Fabrication of downhole drilling tools
A method of forming a composite cutter for a downhole drilling tool is described. The method includes: mixing a polycrystalline diamond powder and a cubic boron nitride powder with a molar ratio between 0.1 and 0.9 to form a catalyst-free composite mixture; placing the catalyst-free composite mixture into a mold configured in a shape of a cutter; exposing the catalyst-free composite mixture to an ultra-high-pressure, high-temperature treatment including a pressure between 11 Gigapascals (GPa) and 20 GPa, and a temperature between 1300 Kelvins (K) and 2600 K to form a solid composite body; and cooling the solid composite body to form the composite cutter.
1. A method of forming a composite cutter for a downhole drilling tool, the method comprising:
mixing a polycrystalline diamond powder and a cubic boron nitride powder with a molar ratio between 0.1 and 0.9 to form a catalyst-free composite mixture;
placing the catalyst-free composite mixture into a mold configured in a shape of a cutter;
exposing the catalyst-free composite mixture to an ultra-high-pressure, high-temperature treatment comprising a pressure between 11 Gigapascals (GPa) and 20 GPa, and a temperature between 1300 Kelvins (K) and 2600 K to form a solid composite body; and
cooling the solid composite body to form the composite cutter having a hardness greater than 70 GPa, wherein cooling the solid composite body includes between 2 and 10 hours of decompression.
2. The method of claim 1 , wherein providing the catalyst-free synthesized composite mixture comprises the polycrystalline diamond powder and the cubic boron nitride powder with a characteristic grain size between 0.1 and 50 μm.
3. The method of claim 1 , further comprising drying the catalyst-free synthesized composite mixture in a vacuum furnace at a temperature between 1100 K and 1350 K for a duration between 1 hour and 2 hours.
4. The method of claim 1 , wherein the ultra-high-pressure, high-temperature treatment comprises between 1 minute and 10 minutes.
5. The method of claim 1 , wherein sintering comprises forming a strong covalent bonding using the cubic boron nitride powder.
6. The method of claim 5 , wherein the cubic boron nitride powder acts as a binder.
7. The method of claim 1 , further comprises forming new chemical bonds at or near the diamond and cBN grain boundaries of the diamond-cBN composite.
8. The method of claim 7 , wherein forming the new chemical bonds include B—C and C—N.
9. The method of claim 1 , wherein the drilling tool comprises a PDC drill bit, a reamer, a hole opener, a milling tool, or a stabilizer.
10. The method of claim 1 , wherein the composite cutter has an onset oxidation temperature greater than 1070 K.