Diamond metal composite cutter and method for making same

A superhard cutter for an earth boring bit, comprising

• a base member,
• a superhard component bonded to said base member,
• said superhard component comprising a first set of superhard particles having a size in the range of about 50 to 2,000 microns in diameter, and a second set of abrasive particles having a size in the range of about 25 to 75 microns in diameter, said second set of particles substantially surrounding and being substantially located in the interstices between said particles of said first set,
• said particles of said first set being coated with a metallic coating that is about 2 to 10 microns thick, and said particles of said second set being coated with a metallic coating that is about 1 to 10 microns thick,
• said superhard component further including a binder alloy forming a matrix binding said coated particles to each other and to said base member, said binder alloy having a melting point in the range of about 650 to 1300.degree. C. and being capable of wetting said coated particles,
• said superhard component having a superhard particle content in the range of above about 40% to about 75% by volume.

A method for forming a superhard material-metal composite product at temperatures and pressures below the diamond forming range of temperatures and pressures, comprising

• packing a charge of superhard particles into a container, said superhard particles being coated with a metal coating,
• introducing a binder alloy into said container, said binder alloy having a melting point of less than 1300.degree. C. and being capable of wetting said coated superhard particles when caused to flow,
• heating said superhard particles and said binder alloy to a temperature between about 650 to 1300.degree. C. while applying a pressure in the range of about 1,000 to 20,000 psi, thereby causing said binder alloy to flow and to wet said coated superhard particles, and
• removing said pressure and allowing said superhard particles and said binder alloy to cool.