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, 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.

Claims

1.-6. (canceled)

7. An iron alloy material, comprising in wt. %: 0.01 to 1% C 0.01 to 30% Mn 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 2%, Cu at a content of 2%, Ti at a content of 2%, Co at a content of 2%, Zr at a content of 2%, V at a content of 2%, Nb at a content of 2%, Ta at a content of 2% and B at a content of 0.2%.

9. The iron alloy material according to claim 7, wherein the Ag content of the iron alloy material is 15%, in particular 10% and more particular 5%.

10. The iron alloy material according to claim 7, wherein the Ag content of the iron alloy material is 0.5%, in particular 1% and more particular 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

[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 15%, in particular 10% and more particular 5% of at least one of Ag, Au, Pd and Pt. Further, it is conceivable, to produce a powder mixture which contains 0.5%, in particular 1% and more particular 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, 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 2%, Cu at a content of 2%, Ti at a content of 2%, Co at a content of 2%, Zr at a content of 2%, V at a content of 2%, Nb at a content of 2%, Ta at a content of 2% and B at a content of 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 100 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 710.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 sinksdriven by gravityin 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 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 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 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 250.sup.HL machine (SLM Solutions GmbH) in combination with SLM 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 831.5 mm grinded with 5 m abrasive paper. The servo-hydraulic testing machine was operated with a displacement rate of 20 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 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.