Process to enhance brazability of carbide bits

Abstract

The present invention teaches a method in which a cemented carbide product is prepared such that the ease and quality of brazing is improved. The process involves a controlled heat treatment such that the surface of the carbide is enriched with cobalt from the carbide matrix. This cobalt surface enhances the wettability and flow during brazing and provides for improved bond strength.

1 . A method for treating cemented carbide products comprising the steps of: 
 a. heat treatment in a furnace at a temperature of 1800° F. to 2500° F. under a partial or complete vacuum for 1 to 60 minutes,    b. quenching, or rapidly cooling said products,    whereby the surface of said cemented carbide becomes enriched with the metal or alloy from the matrix of the cemented carbide.    
     
     
         2 . The method of  claim 1  wherein said cemented carbide products primarily consist of a composite of tungsten carbide and cobalt and optionally, additional elements and carbides.  
     
     
         3 . The method of  claim 1  wherein said enrichment of the surface of the carbide product is by the metal cobalt, or by an alloy that comprises at least in part cobalt, which is contained in the matrix of the cemented carbide.  
     
     
         4 . The method of  claim 1  wherein said heat treatment is directly preceded by an initial lower temperature heat treatment step.  
     
     
         5 . The method of  claim 1  wherein a higher temperature sintering operation directly precedes said heat treatment.  
     
     
         6 . The method of  claim 1  wherein said heat treatment is performed at a temperature of 2000° F. to 2200° F., under a 30% partial vacuum for 12 minutes.  
     
     
         7 . The method of  claim 1  wherein said quenching is achieved through the introduction of nitrogen gas into the furnace chamber.  
     
     
         8 . The method of  claim 1  wherein said enrichment of the surface of the cemented carbide is used to enhance the brazing ability of the carbide.  
     
     
         9 . The method of  claim 1  wherein said enrichment of the surface of the cemented carbide is used to enhance the wear resistance and service life of the carbide.  
     
     
         10 . A method for treating cemented carbide products comprising the steps of: 
 a. pre-heating in a furnace at a temperature of 1500° F.,    b. evacuating the furnace resulting in at least a partial vacuum or reduction of atmospheric pressure,    c. increasing the temperature of the furnace at a rate of 5° F.-50° F. per minute until a temperature of 1800° F. to 2500° F. is attained,    d. holding the parts in the furnace for a period of 1 to 60 minutes,    e. quenching, or rapidly cooling said products via the introduction of nitrogen gas into the furnace,    whereby the surface of said cemented carbide becomes enriched with cobalt from the matrix of the cemented carbide.    
     
     
         11 . The method of  claim 10  wherein said cemented carbide products primarily consist of a composite of tungsten carbide and cobalt and optionally, additional elements and carbides.  
     
     
         12 . The method of  claim 10  wherein said heat treatment is preformed under a 20-60% of atmosphere, partial vacuum.  
     
     
         13 . The method of  claim 10  wherein said enrichment of the surface of the cemented carbide is used to enhance the brazing ability of the carbide.  
     
     
         14 . The method of  claim 10  wherein said enrichment of the surface of the cemented carbide is used to enhance the wear resistance and service life of the carbide.  
     
     
         15 . A method for treating cemented carbide products comprising the steps of: 
 a. heat treatment in a furnace at a temperature of 1800° F. to 2500° F. while excluding oxygen from the surface of the products for 1 to 60 minutes,    b. quenching, or rapidly cooling said products,    whereby the surface of said cemented carbide becomes enriched with the metal or alloy from the matrix of the cemented carbide.    
     
     
         16 . The method of  claim 15  wherein said cemented carbide products primarily consist of a composite of tungsten carbide and cobalt and optionally, additional elements and carbides.  
     
     
         17 . The method of  claim 15  wherein said enrichment of the surface of the carbide product is by the metal cobalt, or by an alloy that comprises at least in part cobalt, which is contained in the matrix of the cemented carbide.  
     
     
         18 . The method of  claim 15  wherein said heat treatment is directly preceded by an initial lower temperature heat treatment step.  
     
     
         19 . The method of  claim 15  wherein a higher temperature sintering operation directly precedes said heat treatment.  
     
     
         20 . The method of  claim 15  wherein said exclusion of oxygen is achieved by introducing an inert gas into the furnace chamber.  
     
     
         21 . The method of  claim 15  wherein said exclusion of oxygen is achieved by mechanically encapsulating the product, such as in a metal foil or by a paint or suspension that seals the surface of the product.  
     
     
         22 . The method of  claim 15  wherein said quenching is achieved through the introduction of a gas into the furnace chamber.