U.S. patent application number 16/673563 was filed with the patent office on 2020-02-27 for method for manufacturing a component containing an iron alloy material.
The applicant listed for this patent is SLM Solutions Group AG. Invention is credited to Florian Brenne, Guido Grundmeier, Hans Juergen Maier, Thomas Niendorf, Mirko Schaper, Dieter Schwarze.
Application Number | 20200063230 16/673563 |
Document ID | / |
Family ID | 51399556 |
Filed Date | 2020-02-27 |
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United States Patent
Application |
20200063230 |
Kind Code |
A1 |
Niendorf; Thomas ; et
al. |
February 27, 2020 |
METHOD FOR MANUFACTURING A COMPONENT CONTAINING AN IRON ALLOY
MATERIAL
Abstract
In a method for manufacturing a component containing an iron
alloy material, a pulverulent pre-alloy is provided. The pre-alloy
comprises, in wt. %, 0.01 to 1% C, 0.0.01 to 30% Mn, .ltoreq.6% Al,
and 0.05 to 6.0% Si, the remainder being Fe and usual contaminants.
The pulverulent pre-alloy is mixed with at least one of elementary
Ag powder, elementary Au powder, elementary Pd powder and
elementary Pt powder so as to produce a powder mixture containing
0.1 to 20% of at least one of Ag, Au, Pd and Pt. The powder mixture
is applied onto a carrier (16) by means of a powder application
device (14). Electromagnetic or particle radiation is selectively
irradiated onto the powder mixture applied onto the carrier (16) by
means of an irradiation device (18) so as to generate a component
from the powder mixture by an additive layer construction
method.
Inventors: |
Niendorf; Thomas;
(Beverungen, DE) ; Maier; Hans Juergen; (Neustadt
am Ruebenberge, DE) ; Brenne; Florian; (Paderborn,
DE) ; Schaper; Mirko; (Salzkotten, DE) ;
Grundmeier; Guido; (Wuerzburg, DE) ; Schwarze;
Dieter; (Luebeck, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SLM Solutions Group AG |
Luebeck |
|
DE |
|
|
Family ID: |
51399556 |
Appl. No.: |
16/673563 |
Filed: |
November 4, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14877532 |
Oct 7, 2015 |
10513748 |
|
|
16673563 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61L 31/022 20130101;
C22C 38/34 20130101; B33Y 70/00 20141201; C22C 33/0207 20130101;
Y02P 10/295 20151101; C22C 38/02 20130101; B22F 2999/00 20130101;
B23K 26/342 20151001; C21D 6/007 20130101; C22C 38/06 20130101;
C22C 38/12 20130101; C22C 38/30 20130101; C22C 38/38 20130101; C22C
38/32 20130101; A61L 31/024 20130101; C22C 38/001 20130101; B22F
3/008 20130101; B23K 26/0006 20130101; C22C 38/16 20130101; C22C
38/20 20130101; C22C 38/28 20130101; C22C 38/04 20130101; A61L
31/148 20130101; B23K 2103/02 20180801; C21D 6/002 20130101; C22C
38/14 20130101; C22C 38/24 20130101; C22C 33/0257 20130101; B33Y
80/00 20141201; C22C 38/26 20130101; B22F 2998/10 20130101; C21D
6/008 20130101; C21D 6/005 20130101; C21D 9/0068 20130101; C22C
38/002 20130101; B22F 3/24 20130101; C22C 38/007 20130101; A61L
27/58 20130101; B22F 3/1055 20130101; C22C 38/10 20130101; C22C
38/18 20130101; A61L 27/042 20130101; Y02P 10/25 20151101; A61L
27/08 20130101; B33Y 10/00 20141201; B22F 2999/00 20130101; B22F
3/1055 20130101; B22F 2203/11 20130101; B22F 2999/00 20130101; B22F
3/1055 20130101; B22F 3/1028 20130101; B22F 2998/10 20130101; B22F
3/1055 20130101; B22F 2003/248 20130101 |
International
Class: |
C21D 9/00 20060101
C21D009/00; B22F 3/00 20060101 B22F003/00; C22C 38/38 20060101
C22C038/38; C22C 38/34 20060101 C22C038/34; C22C 38/32 20060101
C22C038/32; C22C 38/30 20060101 C22C038/30; C22C 38/28 20060101
C22C038/28; C22C 38/26 20060101 C22C038/26; C22C 38/24 20060101
C22C038/24; C22C 38/20 20060101 C22C038/20; C22C 38/06 20060101
C22C038/06; C22C 38/04 20060101 C22C038/04; C22C 38/02 20060101
C22C038/02; C22C 38/00 20060101 C22C038/00; C21D 6/00 20060101
C21D006/00; B23K 26/342 20060101 B23K026/342; B23K 26/00 20060101
B23K026/00; B22F 3/24 20060101 B22F003/24; B33Y 10/00 20060101
B33Y010/00; B33Y 70/00 20060101 B33Y070/00; B33Y 80/00 20060101
B33Y080/00; A61L 27/58 20060101 A61L027/58; B22F 3/105 20060101
B22F003/105; A61L 31/02 20060101 A61L031/02; A61L 27/04 20060101
A61L027/04; A61L 31/14 20060101 A61L031/14; A61L 27/08 20060101
A61L027/08; C22C 33/02 20060101 C22C033/02; C22C 38/18 20060101
C22C038/18; C22C 38/10 20060101 C22C038/10; C22C 38/12 20060101
C22C038/12; C22C 38/14 20060101 C22C038/14; C22C 38/16 20060101
C22C038/16 |
Claims
1.-6. (canceled)
7. An iron alloy material, comprising in wt. %: 0.01 to 1% C 0.01
to 30% Mn .ltoreq.6% Al, 0.05 to 6.0% Si, and 0.1 to 20% Ag, the
remainder being Fe and usual contaminants.
8. The iron alloy material according to claim 7, further comprising
at least one of Cr at a content of .ltoreq.2%, Cu at a content of
.ltoreq.2%, Ti at a content of .ltoreq.2%, Co at a content of
.ltoreq.2%, Zr at a content of .ltoreq.2%, V at a content of
.ltoreq.2%, Nb at a content of .ltoreq.2%, Ta at a content of
.ltoreq.2% and B at a content of .ltoreq.0.2%.
9. The iron alloy material according to claim 7, wherein the Ag
content of the iron alloy material is .ltoreq.15%, in particular
.ltoreq.10% and more particular .ltoreq.5%.
10. The iron alloy material according to claim 7, wherein the Ag
content of the iron alloy material is .gtoreq.0.5%, in particular
.gtoreq.1% and more particular .gtoreq.2%.
11. The iron alloy material according to claim 7, wherein, in the
microstructure of the iron alloy material, Ag is present in the
form of Ag particles dispersed in an iron alloy matrix.
12. The iron alloy material according to claim 7, wherein, in the
microstructure of the iron alloy material, an iron alloy matrix is
present which, upon plastic deformation of the iron alloy material,
shows twinning induced plasticity and/or transformation induced
plasticity.
13. Component, in particular implant component, containing an iron
alloy material according to claim 7.
Description
[0001] Medical implants play an important role in modern surgical
techniques. Implants which are intended to maintain in place in the
body of a patient for a limited period of time only may be made of
biodegradable or biocorrodible materials which, over time, are
resorbed by the biological environment. An additional surgical
treatment for removing the implant from the patient's body can thus
be avoided. A biocorrodible iron alloy with the formula Fe--Mn--X
is disclosed in EP 2 087 915 A2. In this iron alloy, the content of
Mn is 5 to 30 wt. %. X is at least one element selected from the
group of Pt, Pd, Ir, Rh, Re, Ru, and Os and is present in the alloy
at a content of 0 to 20 wt. %.
[0002] Powder bed fusion is an additive layering process by which
pulverulent, in particular metallic and/or ceramic raw materials
can be processed to three-dimensional work pieces of complex
shapes. To that end, a raw material powder layer is applied onto a
carrier and subjected to laser radiation in a site selective manner
in dependence on the desired geometry of the work piece that is to
be produced. The laser radiation penetrating into the powder layer
causes heating and consequently melting or sintering of the raw
material powder particles. Further raw material powder layers are
then applied successively to the layer on the carrier that has
already been subjected to laser treatment, until the work piece has
the desired shape and size. An apparatus for producing moulded
bodies from pulverulent raw materials by a powder bed fusion
process is described, for example, in EP 1 793 979 B1. Powder bed
fusion may be used for the production of prototypes, tools,
replacement parts, high value components or medical prostheses on
the basis of CAD data.
[0003] An article by T. Niendorf and F. Brenne entitled "Steel
showing twinning-induced plasticity processed by selective laser
melting--An additively manufactured high performance material",
Materials Characterization 85 (2013) 57-63 describes the processing
of austenitic high-manganese steel showing twinning induced
plasticity (TWIP) by powder bed fusion. In steels showing twinning
induced plasticity, plastic deformation causes the formation of
twin structures within the microstructure of the steel, resulting
in excellent mechanical properties featuring high strength, good
ductility and extraordinary strain hardening. Furthermore,
austenitic high-manganese steels may also show transformation
induced plasticity (TRIP), i.e. a plastic deformation of these
steels may result in a microstructural transformation from
austenite to martensite, leading to enhanced mechanical properties.
TWIP steels processed by powder bed fusion exhibit mechanical
properties which are similar to those of conventionally processed
TWIP steels.
[0004] The invention is directed at the object of providing an
effective and efficient method for manufacturing a component, in
particular an implant component, containing a biocorrodible iron
alloy material. Further, the invention is directed at the object of
providing a cost-effective biocorrodible iron alloy material and a
component, in particular an implant component, containing such an
iron alloy material.
[0005] These objects are addressed by a method for manufacturing an
iron alloy material as defined in claim 1, an iron alloy material
as defined in claim 7 and a component as defined in claim 13.
[0006] In a method for manufacturing a component containing an iron
alloy material, a pulverulent pre-alloy is provided. The pre-alloy
powder may have any suitable particle size or particle size
distribution. It is, however, preferable to process pre-alloy
powders of particle sizes <100 mm. For example, a pre-alloy
powder produced by spray aeration in argon inert atmosphere and
having a mean particle diameter of approximately 40 .mu.m may be
used. The pulverulent pre-alloy comprises, in wt. %, 0.01 to 1% C,
0.0.01 to 30% Mn, .ltoreq.6% Al, and 0.05 to 6.0% Si, the remainder
being Fe and usual contaminants such as, for example, P and/or S.
In a preferred embodiment, the pulverulent pre-alloy comprises, in
wt. %, 0.04 to 1% C, 9.0 to 24.0% Mn, 0.05 to 4% Al, and 0.05 to
6.0% Si, the remainder being Fe and usual contaminants. It is,
however, also conceivable to use a pre-alloy which does not
comprise any Al at all.
[0007] In the pre-alloy, the alloying element Mn, in particular
when added at a content 9.0%, increases the corrosion rate in a
biological environment and thus makes the pre-alloy more suitable
for use as a biocorrodible material than pure iron. Furthermore, Mn
acts as an austenite stabilizer, thus promoting the formation of
face-centered cubic g-iron in the microstructure of the pre-alloy.
As compared to ferromagnetic a-iron, paramagnetic g-iron does not
interfere with the magnetic field of conventional magnetic
resonance (MR) devices and hence should be the main phase in the
microstructure of the pre-alloy in case the pre-alloy is intended
to be used as an implant material. Furthermore, the alloying
elements in the pre-alloy are selected and dosed such that the
pre-alloy has a mixed crystal microstructure having a stacking
fault energy which allows the pre-alloy to show at least one of
twinning induced plasticity and transformation induced
plasticity.
[0008] Addition of the alloying element C leads to a linear
increase of the stacking fault energy. Furthermore, C influences
the deformation mechanisms occurring beside the twin formation as
well as the strength of the pre-alloy. In addition, C, like Mn,
acts as an austenite stabilizer. Addition of the alloying element
Al also leads to a linear increase of the stacking fault energy.
Further, Al acts as a ferrit stabilizer, thus promoting the
formation of body-centered cubic a-iron in the microstructure of
the pre-alloy. Finally, Al counteracts hydrogen induced
embrittlement and delayed cracking.
[0009] When Si is added to the pre-alloy, the stacking fault energy
first is increased with an increasing Si-content, but, when further
Si is added, is again decreased. Si, like Al, also acts as a ferrit
stabilizer and increases both the strength and the wear resistance
of the alloy. Finally, Si counteracts the formation of Fe-carbides
and thus enhances the processing properties of semi-finished
products by metallurgical methods.
[0010] The pulverulent pre-alloy is mixed with at least one of
elementary Ag powder, elementary Au powder, elementary Pd powder
and elementary Pt powder so as to produce a powder mixture
containing 0.1 to 20% of at least one of Ag, Au, Pd and Pt. In a
particularly preferred embodiment of the inventive method,
elementary Ag powder is added to the pre-alloy powder at a content
of 0.1 to 20%. Like the pre-alloy powder, the at least one of
elementary Ag powder, elementary Au powder, elementary Pd powder
and elementary Pt powder may have any suitable particle size or
particle size distribution. It is, however, preferable to process
powders of particle sizes <100 mm.
[0011] The powder mixture containing the pulverulent pre-alloy and
the at least one of elementary Ag powder, elementary Au powder,
elementary Pd powder and elementary Pt powder is applied onto a
carrier by means of a powder application device. The carrier may be
disposed in a process chamber and may be a rigidly fixed carrier
having a surface onto which the powder mixture is applied.
Preferably, however, the carrier is designed to be displaceable in
vertical direction. The process chamber accommodating the carrier
may be sealable against the ambient atmosphere, i.e. against the
environment surrounding the process chamber, in order to be able to
maintain a controlled atmosphere, in particular an inert atmosphere
within the process chamber.
[0012] Finally, electromagnetic or particle radiation is
selectively irradiated onto the powder mixture applied onto the
carrier by means of an irradiation device so as to generate a
component from the powder mixture by an additive layer construction
method. The irradiation device preferably is adapted to irradiate
radiation onto the powder mixture which causes a site-selective
melting of the powder particles. The irradiation device may
comprise at least one radiation source, in particular a laser
source, and at least one optical unit for guiding and/or processing
a radiation beam emitted by the radiation source. The optical unit
may comprise optical elements such an object lens, in particular an
f-theta lens, and a scanner unit, the scanner unit preferably
comprising a diffractive optical element and a deflection
mirror.
[0013] By selectively irradiating a powder layer applied onto the
carrier with electromagnetic or particle radiation, a first layer
of the component is generated on the carrier. The additive layer
construction method employed for generating the component may
further include the steps of repeatedly vertically displacing the
carrier so as to compensate for the height of the already generated
layer(s) of the component, applying a further layer of powder onto
the carrier such that the already generated layer(s) of the
component is/are covered by the powder and selectively irradiating
the layer of powder applied onto the already generated layer(s) of
the component so as to generate a further layer of the
component.
[0014] With the inventive method, a component can be generated from
the powder mixture containing the pulverulent pre-alloy and the at
least one of elementary Ag powder, elementary Au powder, elementary
Pd powder and elementary Pt powder in a very efficient manner, even
if the component has a complex shape. The control of the powder
application device and the irradiation device is performed based on
CAD data of the component to be generated. These CAD data can, for
example, be derived from usual diagnostic data such as MR data,
computed tomography (CT) data and the like. The method thus is in
particular suitable for producing individually designed implant
components.
[0015] The component generated by means of the method according to
the invention may entirely consist of the iron alloy material
generated when irradiating the above described powder mixture. It
is, however, also conceivable that the component only in part is
made of the iron alloy material and contains also other metallic or
non-metallic materials. These materials may be processed either
also in an additive layering process or may be joined to the
part(s) made of the iron alloy material by any suitable joining
method.
[0016] The component manufactured by the method according to the
invention consists of an iron alloy material which, due to the
composition of the pulverulent pre-alloy used for making the
component, upon deformation shows at least one of twinning induced
plasticity and transformation induced plasticity and hence exhibits
excellent mechanical properties. Furthermore, by adding at least
one of Ag, Au, Pd and Pt, the corrosion rate of the material in a
biological environment can be significantly increased. Corrosion
tests, which have been conducted for seven days in 0.9% NaCl
aqueous solution at a pH of 6.5, revealed a mass loss of an iron
pre-alloy containing (beside Fe and usual contaminants), in wt. %,
0.6 C, 22.4% Mn, 0.25% V, 0.2% Cr, and 0.25% Si of 1.7 mg per
cm.sup.2 sample surface per day as compared to 2.3 mg per cm.sup.2
sample surface per day for the pre-alloy with an addition of 5 wt.
% Ag.
[0017] The component thus is particularly suitable for use as a
biocorrodible implant component.
[0018] While Au and Pt are effective in increasing the corrosion
rate of the material in a biological environment, these alloying
elements are rather expensive. However, the additive layer
construction method according to the invention allows the component
to be produced in a raw material saving manner so that even
components containing expensive raw materials like Au and Pt can be
manufactured at reasonable costs. Pd is cheaper than Au and Pt, but
might not be entirely unproblematic regarding its toxicity when
being releasing in a living body. Ag is less expensive than Au.
However, due to its insolubility in liquid Fe, an Ag containing
iron alloy material cannot be produced by conventional casting
methods. Surprisingly, a material containing the above defined iron
pre-alloy and Ag as an addition, however, can be manufactured by
the additive layer construction method according to the invention.
The inventive method thus can be employed to produce a
biocorrodible material which has not only excellent mechanical
properties, but also desirable biocorrosion properties and which
cannot be manufactured by conventional metallurgical methods.
[0019] In a preferred embodiment of the method for manufacturing a
component containing an iron alloy material, the pulverulent
pre-alloy further comprises at least one of Cr at a content of
.ltoreq.2%, Cu at a content of .ltoreq.2%, Ti at a content of
.ltoreq.2%, Co at a content of .ltoreq.2%, Zr at a content of
.ltoreq.2%, V at a content of .ltoreq.2%, Nb at a content of
.ltoreq.2%, Ta at a content of .ltoreq.2% and B at a content of
.ltoreq.0.2%. In any case, the addition of the alloying elements
has to be tailored in such a manner that the TWIP effect of the
pre-alloy at room temperature is maintained. Furthermore, the
biocompatibility of the alloying elements has to be considered, Ti,
Zr, Nb and Ta being in particular suitable in this regard.
[0020] In the method for manufacturing a component containing an
iron alloy material, the pulverulent pre-alloy may be mixed with at
least one of elementary Ag powder, elementary Au powder, elementary
Pd powder and elementary Pt powder so as to produce a powder
mixture containing .ltoreq.20%, preferably .ltoreq.15%, in
particular .ltoreq.10% and more particular .ltoreq.5% of at least
one of Ag, Au, Pd and Pt. Additionally or alternatively thereto,
the pulverulent pre-alloy may be mixed with at least one of
elementary Ag powder, elementary Au powder, elementary Pd powder
and elementary Pt powder so as to produce a powder mixture
containing .gtoreq.0.5%, in particular .gtoreq.1% and more
particular .gtoreq.2% of at least one of Ag, Au, Pd and Pt.
[0021] A suitable amount of at least one of elementary Ag powder,
elementary Au powder, elementary Pd powder and elementary Pt powder
to be mixed with the pre-alloy powder should be tailored in
dependence on the desired properties of the iron alloy material
component to be generated. At the one hand, the content of the
addition Ag, Au, Pd and/or Pt should be high enough in order to
provide for the desired high biocorrosion rate of the component to
be generated. On the other hand, to much Ag, Au, Pd and/or Pt could
affect the biocompatibility of the component if the amount of Ag,
Au, Pd and/or Pt which is released upon degradation of the
component within a living body exceeds a tolerance threshold.
Furthermore, the amount of Ag, Au, Pd and/or Pt present in the
microstructure of the generated iron alloy material should be low
enough in order to ensure that the desired twinning induced
plasticity and/or transformation induced plasticity behavior of the
pre-alloy is not affected.
[0022] In a particular preferred embodiment of the method for
manufacturing a component containing an iron alloy material, the
operation of the powder application device and the irradiation
device is controlled in such a manner that local melt pools are
formed in the powder mixture upon being irradiated with
electromagnetic or particle radiation. Within the melt pools both
the pre-alloy and the at least one of elementary Ag, elementary Au,
elementary Pd and elementary Pt are in the liquid state. The size
of the melt pools depends on the size and the energy of the
radiation beam irradiated onto the powder mixture and usually is
larger than the diameter of the spot of the radiation beam. A
typical spot diameter of the radiation beam irradiated onto the
powder mixture is .ltoreq.100 .mu.m. However, in any case, the size
of the melt pools is very small as compared to the size of the
component to be manufactured. As a result, the liquid metal in the
melt pools solidifies at a high solidification rate. Preferably,
the operation of the powder application device and the irradiation
device is controlled in such a manner that the melt in the local
melt pools solidifies at a solidification rate of up to
approximately 7.times.10.sup.6 K/s.
[0023] Due to having a higher density than the pre-alloy, the
elementary addition does not "float" on the surface of the melt
pool, but instead sinks--driven by gravity--in the direction of the
bottom of the melt pools, i.e. in the direction of the already
generated layers of the component to be produced. However, due to
the high solidification rate of the liquid metal in the melt pools,
the melt solidifies before accumulations of the elementary addition
form at the bottom of the melt pools. Thus, upon solidification of
the melt, the liquid elementary addition is more or less evenly
distributed within the pre-alloy melt, even in case the elementary
addition has a low solubility or, like Ag, is entirely insoluble in
liquid Fe. Hence, in the resulting iron alloy material, a
microstructure is obtained, wherein the elementary addition is
finely dispersed and evenly distributed within a pre-alloy
matrix.
[0024] The generated component may be heat-treated in order to
modify its mechanical properties. For example, a heat treatment in
an inert atmosphere, in particular in vacuum, for 1 hour at a
temperature of 1050.degree. C. is effective for increasing the
average grain size of the material. As a result, the yield strength
is reduced. However, the TWIP effect leads to a significant
strengthening of the material and hence an increase of the failure
strain. By suitably varying the time and the temperature of the
heat treatment, the yield strength and the failure strain may be
tailored. Further heat treatments may be performed in order to
promote recovery and/or recrystallization. Thus, heat treatments
for 1 minute to 24 hours at temperatures between 200.degree. C. and
1100.degree. C. may be performed as desired.
[0025] An iron alloy material according to the invention comprises,
in wt. %, 0.01 to 1% C, 0.0.01 to 30% Mn, .ltoreq.6% Al, 0.05 to
6.0% Si, and 0.1 to 20% Ag, the remainder being Fe and usual
contaminants such as, for example, P and/or S. In a preferred
embodiment, the iron alloy material comprises, in wt. %, 0.04 to 1%
C, 9.0 to 24.0% Mn, 0.05 to 4% Al, and 0.05 to 6.0% Si, and 0.1 to
20% Ag, the remainder being Fe and usual contaminants. It is,
however, also conceivable to use a pre-alloy which does not
comprise any Al at all. Due to the insolubility of liquid Ag in an
Fe melt, the iron alloy material according to the invention cannot
be produced by conventional metallurgical methods. Surprisingly, it
is, however, possible to manufacture the iron alloy material by
using an additive layer construction method as described above.
[0026] The iron alloy material preferably further comprises at
least one of Cr at a content of .ltoreq.2%, Cu at a content of
.ltoreq.2 Ti at a content of .ltoreq.2%, Co at a content of
.ltoreq.2%, Zr at a content of .ltoreq.2%, V at a content of
.ltoreq.2%, Nb at a content of .ltoreq.2%, Ta at a content of
.ltoreq.2% and B at a content of .ltoreq.0.2%.
[0027] The Ag content of the iron alloy material preferably is
.ltoreq.15%, in particular .ltoreq.10% and more particular
.ltoreq.5%. Additionally or alternatively thereto, the Ag content
of the iron alloy material may be .gtoreq.0.5%, in particular
.gtoreq.1% and more particular .gtoreq.2%.
[0028] In the microstructure of the iron alloy material, Ag
preferably is present in the form of Ag particles dispersed in an
iron alloy matrix. The Ag particles may have particle sizes in the
range of 30 to 50 .mu.m. In general, in order to achieve a high
corrosion rate, the Ag particles should be small in size and finely
distributed within the iron alloy matrix. Additionally or
alternatively thereto, in the microstructure of the iron alloy
material, an iron alloy matrix is present which, upon plastic
deformation of the iron alloy material, shows twinning induced
plasticity and/or transformation induced plasticity. As a result,
the iron alloy material exhibits excellent mechanical
properties.
[0029] A component according to the invention contains an above
described iron alloy material. The component may entirely consist
of the iron alloy material. It is, however, also conceivable that
the component only in part is made of the iron alloy material. The
component in particular is an implant component which is intended
to be implanted in a living body. Preferably the component is a
biocorrodible component which corrodes and thus degrades over time
when exposed to a biological environment.
[0030] Preferred embodiments of the invention in the following are
explained in greater detail with reference to the accompanying
schematic drawings, in which:
[0031] FIG. 1 shows an apparatus for manufacturing a component
containing an iron alloy material by an additive layer construction
method, and
[0032] FIG. 2 shows a SEM/BSE micrograph of the microstructure of
an iron alloy material.
[0033] FIG. 1 shows an apparatus 10 for manufacturing a component
by an additive layer construction method. The apparatus 10
comprises a process chamber 12. A powder application device 14,
which is disposed in the process chamber 12, serves to apply a raw
material powder onto a carrier 16. The process chamber 12 is
sealable against the ambient atmosphere, i.e. against the
environment surrounding the process chamber 12. The carrier 16 is
designed to be displaceable in a vertical direction so that, with
increasing construction height of a component, as it is built up in
layers from the raw material powder on the carrier 16, the carrier
16 can be moved downwards in the vertical direction.
[0034] In case the apparatus 10 should be used for manufacturing a
component containing an iron alloy material, the powder application
device 14 is fed with a powder mixture obtained by mixing a
pulverulent pre-alloy powder with at least one of elementary Ag
powder, elementary Au powder, elementary Pd powder and elementary
Pt powder so as to produce a powder mixture containing 0.1 to 20%
of at least one of Ag, Au, Pd and Pt. If desired, a powder mixture
may be produced which contains .ltoreq.15%, in particular
.ltoreq.10% and more particular .ltoreq.5% of at least one of Ag,
Au, Pd and Pt. Further, it is conceivable, to produce a powder
mixture which contains .gtoreq.0.5%, in particular .gtoreq.1% and
more particular .gtoreq.2% of at least one of Ag, Au, Pd and
Pt.
[0035] The pre-alloy powder comprises, in wt. %, 0.01 to 1% C, 0.01
to 30% Mn, .ltoreq.6% Al, and 0.05 to 6.0% Si, the remainder being
Fe and usual contaminants. If desired, the pre-alloy powder may
further comprise at least one of Cr at a content of .ltoreq.2%, Cu
at a content of .ltoreq.2%, Ti at a content of .ltoreq.2%, Co at a
content of .ltoreq.2%, Zr at a content of .ltoreq.2%, V at a
content of .ltoreq.2%, Nb at a content of .ltoreq.2%, Ta at a
content of .ltoreq.2% and B at a content of .ltoreq.0.2%.
[0036] The apparatus 10 further comprises an irradiation device 18
for selectively irradiating laser radiation onto the raw material
powder applied onto the carrier 16. By means of the irradiation
device 18, the raw material powder applied onto the carrier 18 may
be subjected to laser radiation in a site-selective manner in
dependence on the desired geometry of the component that is to be
produced. The irradiation device 18 has a hermetically sealable
housing 20. A radiation beam 22, in particular a laser beam,
provided by a radiation source 24, in particular a laser source
which may, for example, comprise a diode pumped Ytterbium fibre
laser emitting laser light at a wavelength of approximately 1070 to
1080 nm is directed into the housing 20 via an opening 26.
[0037] The irradiation device 18 further comprises an optical unit
28 for guiding and processing the radiation beam 22. The optical
unit 28 may comprise a beam expander for expanding the radiation
beam 22, a scanner and an object lens. Alternatively, the optical
unit 28 may comprise a beam expander including a focusing optic and
a scanner unit. By means of the scanner unit, the position of the
focus of the radiation beam 22 both in the direction of the beam
path and in a plane perpendicular to the beam path can be changed
and adapted. The scanner unit may be designed in the form of a
galvanometer scanner and the object lens may be an f-theta object
lens. The operation of the irradiation device 18 and the operation
of the powder application device 14 is controlled by means of a
control unit 38.
[0038] During operation of the apparatus 10, a first layer of a
component to be produced is generated on the carrier 16 by
selectively irradiating the raw material powder layer applied onto
the carrier 16 with the radiation beam 22. The radiation beam 22 is
directed over the raw material powder layer applied onto the
carrier 16 in accordance with CAD data of the component to be
produced. After the first layer of the component to be produced is
completed, the carrier 16 is lowered in a vertical direction
allowing the application of a successive powder layer by means of
the powder application device 14. Thereafter, the successive powder
layer is irradiated by means of the irradiation device 18. Thus,
layer by layer, the component is built up on the carrier 16.
[0039] In case the apparatus 10 is operated for manufacturing a
component containing an iron alloy material, the operation of the
powder application device 14 and the irradiation device 18, by
means of the control unit 38, is controlled in such a manner that,
due to the energy input from the radiation beam 22, local melt
pools are formed in the powder mixture applied onto the carrier 16
upon being irradiated with the radiation beam 22. Within the melt
pools, which are usually larger than the diameter of the spot of
the radiation beam having a typical diameter of .ltoreq.100 .mu.m,
both the pre-alloy and the at least one of elementary Ag,
elementary Au, elementary Pd and elementary Pt are in the liquid
state, but solidify at a high a solidification rate up to
approximately 7.times.10.sup.6 K/s.
[0040] Due to having a higher density than the pre-alloy, the
elementary addition does not "float" on the surface of the melt
pool, but instead sinks--driven by gravity--in the direction of the
bottom of the melt pools. However, due to the high solidification
rate of the liquid metal in the melt pools, the melt solidifies
before accumulations of the elementary addition form at the bottom
of the melt pools. Thus, upon solidification of the melt, the
liquid elementary addition is more or less evenly distributed
within the pre-alloy melt, even in case the elementary addition has
a low solubility or, like Ag, is entirely insoluble in liquid Fe.
Hence, in the resulting iron alloy material, a microstructure is
obtained, wherein the elementary addition is finely dispersed and
evenly distributed within a pre-alloy matrix. In particular, in the
microstructure of the iron alloy material, the elementary addition
is present in the form of particles dispersed in an iron alloy
matrix. The particles, for example, may have particle sizes in the
range of 30 to 50 .mu.m.
[0041] Due to the composition of the pre-alloy matrix, the iron
alloy material, upon deformation, shows twinning induced plasticity
and/or transformation induced plasticity. As a result, the iron
alloy material exhibits excellent mechanical properties.
Furthermore, due to the presence of at least one of Ag, Au, Pd and
Pt in the microstructure of the iron alloy material, the iron alloy
material shows high corrosion rates when exposed to a biological
environment. The component therefore is particularly suitable for
use as a biocorrodible implant component which is implanted in a
living body, but corrodes and thus degrades over time when exposed
to a biological environment.
EXAMPLE
[0042] For producing an iron alloy material by an additive layer
construction method, a pulverulent pre-alloy powder having a mean
particle diameter of 40 .mu.m was produced by spray aeration in
argon inert gas atmosphere. The composition of the pre-alloy powder
was investigated by spark spectrometry and was determined to be, in
wt. %, 0.6 C, 22.4% Mn, 0.25% V, 0.2% Cr, and 0.25% Si, the balance
being Fe and usual impurities.
[0043] The pre-alloy powder was mixed with elementary Ag powder
having particle diameters of 25 to 63 .mu.m in a drum hoop mixer.
The Ag powder was obtained by spray aeration in argon inert gas
atmosphere. Powder mixtures containing 1 wt. %, 2 wt. % and 5 wt %
Ag were obtained. The powder mixtures were processed in argon
atmosphere using a SLM.RTM. 250.sup.HL machine (SLM Solutions GmbH)
in combination with SLM.RTM. AutoFab software (Marcam Engineering
GmbH) employing an yttrium fibre laser with a maximum power of 400
W. The microstructure of the iron alloy material generated from the
powder mixture by an additive layer construction method was
examined by SEM/BSE. Corrosion tests, were conducted for seven days
in 0.9% NaCl aqueous solution at a pH of 6.5. The mechanical
properties of the material were examined using samples having a
size of 8.times.3.times.1.5 mm grinded with 5 .mu.m abrasive paper.
The servo-hydraulic testing machine was operated with a
displacement rate of 20 .mu.m/s.
[0044] The microstructure of an iron alloy material generated from
the powder mixture containing 1 wt. % Ag by an additive layer
construction method is depicted in FIG. 2. In the microstructure of
the iron alloy material, Ag is present in the form of particles
finely dispersed more or less in an iron alloy matrix. The
particles have particle sizes in the range of 30 to 50 .mu.m.
[0045] Furthermore, it was determined that the iron alloy material,
due to the composition of the iron alloy matrix, upon deformation,
shows transformation induced plasticity. The mechanical properties
of the material at ambient temperature are summarized in Table 1
below.
TABLE-US-00001 TABLE 1 R.sub.m, MPa R.sub.p0.2, MPa pre-alloy 850
460 pre-alloy + 1 wt. % Ag 645 320 pre-alloy + 2 wt. % Ag 690 425
pre-alloy + 5 wt. % Ag 545 360
[0046] The presence of Ag in the microstructure of the iron alloy
material leads to high corrosion rates. The corrosion test revealed
a mass loss of the iron pre-alloy of 1.7 mg per cm.sup.2 sample
surface per day as compared to 2.3 mg per cm.sup.2 sample surface
per day for the pre-alloy with an addition of 5 wt. % Ag. The iron
alloy material therefore is particularly suitable for making
biocorrodible implant components.
* * * * *