Cold spray formation of thin metal coatings

Abstract

The invention relates to an adaptation of the cold spray process to provide a method of coating fine metal particles, including aluminum and copper, onto a work piece. In one embodiment, the invention is a metal agglomerated hard sphere composition capable of providing about a 1 micron or thicker coating of a metal on a work piece in a cold spray process. In another embodiment the invention is a method of coating metal particles, including metal particles having a particle size of about 0.01 to about 10 micron, onto a work piece. The method of the invention circumvents many of the problems associated with cold spray processing of very fine particles.

1 . A metal agglomerated hard sphere composition capable of providing about a 1 μm or thicker coating of a metal on a work piece in a cold spray process comprising: a plurality of non-ductile hard spheres, said spheres comprised essentially of material characterized by an elongation at break of less than 7% at room temperature, and further characterized by an average sphere diameter of about 10 to 300 μm; and about 0.1 to about 20 wt % metal powder comprising a plurality of metal particles characterized by an average particle size of about 10 nm to about 10 μm, said plurality of metal particles being agglomerated onto said hard spheres.  
   
   
       2 . A metal agglomerated hard sphere composition of  claim 1 , wherein said non-ductile hard spheres have an average sphere diameter of about 50 to about 100 μm.  
   
   
       3 . A metal agglomerated hard sphere composition of  claim 1  wherein the non-ductile hard spheres are comprised essentially of material selected from the group: glass, including A-glass (soda-lime) and E-glass (borosilicate), titanium oxide, zirconium oxide, magnesium oxide, scandium oxide, hafnium oxide, yttrium oxide, cerium oxide, garnet, steel and steel alloys.  
   
   
       4 . A metal agglomerated hard sphere composition of  claim 2 , wherein the non-ductile hard spheres are comprised essentially of material selected from the group: A-glass (soda-lime), E-glass (borosilicate), steel and steel alloys.  
   
   
       5 . A metal agglomerated hard sphere composition of  claim 1 , wherein said composition comprises about 1 to about 10 wt % metal powder.  
   
   
       6 . A metal agglomerated hard sphere composition of  claim 4 , wherein said composition comprises about 4 to about 6 wt % metal powder.  
   
   
       7 . A metal agglomerated composition of  claim 1 , wherein the metal powder is selected from the group of aluminum, copper, nickel, zinc, cobalt, iron, titanium, silver, gold, chromium, tungsten, and alloys thereof, and the intermetallics titanium aluminide, iron aluminide and nickel aluminide.  
   
   
       8 . A metal agglomerated composition of  claim 1 , wherein the metal powder is selected from the group of aluminum and copper.  
   
   
       9 . A metal agglomerated composition of  claim 6 , wherein the metal powder is selected from the group of aluminum and copper.  
   
   
       10 . A metal agglomerated composition of  claim 1 , wherein said metal powder is characterized by an average particle size of about 0.1 to about 5 μm and is comprised essentially of material characterized by an elongation at break greater than 10% at room temperature.  
   
   
       11 . A metal agglomerated hard sphere composition of  claim 2  wherein the non-ductile hard spheres are comprised essentially of A glass (soda-lime), and said composition comprises 4 to about 6 wt % aluminum powder characterized by a purity of greater than 99.0% and an average particle size of about 0.1 to about 5 μm.  
   
   
       12 . A method of coating metal particles, including metal particles having a particle size of about 0.01 to about 10 μm, onto a work piece surface with cold spray processing, comprising: 
 mixing, into a gas stream characterized by a working pressure and working temperature, a metal agglomerated hard sphere composition to provide a particle-gas stream, wherein said metal agglomerated hard sphere composition comprises a plurality of non-ductile hard spheres, said spheres comprised essentially of material characterized by an elongation at break of less than 7% at room temperature, and further characterized by an average sphere diameter of about 10 to 300 μm; and about 0.1 to about 20 wt % metal powder comprising a plurality of metal particles characterized by an average particle size of about 10 nm to about 10 μm, said plurality of metal particles being agglomerated onto said hard spheres;    accelerating said particle-gas stream into a supersonic jet; and    directing said supersonic jet onto a work piece, wherein said metal agglomerated hard sphere composition impinges said work piece surface at sufficient velocity to deposit said metal particles from said non-ductile hard spheres onto said work piece surface, thereby coating said work piece surface with a desired thickness of metal particles to provide a metal coating.    
   
   
       13 . A method of  claim 12  wherein said pressurized gas is selected from the group: nitrogen, air, helium, argon, other noble gases, carbon dioxide, and mixtures thereof.  
   
   
       14 . A method of  claim 13  wherein said pressurized gas is selected from the group: nitrogen, air, argon, and mixtures thereof.  
   
   
       15 . A method of  claim 12  wherein accelerating said particle-gas stream into a supersonic jet, is provided for by passing said particle-gas stream through a Laval nozzle.  
   
   
       16 . A method of  claim 14  wherein accelerating said particle-gas stream into a supersonic jet, is provided for by passing said particle-gas stream through a Laval nozzle.  
   
   
       17 . A method of  claim 12  wherein said working pressure is about 70 to about 500 psi and said working temperature is about 30 to about 600° C.  
   
   
       18 . A method of  claim 16  wherein said working pressure is about 90 to about 300 psi and said working temperature is about 200 to 400° C.  
   
   
       19 . A method of  claim 12  wherein said non-ductile hard spheres have an average sphere diameter of about 50 to about 100 μm and are comprised essentially of material selected from the group: A-glass (soda-lime), E-glass (borosilicate), steel and steel alloys.  
   
   
       20 . A method of  claim 18  wherein said non-ductile hard spheres have an average sphere diameter of about 50 to about 100 μm and are comprised essentially of material selected from the group: A-glass (soda-lime), E-glass (borosilicate), steel and steel alloys.  
   
   
       21 . A method of  claim 12 , wherein said non-ductile hard spheres are comprised essentially of A-glass (soda-lime).  
   
   
       22 . A method of  claim 20 , wherein said non-ductile hard spheres are comprised essentially of A-glass (soda-lime).  
   
   
       23 . A method of  claim 12  wherein said wherein said metal agglomerated hard sphere composition comprises about 1 to about 10 wt % metal powder.  
   
   
       24 . A method of  claim 12  wherein said wherein said metal agglomerated hard sphere composition comprises about 4 to about 6 wt % metal powder.  
   
   
       25 . A method of  claim 22  wherein said metal agglomerated hard sphere composition comprises about 4 to about 6 wt % metal powder.  
   
   
       26 . A method of  claim 12 , wherein said metal powder is selected from the group of aluminum, copper, nickel, zinc, cobalt, iron, titanium, silver, gold, chromium, tungsten, and alloys thereof; and the intermetallics titanium aluminide, iron aluminide and nickel aluminide.  
   
   
       27 . A method of  claim 12 , wherein said metal powder is selected from the group of aluminum and copper.  
   
   
       28 . A method of  claim 25 , wherein said metal powder is selected from the group of aluminum and copper.  
   
   
       29 . A method of  claim 12 , wherein said metal powder is characterized by an average particle size of about 0.1 to about 5 μm and is comprised essentially of material characterized by an elongation at break greater than 10% at room temperature.  
   
   
       30 . A method of  claim 28 , wherein said metal powder is characterized by an average particle size of about 0.1 to about 5 μm.  
   
   
       31 . A method of  claim 12  wherein said work piece comprises material selected from the group: metal, metal alloy, ceramic, organic polymer including dielectrics, concrete and wood.  
   
   
       32 . A method of  claim 31  wherein said work piece comprises aluminum coated steel.  
   
   
       33 . A method of  claim 28  wherein said work piece comprises aluminum coated steel.  
   
   
       34 . A method of  claim 12  comprising the additional and preliminary step of cleaning said work piece surface by providing a stream of non-ductile hard particles in a carrier gas, said particles characterized by an average particle diameter of about 10 to about 300 μm and selected from the group of: ceramic material having a Mohs hardness greater than 4.0 and metallic material having a Rockwell hardness on the C scale greater than 40; said stream being directed onto said work piece surface at a velocity sufficient to abrade said work piece surface to provide a clean work piece surface.  
   
   
       35 . A method of  claim 33  comprising the additional and preliminary step of cleaning said work piece surface by providing a stream of non-ductile hard particles in a carrier gas, said particles characterized by an average particle diameter of about 10 to about 300 μm and selected from the group of: ceramic material having a Mohs hardness greater than 4.0 and metallic material having a Rockwell hardness on the C scale greater than 40; said stream being directed onto said work piece surface at a velocity sufficient to abrade said work piece surface to provide a clean work piece surface.  
   
   
       36 . A method of  claim 12  comprising the additional step of shot-peening said metal coating by providing a stream of non-ductile hard particles in a carrier gas, said particles characterized by an average particle diameter of about 10 to about 300 μm and selected from the group of: ceramic material having a Mohs hardness greater than 4.0 and metallic material having a Rockwell hardness on the C scale greater than 40; said stream being directed onto said work piece surface at a velocity sufficient to densify said metal coating and/or act to modify said coating thickness.  
   
   
       37 . A method of  claim 35  comprising the additional step of shot-peening said metal coating by providing a stream of non-ductile hard particles in a carrier gas, said particles characterized by an average particle diameter of about 10 to about 300 μm and selected from the group of: ceramic material having a Mohs hardness greater than 4.0 and metallic material having a Rockwell hardness on the C scale greater than 40; said stream being directed onto said work piece surface at a velocity sufficient to densify said metal coating and/or act to modify said coating thickness.  
   
   
       38 . A metal coating derived from the method of  claim 12 .  
   
   
       39 . A metal coating of  claim 38  wherein said metal powder is selected from the group of aluminum and copper.  
   
   
       40 . A metal coating of  claim 39  wherein said work piece comprises material selected from the group: metal, metal alloy, ceramic, organic polymer including dielectrics, concrete and wood.