Wear Resistant Coatings For Radial Bearings and Downhole Tools

Abstract

Abrasion resistant coatings useful for improving abrasive wear and/or corrosion resistance in radial bearings and downhole tools exposed to drilling forces as well as abrasive and/or corrosive drilling fluids. An abrasion resistant coating is disposed on at least one surface of a component body to increase the resistance of the component to abrasive wear and corrosion. The abrasion resistant coating includes a plurality of spherical tungsten cobalt carbide particles and a plurality of tungsten carbide particles. At least 65% by volume of the spherical tungsten cobalt carbide particles have a diameter of less than about 25 microns.

What is claimed is: 
     
         1 . A downhole component, comprising:
 a component body having at least one surface; and   an abrasion resistant coating disposed on the at least one surface of the component body, the abrasion resistant coating including a plurality of spherical tungsten cobalt carbide particles and a plurality of tungsten carbide particles;   wherein at least 65% by volume of the spherical tungsten cobalt carbide particles have a diameter of less than about 25 microns.   
     
     
         2 . The downhole component of  claim 1 , wherein the spherical tungsten cobalt carbide particles in the abrasion resistant coating have a mean free path of less than about 15 microns, as measured using image analysis and Scanning Electron Microscopy (SEM). 
     
     
         3 . The downhole component of  claim 1 , wherein the spherical tungsten cobalt carbide particles comprise less than 5% by volume of particles having a diameter of less than about 5 microns. 
     
     
         4 . The downhole component of  claim 3 , wherein the spherical tungsten cobalt carbide particles comprises essentially no particles having a diameter of less than about 5 microns and essentially no particles having a diameter greater than about 38 microns. 
     
     
         5 . The downhole component of  claim 1 , wherein the spherical tungsten cobalt carbide particles are spherically shaped plasma densified tungsten cobalt carbide particles. 
     
     
         6 . The downhole component of  claim 1 , wherein the spherical tungsten cobalt carbide particles have a particle size D 50  in the range from about 12 to about 24 microns. 
     
     
         7 . The downhole component of  claim 1 , wherein the abrasion resistant coating has an abrasive resistance factor of at least 150. 
     
     
         8 . The downhole component of  claim 1 , wherein a weight ratio of the spherical tungsten cobalt carbide particles to the plurality of tungsten carbide particles is in the range from about 50:50 to about 90:10. 
     
     
         9 . The downhole component of  claim 1 , wherein the spherical tungsten cobalt carbide particles have an oxygen content of less than about 300 ppm by weight. 
     
     
         10 . The downhole component of  claim 1 , wherein an average particle size D 90  of the tungsten carbide particles is less than about 10 microns. 
     
     
         11 . The downhole component of  claim 1 , wherein the tungsten carbide particles comprise at least one of monocrystalline tungsten carbide, cast tungsten carbide, macrocrystalline tungsten carbide, or a eutectic mixture of WC and W 2 C. 
     
     
         12 . The downhole component of  claim 1 , wherein the tungsten carbide particles are spherical. 
     
     
         13 . The downhole component of  claim 1 , wherein a particle size distribution of a mixture of the tungsten carbide particles and the spherical tungsten cobalt carbide particles is bimodal. 
     
     
         14 . The downhole component of  claim 1 , wherein the downhole component is a radial bearing. 
     
     
         15 . A method of manufacturing a downhole component, comprising:
 applying a layer of an abrasion resistant composition to a metal surface of a substrate, the abrasion resistant composition comprising:
 a plurality of spherical tungsten cobalt carbide particles and a plurality of tungsten carbide particles; 
 wherein at least 65% by volume of the spherical tungsten cobalt carbide particles have a diameter of less than about 25 microns. 
   
     
     
         16 . The method of  claim 15 , further comprising heating the abrasion resistant composition and at least the surface of the substrate to effect metallurgical bonding of the abrasion resistant composition with the substrate. 
     
     
         17 . A method of forming an abrasive resistant coating, comprising:
 admixing a spherical tungsten cobalt carbide powder with a tungsten carbide powder to form a mixture, wherein the spherical tungsten cobalt carbide powder comprises at least 65% by volume of particles having a diameter of less than about 25 microns;   pucking the mixture to form a puck;   milling the puck to form a cloth;   applying the cloth to a substrate; and   vacuum brazing the cloth to the substrate.   
     
     
         18 . The method of  claim 17 , further comprising at least one of:
 ultrasonic sieving or air classifying a mixture of tungsten cobalt carbide particles to recover a fraction of tungsten cobalt carbide particles where at least 65% by volume of particles having a diameter of less than about 25 microns;   mixing the fraction of spherical tungsten cobalt carbide particles with tungsten carbide particles;   adhering the cloth to the substrate using an adhesive compound; or   applying a second cloth comprising a braze material powder to the cloth.   
     
     
         19 . The method of  claim 17 , wherein the vacuum brazing is carried out under an inert atmosphere. 
     
     
         20 . The method of  claim 17 , wherein the process does not include vacuum baking of the tungsten cobalt carbide particles to reduce an oxygen content thereof.