Polycrystalline diamond composite compact

1. A polycrystalline diamond (PCD) composite compact element comprising a PCD structure bonded to a cemented carbide substrate, in which only a peripheral region of the substrate comprises cemented carbide material having a mean free path (MFP) characteristic of at least about 0.1 microns and at most about 0.7 microns; and an elastic limit of at least about 1.9 GPa, wherein the cemented carbide material of the peripheral region comprises metal carbide particles and metallic binder material; the content of the metallic binder material of the peripheral region being at least about 1 weight percent and at most 12 weight percent.

2. A PCD composite compact element according to claim 1 , wherein the metal carbide particles within the peripheral region have a mean size of at least about 0.1 micron and at most about 20 microns.

3. A PCD composite compact element according to claim 1 , wherein the peripheral region has magnetic coercivity of at least about 100 Oe and at most about 700 Oe.

4. A PCD composite compact element according to claim 1 , wherein the metallic binder material comprises cobalt and the metal carbide is tungsten carbide.

5. A PCD composite compact element according to claim 1 , wherein the metallic binder material contains a solid solution of at least one of tungsten and carbon in cobalt.

6. A PCD composite compact element according to claim 1 , wherein the metal carbide particles comprise grains of at least one of chromium carbide and vanadium carbide, said grains being dispersed in the metallic binder material.

7. A PCD composite compact element according to claim 1 , wherein the metallic binder material comprises cobalt, and nickel and Cr 3 C 2 .

8. A PCD composite compact element according to claim 1 , wherein the metal carbide is TiC, WC, or TaC.

9. A PCD composite compact element according to claim 1 , wherein the metal carbide is tungsten carbide (WC), and the metallic binder comprises cobalt; and the cemented carbide material of the peripheral region has a magnetic coercive field strength up to about 17.0 kA/m and a magnetic moment, σ in units of micro-Tesla times cubic meter per kilogram, in a range of σ=0.11 X to σ=0.137 X, where X is the Co proportion in weight percent in the cemented carbide material.

10. A PCD composite compact element according to claim 1 , wherein the cemented carbide of the peripheral region is substantially free of eta-phase.

11. A PCD composite compact element according to claim 1 , wherein said metal carbide particles or metal-containing nano-particles having mean size in the range from about 0.1 nm to about 500 nm are dispersed in the metallic binder material.

12. A method for making a PCD composite compact element, the method including providing a cemented carbide substrate in which only a peripheral region comprises cemented carbide material having a mean free path (MFP) characteristic of at least about 0.1 microns and at most about 0.7 microns, and an elastic limit of at least about 1.9 GPa; the cemented carbide material in the peripheral region comprising particles of a metal carbide and a metallic binder material, the content of the metallic binder being at least about 1 weight percent and at most about 12 weight percent; providing an aggregated mass of diamond particles; introducing a solvent/catalyst material for diamond into the aggregated mass; and sintering the aggregated mass in contact with the substrate at a pressure and temperature at which diamond is thermodynamically stable to form a PCD structure bonded to a cemented carbide substrate; wherein the step of introducing the solvent/catalyst for diamond into the aggregated mass of diamond particles comprises introducing by at least one of blending solvent/catalyst material in powder form with the diamond particles, depositing solvent/catalyst material onto surfaces of the diamond particles, and infiltrating solvent/catalyst material into the aggregated mass from a source of the material other than the substrate.

13. A tool comprising a PCD composite compact element according to claim 1 , the tool being for cutting, milling, grinding, drilling, earth boring, rock drilling applications.

14. A tool according to claim 13 , wherein the tool comprises a drill bit for earth boring or rock drilling.

15. A tool according to claim 14 , wherein the tool comprises a rotary fixed-cutter bit for use in the oil and gas drilling industry.