Cutting elements having a non-uniform annulus leach depth, earth-boring tools including such cutting elements, and related methods

1. A polycrystalline diamond compact (PDC) cutting element, comprising:

a substrate; and

a volume of polycrystalline diamond on the substrate, the volume of polycrystalline diamond having a front cutting face, a lateral side surface, and a cutting edge defined between the front cutting face and the lateral side surface;

wherein a first region of the volume of polycrystalline diamond adjacent at least a portion of an interface between the volume of polycrystalline diamond and the substrate includes catalyst material in interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond; and

wherein an annular second region of the volume of polycrystalline diamond adjacent at least a portion of the lateral side surface of the volume of polycrystalline diamond is at least substantially free of the catalyst material; and

wherein the annular second region of the volume of polycrystalline diamond does not extend to the front cutting face of the volume of polycrystalline diamond; and

wherein an inner boundary of the second annular region remote from the lateral side surface of the volume of polycrystalline diamond defines at least a portion of an interface between the first region and the annular second region of the volume of polycrystalline diamond, the interface having a non-linear profile in a plane extending through the PDC cutting element along a longitudinal axis of the cutting element.

2. The PDC cutting element of claim 1 , wherein the non-linear profile has at least one curved section.

3. The PDC cutting element of claim 1 , wherein the non-linear profile is disposed a first distance from the lateral side surface of the volume of polycrystalline diamond at a first location along the profile, and is disposed a second distance from the lateral side surface of the volume of polycrystalline diamond at a second location along the profile, the second location along the profile being closer to an interface between the substrate and the volume of polycrystalline diamond relative to first location along the profile, the second distance being greater than the first distance.

4. The PDC cutting element of claim 1 , wherein a third region of the volume of polycrystalline diamond adjacent the front cutting face of the volume of polycrystalline diamond is at least substantially free of the catalyst material in interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond, and wherein the annular second region of the volume of polycrystalline diamond does not contact the third region of the volume of polycrystalline diamond.

5. The PDC cutting element of claim 4 , wherein the first region of the volume of polycrystalline diamond extends to the lateral side surface of the volume of polycrystalline diamond between the annular second region and the third region of the volume of polycrystalline diamond.

6. The PDC cutting element of claim 5 , wherein an interface between the third region of the volume of polycrystalline diamond and the first region of the volume of polycrystalline material has a planar profile.

7. The PDC cutting element of claim 5 , wherein an interface between the third region of the volume of polycrystalline diamond and the first region of the volume of polycrystalline material has a non-planar profile.

8. The PDC cutting element of claim 1 , wherein the annular second region is in a state of compressive stress at ambient conditions after manufacture and prior to use of the PDC cutting element.

9. The PDC cutting element of claim 1 , wherein the annular second region of the volume of polycrystalline diamond does not contact an interface between the volume of polycrystalline diamond and the substrate.

10. An earth-boring tool, comprising:

a body; and

at least one polycrystalline diamond compact (PDC) cutting element secured to the body, the at least one polycrystalline diamond compact (PDC) cutting element including:

a substrate; and

a volume of polycrystalline diamond on the substrate, the volume of polycrystalline diamond having a front cutting face, a lateral side surface, and a cutting edge defined between the front cutting face and the lateral side surface;

wherein a first region of the volume of polycrystalline diamond adjacent at least a portion of an interface between the volume of polycrystalline diamond and the substrate includes catalyst material in interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond; and

wherein an annular second region of the volume of polycrystalline diamond adjacent at least a portion of the lateral side surface of the volume of polycrystalline diamond is at least substantially free of the catalyst material; and

wherein the annular second region of the volume of polycrystalline diamond does not extend to the front cutting face of the volume of polycrystalline diamond; and

wherein an inner boundary of the second annular region remote from the lateral side surface of the volume of polycrystalline diamond defines at least a portion of an interface between the first region and the annular second region of the volume of polycrystalline diamond, the interface having a non-linear profile in a plane extending through the PDC cutting element along a longitudinal axis of the cutting element.

11. The earth-boring tool of claim 10 , wherein the earth-boring tool comprises at least one of a drill bit, a reamer, and a mill.

12. The earth-boring tool of claim 10 , wherein a third region of the volume of polycrystalline diamond adjacent the front cutting face of the volume of polycrystalline diamond is at least substantially free of the catalyst material in interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond, and wherein the annular second region of the volume of polycrystalline diamond does not contact the third region of the volume of polycrystalline diamond.

13. A method of fabricating a polycrystalline diamond compact (PDC) cutting element, comprising:

forming a volume of polycrystalline diamond having a front cutting face, a lateral side surface, and a cutting edge defined between the front cutting face and the lateral side surface;

providing the volume of polycrystalline diamond on a substrate; and

configuring the volume of polycrystalline diamond (i) such that the volume of polycrystalline diamond includes a first region adjacent at least a portion of an interface between the volume of polycrystalline diamond and the substrate, the first region having catalyst material in interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond, (ii) such that the volume of polycrystalline diamond further includes an annular second region adjacent at least a portion of the lateral side surface of the volume of polycrystalline diamond, the annular second region being at least substantially free of the catalyst material, (iii) such that an inner boundary of the second annular region remote from the lateral side surface of the volume of polycrystalline diamond defines at least a portion of an interface between the first region and the annular second region of the volume of polycrystalline diamond, the interface having a non-linear profile in a plane extending through the PDC cutting element along a longitudinal axis of the cutting element, and (iv) such that the annular second region of the volume of polycrystalline diamond does not extend to the front cutting face of the volume of polycrystalline diamond.

14. The method of claim 13 , wherein providing the volume of polycrystalline diamond on the substrate comprises forming the volume of polycrystalline diamond on the substrate.

15. The method of claim 13 , wherein configuring the volume of polycrystalline diamond comprises removing the catalyst material from the interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond in the annular second region of the volume of polycrystalline diamond.

16. The method of claim 15 , wherein removing the catalyst material comprises leaching the catalyst material out from the interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond in the annular second region of the volume of polycrystalline diamond.

17. The method of claim 16 , wherein leaching the catalyst material out from the interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond in the annular second region of the volume of polycrystalline diamond comprises:

providing an annular mask extending circumferentially around and on the lateral side surface of the volume of polycrystalline diamond; and

exposing the volume of polycrystalline diamond to a leaching agent to leach the catalyst material out from the interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond in the annular second region of the volume of polycrystalline diamond.

18. The method of claim 17 , further comprising:

configuring the annular mask such that the annular mask does not contact the substrate; and

contacting regions of the lateral side surface of the volume of polycrystalline diamond on opposing sides of the annular mask to the leaching agent.

19. The method of claim 18 , further comprising:

removing the annular mask from the volume of polycrystalline diamond; and

contacting at least one region of the lateral side surface previously masked from the leaching agent by the annular mask to a leaching agent to leach catalyst material out from interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond in the at least one region of the lateral side surface previously masked from the leaching agent by the annular mask.

20. The method of claim 13 , wherein configuring the volume of polycrystalline diamond further comprises configuring the volume of polycrystalline diamond (v) such that the volume of polycrystalline diamond includes a third region adjacent the front cutting face of the volume of polycrystalline diamond being at least substantially free of the catalyst material in interstitial spaces between inter-bonded diamond grains of the polycrystalline diamond, the annular second region of the volume of polycrystalline diamond not contacting the third region of the volume of polycrystalline diamond.