Cemented carbide body with increased wear resistance

Abstract

As there is disclosed a cemented carbide body comprising WC with an average grain size of <10 μm in a binder phase. In the cemented carbide body the WC grains can be classified in at least two groups in which a group of smaller grains has a maximum grain size a max and a group of larger grains has a minimum grain size b min and each group contains at least 10 % of the total amount of WC grains. According to the invention b min −a max >0.5 μm and the difference in grain size within each group is >1 μm.

1. A method of making a cemented carbide body comprising wet mixing without milling of at least two different WC-powders with deagglomerated powders of other carbides and a binder metal such that the WC-powers  WC- powders  are coated with the binder phase, said WC-grains being deagglomerated before and after being coated with binder metal, the grains of the WC-powder being classified in at least two groups in which a group of smaller grains has a maximum grain size a max  and a group of larger grains has a minimum grain size b min , each group containing at least 10% of the total amount of WC grains wherein b min −a max   >0.5 mm  μm , the variation in grain size within each group being >1 μm, drying said mixture, pressing to a desired shape and sintering said pressed bodies. 
     
     
       2. The method of  claim 1  wherein said other carbides comprise one or more of TiC, TaC and NbC. 
     
     
       3. The method of  claim 1  wherein said sintered bodies are coated with an Al 2 O 3  layer. 
     
     
       4. The method of  claim 1  wherein said two groups of WC-powder have grain size distributions of 0-1.5 μm and 2.5-6.0 μm, respectively. 
     
     
       5. The method of  claim 4  wherein the weight ratio of particles with a grain size distribution of 0-1.5 μm to 2.5-6.0 μm is from 0.25 to 4.0. 
     
     
       6. The method of  claim 5  wherein said weight ratio is from 0.5-2.0. 
     
     
       7. The method of  claim 1  wherein said sintered bodies have a CW- ratio of  0 . 82 - 1 . 0 .    
     
     
       8. The method of  claim 7  wherein said CW- ratio is  0 . 86 - 0 . 96 .    
     
     
       9. The method of  claim 3  wherein said sintered bodies have a CW- ratio of  0 . 82 - 1 . 0 .    
     
     
       10. The method of  claim 9  wherein said CW- ratio is  0 . 86 - 0 . 96 .    
     
     
       11. The method of  claim 4  wherein said sintered bodies have a CW- ratio of  0 . 82 - 1 . 0 .    
     
     
       12. The method of  claim 11  wherein said CW- ratio is  0 . 86 - 0 . 96 .    
     
     
       13. The method of  claim 5  wherein said sintered bodies have a CW- ratio of  0 . 82 - 1 . 0 .    
     
     
       14. The method of  claim 13  wherein said CW- ratio is  0 . 86 - 0 . 96 .