Abrading – Rigid tool
Reexamination Certificate
1998-08-10
2001-03-06
Scherbel, David A. (Department: 3723)
Abrading
Rigid tool
C451S539000, C451S542000
Reexamination Certificate
active
06196910
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to supported polycrystalline diamond (PCD) compacts made under high temperature/high pressure (HT/HP) processing conditions, and more particularly to supported PCD compacts having improved shear strength, impact resistance properties and cutting performance.
A compact may be characterized generally as an integrally-bonded structure formed of a sintered, polycrystalline mass of abrasive particles, such as diamond, CBN, CBN compounds and ceramics and other like compounds. Although such compacts may be self-bonded without the aid of a bonding matrix or second phase, it generally is preferred, as is discussed in U.S. Pat. Nos. 4,063,909 and 4,601,423 to employ a suitable bonding matrix which usually is a metal such as cobalt, iron, nickel, platinum, titanium, chromium, tantalum, or an alloy or mixture thereof. The bonding matrix, which is provided at from about 10% to 30% by volume, additionally may contain a recrystallization or growth catalyst such as aluminum for CBN or cobalt for diamond.
Abrasive compacts are used extensively in cutting, milling, grinding, drilling, and other abrasive operations. The abrasive compacts typically consist of polycrystalline diamond, CBN or like particles bonded into a coherent hard conglomerate. The abrasive particle content of the abrasive compact is high and there is an extensive amount of direct particle-to-particle bonding. Abrasive compacts are made under elevated temperature and pressure conditions at which the abrasive particles, be it diamond, CBN, CBN compounds or ceramics or like compounds, are crystallographically stable.
Abrasive compacts tend to be brittle and, in use, they are frequently reinforced by a cemented carbide substrate. Such supported abrasive compacts are known in the art as composite abrasive compacts. Composite abrasive compacts may be used as such in the working surface of an abrasive tool. Alternatively, particularly in drilling and mining operations, it has been found advantageous to bond the composite abrasive compact to an elongated cemented carbide pin to produce what is known as a stud cutter. The stud cutter then is mounted, for example, in the working surface of a drill bit or a mining pick.
Fabrication of the composite compact typically is achieved by placing a cemented carbide substrate into the container of a press. A mixture of diamond grains or diamond grains and catalyst binder is placed atop the substrate and compressed under HP/HT conditions. In so doing, metal binder migrates from the substrate and “sweeps” through the diamond grains to promote a sintering of the diamond grains. As a result, the diamond grains become bonded to each other to form a diamond layer which concomitantly is bonded to the substrate along a conventionally planar interface. Metal binder remains disposed in the diamond layer within pores defined between the diamond grains.
For many applications, it is preferred that the compact is supported by its bonding to substrate material to form a laminate or supported compact arrangement. Typically, the substrate material is provided as a cemented metal carbide which comprises, for example, tungsten, titanium, or tantalum carbide particles, or a mixture thereof, which are bonded together with a binder of between about 6% to about 25% by weight of a metal such as cobalt, nickel, or iron, or a mixture or alloy thereof. As is shown, for example, in U.S. Pat. Nos. 3,381,428; 3,852,078, and 3,876,751, compacts and supported compacts have found acceptance in a variety of applications as parts or blanks for cutting and dressing tools, as drill bits, and as wear parts or surfaces.
The basic HT/HP method for manufacturing the polycrystalline compacts and supported compacts of the type herein involved entails the placing of an unsintered mass of abrasive, crystalline particles, such as diamond, CBN, CBN compounds and ceramics and like compounds and/or a mixture thereof, within a protectively shielded metal enclosure which is disposed within the reaction cell of a HT/HP apparatus of a type described further in U.S. Pat. Nos. 2,947,611; 2,941,241; 2,941,248; 3,609,818; 3,767,371; 4,289,503; 4,673,414, and 4,954,139. Additionally, a metal catalyst may be placed in the enclosure with the abrasive particles if the sintering of diamond particles is contemplated, as well as a pre-formed mass of a cemented metal carbide for supporting the abrasive particles and to thereby form a supported compact therewith. The contents of the cell then are subjected to processing conditions selected as sufficient to effect intercrystalline bonding between adjacent grains of the abrasive particles and, optionally, the joining of the sintered particles to the cemented metal carbide support. Such processing conditions generally involve the imposition for about 3 to 120 minutes of a temperature of at least 1300° C. and a pressure of at least 20 kbar.
As to the sintering of polycrystalline diamond compacts or supported compacts, the catalyst metal may be provided in a pre-consolidated form disposed adjacent the crystal particles. For example, the metal catalyst may be configured as an annulus into which is received a cylinder of abrasive crystal particles, or as a disc which is disposed above or below the crystalline mass. Alternatively, the metal catalyst, or solvent as it is also known, may be provided in a powdered form and intermixed with the abrasive crystalline particles, or as a cemented metal carbide or carbide molding powder which may be cold pressed into shape and wherein the cementing agent is provided as a catalyst or solvent for diamond recrystallization or growth. Typically, the metal catalyst or solvent is selected from cobalt, iron, or nickel, or an alloy or mixture thereof, but other metals such as ruthenium, rhodium, palladium, chromium, manganese, tantalum, and alloys and mixtures thereof also may be employed.
Under the specified HT/HP conditions, the metal catalyst, in whatever form provided, is caused to penetrate or “sweep” into the abrasive layer by means of diffusion, capillary action or pressure gradient and is thereby made available as a catalyst or solvent for recrystallization or crystal intergrowth. The HT/HP conditions, which preferably operate in the diamond stable thermodynamic region above the equilibrium between diamond and graphite phases, effect a compaction of the abrasive crystal particles which is characterized by intercrystalline diamond-to-diamond bonding wherein parts of each crystalline lattice are shared between adjacent crystal grains. Preferably, the diamond concentration in the compact or in the abrasive table of the supported compact is at least about 70% by volume. Methods for making diamond compacts and supported compacts are more fully described in U.S. Pat. Nos. 3,141,746; 3,745,623; 3,609,818; 3,850,591; 4,394,170; 4,403,015; 4,797,326, and 4,954,139.
As to polycrystalline CBN compacts, CBN ceramics and supported compacts, such compacts and supported compacts are manufactured in general accordance with the methods suitable for diamond compacts. However, in the formation of CBN compacts or ceramics via the previously described “sweep-through” method, the metal which is swept through the crystalline mass need not necessarily be a catalyst or solvent for CBN recrystallization. Accordingly, a polycrystalline mass of a CBN composition may be joined to a cobalt-cemented tungsten carbide substrate by the sweep through of the cobalt from the substrate and into the interstices of the crystalline mass notwithstanding that cobalt is not a catalyst or solvent for the recrystallization of the CBN composition. Rather, the interstitial cobalt functions as a binder between the polycrystalline CBN compacts or ceramics and the cemented tungsten carbide substrate.
As it was for diamond, the HT/HP sintering process for CBN is effected under conditions in which CBN is the thermodynamically stable phase. It is speculated that under these conditions, intercrystalline bonding between adjacent crystal grains also is effected. The CBN concen
Johnson David M.
Lucek John W.
General Electric Company
McDonald Shantese
Scherbel David A.
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