ADDITIVE MANUFACTURING OF REFRACTORY METALS WITH REDUCED LEVEL OF CONTAMINATION

Abstract

Additive manufacturing method for producing moldings comprising or consisting of an element selected from the group of refractory metals, wherein refractory metal powder having an oxygen content of at least 500 mol ppm is used for the additive manufacturing method.

Claims

1. An additive manufacturing method for producing moldings comprising an element selected from the group of refractory metals, the method comprising the steps of: a) applying a first powder layer onto a substrate, wherein the powder comprises or consists of refractory metal, b) selectively melting at least a portion of the powder layer by means of electron beam, c) cooling the melt below the solidification temperature to obtain a first material layer, d) applying a further powder layer onto the first material layer, wherein the powder comprises or consists of refractory metal, e) selectively melting at least a portion of the further powder layer by means of electron beam, f) cooling the melt below the solidification temperature to obtain a further material layer, g) repeating steps d)-f) until the molding is completely constructed, wherein the powder of the powder layers in step a) and d) respectively has an oxygen content of at least 500 mol ppm.

2. The additive manufacturing method of claim 1, wherein the melting in steps b) and e) respectively takes place with a volume energy of at least 40 J/mm.sup.3.

3. The additive manufacturing method of claim 1, wherein the oxygen content of the powder of the powder layer is at most 5000 mol ppm.

4. The additive manufacturing method of claim 1, wherein the refractory metal is selected from niobium and tungsten.

5. The additive manufacturing method of claim 1, wherein the particles of the powder have an average particle size diameter d.sub.50 in the range from 10 to 150 μm.

6. The additive manufacturing method of claim 1, wherein the molding has an oxygen content which is at least 15% lower than the oxygen content of the powder.

7. The additive manufacturing method of claim 1, wherein the molding has an oxygen content which is at least 25% lower than the oxygen content of the powder.

8. The additive manufacturing method of claim 1, wherein the powder layers in steps a) and d) contain essentially no carbon or carbonaceous compounds.

9. The additive manufacturing method of claim 1, wherein each or essentially each volume element of the molding to be produced is melted and respectively solidifies thereafter at least twice.

10. The additive manufacturing method of claim 1, wherein the powder has a dio value of at least 10 μm and a d.sub.90 value of at most 200 μm.

11. A molding produced from a refractory metal powder having an oxygen content of at least 500 mol ppm by means of additive manufacturing using an electron beam.

12. The molding of claim 11, wherein the refractory metal powder has been produced by means of EIGA or precipitation.

13. The molding of claim 11, wherein the molding has a relative density of at least 95%.

14. The molding of claim 11, wherein the molding has an oxygen content which is at least 15% lower than the oxygen content of the refractory metal powder.

15. The molding of claim 11, wherein the energy input by the electron beam is at least 40 J/mm.sup.3.

16. The additive manufacturing method of claim 1, wherein the refractory metal is niobium.

17. The additive manufacturing method of claim 1, wherein the particles of the powder have an average particle size diameter d.sub.50 in the range from 10 μm-100 μm.

18. The additive manufacturing method of claim 1, wherein the particles of the powder have an average particle size diameter d.sub.50 in the range from 10-50 μm.

Description

EXAMPLES

[0085] The general invention is clarified in the following section based on specific examples.

[0086] Respective cubes (10×10×10 mm) were produced from different refractory metal powders by means of selective electron beam melting, and the oxygen content and the density were determined. The following system was used for electron beam melting: Arcam A2X by Arcam AB. The manufacturing condition and the oxygen content of the respective powders that are used, and of the components produced therefrom, can be found in Table 1. As can be seen from the data, a reduction in oxygen content in the finished molding can be observed as a function of the energy input (indicated as volume energy in J/mm.sup.3). Below a certain value, the oxygen content even increases, whereas the oxygen content in the molding decreases above 20 J/mm.sup.3.

TABLE-US-00001 TABLE 1 Oxygen content in Powder Average molding grain Volume O relative to size d.sub.50 energy content powder Material μm (J/mm.sup.3) mol ppm mol % 1  Niobium Powder 45-106 987 1a Niobium Molding 20 1516 154 2  Niobium Powder 45-106 1413 2a Niobium Molding 120 1123 81 3  Niobium Powder 45-106 1976 3a Niobium Molding 141 1618 82 4  Niobium Powder 45-106 671 4a Niobium Molding 141 549 82 5  Niobium Powder 45-106 2832 5a Niobium Molding 160 2104 74 6  Niobium Powder 45-106 3085 6a Niobium Molding 240 1644 53 6b Niobium Molding 340 1450 47 6c Niobium Molding 440 1385 45 6d Niobium Molding 600 1089 35 7  Tungsten Powder 45-106 2080 7a Tungsten Molding 20 3263 157 7b Tungsten Molding 50 1310 63 7c Tungsten Molding 100 1126 54 8  Tungsten Powder 45-106 569 8a Tungsten Molding 336 236 41 9  Tungsten Powder 45-106 925 9a Tungsten Molding 600 40 4 10  Tungsten Powder 15-45  971 10a  Tungsten Molding 600 46 5

[0087] For example, the oxygen content in an additively manufactured tungsten molding can be reduced by 96 mol % relative to the oxygen content in the powder (cf. Example 9/9a). The oxygen content of a niobium molding can be reduced by 65 mol % relative to the oxygen content of the powder that is used, for example. It is thus also possible to use refractory metal powders having a comparatively high oxygen content in order to produce moldings having a markedly lower oxygen content.