Production of component parts by metal injection moulding (mim)

Abstract

The invention relates to a method for producing component parts with a high degree of dimensional precision, made of NiTi-shape memory alloys. The invention makes it possible to apply a known metal injection moulding method to NiTi-shape memory alloys by adapting the binding system, temperature control and reducing the time necessary for debinding.

1 . A method of making component parts from prealloyed NiTi shape memory alloys with the use of metal injection molding with the steps of 
 prealloyed NiTi powder is mixed with a thermoplastic binder to a feed stock, using an injection stage, the thus formed feed stock is introduced into the mold for the component parts,    the component parts are brought into contact with a capillary-active material and are predebinded,    the component parts are then subjected to a thermal debinding process,    the component parts freed from binder are sintered.    
     
     
         2 . A method according to the preceding claim, characterized by the use of a two-component binder on a wax basis.  
     
     
         3 . A method according to one of the preceding claims, characterized by a binder encompassing polyolefin.  
     
     
         4 . A method according to one of the preceding claims, characterized by a binder encompassing 50 to 65% of amide wax and 35 to 50 weight % polyolefin.  
     
     
         5 . A method according to one of the preceding claims, characterized by a binder with a content of 64.4 weight % amide wax of 42.9 weight % polyolefin.  
     
     
         6 . A method according to one of the preceding claims, characterized by a feed stock with a viscosity between 5 and 30 Pa.s.  
     
     
         7 . A method according to one of the preceding claims, characterized by a partial debinding process in which initially an amide wax is removed from the interior of the green body.  
     
     
         8 . A method according to a preceding claim in which the amide wax is removed by capillary force induced sucking up with the aid of a powder packing.  
     
     
         9 . A method according to a preceding claim in which the powder packing has a particle size which is less than the particle size of the NiTi powder used.  
     
     
         10 . A method according to one of the preceding  claims 7  to  9  in which a filter paper is interposed between the green part and the powder packing.  
     
     
         11 . A method according to one of the preceding  claims 7  to  10  using a ZrO 2  powder packing.  
     
     
         12 . A method according to one of the preceding  claims 7  to  11  in which the powder packing has a particle size which is less than the particle size of the metal powder used, especially with particle sizes in the range of 0.01 to 1 μm.  
     
     
         13 . A method according to one of the preceding  claims 7  to  12  in which the debinding process is carried out at temperatures between 120° C. and 480° C.