Methods for characterizing a polycrystalline diamond element by magnetic measurements

1. A method for adjusting one or more process parameters for fabricating a polycrystalline diamond (“PCD”) element for use in a subterranean drilling apparatus, the method comprising:

providing the PCD element;

measuring one or more of magnetic characteristics of the PCD element; and

adjusting the one or more process parameters for fabricating the PCD element at least partially based on the one or more of the magnetic characteristics.

2. The method of claim 1 wherein the PCD element is selected from the group consisting of an at least partially leached PCD element and an unleached PCD element.

3. The method of claim 1 wherein the measured one or more magnetic characteristics include at least one of magnetic saturation or coercivity.

4. The method of claim 3 , further comprising determining a catalyst concentration in the PCD element at least partially based on the measured magnetic saturation.

5. The method of claim 4 wherein determining a catalyst concentration in the PCD element at least partially based on measured magnetic saturation is performed either before or after a leaching process in which a catalyst is at least partially leached from the PCD element.

6. The method of claim 3 , further comprising determining an extent of diamond-to-diamond bonding within the PCD element at least partially based on the measured coercivity.

7. The method of claim 1 wherein the one or more process parameters affect synthesis of a diamond structure of the PCD element.

8. The method of claim 1 wherein the process parameters affect at least one of wear resistance or thermal stability of the PCD element.

9. The method of claim 1 wherein adjusting one or more process parameters for fabricating the PCD element based on one or more of the measured magnetic characteristics comprises adjusting sintering temperature, sintering pressure, diamond particle size used to form the PCD element, catalyst composition, amount of catalyst used in the fabrication of the PCD element, acid composition used to leach catalyst from the PCD element, pH of an acid composition used to leach catalyst from the PCD element, leaching time used in a leaching process to leach catalyst from the PCD element, leaching temperature used to leach catalyst from the PCD element, leaching pressure used to leach catalyst from the PCD element, or combinations thereof.

10. The method of claim 1 , further comprising fabricating a second PCD element in an adjusted high-pressure, high-temperature process that employs the adjusted one or more process parameters.

11. A method for adjusting one or more process parameters for fabricating a polycrystalline diamond (“PCD”) element for use in a subterranean drilling apparatus, the method comprising:

fabricating the PCD element in a high-pressure, high-temperature (“HPHT”) process;

at least partially leaching a catalyst from the PCD element to form an at least partially leached PCD element;

measuring one or more of a magnetic saturation or a coercivity of the PCD element; and

adjusting the one or more process parameters of the HPHT process for fabricating the PCD element at least partially based on one or more of the measured magnetic saturation or the measured coercivity.

12. The method of claim 11 wherein fabricating a PCD element in an HPHT process includes sintering diamond powder in the presence of a catalyst.

13. The method of claim 11 wherein at least partially leaching a catalyst from the PCD element to form an at least partially leached PCD element comprises immersing the PCD element for a selected period of time at a selected temperature in an acid solution including one or more acids selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, aqua regia, hydrofluoric acid, and combinations thereof.

14. The method of claim 11 , further comprising determining a catalyst concentration in the PCD element at least partially based on the measured magnetic saturation.

15. The method of claim 14 wherein determining a catalyst concentration in the PCD element at least partially based on measured magnetic saturation is performed either before or after the leaching.

16. The method of claim 11 , further comprising determining an extent of diamond-to-diamond bonding within the PCD element at least partially based on the measured coercivity.

17. The method of claim 11 wherein the one or more process parameters affect synthesis of a diamond structure of the PCD element.

18. The method of claim 11 wherein the process parameters affect at least one of wear resistance or thermal stability of the PCD element.

19. The method of claim 11 wherein adjusting one or more process parameters for fabricating the PCD element based on one or more of the measured magnetic saturation or the measured coercivity comprises adjusting sintering temperature, sintering pressure, diamond particle size used to form the PCD element, catalyst composition, amount of catalyst used in the fabrication of the PCD element, acid composition used to leach catalyst from the PCD element, pH of an acid composition used to leach catalyst from the PCD element, leaching time used in a leaching process to leach catalyst from the PCD element, leaching temperature used to leach catalyst from the PCD element, leaching pressure used to leach catalyst from the PCD element, or combinations thereof.

20. A method for adjusting one or more process parameters for fabricating a polycrystalline diamond compact (“PDC”) for use in a subterranean drilling apparatus, the method comprising:

fabricating the PDC in a high-pressure, high-temperature (“HPHT”) process, wherein the PDC includes a substrate having a polycrystalline diamond (“PCD”) table formed thereon;

separating the PCD table from the substrate;

at least partially leaching a catalyst from the PCD table in a leaching process to form a leached region;

measuring one or more of a magnetic saturation or a coercivity of at least the leached region of the PCD table; and

adjusting the one or more process parameters of at least one of the leaching process or the HPHT process at least partially based on one or more of the measured magnetic saturation or the measured coercivity.

21. The method of claim 20 , further comprising:

removing the leached region from the PCD table; and

wherein measuring one or more of a magnetic saturation or a coercivity of at least the leached region of the PCD table comprises measuring the one or more of the magnetic saturation or the coercivity of only the leached region.

22. The method of claim 20 wherein the one or more process parameters affect synthesis of a diamond structure of the PCD table.

23. The method of claim 20 wherein the process parameters affect at least one of wear resistance or thermal stability of the PCD table.

24. The method of claim 20 wherein adjusting one or more process parameters for fabricating the PCD element based on one or more of the measured magnetic saturation or the measured coercivity comprises adjusting sintering temperature, sintering pressure, diamond particle size used to form the PCD element, catalyst composition, amount of catalyst used in the fabrication of the PCD element, acid composition used to leach catalyst from the PCD element, pH of an acid composition used to leach catalyst from the PCD element, leaching time used in a leaching process to leach catalyst from the PCD element, leaching temperature used to leach catalyst from the PCD element, leaching pressure used to leach catalyst from the PCD element, or combinations thereof.

25. The method of claim 20 , further comprising bonding the PCD table to a second substrate using a modified HPHT process.

26. A method of performing quality control on a polycrystalline diamond (“PCD”) element for use in a subterranean drilling apparatus, the method comprising:

fabricating the PCD element in a high-pressure, high-temperature (“HPHT”) process;

at least partially leaching a catalyst from the PCD element to form an at least partially leached PCD element;

measuring a magnetic saturation of the at least partially leached PCD element to determine a catalyst concentration in at least a portion of the at least partially leached PCD element; and

rejecting the at least partially leached PCD element if the measured catalyst concentration exceeds a selected limit, or accepting the at least partially leached PCD element if the measured catalyst concentration is less than the selected limit.

27. The method of claim 26 , further comprising rejecting the at least partially leached PCD element if the measured catalyst concentration is greater than about 5 weight %.

28. The method of claim 26 , further comprising rejecting the at least partially leached PCD element if the measured catalyst concentration is greater than about 2 weight %.

29. The method of claim 26 , further comprising rejecting the at least partially leached PCD element if the measured catalyst concentration is greater than about 1 weight %.

30. The method of claim 26 , further comprising accepting the at least partially leached PCD element if the measured catalyst concentration is less than about 1.5 weight %.

31. The method of claim 26 wherein at least partially leaching a catalyst from the PCD element to form an at least partially leached PCD element comprises immersing the PCD element for a selected period of time at a selected temperature in an acid solution including one or more acids selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, aqua regia, hydrofluoric acid, and combinations thereof.

32. The method of claim 26 , further comprising attaching the at least partially leached PCD element to a substrate if the measured catalyst concentration is less than the selected limit.

33. The method of claim 26 , further comprising adjusting one or more process parameters for fabricating the PCD element at least partially based on the one or more of the magnetic characteristics if the measured catalyst concentration is greater than a selected limit.