Low melting point copper-manganese-zinc alloy for infiltration binder in matrix body rock drill bits

#The invention relates to an alloy which is useful as an infiltration binder for bonding diamond cutting elements to a matrix body. More particularly, the invention relates to a low melting point copper-manganese-zinc alloy that is useful as an infiltration binder to bond diamond or other superhard cutting elements to a matrix body, such as a matrix drill bit body. The invention also relates to a process for producing a coherent matrix body by infiltrating a matrix powder with the new low melting point copper-manganese-zinc alloy.

#The invention described herein is especially useful for the manufacture of rotary drill bits of the kind comprising a bit body having an external surface on which are mounted a plurality of cutting elements for cutting or abrading rock formations, and an inner passage for supplying drilling fluid to one or more nozzles at the external surface of the bit. The nozzles are located at the surface of the bit body so that drilling fluid emerges from the nozzles and flows by the cutting elements during drilling so as to cool and/or clean them. Desirably, the cutting elements are preformed cutting elements having a superhard cutting face formed of polycrystalline diamond or another superhard material.

#As will be understood by persons skilled in the art, the term "superhard" is used to describe diamond and cubic boron nitride materials. For convenience, the term "diamond" is used herein interchangeably with the term "superhard" and is meant to include diamond (single crystal and polycrystalline) materials made at high or low pressure (metastable growth), as well as cubic boron nitride materials.

#FIG. 1 is a schematic, vertical section through a mold showing the manufacture of a rotary drill bit in accordance with the present invention.

#FIG. 2 is a partial sectional view of a rotary drill bit formed in the mold of FIG. 1.

#In accordance with the present invention, a new infiltration alloy is provided which is useful in the manufacture of a matrix body. In its broadest sense, the new infiltration alloy comprises about 5 to 65% by weight of manganese, about 0 to 35% zinc, and the balance copper. More preferably, the infiltration alloy comprises about 20 to 30% by weight of manganese, about 10 to 25% by weight of zinc, and the balance copper.

#Infiltration alloys of these compositions have melting points in the range of about 830.degree. C. to about 980.degree. C., and an infiltration temperature of not greater than about 1050.degree. C. The infiltrating temperature is generally higher than the melting point of the alloy in order to decrease the alloy's viscosity after it has melted, and thus to increase its penetration rate into the matrix powder material. The inventive infiltration alloy may also contain minor amounts of other alloying elements, so long as they do not increase the melting point above about 980.degree. C. For example, the inventive infiltration alloys may also contain about 0.1 to about 5% by weight of silicon, about 0.1 to about 1% by weight of tin, or about 0.1 to about 1% by weight of boron.

#The inventive infiltration alloy may be used to form a matrix drill bit. Referring to FIG. 1, an apparatus and a method for using the new infiltration alloy to form a matrix drill bit are illustrated. The apparatus comprises a two-part mold 10 formed from graphite or another suitable material, such as sand, plaster of Paris, a ceramic material, or a metal coated with a material which is inert to the infiltration binder and the matrix material. The mold 10 has an internal configuration corresponding generally to the required surface of the bit body or portion thereof. The mold 10 includes sockets positioned on its interior surface which are adapted for receiving the diamond cutters 12.