Method of solid pcbn sythesis

Abstract

The invention generally relates to a sintered CBN composite compact having a non-CBN portion. The compact includes about 86 to about 90% CBN and the non CBN portion contains borides and nitrides of Al. The compact is for use as a cutting tool insert in continuous machining of gray cast iron. The sintered compact has a thermal conductivity of 1.25-4 W/cm/° K. in the temperature range of about 200° C. to about 600° C. and sonic velocity of at least about 14.5 Km/sec at room temperature.

1 .- 7 . (canceled) 
     
     
         8 . A process for making a sintered compact, the steps comprising:
 preparing a mixture consisting essentially of about 91 to about 94 weight % cBN and about 6 to about 10 weight % Al; and   producing a sintered compact by applying high pressure and high temperature conditions to the material,   wherein the compact has a cBN grain size distribution that is at least bimodal and comprises about 80% coarse particles ranging in size from about 10 to about 60 μm and about 20% fine particles ranging in size from about 1 about 12 μm.   
     
     
         9 . The process of  claim 8 , wherein the content of said Al is about 6 wt % to about 8 wt %. 
     
     
         10 . The process of  claim 8 , wherein said compact has a thermal conductivity at room temperature of about 1.25 to about 4 W/cm ° K in the temperature range of about 200° C. to about 600° C. 
     
     
         11 . The process of  claim 8 , wherein said compact has a sonic velocity of at least about 14.5 km/s. 
     
     
         12 . (canceled) 
     
     
         13 . (canceled) 
     
     
         14 . A process for making a sintered compact, the steps comprising:
 preparing a mixture consisting essentially of about 91 to about 94 weight % cBN and about 7.5 weight % Al; and   producing a sintered compact by applying high pressure and high temperature conditions to the material,   wherein the compact has a cBN grain size distribution that is at least bimodal and comprises about 80% coarse particles ranging in size from about 10 to about 60 μm and about 20% fine particles ranging in size from about 1 about 12 μm.