Sintered bodies for earth-boring rotary drill bits and methods of forming the same

Abstract

The present invention relates to compositions and methods for forming a bit body for an earth-boring bit. The bit body may comprise hard particles, wherein the hard particles comprise at least one carbide, nitride, boride, and oxide and solid solutions thereof, and a binder binding together the hard particles. The binder may comprise at least one metal selected from cobalt, nickel, and iron, and, optionally, at least one melting point reducing constituent selected from a transition metal carbide in the range of 30 to 60 weight percent, boron up to 10 weight percent, silicon up to 20 weight percent, chromium up to 20 weight percent, and manganese up to 25 weight percent, wherein the weight percentages are based on the total weight of the binder. In addition, the hard particles may comprise at least one of (i) cast carbide (WC+W2C) particles, (ii) transition metal carbide particles selected from the carbides of titanium, chromium, vanadium, zirconium, hafnium, tantalum, molybdenum, niobium, and tungsten, and (iii) sintered cemented carbide particles.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of application Ser. No. 11 / 116,752, filed Apr. 28, 2005, pending, the disclosure of which is incorporated herein by reference in its entirety.FIELD OF TECHNOLOGY [0002] This invention relates to improvements to earth-boring bits and methods of producing earth-boring bits. More specifically, the invention relates to earth-boring bit bodies, roller cones, insert roller cones, cones and teeth for roller cone earth-boring bits and methods of forming earth-boring bit bodies, roller cones, insert roller cones, cones and teeth for roller cone earth-boring bits. BACKGROUND OF THE TECHNOLOGY [0003] Earth-boring bits may have fixed or rotatable cutting elements. Earth-boring bits with fixed cutting elements typically include a bit body machined from steel or fabricated by infiltrating a bed of hard particles, such as cast carbide (WC+W2C), tungsten carbide (WC), and / or sintered cemented carbide with a binder suc...

AI Technical Summary

Benefits of technology

[0017] In the manufacture of bit bodies, hard particles and, optionally, inserts may be placed within a bit body mold. The inserts may be incorporated into the articles of the present invention by any method. For example, the inserts may be added to the mold before filling the mold with the powdered metal or hard particles and any inserts present may be infiltrated with a molten binder, which freezes to form a solid matrix body including a discontinuous phase of hard particles within a continuous phase of binder. Embodiments of the present invention also include methods of forming articles, such as, but not limited to, bit bodies for earth-boring bits, roller cones, and teeth for rolling cone drill bits. An embodiment of the method of forming an article may comprise infiltrating a mass of hard particles comprising at least one transition metal carbide with a binder comprising at least one of nickel, iron, and cobalt and having a melting point less than 1350° C. Another embodiment includes a method comprising infiltrating a mass of hard particles comprising at least one transition metal carbide with a binder having a melting point in the range of 1050° C. to 1350° C. The binder may comprise at least one of iron, nickel, and cobalt, wherein the total concentration of iron, nickel, and cobalt is from 40 to 99 weight percent by weight of the binder. The binder may further comprise at least one of a selected transition metal carbide, tungsten carbide, tungsten, carbon, boron, silicon, chromium, manganese, silver, aluminum, copper, tin, and zinc in a concentration effective to reduce the melting point of the iron, nickel, and / or cobalt. The binder may be a eutectic or near eutectic mixture. The lowered melting point of the binder facilitates proper infiltration of the mass of hard particles.

Problems solved by technology

A difficulty with fabricating a bit body or holder comprising a binder including at least one of cobalt, iron, and nickel by an infiltration method stems from the relatively high melting points of cobalt, iron, and nickel.

The melting point of each of these metals at atmospheric pressure is approximately 1500° C. In addition, since cobalt, iron, and nickel have high solubilities in the liquid state for tungsten carbide, it is difficult to prevent premature freezing of, for example, a molten cobalt-tungsten or nickel-tungsten carbide alloy while attempting to infiltrate a bed of tungsten carbide particles when casting an earth-boring bit body.

This phenomenon may lead to the formation of pin-holes in the casting even with the use of high temperatures, such as greater than 1400° C., during the infiltration process.

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