Diamond tools for machining

Abstract

Diamond tools and superpressure processes for the preparation thereof are described wherein the diamond content is present either in the form of a mass comprising diamond crystals bonded to each other or of a thin skin of diamond crystals bonded to each other. In each instance the diamond content is supported on and directly bonded to an extremely stiff sintered carbide substrate in order to provide mechanical support therefor to more effectively utilize the high elastic modulus of the diamond. The questions raised in reexamination request No. 90/000,610, filed Aug. 15, 1984, have been considered and the results thereof are reflected in this reissue patent which constitutes the reexamination certificate required by 35 U.S.C. 307 as provided in 37 CFR 1.570(e).

What we claim as new and desire to secure by Letters Patent of the United States is: 
     
       1. In a tool for machining with diamond wherein the diamond crystalline material for machining is held by a support material and said diamond crystalline material and said support material comprise a tool insert, which tool insert is in turn to be held by a tool shank adapted to be held in a machine tool, the improvement in tool insert construction in which: a. the diamond crystalline material comprises a concentration of diamond in excess of 70 percent by volume in which .Iadd.the .Iaddend.diamond crystals are .Iadd.disposed in random fashion and substantially all of the diamond crystals are .Iaddend.directly bonded to adjacent diamond crystals,   b. the support material is a mass of cemented carbide considerably larger in volume than the volume of the concentration of said diamond crystalline material and   c. said diamond crystalline material and said cemented carbide being joined at an interface, said interface consisting solely of cemented carbide.Iadd., or its elements .Iaddend.and diamond crystals, the bond therebetween being stronger than the .[.tensile.]. .Iadd.fracture .Iaddend.strength of the diamond.   
     
     
       2. The improvement in claim 1 wherein the tool insert is indexable. 
     
     
       3. The improvement in claim 1 wherein the diamond crystalline material is present as a sheet having a thickness of about 30 mils or less. 
     
     
       4. The improvement in claim 1 wherein at least one exposed face of the diamond crystalline material contains crystals from the group consisting of titanium carbide and zirconium carbide. 
     
     
       5. The improvement in claim 1 wherein the concentration of diamond in the diamond crystalline material is in excess of 90 percent by volume. 
     
     
       6. The improvement in claim 1 wherein the diamond crystalline material is composed of diamond and cemented carbide uniformly distributed therein. 
     
     
       7. The process for preparing a diamond-tipped tool insert comprising the steps of: a. placing within an enclosure of protective metal a mass of carbide molding powder and contiguous thereto a smaller mass containing diamond particles in greater than 70 percent by volume concentration, the carbide being selected from the group consisting of tungsten carbide, titanium carbide, tantalum carbide and mixtures thereof and the bonding metal being selected from the group consisting of cobalt, nickel and iron,   b. simultaneously heating said enclosure and the contents thereof to temperatures in the range of 1,400°-1,600° C and applying pressures in excess of about 45 kilobars for at least 3 minutes,   c. ceasing the input of heat to said enclosure,   d. removing the pressure applied to said enclosure, and   e. removing protective metal from the unified mass produced.   
     
     
       8. The process recited in claim 7 wherein the carbide molding powder is a mixture of tungsten carbide powder and cobalt powder. 
     
     
       9. The process recited in claim 7 wherein the diamond particles are disposed in a layer over at least one flat surface of the mass of carbide molding powder, said layer being about 30mils or less in thickness. 
     
     
       10. The process for preparing a diamond-tipped tool insert comprising the steps of: a. placing within an enclosure of protective metal a body of cemented carbide and contiguous thereto a mass smaller in volume containing diamond particles in greater than 70 percent by volume concentration, the carbide being selected from the group consisting of tungsten carbide, titanium carbide, tantalum carbide and mixtures thereof bonded together with metal selected from the group consisting of cobalt, nickel and iron,   b. simultaneously heating said enclosure and the contents thereof to temperatures in the range of 1,400°-1,600° C and applying pressures in excess of about 45 kilobars for at least 3 minutes,   c. ceasing the input of heat to said enclosure,   d. removing the pressure applied to said enclosure, and   e. removing protective metal from the unified mass produced.   
     
     
       11. The process of claim 10 wherein the cemented carbide body is tungsten carbide cemented with cobalt. 
     
     
       12. The process of claim 10 wherein the diamond particles are disposed in a layer over at least one flat surface of the cemented carbide body, said layer being about 30 mils or less in thickness. 
     
     
       13. A tool insert consisting of a sintered carbide mass supporting at least one mass, smaller in volume, of harder abrasive material, said harder abrasive material comprising a concentration of diamond in excess of 70 percent by volume and a material selected from the class consisting of metals able to function both as sintering agents for carbide powders and as catalyst-solvents for the conversion of graphite to diamond at temperatures and pressures in the diamond-stable region and carbides thereof, said diamond being in the form of crystals .Iadd.disposed in random fashion with substantially all of the diamond crystals being .Iaddend.directly bonded to adjacent diamond crystals, said at least one mass of harder abrasive material and said sintered carbide mass being joined along .Iadd.an .Iaddend.interface area consisting solely of cemented carbide .Iadd.or its elements .Iaddend.and diamond, the bond therebetween being stronger than the .[.tensile.]. .Iadd.fracture .Iaddend.strength of diamond. 
     
     
       14. The tool insert of claim 13 wherein the at least one mass of harder material is present as a sheet having a thickness of about 0.030 inch or less. 
     
     
       15. The tool insert of claim 13 wherein the class recited consists of cobalt metal, nickel metal and iron carbide. 
     
     
       16. The tool insert of claim 15 wherein the material selected is cobalt. 
     
     
       17. The tool insert of claim 13 wherein the at least one mass of harder material also contains cemented carbide uniformly distributed therein. 
     
     
       18. The tool insert of claim 13 wherein the product is an indexable tool insert. .Iadd. 
     
     
       19.  A diamond tipped tool insert made according to a process comprising the steps of: a. placing within an enclosure of protective metal a mass of carbide molding powder and contiguous thereto a smaller mass containing diamond particles in greater than 70 percent by volume concentration, the carbide being selected from the group consisting of tungsten carbide, titanium carbide, tantalum carbide and mixtures thereof and the bonding metal being selected from the group consisting of cobalt, nickel and iron,   b. simultaneously heating said enclosure and the contents thereof to temperatures in the range of 1,400°-1,600° C and applying pressures in excess of about 45 kilobars for a period of time sufficient to bond substantially all of the diamond crystals directly to adjacent diamond crystals,   c. ceasing the input of heat to said enclosure,   d. removing the pressure applied to said enclosure, and   e. removing protective metal from the unified mass produced. .Iaddend. .Iadd.20. A diamond-tipped tool insert made according to a process comprising the steps of:   a. placing within an enclosure of protective metal a body of cemented carbide and contiguous thereto a mass smaller in volume containing diamond particles in greater than 70 percent by volume concentration, the carbide being selected from the group consisting of tungsten carbide, titanium carbide, tantalum carbide and mixtures thereof bonded together with metal selected from the group consisting of cobalt, nickel and iron,   b. simultaneously heating said enclosure and the contents thereof to temperatures in the range of 1,400°-1,600° C and applying pressures in excess of about 45 kilobars for a period of time sufficient to bond substantially all of the diamond crystals directly to adjacent diamond crystals,   c. ceasing the input of heat to said enclosure,   d. removing the pressure applied to said enclosure, and   e. removing protective metal from the unified mass produced. .Iaddend.