Compacts for producing polycrystalline diamond compacts, and related polycrystalline diamond compacts

1. A polycrystalline diamond compact comprising:

a substrate comprising a metal catalyst; and

a diamond layer on the substrate and comprising:

a first region comprising a first concentration of the metal catalyst equal to about twice a concentration of the metal catalyst in the substrate;

a second region comprising a second concentration of the metal catalyst about the same as the concentration of metal catalyst in the substrate; and

a third region comprising a third concentration of the metal catalyst that decreases from a value about the same as the second concentration of the metal catalyst to about a zero value.

2. The polycrystalline diamond compact of claim 1 , wherein the metal catalyst comprises cobalt.

3. The polycrystalline diamond compact of claim 1 , further comprising another diamond layer on the diamond layer.

4. The polycrystalline diamond compact of claim 1 , wherein the first region of the diamond layer is proximate the substrate, the third region of the diamond layer is distal from the substrate, and the second region is between the first region of the diamond layer and the third region of the diamond layer.

5. A compact for producing a polycrystalline diamond compact, comprising:

a substrate comprising a metal catalyst;

a layer of catalyst over the substrate;

a first layer of diamond powder over the layer of catalyst;

a second layer of diamond powder over the first layer of diamond powder; and

a sink over the second layer of diamond powder.

6. The compact of claim 5 , wherein the layer of catalyst comprises cobalt powder.

7. The compact of claim 5 , wherein the first layer of diamond powder comprises diamond powder having a particle size within a range of from approximately 5 microns to approximately 40 microns.

8. The compact of claim 5 , wherein the second layer of diamond powder comprises diamond powder having a particle size within a range of from approximately 100 microns to approximately 500 microns.

9. The compact of claim 5 , wherein the second layer of diamond powder comprises coarse diamond, carbide, graphite, ceramic, metal, or a mixture thereof.

10. The compact of claim 5 , wherein the sink comprises fine diamond powder, graphite powder, metal powder, or metal alloy powder formulated to react at or above the reactivity level of the first layer of diamond powder.

11. The compact of claim 5 , wherein the layer of catalyst comprises a solid disc of a metal or a metal alloy.

12. The compact of claim 11 , wherein the solid disc defines a plurality of apertures.

13. The compact of claim 11 , wherein the solid disc comprises iron and cobalt.

14. The compact of claim 11 , wherein the solid disc comprises nickel.

15. A compact for producing a polycrystalline diamond compact, comprising:

a substrate comprising a metal catalyst;

a layer of powder catalyst over the substrate;

a layer of diamond powder over the layer of powder catalyst;

a layer of material over an upper surface and a circumference of the layer of diamond powder and over a circumference of the substrate; and

a sink over the layer of material.

16. The compact of claim 15 , wherein the sink overlies at least a portion of the circumference of the substrate.

17. The compact of claim 15 , wherein the layer of material comprises another layer of powder catalyst.

18. The compact of claim 15 , wherein the layer of material comprises another layer of diamond powder.

19. The compact of claim 18 , wherein the another layer of diamond powder comprises diamond particles of greater size than that of other diamond particles of the layer of diamond powder.

20. The compact of claim 15 , wherein a mass of the sink is greater than or equal to an overall mass of catalyst material in the substrate, the layer of powder catalyst, the layer of diamond powder, and the layer of material.