Hard Metal Having Toughness-Increasing Microstructure

Abstract

The invention relates to a nanoscale or ultrafine hard metal, comprising tungsten carbide, an additional metal carbide phase that has a cubic crystal structure, and a binder metal phase. The invention further relates to a method for producing said hard metal and to the use of said hard metal to produce tools and wearing parts. The invention further relates to a component that has been produced from the described hard metal.

1 . A cemented carbide, comprising
 a) a tungsten carbide phase having an average grain size of from 0.05 to 0.5 μm, preferably from 0.05 to 0.23 μm, more preferably from 0.05 to 0.09 μm;   b) an additional metal carbide phase; and   c) a binder metal phase,   
       wherein said additional metal carbide phase is in a cubic crystal structure at room temperature, and wherein the proportion of said additional metal carbide phase in said cemented carbide is at least 4% by volume, based on the total volume of the cemented carbide, and wherein the average grain size was determined by the linear-intercept technique according to ISO 4499-2. 
     
     
         2 . The cemented carbide according to  claim 1 , characterized in that said additional metal carbide phase is selected from the group consisting of titanium carbide (TiC), tantalum carbide (TaC), niobium carbide (NbC), hafnium carbide (HfC), zirconium carbide, mixtures thereof, and mixed carbides of these compounds. 
     
     
         3 . The cemented carbide according to  claim 1  or  2 , characterized in that said additional metal carbide phase has an average grain size of from 0.3 to 4 μm, preferably from 0.5 to 1.5 μm, as determined by the linear-intercept technique according to ISO 4499-2. 
     
     
         4 . The cemented carbide according to at least one of the preceding claims, characterized in that said additional metal carbide phase in the cemented carbide is in a periodically repeated distribution with an average distance of from 0.5 to 10 μm, preferably from 1 to 3 μm, as determined by linear analysis (linear-intercept technique) on electron micrographs of sections. 
     
     
         5 . The cemented carbide according to at least one of the preceding claims, characterized in that a tungsten carbide powder having an average particle size d BET  of from 0.05 to 0.3 μm, preferably from 0.05 to 0.25 μm, more preferably from 0.05 to 0.2 μm, is used as a starting material, as determined according to the BET surface area by converting it according to the formula d BET =6/(BET surface area*density). 
     
     
         6 . The cemented carbide according to at least one of the preceding claims, characterized in that a metal carbide powder having an average particle size d BET  of from 0.3 to 5 μm, more preferably from 0.4 to 1 μm, is used as a starting material, as determined according to the BET surface area, and by conversion according to the formula d BET =6/(BET surface area*density). 
     
     
         7 . The cemented carbide according to at least one of the preceding claims, characterized in that said binder metal phase is selected from the group consisting of iron, cobalt, nickel, and mixtures thereof. 
     
     
         8 . The cemented carbide according to  claim 7 , characterized in that said binder metal phase is a mixture consisting of iron, cobalt, and nickel, in which the respective contents of the components are more than 1% by mass. 
     
     
         9 . The cemented carbide according to at least one of the preceding claims, characterized in that said cemented carbide further includes grain growth inhibitors, preferably those selected from the group consisting of vanadium carbide, chromium carbide, mixtures thereof, and mixed carbides of such compounds. 
     
     
         10 . The cemented carbide according to at least one of the preceding claims, characterized in that said tungsten carbide phase in the cemented carbide comprises from 40 to 90% by volume, based on the total volume of the cemented carbide. 
     
     
         11 . The cemented carbide according to at least one of the preceding claims, characterized in that said cemented carbide has a thermal conductivity of less than 50 W/m*K, as determined by the laser flash technique at 40° C. 
     
     
         12 . A process for the preparation of a cemented carbide according to one or more of  claims 1  to  11 , comprising the steps of:
 i) providing a powder mixture, including
 a) a tungsten carbide powder having an average particle size d BET  of from 0.05 to 0.3 μm; 
 b) an additional metal carbide powder that is in a cubic crystal structure at room temperature (25° C.) and has an average particle size d BET  of from 0.3 to 5 μm; and 
 c) a binder metal powder; and 
 
 ii) forming and sintering the mixture. 
 
     
     
         13 . The process according to  claim 12 , characterized in that said sintering is effected at a temperature of from 1150 to 1550° C. 
     
     
         14 . Use of a cemented carbide according to one or more of  claims 1  to  11  for the production of tools. 
     
     
         15 . A component, characterized by being obtained by forming the cemented carbide according to one or more of  claims 1  to  11 . 
     
     
         16 . The component according to  claim 15 , characterized in that said component is drills, solid carbide cutters, indexable inserts, saw teeth, forming dies, sealing rings, extrusion punches, press dies, and wear parts.