspect of the present invention, there is provided the
method
described herein, wherein the surface coating deposited on the substrate core
comprises multiple coatings.
According to still another aspect of the present invention, there is provided
the
method described herein, wherein the multiple coatings on the substrate core
are of
more than one composition.
According to yet another aspect of the present invention, there is provided
the
method described herein, wherein the surface coating deposited on the first
substrate
core comprises multiple coatings wherein the suspension/dispersion with each
coating is of a different composition and/or a different layer thickness.
According to a further aspect of the present invention, there is provided the
method
described herein, wherein the metal powder has been subjected to high energy
grinding.
According to yet a further aspect of the present invention, there is provided
the
method described herein, wherein the sintering is carried out at a temperature
of
above 1000 C, and in a reducing or inert atmosphere.
According to still a further aspect of the present invention, there is
provided a
component coated with a nickel based alloy, wherein the component is
manufactured
by the method described herein, wherein the component is coated with a
graduated
alloy composition.
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According to another aspect of the present invention, there is provided a
component
coated with a nickel based alloy, wherein the component is manufactured by the
method described herein, wherein a graduated alloy composition is developed at
least inside a joining area of a closure by adhesive force type connection.
For the production of components with a nickel base alloy, the proceeding in
accordance with the invention takes place such that a substrate core
consisting of
pure nickel or a nickel base alloy will be provided with a surface coating at
least in
areas. The surface coating is formed from a binding agent as well as from a
metal
powder. The metal powder to be employed according to the invention includes
additional alloy forming
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developed at least inside a joining area of a closure by
adhesive force type connection.
For the production of components with a nickel base alloy,
the proceeding in accordance with the invention takes place
such that a substrate core consisting of pure nickel or a
nickel base alloy will be provided with a surface coating at
least in areas. The surface coating is formed from a
binding agent as well as from a metal powder. The metal
powder to be employed according to the invention includes
additional alloy forming
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elements which are still to be referred to subsequently, in
addition to a content of at least 20 wt% of nickel.
A substrate core consisting of a nickel base alloy should
include nickel of at least 20 wt%.
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The metal powder to be employed according to the invention may
be a powder of the respective nickel base alloy but also a
powder mixture of the respective alloy forming elements with
the nickel which has been preferably subjected to high energy
grinding.
According to the invention, the substrate core provided with
the surface coating is subsequently subjected to a stepped
thermal treatment. On that occasion, in a first step the
binding agent is expelled from the surface coating. Subsequent
to expelling of binder agent sintering of metal powder is then
achieved. During sintering, sinter-fusing of a nickel
substrate core and/or a solid surface coating formed of a
nickel base alloy is developed.
In case if a substrate core made of nickel base alloy has been
employed as a semi-finished product, the content of nickel
which is included in the metal powder should be smaller than
the nickel content in the substrate core material.
The thermal treatment, however, at least such sintering should
be carried out at temperatures of above 1000 C and in a
reducing or inert atmosphere, but preferably in a hydrogen
atmosphere.
As the substrate cores such one can be employed which have
already substantially the geometric form of the components to
be finally manufactured such that they are allowed to be
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completely refrained from final shaping re-machining or merely
minimum re-machining of the shape is correspondingly required.
However, with the solution according to the invention,
substrate cores can also be employed in the form of porous
send-finished products having a preferably porous structure
which one may denote as foam bodies as well.
In particular, with the production of such porous foam body
structures the surface coating should be developed with a
suspension/ dispersion which is made of the binding agent,
metal powder and an additional solvent, as the case may be, or
is made of a liquid.
Of course, it is also possible to deposit such suspensions/
dispersions upon non-porous substrate cores.
Such substrate cores having a porous structure are allowed to
be fully immersed into such a suspension/ dispersion, and
subsequently such a substrate core charged with suspension/
dispersion is allowed to be compressed in order to remove the
suspension/ dispersion from the pores such that merely the
webs remain wetted.
In the following, the stepped thermal treatment can then be
carried out.
However, during the production of components in the form of
porous foam bodies proceeding is also allowed to be such that
a binding agent which has an appropriate viscosity by means of
a solvent, as the case may be, will be employed for wetting
the surfaces of the porous structure of such a substrate core
wherein grouting can be also carried out herein for removing
excess binding agent from the pores.
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Subsequently, the respective metal powder is then allowed to
be deposited upon the wetted surfaces, wherein a more uniform
distribution of the metal powder can be achieved by vibration.
Subsequent to this, the stepped thermal treatment takes place
then again.
It is also possible to deform substrate cores, preferentially
such ones with a porous structure, after the development of
surface coating and before the stepped thermal treatment.
Thus, for example, bending can be carried out under compliance
of defined minimum bending radii. Thus, it is possible to
manufacture hollow-cylinder shaped components or rather
components shaped in a helical form.
With the solution according to the invention, however, it is
also possible to readily manufacture composite members. On
that occasion, proceeding is allowed to be such that at least
one surface area of a substrate core will be provided with a
surface coating as previously set forth.
Then, this surface area is allowed to be brought into touching
contact with at least another substrate core, wherein on that
occasion the adhesive effect of the binding agent can be used
advantageously. Subsequent to this, the thermal treatment
takes place during which a closure by adhesive force type
connection of the respective substrate cores is then formed.
However, it is also possible to provide surface areas of two
or several substrate cores to be connected together with
closure by adhesive force with a surface coating and to bring
those into touching contact, and then to connect with closure
by adhesive force by means of the thermal treatment.
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In this manner, composite members can be manufactured with
complex geometries, which, for example, comprise undercuts or
cavities, without shaping is required to occur subsequently.
However, it is also possible to manufacture composite members
which are formed from a substrate core having a dense
structure and a substrate core having a porous structure.
The metal powders to be employed according to the invention
may also include preferably at least 50 wt% of carbon,
molybdenum, iron, cobalt, niobium, titanium, aluminium, boron,
zircon, manganese, silicon and/or lanthanum in addition to
nickel having a minimum content of 20 wt%.
However, in addition to the respective powder composition, the
properties of the components manufactured according to the
invention can also be changed in that the surface coating will
be developed in a different form on defined surface areas of
substrate cores.
This relates to the respective thickness of the surface
coating which can also be carried out by means of a repeated
application in a different form, on the one hand, wherein a
locally different consistency of the surface coating with
different contents of metal powder, compositions of metal
powder and granularity of metal powder can also be provided,
on the other hand.
As a result, locally different properties on such a component
manufactured according to the invention can be achieved.
With the solution according to the invention it is possible to
manufacture components which comprise a graduated alloy
composition starting from the surface. 'Thus, for example, it
is possible with the use of a substrate core made of pure
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nickel to manufacture a component which still has a core area
of pure nickel after sintering, wherein the content of
additional alloy elements changes/ increases successively
towards the respective surfaces.
With the production of composite members as already mentioned,
the graduated alloy compositions can also be developed in the
joining area which has been formed by means of the closure by
adhesive force type connections.
Components manufactured according to the invention have a
higher ductility, creep resistance and strength compared with
components which have been manufactured from nickel only,
wherein this circumstance also applies in comparison with
nickel aluminide.
The tendency of oxidation compared with nickel components can
be reduced as well.
The components achieve a thermal stability of up to 1000 C,
wherein components manufactured according to the invention
with porous structures, in particular, present such extended
possibilities of application themselves, which e.g. exclude
the use of foams of nickel aluminide due to the brittleness
thereof.
The components manufactured according to the invention, in
particular, can be employed at higher dynamic loads.
In the following, the invention shall be explained by way of
example.
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Embodiment 1
A substrate core made of nickel and having the size of 300 mm
* 150 mm * 1.9 mm, and having a porosity of 94 % has been
immersed in an aqueous 1% solution of polyvinylpyrrolidone
with a volume of 50 ml. Subsequently, pressing out on an
absorbent pad has been carried out to remove the binding agent
from the cavities of the pores such that merely the webs of
the porous structure have been wetted.
Subsequent to this, the porous substrate core wetted with the
binding agent has been fixed in a vibration device and has
been strewed with metal powder. As a result of the vibration,
a uniform distribution of the metal powder on the surfaces of
the substrate core wetted with the binding agent could be
achieved, wherein the open porosity of the structure has been
maintained.
The metal powder comprised a composition of 0.1 wt% of carbon,
22.4 wt% of chromium, 10.0 wt% of molybdenum, 4.8 wt% of iron,
0.3 wt% of cobalt, 3.8 wt% of niobium and 58.6 wt% of nickel.
Such a metal powder is commercially available under the trade
name of "Inconel 625".
The substrate core surface coated with the metal powder and
binding agent has been rolled to a cylinder shaped body. On
that occasion, the adhesion of the metal powder has been
ensured by means of the binding agent.
Subsequent to this, stepped thermal treatment has been carried
out wherein it has been worked in a first step inside a drying
oven in a water atmosphere. The temperature has been
increased, while a heating rate of 5 K/ndn was maintained.
Expelling the binding agent starts at around 300 C and has
been completed at 600 C. A detention time of around 30 min
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should be adhered in order to ensure a complete release from
the binding agent.
Subsequently, sintering has been carried out in a temperature
range of 1150 C and 1250 C with adhering detention time of
around 30 min.
The component thus manufactured consisted of a nickel base
alloy wherein the composition thereof at the surface is at
least approximately equivalent to the composition of the
employed metal powder. The porosity is equal to 91 %. In the
air, the component has been oxidation-resistant at
temperatures of up to 1000 C, comprised a high strength,
creep resistance and toughness as well. After sintering, a
limited deformability of the porous foam body structure was
still possible considering particular minimum bending radii.
Embodiment 2
A corrugated sheet of pure nickel with the size of 200 mm *
200 mm * 0.15 mm has been employed as a substrate core.
Surface coating for this substrate core has been developed
from 18 milliliters of an aqueous 6% solution of polyvinyl-
pyrrolidone and a metal powder the composition thereof is
equivalent to the metal powder used in the embodiment 1.
The suspension manufactured from the metal powder and binding
agent after intensive stirring has been atomized by means of
compressed air, and sprayed upon the substrate core from both
sides. The surface coating comprised a thickness of 150 pm.
After drying over a time period of 1 min, approximately, the
layer comprised a sufficiently great green strength such that
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the stepped thermal treatment could be carried out analogous
to the embodiment 1.
The final component comprised a nickel base alloy, wherein the
alloy composition thereof at the surface was approximately
equivalent to the alloy composition of the used metal powder.
In the air, it was oxidation-resistant at temperatures up to
1000 C. The high strength, creep resistance and toughness
were increased in comparison with the substrate core made of
pure nickel.
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