Bit leg and cone hardfacing for earth-boring bit
View Patent ↗An earth-boring bit has a bit body, and a bit leg depending from the bit body with a circumferentially extending outer surface, a leading side and a trailing side. A cone is rotatably mounted on a cantilevered bearing shaft depending inwardly from the bit leg. A first layer of a hardfacing composition of carbide particles dispersed in a nickel-based matrix is formed on the bit leg. A second layer of a hardfacing composition of carbide particles dispersed in an iron-based matrix that is formed on the cone. The first layer of hardfacing is applied by conveying carbide particles in a nickel-based matrix through a pulsed plasma transferred arc process. The second layer of hardfacing is applied with a torch and a hardfacing tube comprising carbide particles held within an iron-based tube.
1. An earth-boring bit comprising:
a bit body;
a bit leg depending from the bit body and having a circumferentially extending outer surface, a leading side and a trailing side;
a cone rotatably mounted on a cantilevered bearing shaft depending inwardly from the bit leg;
a first layer formed on the bit leg of a hardfacing composition of carbide particles dispersed in a nickel-based matrix, defining a first hardfacing layer wherein nickel comprises a primary metal of the nickel-based matrix; and
a second layer formed on the cone of a hardfacing composition of carbide particles dispersed in an iron-based matrix, defining a second hardfacing layer wherein iron comprises a primary metal of the iron-based matrix.
2. The earth-boring bit of claim 1 , further comprising a shirttail being defined along an edge of the bit leg that corresponds with the cone, and at least a portion of the first layer of hardfacing is formed on the shirttail.
3. The earth-boring bit of claim 1 , wherein the cone further comprises a plurality of teeth on the cone, and the second hardfacing layer is also formed on at least a portion of the teeth.
4. The earth-boring bit of claim 3 , wherein the gage hardfacing layer comprises the first hardfacing layer.
5. The earth-boring bit of claim 1 , wherein the cone further comprises a gage surface, and a gage hardfacing layer selected from a group consisting of the first hardfacing layer and the second hardfacing layer is formed the gage surface.
6. The earth-boring bit of claim 1 , wherein the first hardfacing layer is formed on the leading side of the bit leg and extends toward the trailing side of the bit leg.
7. The earth-boring bit of claim 1 , wherein the first hardfacing layer extends from the shirttail along the leading side of the bit leg.
8. The earth-boring bit of claim 1 , wherein the first hardfacing layer comprises sintered carbide pellets in a size range between about 37 to about 420 microns in diameter, each pellet comprising tungsten carbide within a binder of cobalt.
9. The earth-boring bit of claim 1 , the first hardfacing layer comprises sintered carbide pellets in a size range between about 75 to about 177 microns in diameter, each pellet comprising tungsten carbide within a binder of cobalt.
10. The earth-boring bit of claim 1 , wherein the first hardfacing layer comprises spherical cast carbide pellets in a size range between about 45 to about 160 microns in diameter and spherical sintered carbide pellets in a size range between about 75 to about 177 microns in diameter.
11. The earth-boring bit of claim 1 , wherein:
the first hardfacing layer comprises spherical cast carbide pellets in a size range between about 45 to about 160 microns in diameter and sintered carbide pellets in a size range between about 75 to about 177 microns in diameter; and
the second hardfacing layer comprises spherical sintered carbide pellets in a size range between about 590 to about 1190 microns in diameter.
12. The earth-boring bit of claim 1 , wherein:
the first hardfacing layer comprises spherical cast carbide pellets in a size range between about 45 to about 160 microns in diameter and sintered carbide pellets in a size range between about 75 to about 177 microns in diameter; and
the second hardfacing layer comprises spherical sintered carbide pellets in a size range between about 590 to about 1190 microns in diameter, and spherical cast carbide pellets in a size range between about 177 to about 250 microns in diameter.
13. An earth-boring bit comprising:
a bit body;
a bit leg depending from the bit body and having a circumferentially extending outer surface, a leading side and a trailing side;
a cone rotatably mounted on a cantilevered bearing shaft depending inwardly from the bit leg;
a shirttail being defined along an edge of the bit leg that corresponds with the cone;
a layer of hardfacing formed on the shirttail, the hardfacing having a composition of carbide particles dispersed in a nickel-based matrix, defining a first hardfacing layer that contains more nickel than any other metal;
a plurality of teeth on the cone; and
a layer formed on at least a portion of the teeth of a hardfacing composition of carbide particles dispersed in an iron-based matrix, defining a second hardfacing layer that contains more iron than any other metal.
14. An earth-boring bit comprising:
a bit body;
a bit leg depending from the bit body and having a circumferentially extending outer surface, a leading side and a trailing side;
a cone rotatably mounted on a cantilevered bearing shaft depending inwardly from the bit leg;
a layer formed on the bit leg of a hardfacing composition of sintered tungsten carbide pellets less than about 177 microns in diameter dispersed in a nickel-based matrix consisting essentially of nickel; and
a layer formed on the cone of a hardfacing composition of carbide particles dispersed in an iron-based matrix wherein iron comprises a primary metal of the iron-based matrix.