Method for the powder-metallurgical production of metal foamed material and of parts made of metal foamed material

1. A method for a powder-metallurgical production of a metal foamed material and of parts made of metal foamed material, the method comprising:

mixing a pulverulent metallic material including at least one of a metal and a metal alloy;

pressing, under mechanical pressure, the mixed pulverulent metallic material so as to form a dimensionally stable semi-finished product;

placing the semi-finished product into a chamber that is configured to be sealed pressure-tight;

sealing the chamber;

heating the semi-finished product to a melting or solidus temperature of the pulverulent metallic material;

once the melting or solidus temperature has been reached, reducing the pressure in the chamber from an initial pressure to a final pressure of at least 1 bar so that the semi-finished product foams without the use of a foaming agent so as to form a metal foam; and

lowering the temperature of the metal foam so as to solidify the metal foam.

2. The method according to claim 1 , further comprising pretreating the pulverulent metallic material by modifying a surface of an individual powder grains of the pulverulent metallic material.

3. The method according to claim 2 , wherein the pulverulent metallic material is pretreated through oxidation or moistening.

4. The method according to claim 1 , wherein the pulverulent metallic material includes powder grains having dimensions that average about 1 μm to 100 μm.

5. The method according to claim 1 , wherein the pressing includes compacting the mixed pulverulent metallic material at a gas pressure between 1 bar and 50 bar as well as at a mechanical pressure ranging from 200 MPa to 400 MPa at a temperature of less than 400° C.

6. The method according to claim 1 , further comprising pretreating the semi-finished product so as to modify the surface by at least one of oxidation, electrolytic oxidation or moistening.

7. The method according to claim 1 , wherein the sealed chamber has a defined gas atmosphere.

8. The method according to claim 7 , wherein the defined gas atmosphere is an oxygen atmosphere.

9. The method according to claim 7 , wherein the defined gas atmosphere is moist air.

10. The method according to claim 1 , wherein the initial pressure is less than approximately 50 bar before or while the semi-finished product is heated.

11. The method according to claim 10 , wherein, once the melting or solidus temperature of the pulverulent metallic material has been reached, the pressure in the sealed chamber is reduced according to a prescribed gradient from the initial pressure to the final pressure, the final pressure being about 1 bar.

12. The method according to claim 1 , wherein the reducing is performed from the initial pressure to the final pressure within a time span of about 1 second to 1000 seconds.

13. The method according to claim 1 , wherein the temperature in the chamber is only lowered after the beginning of the pressure reduction according to a prescribed gradient, whereby the solidification temperature of the pulverulent metallic material is only reached after the final pressure has been reached.

14. The method according to claim 1 , further comprising systematically setting the size of the pores in the metal foam within a range from approximately 0.1 mm to approximately 10 mm by selecting a pressure differential between the initial pressure and the final pressure.

15. The method according to claim 13 , wherein the reducing the pressure is terminated and the lowering the temperature is subsequently performed so as to lower the temperature of the metal foam below the solidification temperature of the pulverulent metallic material so as to terminate an increase of a pore size in the metal foam.

16. The method according to claim 1 , wherein the reducing the pressure is performed so as to set a volume expansion of the metal foam to about ten times an initial volume.

17. The method according to claim 16 , wherein the reducing the pressure is terminated and the lowering of the temperature is subsequently performed so as to lower the temperature of the metal foam below the solidification temperature so as to terminate a volumetric expansion of the metal foam.

18. The method according to claim 1 , wherein the lowering the temperature is performed so as to solidly the metal foam so as to provide a dimensionally stable metal foam object.