USE OF POWDERS OF HIGHLY REFLECTIVE METALS FOR ADDITIVE MANUFACTURE

Abstract

The present invention relates to the use of a metal powder for additively manufacturing a shaped metal body by means of laser beam melting, wherein the metal is a metal of Group 11 of the periodic table of the elements or aluminium or an alloy or intermetallic phase of one of these metals and has an oxygen content of at least 2500 ppm by weight.

Claims

1. Method for additively manufacturing a shaped metal body by means of laser beam melting, comprising (i) applying a metal powder in the form of a layer onto a substrate in a build chamber, wherein the metal is a metal of Group 11 of the periodic table of the elements or aluminium or an alloy or intermetallic phase of said metal and has an oxygen content of at least 2500 ppm by weight; (ii) selectively melting the metal powder in the layer by means of at least one laser beam and allowing the molten metal to solidify, (iii) applying a further layer of the metal powder onto the previously applied layer, (iv) selectively melting the metal powder in the further layer by means of the laser beam and allowing the molten metal to solidify; (v) repeating steps (iii)-(iv) until the shaped metal body has been completed.

2. Method according to claim 1, wherein the metal is copper, silver or gold or an alloy or intermetallic phase of one of these metals.

3. Method according to claim 1 or 2, wherein the oxygen content of the metal powder is 2500-15 000 ppm by weight, more preferably 3500-10 000 ppm by weight, more preferably still 5000-10 000 ppm by weight, most preferably 5500-10 000 ppm by weight.

4. Method according to any of the preceding claims, wherein the metal powder is produced via atomization in an oxygen-containing atmosphere.

5. Method according to any of the preceding claims, wherein the metal powder has particle sizes in the range of 1 to 100 μm.

6. Method according to any of the preceding claims, wherein the build chamber contains an inert or reducing gas atmosphere.

7. Method according to any of the preceding claims, wherein, after solidification of the molten metal and before application of a further layer, the solidified metal is subjected to a thermal treatment under reduced pressure or in a reducing gas atmosphere; and/or the shaped metal body is subjected to a thermal treatment under reduced pressure or in a reducing gas atmosphere after its completion.

8. Use of the metal powder according to any of claims 1-5 for additive manufacturing by means of laser beam melting.

Description

EXAMPLES

[0048] In the following examples and comparative examples, the following laser was used for the selective laser melting: Yb fibre laser, 1060-1100 nm.

Example 1

[0049] In Example 1, a copper powder having an oxygen content of 7300 ppm by weight was used. The powder had a volume-based particle size distribution having a d.sub.10 value of 20 μm and a d.sub.90 value of 52 μm.

[0050] The copper powder was applied to the build platform in the build chamber of the apparatus in the form of a thin layer (layer thickness of approximately 20 μm). Melting of the metal powder in defined regions of the applied layer was effected at room temperature. Argon was used as gas atmosphere in the build chamber. The laser melting step was subsequently started. The laser beam moved at a speed of 500 mm/s, with a beam power of 370 W and a spacing between adjacent lines of 70 μm, over a predefined area of 10×10 mm.sup.2 of the applied layer.

[0051] A stable melt bath formed with the copper powder used in Example 1.

[0052] Micrographs were produced of the area covered by the laser beam. The micrographs show a high-density structure. Porosity was only 0.3%.

[0053] The electrical conductivity (% IACS) of the shaped body before and after annealing (10 h at 800° C. under reduced pressure) was determined:

[0054] Before: 64%

[0055] After: 84%

[0056] Electrical conductivity was determined by the four-point method.

Example 2

[0057] In Example 2, a copper powder having an oxygen content of 5740 ppm by weight was used. The powder had a volume-based particle size distribution having a d.sub.10 value of 16 μm and a d.sub.90 value of 53 μm.

[0058] The experimental parameters were identical to those in Example 1.

[0059] A stable melt bath formed with the copper powder used in Example 2.

[0060] Micrographs were produced of the area covered by the laser beam. The micrographs show a high-density structure. Porosity was only 0.2%.

[0061] The electrical conductivity (% IACS) of the shaped body before and after annealing (15 h at 600° C. under reduced pressure) was determined:

[0062] Before: 66%

[0063] After: 82%

[0064] Electrical conductivity was determined by the four-point method.

Comparative Example 1

[0065] In Comparative Example 1, a copper powder having an oxygen content of 318 ppm by weight was used. The powder had a volume-based particle size distribution having a d.sub.10 value of 20 μm and a d.sub.90 value of 56 μm.

[0066] The copper powder was applied to a build platform under the same conditions as in Example 1 and subjected to laser beam treatment.

[0067] A stable melt bath could not be formed with the copper powder used in Comparative Example 1 and accordingly a mechanically stable high-density component could not be obtained.

[0068] Micrographs were produced of the area covered by the laser beam. The micrographs show a defect-rich structure. Porosity was >5%.

Comparative Example 2

[0069] In Comparative Example 2, a copper powder having an oxygen content of 2219 ppm by weight was used. The powder had a volume-based particle size distribution having a d.sub.10 value of 15 μm and a d.sub.90 value of 41 μm.

[0070] The copper powder was applied to a build platform under the same conditions as in Example 1 and subjected to laser beam treatment.

[0071] A stable melt bath could not be formed with the copper powder used in Comparative Example 2 and accordingly a mechanically stable high-density component could not be obtained.

[0072] Micrographs were produced of the area covered by the laser beam. The micrographs show a defect-rich structure. Porosity was 4.4%.

[0073] The results of the examples described above are summarized in Table 1 below.

TABLE-US-00001 TABLE 1 Stability of the melt bath and porosity of the solidified metal Example 1 Example 2 Comp. Ex. 1 Comp. Ex. 2 Oxygen content 7300 ppm 5740 ppm 318 ppm 2219 ppm of the powder by weight by weight by weight by weight Stable melt bath Yes Yes No No Porosity of the 0.3% 0.2% >5% 4.4% solidified metal