High energy cutting elements and bits incorporating the same
High energy sheer cutting elements and bits incorporating the same are provided. The cutting elements have at least a portion of their cutting layers which will be exposed to high temperatures during drilling formed from a PCBN material capable of operating at temperatures of at least 1000° C.
1. A bit for drilling earth formations, said bit having a shear cutting element mounted thereon, the shear cutting element comprising:
a substrate;
a cutting layer over the substrate comprising a PCBN portion for contacting a formation during drilling, wherein said PCBN portion has a thermal gradient ranging from about 200 to 2000° C./mm.
2. A bit as recited in claim 1 wherein said entire cutting layer is a PCBN cutting layer.
3. A bit as recited in claim 1 wherein the cutting layer further comprises another portion comprising an ultra hard material adjacent to the PCBN portion.
4. A bit as recited in claim 3 wherein the ultra hard material is PCD.
5. A bit as recited in claim 2 wherein the cutting element further comprises a PCD layer interposed between the PCBN layer and the substrate.
6. A bit as recited in claim 5 wherein the PCD layer is completely encapsulated by the PCBN layer and the substrate.
7. A bit as recited in claim 1 wherein said bit is driven by a turbine and is operable at least at 1000 RPM.
8. A bit as recited in claim 1 wherein the bit is operable at a rotational speed of at least 300 RPM.
9. A bit as recited in claim 1 wherein the bit is operable at a rotational speed in the range of 400 to 1400 RPM.
10. A bit as recited in claim 1 wherein said bit is operable with a weight in the range of 10,000 lbs. to 45,000 lbs. acting on said bit.
11. A bit as recited in claim 1 wherein said bit is operable with a weight in the range of 10,000 lbs. to 15,000 lbs. acting on said bit.
12. A bit as recited in claim 1 wherein said bit is operable with a weight in the range of 15,000 lbs. to 45,000 lbs. acting on said bit.
13. A bit as recited in claim 1 wherein the bit is a turbine drag bit.
14. A bit as recited in claim 1 wherein the bit is a turbine rotary cone bit.
15. A bit as recited in claim 1 wherein said cutting layer comprises a plurality of PCBN portions.
16. A bit as recited in claim 1 wherein said cutting layer is formed from a plurality of PCBN layers bonded together.
17. A bit as recited in claim 16 wherein said PCBN portion is part of one of said plurality of layers.
18. A bit as recited in claim 1 wherein the PCBN portion has a strength of at least 100 ksi.
19. A bit as recited in claim 1 wherein the PCBN portion has a strength of 200 ksi.