Method and apparatus for forming ultrafine metal powders

A method for producing metal powders from a pre-formed metal workpiece comprising:

• (a) focusing a laser beam below the surface of the workpiece;
• (b) moving the focal point of the laser beam relative to the workpiece;
• (c) creating a cavity within the workpiece through melting and vaporization with the laser beam, the cavity having a depth approximately 3 to 4 times greater than its width, the depth being between approximately one-quarter to one-half inch deep, the cavity containing the metal melted to form the cavity;
• (d) directing a pulsating blast of inert gas at the cavity to atomize the molten metal, rapidly cool the resulting droplets, and transport the droplets to a collection area.

A method for producing alloy metal powders by means of laser blast atomization, the steps comprising:

• (a) forming a workpiece of the base metal;
• (b) providing an alloying metal to the base metal;
• (c) focusing a laser beam below the surface of the workpiece;
• (d) moving the focal point of the laser beam relative to the workpiece;
• (e) creating a cavity within the workpiece through melting and vaporization with the laser beam;
• (f) melting the alloying material within the cavity and combining the melted alloy material with the base metal to form a molten metal solution;
• (g) directing a pulsating blast of inert gas at the cavity to atomize the molten metal solution, rapidly cool the resulting droplets, and transport the droplets to a collection area.

A method for producing alloy metal powders by means of laser blast atomization wherein the alloying metal has a higher vapor pressure in its molten state than the base metal, the steps comprising:

• (a) forming a workpiece of the base metal with a layer of alloying material a pre-determined distance below the surface thereof;
• (b) focusing a laser beam below the surface of the workpiece;
• (c) moving the focal point of the laser beam relative to the workpiece;
• (d) creating a cavity within the workpiece with the laser beam to the depth of the layer of alloying material, the cavity containing the metal and alloy addition melted during the formation of the cavity;
• (e) melting the layer of alloying material at the base of the cavity, where high vapor pressures, caused by the weight of the molten metal that forms the cavity walls, to prevent the alloying material from vaporizing prior to forming a solution with the molten base metal;
• and
• (f) directing a pulsating blast of inert gas at the cavity to atomize the molten metal solution, rapidly cool the resulting droplets, and transport the droplets to a collection area.

A method of producing alloy metal powders by means of laser blast atomization wherein the alloying metal has a melting temperature higher than the base metal, the steps comprising:

• (a) distributing the alloying metal over the surface of a workpiece made of the base metal;
• (b) focusing a laser beam below the surface of the workpiece;
• (c) moving the focal point of the laser beam relative to the workpiece;
• (d) creating a cavity within the workpiece through melting and vaporization with the laser beam, the cavity containing the metal and alloy addition melted to form a molten solution during the formation of the cavity;
• and
• (e) directing a pulsating blast of inert gas at the cavity to atomize the molten solution, rapidly cool the resulting droplets, and transport the droplets to a collection area.

A method of removing nonmetallic impurities from a workpiece when producing metal powders comprising:

• (a) focusing a laser beam below the surface of the workpiece;
• (b) slowly moving the focal point of the laser beam across the workpiece;
• (c) creating a cavity within the workpiece through melting and vaporization with the laser beam, the cavity containing the metal melted to form the cavity;
• (d) suspending the impurities in the molten metal within the cavity;
• (e) vaporizing the impurities with the laser beam;
• and
• (f) directing a pulsating blast of inert gas at the cavity to atomize the molten metal, rapidly cool the resulting droplets, and transport the droplets to a collection area.

An apparatus for producing ultrafine metal powders comprising, in combination,

• (a) containment means having an inert gas atmosphere therein;
• (b) means for supporting and moving a workpiece associated with the containment means;
• (c) laser beam means associated with the containment vessel so that the focal point of the laser beam is coincident with and penetrating into the workpiece;
• and
• (d) pulsating gas jet means associated with the containment vessel and directed toward the workpiece.