Infiltrated cobalt attachment ring for a CBN sintered body and its fabrication process

Abstract

A ring of infiltrated cobalt improves the attachment of CBN sintered bodies to its tungsten carbide substrate. A high concentration of cobalt found within the periphery of the CBN sintered body, but concentrated near its edges, creates a lattice of cobalt bonds intermixed with a lattice of CBN bonds and strengthen the connection of the two materials. Our process for improving CBN sintered bodies' attachment comprises of providing a mixture of aluminum grains, aluminum nitride grains, titanium grains, diamond grains and CBN grains to reacts in situ to form a preform of TiC, TiN, Al and CBN. Further, diamond will react as a reducing agent for the oxides found on surface areas of the grains in the mixture. The unique preform treated under high temperature and high pressure while adjacent to a tungsten carbide substrate allows for the cobalt infiltration.

1 . A CBN sintered body comprising of: 
 CBN grains;    metal binders;    and an attachment ring of infiltrated cobalt extending from an adjacent, cemented substrate and expanding into the sintered body;    and demonstrating a hardness of 3500 HV to 3900 HV.    
     
     
         2 . The CBN sintered body of  claim 1 , wherein the substrate is tungsten carbide with 6% cobalt.  
     
     
         3 . The CBN sintered body of  claim 1 , wherein the CBN grains are 90 to 93 weight percent of the sintered body.  
     
     
         4 . The CBN sintered body of  claim 1 , wherein the CBN grains are 93 to 97 weight percent of the sintered body.  
     
     
         5 . The CBN sintered body of  claim 1 , wherein the CBN grains are 50 to 70 weight percent of the sintered body.  
     
     
         6 . The CBN sintered body of  claim 1 , wherein the CBN grains are 1 to 3 microns.  
     
     
         7 . The CBN sintered body of  claim 1 , wherein 60% of the CBN grains are 4 to 8 microns, 30% of the CBN grains are 12 to 22 microns, and 10% of the CBN grains 1-2 microns.  
     
     
         8 . The CBN sintered body of  claim 1 , wherein the thickness of the attachment ring is 15 to 30 microns.  
     
     
         9 . The CBN sintered body of  claim 1 , wherein titanium carbide is a metal binder.  
     
     
         10 . The CBN sintered body of  claim 1 , wherein titanium nitride is a metal binder.  
     
     
         11 . The CBN sintered body of  claim 1 , wherein aluminum is a metal binder.  
     
     
         12 . A process for making a CBN sintered body according to  claim 1 , which comprises: 
 providing a mixture consisting of CBN grains, with some aluminum nitride grains, some aluminum grains, some titanium grains, and some diamond grains; 
 compacting the mixture adjacent to a substrate into a refractory metal container;  
 then heating the container in vacuum where the diamond reduces the mixture to form a preform of titanium carbide, titanium nitride, and aluminum;  
   and then sintering the preform by exposing it to high temperature and high pressure where cubic boron nitride is stable.    
     
     
         13 . The process of  claim 12 , where the CBN grains comprise 93 to 97 weight percent of the mixture.  
     
     
         14 . The process of  claim 12;  where the CBN grains comprise 90 to 93 weight percent of the mixture.  
     
     
         15 . The process of  claim 12 , where the CBN grains are 50 to 70 weight percent of the sintered body.  
     
     
         16 . The process of  claim 12 , where the CBN grains are 1 to 3 microns.  
     
     
         17 . The process of  claim 12 , where the 60% of the CBN grains are 4 to 8 microns, 30% of the CBN grains are 12 to 22 microns, and 10% of the CBN grains 1-2 microns.  
     
     
         18 . The process of  claim 12 , where the aluminum nitride grains comprise 0.5 to 1.5 weight percent of the mixture.  
     
     
         19 . The process of  claim 12 , where the aluminum nitride grains are 0.3 to 1 microns.  
     
     
         20 . The process of  claim 12 , where the aluminum grains comprise 0.5 to 1.5 weight percent of the mixture.  
     
     
         21 . The process of  claim 12 , where the aluminum grains are less than 1.5 microns.  
     
     
         22 . The process of  claim 12 , where the titanium grains comprise 0.5 to 1.5 weight percent of the mixture.  
     
     
         23 . The process of  claim 12 , where the titanium grains comprise 3 to 6 weight percent of the mixture.  
     
     
         24 . The process of  claim 12 , where the titanium grains are less than 1.5 microns.  
     
     
         25 . The process of  claim 12 , where the diamond grains comprise 1.5 to 2.5 weight percent of the mixture.  
     
     
         26 . The process of  claim 12 , where the diamond grains are 0.5 to 1.5 microns.  
     
     
         27 . The process of  claim 12 , where the substrate is tungsten carbide.  
     
     
         28 . The process of  claim 12 , where the vacuum is 10{circumflex over ( )}-5 torr to 10{circumflex over ( )}-6 torr.  
     
     
         29 . The process of  claim 12 , where the temperature in vacuum is 1200 to 1350 degrees C.