Cutting elements having non-planar cutting faces with selectively leached regions and earth-boring tools including such cutting elements

1. A cutting element, comprising:

a substrate; and

a volume of polycrystalline diamond material affixed to the substrate at an interface, the volume of polycrystalline diamond material comprising:

a front cutting face including a first substantially planar portion located adjacent to a lateral side surface of the cutting element, a second, discrete substantially planar portion located in a central region of the cutting element, and a recess located between the first substantially planar portion and the second, discrete substantially planar portion, the recess extending from a plane defined by the first and second substantially planar portions a first depth into the volume of polycrystalline diamond material in an axial direction parallel to a central axis of the cutting element;

a region including a catalyst material disposed in interstitial spaces between diamond grains of the volume of polycrystalline diamond material extending from the interface to an exposed surface of the volume of polycrystalline diamond material within at least one recess of the front cutting face, the region including the catalyst material extending substantially entirely along the exposed surface of the volume of polycrystalline diamond material within the recess;

a region substantially free of the catalyst material disposed in the interstitial spaces between the diamond grains of the volume of polycrystalline diamond material, the region substantially free of the catalyst material extending from the first substantially planar portion of the front cutting face a second depth into the volume of polycrystalline diamond material in the axial direction, wherein the second depth is less than or substantially equal to the first depth; and

an additional, discrete region substantially free of the catalyst material disposed in the interstitial spaces between the diamond grains of the volume of polycrystalline diamond material extending from the second, discrete substantially planar portion of the front cutting face a third depth into the volume of polycrystalline diamond material in the axial direction, the third depth greater than the second depth.

2. The cutting element of claim 1 , wherein the region including the catalyst material further extends from the interface to the region substantially free of the catalyst material formed to the second depth.

3. The cutting element of claim 1 , wherein the region substantially free of the catalyst material further extends about a cutting edge formed between the front cutting face and a generally cylindrical lateral side surface of the cutting element.

4. The cutting element of claim 1 , wherein the region including the catalyst material further extends from the interface to the additional, discrete region substantially free of the catalyst material formed to the third depth.

5. An earth-boring tool comprising:

a tool body; and

the cutting element of claim 1 affixed to the tool body.

6. A cutting element comprising:

a substrate; and

a volume of polycrystalline diamond material affixed to the substrate at an interface, the volume of polycrystalline diamond material comprising:

a front cutting face comprising:

a first substantially planar portion located adjacent to a lateral side surface of the cutting element;

a second, discrete substantially planar portion located in a central region of the front cutting face; and

a recess located at least partially between the first and second substantially planar portions, the recess extending from a plane defined by the first and second substantially planar portions to a first depth in the volume of polycrystalline diamond material in an axial direction parallel to a central axis of the cutting element;

a region including a catalyst material disposed in interstitial spaces between diamond grains of the volume of polycrystalline diamond material, the region including the catalyst material extending through the volume of polycrystalline diamond material from the interface to an exposed surface of the volume of polycrystalline diamond material within the recess of the front cutting face; and

a first region substantially free of the catalyst material disposed in the interstitial spaces between the diamond grains of the volume of polycrystalline diamond material, wherein the first region substantially free of the catalyst material extends from the first substantially planar portion of the front cutting face to a second depth in the volume of polycrystalline diamond material in the axial direction; and

a second region substantially free of the catalyst material disposed in the interstitial spaces between the diamond grains of the volume of polycrystalline diamond material, wherein the second region substantially free of the catalyst material extends from the second, discrete substantially planar portion of the front cutting face to a third depth in the volume of polycrystalline diamond material in the axial direction, the second region substantially free of the catalyst material discrete from and separated from the first region substantially free of the catalyst material by the region including catalyst material, wherein the second depth and the third depth are substantially equal to the first depth.

7. The cutting element of claim 6 , wherein at least one of the first region substantially free of the catalyst material and the second region substantially free of the catalyst material extends partially along the exposed surface of the volume of polycrystalline diamond material within the recess.

8. The cutting element of claim 6 , wherein the region including a catalyst material extends substantially entirely along the exposed surface of the volume of polycrystalline diamond material within the recess.

9. An earth-boring tool comprising:

a tool body; and

the cutting element of claim 6 affixed to the tool body.