Methods of forming borided down hole tools

1. A method of forming a down-hole tool, comprising:

directly contacting a surface of a ceramic-metal composite material of a down-hole structure with a molten electrolyte comprising Na 2 B 4 O 7 and PbO, wherein the molten electrolyte comprises from about 50 wt % to about 90 wt % of Na 2 B 4 O 7 and from about 10 wt % to about 50 wt % PbO, the ceramic-metal composite material of the down-hole structure comprising hard ceramic phase particles in a meta material matrix; and

applying electrical current to the down-hole structure to convert at least a portion of the metal material matrix of the ceramic-metal composite material into a metal boride matrix and provide the ceramic-metal composite material with a metal boride-containing surface.

2. The method of claim 1 , wherein directly contacting a surface of a ceramic-metal composite material of a down-hole structure further comprises selecting the down-hole structure to comprise a component of an earth-boring rotary drill bit, a completion tool, an expandable reamer, an expandable stabilizer, a fixed stabilizer, a slip-on stabilizer, a clamped-on stabilizer, an integral stabilizer, an optimized rotational density tool, a slimhole neutron density tool, a calibrated neutron density tool, a drill motor, a bearing, an upper bearing housing, a lower bearing housing, a rotor, a stator, a pump, or a valve.

3. The method of claim 1 , further comprising selecting the ceramic-metal composite material to comprise tungsten carbide particles in a matrix of nickel.

4. The method of claim 1 , further comprising maintaining a temperature of the molten electrolyte within a range of from about 550° C. to about 700° C.

5. The method of claim 1 , wherein directly contacting a surface of a ceramic-metal composite material of a down-hole structure with a molten electrolyte comprises directly contacting only a portion of the surface of the ceramic-metal composite material with the molten electrolyte.

6. The method of claim 1 , wherein applying electrical current to the down-hole structure comprises applying a current density within a range of from about 100 mA/cm 2 to about 700 mA/cm 2 for a period of time within a range of from about one (1) minute to about five (5) hours.

7. The method of claim 1 , further comprising soaking the down-hole structure in the molten electrolyte in the absence of the electrical current after the application thereof to increase the phase homogeneity of at least a portion of the ceramic-metal composite material.

8. The method of claim 7 , wherein soaking the down-hole structure in the molten electrolyte in the absence of the electrical current after the application thereof comprises at least partially immersing the down-hole structure in the molten electrolyte for a period of time within a range of from about one (1) minute to about one (1) hour.

9. A method of forming a down-hole tool, comprising:

at least partially inserting at least one down-hole structure having a surface comprising hard ceramic phase particles in a metal matrix into a molten electrolyte consisting of anhydrous Na 2 B 4 O 7 at a temperature of from about 770° C. to about 1400° C.;

applying electrical current to the at least one down-hole structure for a period of time within a range of from about one (1) minute to about five (5) hours to convert at least a portion of the metal matrix into a metal boride matrix and form at least one borided down-hole structure;

masking the ceramic-metal composite material;

carburizing at least one non-borided portion of the at least one borided down-hole structure after masking the ceramic-metal composite material; and

securing the at least one borided down-hole structure to at least one other down-hole structure.

10. The method of claim 9 , wherein securing the at least one borided down-hole structure to at least one other down-hole structure comprises securing the at least one borided down-hole structure to at least one other borided down-hole structure.

11. The method of claim 10 , wherein securing the at least one borided down-hole structure to at least one other down-hole structure comprises securing the at least one borided down-hole structure to at least one structure exhibiting a different thickness of metal boride matrix than the at least one borided down-hole structure.

12. The method of claim 9 , wherein securing the at least one borided down-hole structure to at least one other down-hole structure comprises coupling the at least one borided down-hole structure with the at least one other down-hole structure to form at least one of an earth-boring rotary drill bit, an expandable reamer, an expandable stabilizer, a fixed stabilizer, a rotor, a stator, a pump, and a valve.

13. The method of claim 1 , wherein applying electrical current to the down-hole structure further comprises boronizing the hard ceramic phase particles of the ceramic-metal composite material.

14. The method of claim 13 , wherein boronizing the hard ceramic phase particles of the ceramic-metal composite material comprises reacting metal atoms of the hard ceramic phase particles with boron liberated from the Na 2 B 4 O 7 during the application of the electrical current.

15. The method of claim 1 , further comprising selecting the ceramic-metal composite material to exhibit a substantially homogeneous distribution of the hard ceramic phase particles in the metal matrix material.

16. The method of claim 1 , wherein directly contacting a surface of a ceramic-metal composite material of a down-hole structure with a molten electrolyte comprises selecting the molten electrolyte to consist of Na 2 B 4 O 7 and PbO.

17. The method of claim 1 , further comprising selecting the down-hole structure to comprise a layer of the ceramic-metal composite material only partially covering another material.

18. The method of claim 1 , further comprising:

masking the ceramic-metal composite material; and

carburizing at least one non-borided portion of the borided down-hole structure after masking the ceramic-metal composite material.