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1. WO2010078182 - ENGINEERED BEARING SURFACE FOR ROCK DRILLING BIT

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

We claim:

1 An earth boring bit, comprising: a bit body; bearing pin depending from the body; a cone having a plurality of cutting elements; a cavity in the cone having a surface that rotably engages the bearing pin; a surface coating on at least one of the pin and the surface of the cavity, the surface coating comprising epoxy and polyurethane.

2 The bit of claim 1, wherein rounded abrasive particles are embedded in the surface coating.

3 The bit of claim 1, wherein the epoxy cement and polyurethane are in a ratio of between about 25:75 to about 90:10 by weight.

4 The bit of claim 1, wherein the epoxy cement and polyurethane are in a ratio of between about 1 :2 to about 2: 1 by weight 5 The bit of claim 1, the surface and the surface coating are contained in the cone.

6 The bit of claim 1, wherein the surface and the surface coating are applied to the bearing pin.

7 The bit of claim 1, wherein the surface coating comprises an amorphous hydrogenated carbon. 8 The bit of claim 1, wherein the surface coating comprises a transition-metal chalcogenide. 9 The bit of claim 1, wherein the surface coating repels lubricant.

10 A method for making a roller cone drill bit:

(a) providing a rock bit body having at least one leg depending from said body, a bearing pin depending from said rock bit body, said bearing pin having an exterior contacting surface and a roller cone having a cone cavity, said cone cavity having an interior contacting surface, wherein the interior contacting surface of the cone rotatably engages the exterior contacting surface of the bearing pin; and

(b) polishing at least one contacting surface by positioning an abrasive paste comprising aluminum oxide and a polymer between a polishing instrument and the at least one contacting surface and polishing the at least one contacting surface thereby reducing the surface roughness of the at least one contacting surface and imparting a polymer coating on the contacting surface.

11 The method of claim 10 wherein the surface is polished to a surface roughness of less than about 10 μin Ra before the polymer coating is imparted to the surface.

12 The method of claim 10 wherein step (b) comprises coating a working surface of the polishing instrument with an epoxy cement and a polyurethane.

13 The method of claim 10, wherein step (b) comprises imparting a second polymer coating on a second contacting surface, wherein the polymer coating attracts a lubricant and the second polymer coating repels the lubricant.

14 The method of claim 12, wherein step (b) comprises embedding abrasive particles into the polymer coating.

15 The method of claim 10 wherein the coating on the working surface of the polishing instrument has a thickness of between about 0.05 mm and 0.4 mm.

16 The method of claim 10, wherein step (b) comprises removing a portion of surface material of the contacting surface and increasing the hardness of the contacting surface causing plastic deformation of the contacting surface.

17 The method of claim 10, wherein the polishing device has an impact resistance of between about 3 and 12 kJ/m2. 18 A method for making a roller cone drill bit, the method comprising:

(a) providing a rock bit body having at least one leg depending from said body, a bearing pin depending from said rock bit body, said bearing pin having an exterior contacting surface and a roller cone having a cone cavity, said cone cavity having an interior contacting surface, wherein the interior contacting surface of the cone rotatably engages the exterior contacting surface of the bearing pin;

(b) polishing at least one contacting surface by positioning an abrasive paste comprising aluminum oxide and a polymer between a polishing instrument and the at least one contacting surface and polishing the at least one contacting surface thereby reducing the surface roughness of the at least one contacting surface to less than 10 micro-inches Ra;

(c) imparting a polymer coating on the at least one contacting surface, the polymer coating having a thickness of between 4 and 10 mm and adhereing to the at least one contacting surface with an adhesive strength of at least 100 kilograms per square centimeter;

19 The method of claim 18, wherein step (b) further comprises creating a non-directional surface texture on the at least one contacting surface.

20 The method of claim 18, wherein step (b) comprises embedding abrasive particles into the polymer coating.