Double-layer metal sheet and method of fabricating the same

Abstract

A method of bonding two powder components having different shrinkage factors, one of which is metal powder, is disclosed herein. In the preferred method, at step 1.1 , each powder component is separately mixed with a powder binder to substantially match the other powder component's shrinkage factor. Then at steps 1.2 to 1.4 , the powder component mixtures are compacted in a die set to form a green compact. Next at step 1.5 , the green compact is debindered and at step 1.6 , the green compact is sintered in a furnace while applying pressure on a surface of the green compact during the sintering process. In this way, the two powder components can be bonded directly without a need for an intermediate gradient zone and a double-layer metal sheet can be thus formed.

1 . A method of bonding two metal powder components having different shrinkage factors, the method comprising the steps of: 
 i. mixing one of the powder components with a powder binder to reduce the shrinkage difference between the powder components,    ii. forming a green compact from the powder component mixtures,    iii. sintering the compact to form a permanent bond between the two powder components, and    iv. applying pressure on a surface of the compact during the sintering step (iii).    
     
     
         2 . A method according to  claim 1 , further comprising mixing the other metal powder component with powder binder before the compacting step (ii).  
     
     
         3 . A method according to  claim 2 , wherein one of the metal powder is mixed with three to five weight % of powder binder.  
     
     
         4 . A method according to  claim 2 , wherein one of the metal powder is mixed with five to fifteen weight % of powder binder.  
     
     
         5 . A method according to  claim 1 , further comprising a step of removing the powder binder in a debinding furnace prior to the sintering step.  
     
     
         6 . A method according to  claim 1 , wherein the powder binder is removed in a sintering furnace followed by the sintering step.  
     
     
         7 . A method according to  claim 1 , wherein the green compact is formed in a die.  
     
     
         8 . A method according to  claim 7 , further comprising the steps of arranging one of the powder component mixtures in the die as a base layer, arranging the other powder component mixture on top of the base layer; and compressing the powder component mixtures together to form a desired shape of the compact.  
     
     
         9 . A method according to  claim 1 , wherein the pressure applied on the surface of the compact during the sintering step is between 2 g/cm 2  and 10 g/cm 2 .  
     
     
         10 . A method according to  claim 1 , wherein the pressure applied on the surface of the compact during the sintering step is more than 10 g/cm 2 .  
     
     
         11 . A method according to  claim 9 , wherein the pressure is produced by a ceramic plate.  
     
     
         12 . A method according to  claim 11 , wherein the ceramic plate is placed directly on the surface of the compact during the sintering step.  
     
     
         13 . A method according to  claim 11 , wherein the ceramic plate is spaced from the compact.  
     
     
         14 . A method according to  claim 13 , wherein the space between the plate and the compact is 50 to 100 microns.  
     
     
         15 . A method according to  claim 1 , wherein the green compact is formed by tape casting.  
     
     
         16 . A method according to  claim 15 , further comprising the step of mixing the powder component mixtures with a solvent and polymer binder to form respective slurry mixtures prior to the compacting step.  
     
     
         17 . A method according to  claim 16 , further comprising the step of layering one slurry mixture on top of the other to form a double layer slurry.  
     
     
         18 . A method according to  claim 17 , further comprising the step of heating the double layer slurry to form the compact.  
     
     
         19 . A method according to  claim 1 , wherein the compact is formed by powder rolling.  
     
     
         20 . A metal part produced using the method according to  claim 1 .  
     
     
         21 . A double layer plate produced using the method according to  claim 1 .  
     
     
         22 . A method of preparing a green compact from two metal powder components having different shrinkage factors, the method comprising the steps of: 
 i. mixing at least one powder component with a powder binder to reduce the shrinkage difference between the two metal powder components; and    ii. foirming a green compact from the powder component mixtures.    
     
     
         23 . A method of producing a metal part from a green compact formed from two metal powder components having different shrinkage factors, the method comprising the steps of: 
 i. sinteling the green compact to form a permanent bond between the two powder components; and    ii. applying pressure on a surface of the green compact during the sintering step (i).