Method of producing a cold compactible metallic powder

Abstract

The invention provides a method of producing a cold compactible metallic powder, the method comprising: providing (i) a first metallic powder comprising large metal particles and (ii) a second metallic powder comprising small metal particles, wherein the d50 particle size of the second metallic powder is less than the d50 particle size of the first metallic powder; combining at least the first metallic powder and the second metallic powder to provide a precursor powder comprising the large metal particles and the small metal particles; and subjecting the precursor powder to an impact blending process to adhere the small metal particles to the large particles, thereby producing a cold compactible metallic powder comprising non-spherical particles, wherein the non-spherical particles comprise one of the large metal particles as a core and a plurality of the small metal particles as protrusions from the core.

The invention claimed is: 
     
         1 . A method of producing a cold compactible metallic powder, the method comprising:
 providing (i) a first metallic powder comprising large metal particles and (ii) a second metallic powder comprising small metal particles, wherein the d50 particle size of the second metallic powder is less than the d50 particle size of the first metallic powder;   combining at least the first metallic powder and the second metallic powder to provide a precursor powder comprising the large metal particles and the small metal particles; and   subjecting the precursor powder to an impact blending process to adhere the small metal particles to the large particles, thereby producing a cold compactible metallic powder comprising non-spherical particles, wherein the non-spherical particles comprise one of the large metal particles as a core and a plurality of the small metal particles as protrusions from the core.   
     
     
         2 . The method of  claim 1 , wherein at least a portion of the small metal particles adhered to the large metal particles are metallurgically bonded to the large metal particles. 
     
     
         3 . (canceled) 
     
     
         4 . The method of  claim 1 , wherein the d50 particle size of the second metallic powder is no more than 40% of the d50 particle size of the first metallic powder. 
     
     
         5 . (canceled) 
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . The method of  claim 1 , wherein the large metal particles and the small metal particles have substantially the same metallic composition. 
     
     
         9 . The method of  claim 1 , wherein the large metal particles in the first metallic powder are substantially spherical. 
     
     
         10 . The method of  claim 1 , wherein subjecting the precursor powder to the impact blending process comprises impact blending the precursor powder in an impact blending chamber of an apparatus comprising (i) a stator which defines a cylindrical outer wall of the impact blending chamber, and (ii) a rotor operable to rotate in the impact blending chamber, the rotor comprising a plurality of impact blades having an impact face and an outer edge at the periphery of the rotor, wherein the apparatus further comprises a recirculation conduit between an entry port located in the cylindrical outer wall of the impact blending chamber and an exit port directed to a central portion of the impact blending chamber, wherein the precursor powder continuously recirculates through the recirculation conduit during the impact blending. 
     
     
         11 . (canceled) 
     
     
         12 . The method of  claim 10 , wherein the outer edge of each impact blade is spaced apart from the cylindrical outer wall by a gap distance in the range of 1 mm to 5 mm, and wherein the rotor is rotated such that the outer edge of each impact blade has a peripheral velocity of above 35 m/s during the impact blending. 
     
     
         13 . (canceled) 
     
     
         14 . The method of  claim 1 , wherein the precursor powder is impact blended for a time between 1 second and 10 minutes in a dry inert gas atmosphere. 
     
     
         15 . (canceled) 
     
     
         16 . The method of  claim 1 , wherein the large metal particles comprise a metallic composition having a yield stress of at least 600 MPa. 
     
     
         17 . The method of  claim 1 , wherein the large metal particles comprise a metallic composition having an elongation at break of at least 1%. 
     
     
         18 . The method of  claim 1 , wherein the large metal particles, and optionally also the small metal particles, comprise a metallic composition selected from the group consisting of titanium, tantalum, rhenium, niobium, vanadium, molybdenum, hafnium, zirconium, tungsten, chromium, nickel, cobalt, alloys thereof, metal matrix composites thereof, alloys of iron, alloys of zinc, alloys of magnesium, and alloys comprising both aluminium and copper. 
     
     
         19 . The method of  claim 1 , wherein the large metal particles, and optionally also the small metal particles, comprise a metallic composition selected from the group consisting of titanium, tantalum, niobium, and alloys thereof. 
     
     
         20 . The method of  claim 1 , wherein the large metal particles, and optionally also the small metal particles, comprise titanium or titanium alloy. 
     
     
         21 . The method of  claim 1 , wherein the large metal particles comprise titanium alloy and the small metal particles comprise a metallic composition selected from the group consisting of commercially pure titanium, titanium alloy, a master alloy for titanium, and mixtures thereof. 
     
     
         22 . (canceled) 
     
     
         23 . The method of  claim 1 , wherein the first metallic powder has a d50 particle size of between 80 μm and 500 μm. 
     
     
         24 . (canceled) 
     
     
         25 . (canceled) 
     
     
         26 . (canceled) 
     
     
         27 . (canceled) 
     
     
         28 . A cold compactible metallic powder comprising non-spherical particles, the non-spherical particles comprising a large titanium or titanium alloy particle as a core and a plurality of small metal particles as protrusions from the core, wherein at least a portion of the small metal particles are metallurgically bonded to the large titanium or titanium alloy particle. 
     
     
         29 . (canceled) 
     
     
         30 . A method of producing a porous metallic article, the method comprising:
 providing (i) a first metallic powder comprising large metal particles and (ii) a second metallic powder comprising small metal particles, wherein the d50 particle size of the second metallic powder is less than the d50 particle size of the first metallic powder;   combining at least the first metallic powder and the second metallic powder to provide a precursor powder comprising the large metal particles and the small metal particles;   subjecting the precursor powder to an impact blending process to adhere the small metal particles to the large particles, thereby producing a cold compactible metallic powder comprising non-spherical particles, wherein the non-spherical particles comprise one of the large metal particles as a core and a plurality of the small metal particles as protrusions from the core; and   subjecting the cold compactible metallic powder to a cold compaction process at a pressure sufficient to consolidate the cold compactible metallic powder, thereby producing a porous metallic article.   
     
     
         31 . The method of  claim 30 , wherein the porous metallic article has a density of at least 70% of theoretical density. 
     
     
         32 . The method of  claim 30 , wherein the pressure is below 450 MPa, and wherein the cold compactible metallic powder is subjected to the cold compaction process in the absence of a binder. 
     
     
         33 . (canceled) 
     
     
         34 . The method of  claim 30 , wherein the cold compaction process is selected from cold isostatic pressing, cold die pressing and direct powder rolling.