Ni-coated ti powders

Abstract

The present invention relates to coated powder, comprising a Ti-bearing core and a Ni-bearing coating, which can be used for the production of porous Ni—Ti articles by the self-propagating high temperature synthesis (SHS) method. The obtained articles are ideally suited for use in biomedical applications. According to the invention, a coated powder is used comprising a metallic Ti-bearing core and a metallic Ni-bearing coating, characterised by a Ni:Ti atomic ratio of more than 0.5, preferably between 0.9 and 1.1, and more preferably between 0.96 and 1.04. By using coated powders, local fluctuations in composition are limited and well under control. Milling of powders and the ensuing contamination risks are avoided. The sintered objects obtained using coated powders have a more homogeneous porosity than that using mixed Ni and Ti powders.

1 . Coated powder, comprising a metallic Ti-bearing core and a metallic Ni-bearing coating, characterised by a Ni:Ti atomic ratio of more than 0.5, preferably between 0.9 and 1.1, and more preferably between 0.96 and 1.04.  
   
   
       2 . Coated powder according to  claim 1 , wherein the Ti-bearing core consists of metallic Ti and the Ni-bearing coating consists of metallic Ni.  
   
   
       3 . Powder mixture comprising coated powder according to  claim 1 , further comprising one or both of Ni-bearing powder and Ti-bearing powder, wherein the Ni:Ti atomic ratio of the mixture is between 0.9 and 1.1, preferably between 0.99 and 1.01.  
   
   
       4 . Coated powder according to  claim 1 , characterized by a particle size finer than 150 mesh.  
   
   
       5 . Use of a coated powder according to  claim 1  for the manufacture of a sintered body.  
   
   
       6 . Use of a coated powder according to  claim 5 , characterised in that the sintered body is obtained by a self-propagating high temperature process.  
   
   
       7 . A sintered body obtainable by a self-propagating high temperature process using powders according to  claim 1 .  
   
   
       8 . Process of manufacturing a coated powder according to  claim 1 , comprising the steps of: 
 providing for suitable quantities of a Ti-bearing powder and of a Ni salt bearing aqueous solution;    feeding said powder and said solution in an autoclave together with a quantity of NH 4 OH, and, optionally, with a quantity of ammonium salts;    precipitating the Ni onto the Ti-bearing powder by hydrogen reduction;    washing, filtering and drying the slurry obtained, thereby obtaining a Ni-coated Ti powder.    
   
   
       9 . Process according to  claim 8 , whereby the Ni is precipitated onto the Ti-bearing powder at a temperature of at least 100° C. and a hydrogen pressure in the autoclave of at least 1.4 MPa.  
   
   
       10 . Process of manufacturing a coated powder according to  claim 3 , comprising the steps of: 
 providing for suitable quantities of a Ti-bearing powder and of a Ni salt bearing aqueous solution;    feeding said powder and said solution in an autoclave together with a quantity of NH 4 OH, and, optionally, with a quantity of ammonium salts;    precipitating the Ni onto the Ti-bearing powder by hydrogen reduction: and washing, filtering and drying the slurry obtained, thereby obtaining a Ni-coated Ti powder; and    further comprising the step of intimately mixing the Ni-coated Ti powder with one or both of Ni-bearing and Ti-bearing powder.    
   
   
       11 . Process of manufacturing a porous sintered body based on a Ni—Ti alloy, comprising the steps of  claim 8 , and further comprising the step of subjecting the powder or powder mixture to a self-propagating high temperature synthesis operation.  
   
   
       12 . A sintered body obtainable by a process according to  claim 11.