Superabrasive cutting elements with cutting edge geometry having enhanced durability and cutting efficiency and drill bits so equipped

1. A drill bit for drilling a subterranean formation, comprising:

a bit body having a shank secured thereto for affixing the bit to a drill string; and

a plurality of cutting elements secured to the bit body, at least one of the cutting elements having a longitudinal axis and comprising:

a substantially planar table of superabrasive material substantially facing a direction of intended bit rotation, a plane of the table extending perpendicular to the longitudinal axis of the cutting element, the plane of the table oriented at a backrake angle with respect to an axis of the drill bit, the superabrasive table having a cutting face, a side surface and a peripheral edge therebetween, the peripheral edge being defined at least in part by:

at least one chamfer between the side surface and the cutting face oriented at an acute angle to the side surface;

an arcuate surface extending directly between an outermost boundary of the cutting face and an innermost boundary of a chamfer of the at least one chamfer; and

a sharp, angular transition between an outermost boundary of a chamfer of the at least one chamfer and the side surface;

wherein the acute angle of a radially outermost chamfer of the at least one chamfer with respect to the side surface of the table is approximately the same as or slightly more than the backrake angle of the plane of the table with respect to the axis of the drill bit; and

wherein an included angle between the cutting face and the at least one chamfer is greater than about 135°.

2. The drill bit of claim 1 , wherein the peripheral edge is nonlinear.

3. The drill bit of claim 1 , wherein the cutting element includes a supporting substrate affixed to the table of superabrasive material.

4. The drill bit of claim 1 , wherein the superabrasive material comprises a polycrystalline diamond compact.

5. The drill bit of claim 1 , wherein the arcuate surface comprises, in cross-section, a radius of curvature.

6. The drill bit of claim 1 , wherein at least one of an innermost boundary of the chamfer of the at least one chamfer and the outermost boundary of the cutting face contacts the arcuate surface substantially tangentially.

7. The drill bit of claim 1 , wherein the at least one chamfer comprises a single chamfer between the cutting face and the side surface.

8. The drill bit of claim 1 , wherein the at least one chamfer comprises a radially outer chamfer adjacent the side surface, and a radially inner chamfer adjacent the arcuate surface, an outermost boundary of the radially inner chamfer coinciding with an innermost boundary of the radially outer chamfer.

9. The drill bit of claim 8 , wherein the radially inner chamfer is oriented at an acute angle to the side surface greater than an acute angle of the radially outer chamfer to the side surface.

10. A drill bit for drilling a subterranean formation, comprising:

a bit body having a shank secured thereto for affixing the bit to a drill string; and

a plurality of cutting elements secured to the bit body, at least one of the cutting elements having a longitudinal axis and comprising:

a substantially planar table of superabrasive material substantially facing a direction of intended bit rotation, a plane of the table extending perpendicular to the longitudinal axis of the cutting element, the plane of the table oriented at a backrake angle with respect to an axis of the drill bit, the superabrasive table having a cutting face, a side surface and a peripheral edge therebetween, the peripheral edge being defined at least in part by:

a chamfer extending directly from the side surface toward the cutting face and oriented at an acute angle to the side surface;

an arcuate surface extending directly between an outermost boundary of the cutting face to an innermost boundary of a chamfer adjacent the cutting face; and

a sharp, angular transition between an outermost boundary of the chamfer of the at least one chamfer and the side surface;

wherein the acute angle of a radially outermost chamfer of the at least one chamfer with respect to the side surface of the table is approximately the same as or slightly more than the backrake angle of the plane of the table with respect to the axis of the drill bit; and

wherein the side surface is substantially parallel to a longitudinal axis of the cutting element and the acute angle is between about 15° and about 70°.

11. A rotary drilling structure for removing material from a subterranean formation, the rotary drilling structure comprising:

a body having structure secured thereto for affixing the rotary drilling structure to a drill string; and

a plurality of cutting elements carried by the body, at least one of the cutting elements having a longitudinal axis and comprising:

a substantially planar table of superabrasive material substantially facing a direction of intended rotation of the rotary drilling structure, a plane of the table oriented at a backrake angle with respect to an axis of the rotary drilling structure, the superabrasive table having a cutting face, a side surface and a peripheral edge therebetween, the peripheral edge being defined at least in part by:

at least one chamfer between the side surface and the cutting face oriented at an acute angle to the side surface;

an arcuate surface extending directly between an outermost boundary of the cutting face and an innermost boundary of a chamfer of the at least one chamfer; and

a sharp, angular transition between an outermost boundary of a chamfer of the at least one chamfer and the side surface;

wherein the acute angle of an outermost chamfer of the at least one chamfer with respect to the side surface of the table is approximately the same as or slightly more than the backrake angle of the plane of the table with respect to the axis of the rotary drilling structure; and;

wherein an included angle between the cutting face and the at least one chamfer is greater than about 135°.

12. The rotary drilling structure of claim 11 , wherein the peripheral edge is nonlinear.

13. The rotary drilling structure of claim 11 , wherein the cutting element includes a supporting substrate affixed to the table of superabrasive material.

14. The rotary drilling structure of claim 11 , wherein the superabrasive material comprises a polycrystalline diamond compact.

15. The rotary drilling structure of claim 11 , wherein the arcuate surface comprises, in cross-section, a radius of curvature.

16. The rotary drilling structure of claim 11 , wherein at least one of an innermost boundary of the chamfer of the at least one chamfer and the outermost boundary of the cutting face contacts the arcuate surface substantially tangentially.

17. The rotary drilling structure of claim 11 , wherein the at least one chamfer extends directly from the side surface toward the cutting face, the side surface is substantially parallel to a longitudinal axis of the cutting element and the acute angle is between about 15° and about 70°.

18. The rotary drilling structure of claim 11 , wherein the at least one chamfer comprises a single chamfer between the cutting face and the side surface.

19. The rotary drilling structure of claim 11 , wherein the at least one chamfer comprises a radially outer chamfer adjacent the side surface, and a radially inner chamfer adjacent the arcuate surface, an outermost boundary of the radially inner chamfer coinciding with an innermost boundary of the radially outer chamfer.

20. The rotary drilling structure of claim 11 , wherein the radially inner chamfer is oriented at an acute angle to the side surface greater than an acute angle of the radially outer chamfer to the side surface.