Methods of forming a hardfacing composition, methods of hardfacing a downhole tool, and methods of forming an earth-boring bit
View Patent ↗A hardfacing composition for downhole well tools, such as earth-boring bits, contains sintered ultrahard particles. The ultrahard particles consist of tungsten carbide grains, cobalt and vanadium. The ultrahard particles are dispersed within a matrix metal of iron, nickel or alloys thereof. The composition may also have sintered tungsten carbide particles of a larger size than the ultrahard particles. The ultrahard particles have a greater hardness than the sintered tungsten carbide particles. The ultrahard particles and the sintered tungsten carbide particles may be in a spherical pellet form. Other hard metal particles may be in the composition.
1. A method of forming a hardfacing composition, comprising:
forming ultrahard pellets each comprising tungsten carbide grains, elemental cobalt, and elemental vanadium;
crushing at least a portion of the ultrahard pellets to form crushed ultrahard particles;
mixing the crushed ultrahard particles with spherical sintered tungsten carbide pellets; and
dispersing the crushed ultrahard particles and the spherical sintered tungsten carbide pellets in a matrix metal comprising iron, nickel, or alloys thereof.
2. The method of claim 1 , wherein forming ultrahard pellets comprises:
forming a powder mixture comprising tungsten carbide grains, a cobalt binder, and vanadium powder; and
sintering the powder mixture.
3. The method of claim 1 , wherein forming ultrahard pellets comprises forming each of the ultrahard pellets to comprise from 0.25 percent by weight to 2 percent by weight elemental vanadium.
4. The method of claim 3 , wherein forming ultrahard pellets further comprises forming each of the ultrahard pellets to comprise from 4 percent by weight to 8 percent by weight of the elemental cobalt.
5. The method of claim 1 , wherein forming ultrahard pellets comprises forming each of the ultrahard pellets to have a hardness within a range of from about 95 HRA to about 96 HRA.
6. The method of claim 1 , wherein forming ultrahard pellets comprises forming at least one of the ultrahard pellets to have a spherical shape.
7. The method of claim 1 , wherein:
crushing at least a portion of the ultrahard pellets to form crushed ultrahard particles comprises crushing only a portion of the ultrahard pellets to form the crushed ultrahard particles;
mixing the crushed ultrahard particles with spherical sintered tungsten carbide pellets comprises mixing the crushed ultrahard particles with the spherical sintered tungsten carbide pellets and a remaining portion of the ultrahard pellets; and
dispersing the crushed ultrahard particles and the spherical sintered tungsten carbide pellets in a matrix metal comprises dispersing the crushed ultrahard particles, the spherical sintered tungsten carbide pellets, and the remaining portion of the ultrahard pellets in the matrix metal.
8. A method of forming a hardfacing composition, comprising:
forming ultrahard pellets each comprising tungsten carbide grains, elemental cobalt, and elemental vanadium;
crushing a portion of the ultrahard pellets to form crushed ultrahard particles;
mixing the ultrahard pellets and the crushed ultrahard particles with spherical sintered tungsten carbide pellets, spherical cast carbide pellets, and monocrystalline particles comprising tungsten carbide; and
dispersing the ultrahard pellets, the crushed ultrahard particles, the spherical sintered tungsten carbide pellets, the spherical cast carbide pellets, and the monocrvstalline particles in a matrix metal comprising iron, nickel, or alloys thereof.
9. A method of hardfacing a downhole tool, comprising:
forming ultrahard pellets comprising tungsten carbide grains, elemental cobalt, and elemental vanadium;
crushing a portion of the ultrahard pellets to form crushed ultrahard particles;
mixing the ultrahard pellets and the crushed ultrahard particles with spherical sintered tungsten carbide pellets;
dispersing the ultrahard pellets, the crushed ultrahard particles, and the spherical sintered tungsten carbide pellets in a matrix metal comprising iron, nickel, or alloys thereof to form a hardfacing composition; and
applying the hardfacing composition over at least one portion of the downhole tool to form a hardfacing layer over the downhole tool.
10. The method of claim 9 , wherein applying the hardfacing composition over at least one portion of the downhole tool comprises applying the hardfacing composition using a plasma transferred arc process.
11. The method of claim 9 , wherein applying the hardfacing composition over at least one portion of the downhole tool comprises applying the hardfacing composition using an oxyacetylene torch and a rod.
12. A method of forming an earth-boring bit, comprising:
forming a bit body, bit legs, and cones rotatably mounted to the bit legs; and
forming at least one hardfacing layer over outer surfaces of the bit legs, the at least one hardfacing layer comprising:
ultrahard pellets comprising tungsten carbide, elemental vanadium, and at least one of cobalt, iron, and nickel; and
a matrix metal comprising iron, nickel, or alloys thereof, the ultrahard pellets dispersed in the matrix metal.
13. The method of claim 12 , further comprising forming the at least one hardfacing layer over one or more of teeth of the cones and gage surfaces of the cones.
14. A method of forming an earth-boring bit, comprising:
forming a bit body, bit legs, and cones rotatably mounted to the bit legs; and
forming at least one hardfacing layer over one or more of leading edges and trailing edges of the bit legs, the at least one hardfacing layer comprising:
ultrahard pellets comprising tungsten carbide, elemental vanadium, and at least one of cobalt, iron, and nickel; and
a matrix metal comprising iron, nickel, or alloys thereof, the ultrahard pellets dispersed in the matrix metal.