DLC coating for earth-boring bit bearings

Abstract

An earth-boring bit has a bearing member having a DLC coating. The bearing member locates between a bearing pin and a cone of the bit. The bearing member may be a thrust washer or a bearing sleeve. The DLC coating is diamond-like carbon that may be coated by different processes onto bearing member.

1 . An earth-boring bit, comprising: 
 a bit body;    a cantilevered bearing pin depending from the bit body;    a cone mounted for rotation on the bearing pin; and    a bearing surface between the cone and the bearing pin, the bearing surface having a DLC coating formed thereon.    
     
     
         2 . The bit according to  claim 1 , wherein the DLC coating has a thickness in the range from 1 to 10 micrometers.  
     
     
         3 . The bit according to  claim 1 , wherein the DLC coating has a thickness in the range from 2 to 5 micrometers.  
     
     
         4 . The bit according to  claim 1 , wherein the DLC coating has a thickness in the range from 2 to 3 micrometers.  
     
     
         5 . The bit according to  claim 1 , wherein the DLC coating has a Knoop Scale hardness in the range from 2000 to 5000.  
     
     
         6 . The bit according to  claim 1 , wherein the DLC coating is of carbon with a mixture of sp3 and sp2 bonds between atoms of the carbon.  
     
     
         7 . The bit according to  claim 1 , wherein the DLC coating is formed of amorphous and hydrogenated amorphous carbon.  
     
     
         8 . The bit according to  claim 1 , wherein the DLC coating is doped with an alloying element from the group consisting essentially of silicon, boron and boron nitride and a refractory metallic element from the group consisting essentially of tantalum, titanium, tungsten, niobium and zirconium.  
     
     
         9 . The bit according to  claim 1 , further comprising a thrust washer located between a thrust shoulder of the bearing pin and the cone, the bearing surface containing the DLC coating being on at least one side of the thrust washer.  
     
     
         10 . The bit according to  claim 1 , further comprising a sleeve located between the bearing pin and the cone, the bearing surface containing the DLC coating being on at least one side of the sleeve.  
     
     
         11 . The bit according to  claim 1 , further comprising a thrust washer located between a thrust shoulder formed on the bearing pin and the cone, and a sleeve located between the bearing pin and the cone, the bearing surface containing the DLC coating being on at least one side of the thrust washer and on at least one side of the sleeve.  
     
     
         12 . The bit according to  claim 1 , wherein the bearing surface having the DLC coating is formed on a journal surface of the bearing pin.  
     
     
         13 . The bit according to  claim 1 , wherein the bearing surface having the DLC coating is formed within a cavity of the cone.  
     
     
         14 . An earth-boring bit, comprising: 
 a bit body;    a cantilevered bearing pin depending from the bit body, the bearing pin having a thrust shoulder that is in a plane perpendicular to the axis of the bearing pin;    a cone mounted for rotation on the bearing pin, the cone having a thrust shoulder facing toward the thrust shoulder of the bearing pin; and    a thrust washer located between and in engagement with the thrust shoulders of the bearing pin and the cone, the thrust washer having a DLC coating formed thereon on at least one side.    
     
     
         15 . The bit according to  claim 14 , wherein the DLC coating is formed on both sides of the thrust washer.  
     
     
         16 . The bit according to  claim 14 , wherein the thrust shoulder of the bearing pin contains an inlay of a hard wear resistant material.  
     
     
         17 . The bit according to  claim 14 , wherein the thrust shoulder of the bearing pin has a DLC coating formed thereon.  
     
     
         18 . The bit according to  claim 14 , wherein the coating is of carbon with a mixture of sp3 and sp2 bonds between atoms of the carbon.  
     
     
         19 . The bit according to  claim 14 , wherein the coating is formed of amorphous and hydrogenated amorphous carbon.  
     
     
         20 . The bit according to  claim 14 , wherein the DLC coating is doped with an alloying element from the group consisting essentially of silicon, boron and boron nitride and a refractory metallic element from the group consisting essentially of tantalum, titanium, tungsten, niobium and zirconium.  
     
     
         21 . An earth-boring bit, comprising: 
 a bit body;    a cantilevered bearing pin depending from the bit body;    a cone mounted for rotation on the bearing pin; and    a sleeve located between the bearing pin and a cavity in the cone and having a DLC coating formed thereon that is on at least one side.    
     
     
         22 . The bit according to  claim 21 , wherein the DLC coating is on both sides of the sleeve.  
     
     
         23 . The bit according to  claim 21 , wherein the bearing pin also contains a DLC coating.  
     
     
         24 . The bit according to  claim 21 , wherein the cavity of the cone also contains a DLC coating.