hard-metal body

Abstract

The invention relates to hard-metal body comprising a hard-metal, the hard-metal comprising tungsten carbide grains and metal binder comprising cobalt having a concentration of tungsten dissolved therein, the body comprising a surface region adjacent a surface and a core region remote from the surface, the surface region and the core region being contiguous with each other; the mean binder fraction of the core region being greater than that of the surface region; the mean carbon concentration within the binder being higher in the surface region than in the core region; to tools comprising same and methods of making same.

1 . A hard-metal body comprising a hard-metal, the hard-metal comprising tungsten carbide grains and metal binder comprising cobalt having a concentration of tungsten dissolved therein, the body comprising a surface region adjacent a surface and a core region remote from the surface, the surface region and the core region being contiguous with each other; the mean binder fraction of the core region being greater than that of the surface region; the mean carbon concentration within the binder being higher in the surface region than in the core region; and the mean magnetic moment of the hard-metal in the surface region being greater than that in the core region; the hard-metal body being substantially devoid of eta-phase and free carbon; and the concentration in weight percent of tungsten dissolved in the binder in the surface region being less than that in the core region, the concentration in weight percent of tungsten dissolved in the binder being determined as (16.1−σ B )/0.275; σ B  being the magnetic moment of the hard-metal within a region of the hard-metal body divided by the binder weight fraction in the region, in which the mean magnetic moment of the hard-metal body in units of micro-Tesla times cubic metre per kilogram of the material is in the range from 0.131X to 0.161X within the surface region, and in the range from 0.110Y to 0.147Y within the core region, X and Y being respectively the weight percent of the cobalt within the surface and core regions; both X and Y being at least about 1 and at most about 50 weight percent. 
     
     
         2 . (canceled) 
     
     
         3 . A hard-metal body as claimed in  claim 1 , in which the concentration of tungsten dissolved in the binder within the surface region is less than 7.6 weight percent. 
     
     
         4 . (canceled) 
     
     
         5 . A hard-metal body as claimed in  claim 1 , in which the hardness-toughness coefficient of the surface region is at least 20,000 in units of Vickers hardness times MPa·m 1/2 , the fracture toughness being the K 1C  value measured by the Palmquist method. 
     
     
         6 . A hard-metal body as claimed in  claim 1 , in which the surface region comprises binder phase in a state of residual stress in the range from −500 MPa to 300 MPa. 
     
     
         7 . (canceled) 
     
     
         8 . A hard-metal body as claimed in  claim 1 , in which the mean grain size of the metal carbide grains within the core region is within 5 percent of that within the surface region. 
     
     
         9 . (canceled) 
     
     
         10 . A hard-metal body as claimed in  claim 1 , in which the mean hardness of the hard-metal within the surface region is within the range from 2 percent to 50 percent higher than the mean hardness of the hard-metal within the core region. 
     
     
         11 . A tool insert for cutting, machining, drilling or otherwise forming or degrading a workpiece or other body, the tool insert comprising a hard-metal body as claimed in  claim 1 . 
     
     
         12 . A tool insert as claimed in  claim 11 , comprising polycrystalline diamond (PCD) or a polycrystalline cubic boron nitride (PCBN) structure joined to the hard-metal body. 
     
     
         13 . A tool comprising a tool insert as claimed in  claim 12 . 
     
     
         14 . (canceled)