US20060213128A1

US20060213128A1 - Methods of maximizing retention of superabrasive particles in a metal matrix

Info

Publication number: US20060213128A1
Application number: US11/351,283
Authority: US
Inventors: Chien-Min Sung
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-09-24
Filing date: 2006-02-08
Publication date: 2006-09-28

Abstract

Methods of making superabrasive tools having improved retention of superabrasive particles in a metal matrix are provided. Such methods may include providing a substrate, providing superabrasive particles, chemically bonding the superabrasive particles with the metal matrix to a degree which holds the superabrasive particles in the metal matrix without substantially degrading the superabrasive particles, and metallurgically bonding the superabrasive particles to the substrate with the metal matrix.

Description

PRIORITY DATA

This application is a continuation-in-part of U.S. patent application Ser. No. 11/223,790, filed Sep. 8, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 11/009,370, filed Dec. 9, 2004, which is a continuation-in-part of U.S. patent application Ser. No. 10/627,441, filed Jul. 25, 2003, which is a continuation-in-part of U.S. patent application Ser. No. 10/254,057, filed Sep. 24, 2002, which has issued as U.S. Pat. No. 6,830,598, each of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to devices that incorporate superabrasive materials, and methods for the production and use thereof. Accordingly, the present invention involves the fields of chemistry, physics, and materials science.

BACKGROUND OF THE INVENTION

Various industries use chemical mechanical planarization (CMP) for polishing certain work pieces. Specifically, the computer manufacturing industry has begun to rely heavily on CMP processes for polishing wafers of ceramics, silicon, glass, quartz, and metals. Such polishing processes generally entail applying the wafer against a rotating pad made from a durable organic substance such as polyurethane. A chemical slurry containing abrasive particles and chemical compounds is applied to the pad during the polishing operation. The chemical compounds break down the substance of the wafer, and the abrasive particles act to physically erode the wafer surface. This slurry is continually added to the spinning CMP pad, and the dual chemical and mechanical forces exerted on the wafer cause it to be polished in a desired manner.
Of particular importance to the quality of the polishing achieved is the distribution of the abrasive particles throughout the pad. The top of the pad holds the particles within fibers or small pores which provide a friction force sufficient to prevent the particles from being thrown off of the pad due to the centripetal force exerted by the pad's spinning motion. Therefore, it is important to keep the top of the pad as flexible as possible, and to keep the fibers as erect as possible, or to assure that there are an abundance of openings and pores available to receive new abrasive particles.
A problem with maintaining the top of the pad is caused by an accumulation of polishing debris coming from the work piece, abrasive slurry, and dressing disk. This accumulation causes a “glazing” or hardening of the top of the pad, and mats the fibers down, thus making the pad less able to hold the abrasive particles of the slurry, and thus significantly decreases the pad's overall polishing performance. Further, with many pads the pores used to hold the slurry become clogged, and the overall asperity of the pad's polishing surface becomes depressed and matted. Attempts have been made to revive the top of the pad by “combing” or “cutting” it with various devices. This process has come to be known as “dressing” or “conditioning” the CMP pad. Many types of devices and processes have been used for this purpose. One such device is a disk with a plurality of attached super hard crystalline particles.
Various methods have been utilized to attach superabrasive particles to a substrate to form a CMP pad dresser. One method includes embedding the superabrasive particles in a metal matrix where they are held in place by mechanical forces created by a portion of the metal matrix directly surrounding the particles. A variety of consolidation techniques, such as electroplating, sintering, or hot pressing a matrix around superabrasive particles is known. However, because the matrix surrounding the superabrasive particles is softer than the superabrasive particles, it wears away more quickly during use, and leaves the diamond particles overexposed, and unsupported. As a result, the diamond particles become prematurely dislodged and shorten the service life of the tool.
A number of attempts have been made to overcome the above-recited shortcoming. Most notably, several techniques that attempt to chemically bond the superabrasive particles to the matrix, or other substrate material, have been employed. The main focus of such techniques is to coat or otherwise contact the superabrasive particle with a reactive element that is capable of forming a carbide bond between the superabrasive particle and the metal matrix. Such reactive elements may include materials such as titanium, chromium, tungsten, etc. Examples of specific processes include those disclosed in U.S. Pat. Nos. 3,650,714, 4,943,488, 5,024,680, and 5,030,276, each of which is incorporated herein by reference. Such processes, however, may be difficult for a variety of reasons, including the highly inert nature of most superabrasive particles, and the high melting point of most reactive materials. Moreover, while chemically bonding the superabrasive particle to the matrix material via carbide bonds creates a much stronger relationship between the superabrasive particle and the matrix material, the carbide materials formed are not as strong as the superabrasive materials, thus potentially decreasing the integrity of the relationship.
Further, the melting point of most reactive metal materials is well above the stability threshold temperature of most superabrasives. To this end, the method by which the reactive material may be applied to the superabrasives is generally limited to either solid-state reactions or gas reactions that are carried out at a temperature that is sufficiently low so that damage to the diamond does not occur. Such processes are only capable of achieving a monolithic coating, and cannot produce an alloy coating. While the strength of the carbide bonds formed using these techniques generally improves particle retention over mere mechanical bonds, they still allow superabrasive particles to become dislodged prematurely.
Another method of forming carbide bonds is by using a braze alloy that contains a reactive element. The braze alloy is consolidated around the superabrasive particles by sintering. One example of a specific process of this type is found in U.S. Pat. No. 6,238,280, which is incorporated herein by reference. While such processes may yield a tool that has greater grit retention than tools having no chemical bonding of the superabrasive particles, as a general matter, solid-state sintering of the braze alloy only consolidates the matrix material, and does not attain as much chemical bonding as the solid and gas state deposition techniques.
Additionally, the use of conventional braze may be limited, as it generally also serves as the matrix material for the body of the dresser. Most braze alloys are ill equipped to act as a bonding medium and simultaneously act as the matrix material, due to the specific characteristics required by each of these elements during use. For example, in order to achieve greater carbide bonding, some superabrasive particles may require alloys that are too soft for the intended dressing application. A matrix that is made of a material that is too soft may wear away too quickly and allow the superabrasive particles to dislodge prematurely.
As such, CMP pad dressers that display improved superabrasive particle retention and wear characteristics, including methods for the production thereof, continue to be sought through ongoing research and development efforts.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides superabrasive tools having improved superabrasive particle retention, and methods of making such tools. As such, in one aspect a method is provided for making a superabrasive tool having improved retention of superabrasive particles in a metal matrix. Such a method may comprise providing a substrate, providing superabrasive particles, chemically bonding the superabrasive particles with the metal matrix to a degree which holds the superabrasive particles in the metal matrix without substantially degrading the superabrasive particles, and metallurgically bonding the superabrasive particles to the substrate with the metal matrix. Various methods of avoiding substantially degrading the superabrasive particles further are contemplated, including protecting the superabrasive particles from over-bonding during the chemical bonding process. Such protection from over-bonding may further include, for example, moderating chemical bonding between the superabrasive particles and the metal matrix to a degree which is sufficient to retain the superabrasive particles in the metal matrix but minimize superabrasive particle degradation. In one aspect, superabrasive particle degradation may include conversion of the superabrasive particles to a different material. Different materials may include any material into which a superabrasive is converted during chemical bonding, including non-diamond forms of carbon, carbides, nitrides, borides, and combinations thereof.
Various mechanisms of moderating chemical bonding between the superabrasive particles and the metal matrix are contemplated, all of which are intended to be included within the scope of the present invention. Such moderation may include varying the available amount of a reactive element in the metal matrix. In one aspect, for example, moderating chemical bonding may include moderating or even minimizing the relative amount of a reactive element in the metal matrix.
The moderation of chemical bonding may also be accomplished by diluting the metal matrix with a protective material which moderates chemical bonding between the superabrasive particles and the metal matrix. In one aspect, dilution of the metal matrix may include coating the superabrasive particles with the protective material prior to chemically bonding with the metal matrix. In another aspect, dilution of the metal matrix may include admixing the protective material with the metal matrix prior to chemically bonding to the superabrasive particles.
Various protective materials are contemplated that may function to protect the superabrasive particles from over-bonding during chemical bonding to the metal matrix. Examples include, without limitation, copper, silver, zinc, tin, titanium, silicon, chromium, tungsten, zirconium, and mixtures thereof, including carbides, nitrides, and alloys thereof. In one aspect, the protectant may be copper.
In one aspect, the superabrasive particles may be coated with the protective material prior to chemically bonding with the metal matrix. In another aspect, uncoated superabrasive particles may be incorporated into a superabrasive tool, provided that the metal matrix is diluted with the protective material to protect the superabrasive particles from over-bonding during the process of chemically bonding them to the metal matrix. Such a dilution may be accomplished by admixing the protective material with the metal matrix prior to chemically bonding to the superabrasive particles.
Concerning superabrasive particles, any super hard material suitable for use as a superabrasive is considered to be within the scope of the present invention. Specific examples include, without limitation, diamond, polycrystalline diamond, cubic boron nitride, polycrystalline cubic boron nitride, and combinations thereof.
The present invention also provides superabrasive tools made by the methods as described. In one aspect, a superabrasive tool is provided which may include a substrate, and a plurality of superabrasive particles metallurgically bonded to the substrate with a metal matrix, at least a portion of each of the plurality of superabrasive particles being chemically bonded to the metal matrix as recited herein. Various superabrasive tools are contemplated, including, without limitation, CMP pad dressers, wire saws, chain saws, saw blades, circular saws, frame saws, profile wheels, grinding wheels, drill bits, hole saws, and combinations thereof.
There has thus been outlined, rather broadly, various features of the invention so that the detailed description thereof that follows may be better understood, and so that the present contribution to the art may be better appreciated. Other features of the present invention will become clearer from the following detailed description of the invention, taken with the accompanying claims, or may be learned by the practice of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 a is a side view of a coated superabrasive particle in accordance with one embodiment of the present invention.
FIG. 1 b is a side view of a coated superabrasive particle in accordance with one embodiment of the present invention.
FIG. 1 c is a side view of a coated superabrasive particle having superabrasive particles of a smaller size chemically bonded thereto in accordance with one embodiment of the present invention.
FIG. 2 is a side view of a tool precursor in accordance with one embodiment of the present invention.
FIG. 3 is a side view of a tool precursor in accordance with another embodiment of the present invention.
FIG. 4 is a perspective view of a superabrasive tool having a plurality of precursors metallurgically bonded thereto such that the superabrasive particles are arranged according to a predetermined pattern in accordance with one embodiment of the present invention.
FIG. 5 is a sectional view of a superabrasive tool having a plurality of coated superabrasive particles randomly placed in a porous support matrix.
FIG. 6 is a front end view of a superabrasive tool having a plurality of diamond and substrate layers bonded together in accordance with one embodiment of the present invention.
FIG. 7 is a sectional view of a superabrasive tool having a plurality of braze coated diamond particles metallurgically bonded together, along with a plurality of spacer particles chemically bonded to the braze alloy, and having pores in the alloy in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

Before the present invention is disclosed and described, it is to be understood that this invention is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.
It must be noted that, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a diamond particle” includes one or more of such particles, reference to “a carbon source” includes reference to one or more of such carbon sources, and reference to “a reactive material” includes reference to one or more of such materials.
Definitions
In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set forth below.
As used herein, “super hard” and “superabrasive” may be used interchangeably, and refer to a crystalline, or polycrystalline material, or mixture of such materials having a Vicker's hardness of about 4000 Kg/mm²or greater. Such materials may include without limitation, diamond, and cubic boron nitride (cBN), as well as other materials known to those skilled in the art. While superabrasive materials are very inert and thus difficult to form chemical bonds with, it is known that certain reactive elements, such as chromium and titanium are capable of chemically reacting with superabrasive materials at certain temperatures.
As used herein, “superabrasive particles” and “superabrasive grits” may be used interchangeably, and refer to particles of either natural or synthetic diamond, super hard crystalline, or polycrystalline substance, or mixture of substances and include but are not limited to diamond, polycrystalline diamond (PCD), cubic boron nitride (CBN), and polycrystalline cubic boron nitride (PCBN). Further, the terms “abrasive particle,” “grit,” “diamond,” “PCD,” “CBN,” and “PCBN,” may be used interchangeably. Such particles or grits may take a variety of shapes, including round, oblong, square, euhedral, etc., as well as a number of specific mesh sizes. As is known in the art, “mesh” refers to the number of holes per unit area as in the case of U.S. meshes.
As used herein, “superabrasive tool” refers to a tool having at least one associated superabrasive particle.
As used herein, “centrally located particle” means any particle of a superabrasive tool that under normal working circumstances receives a reduced work load as compared to a peripherally located particle. In some aspects, “central” or “centrally located” refers to an area of a CMP pad dresser or other superabrasive tool that originates at a center point of the tool and extends outwardly towards the tool's edge for up to about 90% of the radius of the tool. In some aspects, the area may extend outwardly from about 20% to about 90% of the radius. In other aspects, the area may extend out to about 50% of the radius. In yet another aspect, the area may extend out to about 33% of the radius of the tool.
As used herein, “peripherally located” means any particle of a superabrasive tool that under normal working circumstances that receives an excess work load as compared to the centrally located particles. In some aspects, “periphery” or “peripheral” or “peripherally located” may refer to an area that originates at the leading edge or outer rim of a CMP pad dresser or other superabrasive tool and extends inwardly towards the center for up to about 90% of the radius of the tool. In some aspects, the area may extend inwardly from about 20% to 90% of the radius. In other aspects, the area may extend in to about 50% of the radius. In yet another aspect, the area may extend in to about 33% of the radius of the tool (i.e. 66% away from the center).
As used herein, “metallic” refers to a metal, or an alloy of two or more metals. A wide variety of metallic materials is known to those skilled in the art, such as aluminum, copper, chromium, iron, steel, stainless steel, titanium, tungsten, zinc, zirconium, molybdenum, etc., including alloys and compounds thereof.
As used herein, “alloy” refers to a solid or liquid mixture of a metal with a second material, said second material may be a non-metal, such as carbon, a metal, or an alloy which enhances or improves the properties of the metal.
As used herein, “braze alloy,” “brazing alloy,” “metal matrix,” and “metal alloy” may be used interchangeably, and refer to an alloy containing a sufficient amount of a reactive element to allow the formation of chemical bonds between the alloy and a superabrasive particle. The alloy may be either a solid or liquid solution of a metal carrier solvent having a reactive element solute therein. Moreover, “brazed” may be used to refer to the formation of chemical bonds between a superabrasive particle and a braze alloy.
As used herein, “amorphous braze” refers to a homogenous braze composition having a non-crystalline structure. Such alloys contain substantially no eutectic phases that melt incongruently when heated. Although precise alloy composition is difficult to ensure, the amorphous brazing alloy as used herein should exhibit a substantially congruent melting behavior over a narrow temperature range.
As used herein, “support matrix,” “tool matrix,” and “substrate” may be used interchangeably, and refer to a material or substance that is capable of receiving superabrasive elements, including tools, tool precursors, and precursor elements as recited herein, which may be of the same or a different material than that used for the metal matrix. In some aspects, a support matrix may be a complete tool body, and in other aspects, a support matrix may be only a portion or segment of a tool body.
As used herein, “reactive element” and “reactive metal” may be used interchangeably, and refer to a metal element that can chemically react with and chemically bond to a superabrasive particle. Examples of reactive elements may include without limitation, transition metals such as titanium (Ti) and chromium (Cr), including refractory elements, such as zirconium (Zr) and tungsten (W), as well as non-transition metals and other materials, such as aluminum (Al). Further, certain elements such as silicon (Si) which are technically non-metals may be included as a reactive element in a brazing alloy.
As used herein, the term “protective material” refers to a metal element, a mixture of metal elements, a mixture of metal and non-metal elements, a non-metal element, or a mixture of non-metal elements that do not significantly react with and chemically bond to a superabrasive particle. Examples of protective materials may include without limitation, copper (Cu), gold (Au), silver (Ag), tin (Sn), zinc (Zn), and mixtures thereof. “Protective material” may also refer to reactive elements that react with superabrasive particles to a lesser extent than other reactive elements in the metal matrix. As such, these “less reactive” elements may function to protect superabrasive particles from over-bonding when utilized with a metal matrix containing elements of greater reactivity.
As used herein “wetting” refers to the process of flowing a molten metal across at least a portion of the surface of a superabrasive particle. Wetting is often due, at least in part, to the surface tension of the molten metal, and may lead to the forming of chemical bonds between the superabrasive particle and the molten metal at the interface thereof, when a reactive element is present.
As used herein, “metallurgical bond” refers to a bond between two or more metals. Such bonds may be a simple mechanical lock or bond between the metals, such as one created by the intertwining of liquid metals and the solidification thereof. Further, such bonds may be chemical in nature, such as typical ionic bonding that occurs between metals.
As used herein, “chemical bond” and “chemical bonding” may be used interchangeably, and refer to a molecular bond that exert an attractive force between atoms that is sufficiently strong to create a binary solid compound at an interface between the atoms. Chemical bonds involved in the present invention are typically carbides in the case of diamond superabrasive particles, or nitrides or borides in the case of cubic boron nitride.
As used herein, “coat,” “coating,” and “coated,” refers to an area along at least a portion of an outer surface of the superabrasive particle that has been intimately contacted with a reactive metal, a reactive metal alloy, or a protective material. In the case of the reactive metal, chemical bonds may be formed between the particle and the metal or alloy, or such chemical bonding may form upon the liquification and solidification of the reactive metal, or reactive metal alloy. Because protective materials generally do not react with the superabrasive particle, protective material coatings may be coupled thereto by mechanical or other non-chemical bonds, though chemical bonding may occur depending on the specific protective material utilized. In some aspects, the reactive metal or protective material coating may be a layer which substantially encases or encloses the entire superabrasive particle. It is to be understood that such layers are limited in some instances to a certain minimum thickness. Further, it is to be understood that such a coating may be applied to particles on an individual basis, or as a group of particles, and that such a coating may be effected as a separate step made prior to incorporation of the superabrasive particles into a tool, for example, in order to form a tool precursor which can be combined with a support matrix to form certain tools. Moreover, it is possible that a number of coated particles be consolidated together, either with or without additional abrasive particles and used as a tool in and of itself, without the need for incorporation into a support matrix.
As used herein, “separator” refers to any form of a material that is capable of separating superabrasive particles during the process of coating such superabrasive particles with a metal matrix. In one aspect, the separator may be thermally resistant powder that has no affinity to chemically react with the metal matrix. In another aspect, the separator may be a sheet, tray, or other forms with a plurality of apertures for separating the particles.
As used herein, “substantially” refers to situations close to and including 100%. Substantially is used to indicate that, though 100% is desirable, a small deviation therefrom is acceptable. For example, substantially all superabrasive particles includes groups of all superabrasive particles and groups of all superabrasive particles minus a relatively small portion of superabrasive particles.
As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary.
Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of “about 1 to about 5” should be interpreted to include not only the explicitly recited values of about 1 to about 5, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3, and 4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc.
This same principle applies to ranges reciting only one numerical value. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described.
Invention
The present invention encompasses superabrasive tools having improved superabrasive particle retention, as well as various components thereof, such as coated superabrasive particles, and tool precursors. Additionally, the present invention encompasses various methods for the fabrication of such tools and components. In one aspect, a method is provided for making a superabrasive tool having improved retention of superabrasive particles in a metal matrix. Such a method may comprise providing a substrate, providing superabrasive particles, chemically bonding the superabrasive particles with the metal matrix to a degree which holds the superabrasive particles in the metal matrix without substantially degrading the superabrasive particles, and metallurgically bonding the superabrasive particles to the substrate with the metal matrix. Various methods of avoiding substantially degrading the superabrasive particles further are contemplated, including protecting the superabrasive particles from over-bonding during the chemical bonding process. Such protection from over-bonding may further include, for example, moderating chemical bonding between the superabrasive particles and the metal matrix to a degree which is sufficient to retain the superabrasive particles in the metal matrix but minimize superabrasive particle degradation. In one aspect, superabrasive particle degradation may include conversion of the superabrasive particles to a different material. Different materials may include any material into which a superabrasive is converted during chemical bonding, including non-diamond forms of carbon, carbides, nitrides, borides, and combinations thereof.
Notably, the retention of the superabrasive particles of the present invention in a metal matrix are due in large measure to the amount of chemical bonding that is achieved between the metal matrix and the superabrasive particle. The absence or nominal presence of such chemical bonding is a primary cause of premature particle pullout in tools employing known methods, such as electroplating and sintering. Chemical bonding, however, may compromise the strength of a superabrasive particle. It is now thought that an optimal balance between the strength of a superabrasive particle and retention of that particle in a metal matrix may be achieved by actually reducing the number of chemical bonds formed through methods such as dilution of the metal braze with a protective material, while yet maintaining sufficient chemical bonding for the desired retention.
Various mechanisms are thought to be responsible for superabrasive particle degradation as a result of chemical bonding. In one aspect, the superabrasive material along the surface where chemical bonding takes place may be back-converted to a form of the superabrasive material, or a different material, of a lower strength. Such weakening at the surface of the particle can cause it to pull out of the metal matrix when under mechanical stress. As an example, diamond superabrasive particles may back-convert along the surface during chemical bonding to graphite, amorphous carbon, diamond-like carbon, etc. These non-diamond forms of carbon may be weaker than the diamond lattice of the superabrasive particle, and thus its strength may be compromised at the metal matrix interface.
In another aspect, the strength of a superabrasive particle may be compromised due to the formation of a material along the boundary between the particle and the metal matrix that is different from both the superabrasive particle and the metal matrix. The metal matrix often contains reactive elements that are carbide or nitride formers that tend to create carbide or nitride bonds with the surface of the superabrasive particles upon chemically bonding to them. For example, if the superabrasive particles are diamond and the metal matrix is a braze alloy containing titanium, titanium carbide bonds will be formed between the diamond and the braze alloy. The formation of such bonding occurs, in part, due to the conversion of carbon along the surface of the diamond into carbide. This conversion to carbide may cause some deterioration of the superabrasive particle and, since carbides are weaker than the superabrasive, decrease the overall strength of the coated superabrasive particle. Such weakening may be due to superabrasive material being leached from the surface of the particle to form the carbide bonds.
As such, in one aspect chemical bonding can be moderated between the superabrasive particles and the metal matrix to a degree which is sufficient to retain the particles in the metal matrix but minimize superabrasive particle degradation. In another aspect, chemical bonding can be moderated to a degree which is sufficient to retain the particles in the metal matrix but minimize conversion of the superabrasive particles to a different material. The different material may include any material into which the superabrasive particle can be converted into, including, without limitation, carbides, nitrides, borides, and combinations thereof.
Accordingly, various methods of moderating chemical bonding are contemplated. In one method, the metal matrix containing a brazing material may be diluted with a protective material which moderates chemical bonding between the superabrasive particles and the metal matrix. Various mechanisms of dilution are contemplated that may achieve a balance between chemical bonding and minimizing conversion of the superabrasive particles. In one aspect, the protective material can be applied as coating on the superabrasive particle prior to chemically bonding with the metal matrix. The metal matrix would be diluted as the coating of protective material liquefies and mixes therewith. Because the protective coating is essentially non-reactive with the superabrasive particles, or less reactive as compared with the brazing material of the metal matrix, such dilution would reduce the proportion of chemical bonds formed. Protective coatings may be applied in single or multiple layers.
Such a coating can be applied by any means know to one skilled in the art, such as gaseous vapor deposition techniques, electroplating, sintering, sputtering, etc. The thickness of the coating may be adjusted to form the desired proportion of chemical bonds with the superabrasive particles. As such, there may be a wide variation in coating thicknesses depending on the various physical and chemical characteristics of the superabrasive material, the protective material, the metal matrix material, and the intended purpose of the tool. As an example, however, in one aspect the thickness of the coating may be less than about 50 microns. In another example, the thickness of the coating may be from about 1 micron to about 40 microns. In yet another example, the thickness of the coating may be from about 5 micron to about 30 microns. In a further example, the thickness of the coating may be about 10 microns. In yet another example, the thickness of the coating may be less than about 20 microns.
In another aspect, dilution may include admixing the protective material with the metal matrix prior chemically bonding to the superabrasive particles. The amount of admixed protective material may be adjusted to form the desired proportion of chemical bonds with the superabrasive particles. As with coating the superabrasive particles with the protective material, there may be a wide variation in the amount of protective material used to dilute the metal matrix depending on the various physical and chemical characteristics of the superabrasive material, the protective material, the metal matrix material, and the intended purpose of the tool. The diluted metal matrix can be reacted with naked superabrasive particles, or superabrasive particles that have been coated with additional protective material and/or a reactive element. Additionally, in another method of moderating chemical bonding between superabrasive particles and a metal matrix, a relative amount of a reactive element in the metal matrix may be reduced.
Protective materials may include any material known that functions to moderate chemical bonding when used to dilute a metal matrix. Though many protective materials may show little or no reactivity with the superabrasive particle, it should be noted that other protective materials may also be utilized as reactive elements known to form carbide or nitride bonds. In these cases, it is the relative reactivity compared to the metal matrix that defines a material as protective. Though a material such as titanium may be reactive, if it is less reactive than components of the metal matrix, it will provide a protective function when admixed therein. Accordingly, protective materials can include, without limitation, copper, gold, silver, zinc, tin, titanium, silicon, chromium, tungsten, zirconium, and mixtures thereof, including carbides, nitrides, and alloys.
The superabrasive particles used may be selected from a variety of specific types of diamond (e.g., polycrystalline diamond) and cubic boron nitride (e.g., polycrystalline cBN), and should be capable of chemically bonding with a reactive material. Further, such particles may take a number of different shapes as required to accommodate a specific purpose for the tool into which it is anticipated that they will be incorporated. However, in one aspect, the superabrasive particle may be diamond, including natural diamond, synthetic diamond, and polycrystalline diamond (PCD). In yet another aspect, the superabrasive particle may be cubic boron nitride (cBN), either single crystals or polycrystalline. In yet another aspect, the superabrasive particle may be a member selected from the group consisting of SiC, Al₂O₃, Zr O₂, and WC.
A number of reactive elements may be used in the metal matrix in order to achieve the desired chemical bonding with the superabrasive particles. The metal matrix can chemically bond the superabrasive particles to a tool, or it can be a coating on the outside of the superabrasive particles. Such coated superabrasive particles may be incorporated into a variety of tools. Accordingly, a wide variety of reactive elements that can be alloyed with a metallic carrier is known to those skilled in the art, and the selection of a particular reactive element may depend on various factors. Examples of suitable reactive elements for inclusion in the metal matrix used in the present invention include, without limitation, aluminum (Al), boron (B), chromium (Cr), lithium (Li), magnesium (Mg), molybdenum (Mo), manganese (Mn), nirobium (Nb), silicon (Si), tantalum (Ta), titanium (Ti), vanadium (V), tungsten (W), zirconium (Zr), and mixtures thereof. In addition to the reactive element or elements, the metal matrix used to form the chemical bonds in accordance with aspects of the present invention includes at least one other metal as a carrier or solvent. Any metal recognized by one of ordinary skill in the art may be used as such a carrier or solvent, especially those known for use in making superabrasive tools. However, by way of example, in one aspect of the present invention such metals may include, without limitation, Co, Cu, Fe, Ni, and alloys thereof.
As alluded to above, one goal of alloying a reactive element with another metal is to reduce the effective melting point of the reactive element while maintaining its ability to chemically bond with a superabrasive particle. As is known in the art, the thermal stability limit of many superabrasive materials, such as diamond, ranges from about 900° C. to about 1200° C. As such, in one aspect of the invention, the components and exact ratios of the reactive metal alloy may be selected to provide an alloy that has a melting point within or below the thermal stability limit of the particular superabrasive material being used. In practice, a solvent metal may be selected and combined with a reactive element in proper amounts to reduce the melting temperature of both elements and yield a braze alloy having a melting temperature of less than about 1200° C. In yet another aspect, the melting temperature may be below about 900° C. Furthermore, the addition of a protective material to the metal matrix may reduce superabrasive particle deterioration and thus increase the overall strength of the coated superabrasive particle.
As will be recognized by those of ordinary skill in the art, numerous combinations of specific reactive metals and other specific carrier metals may be alloyed in different ratios or amounts to achieve an alloy that chemically bonds to the superabrasive particle, and has a suitable melting point. However, in one aspect, the content of the reactive element may be at least about 1% of the alloy. In another aspect, the amount of element may be at least about 5% of the alloy.
In another aspect of the present invention, superabrasive particles coated with a metal matrix may further include at least one metallic overcoat layer that is bonded to an outside portion of the coating. A number of materials may be used for such a metallic overcoat, as will be recognized by those of ordinary skill in the art, and specific selection may be based on a number of factors, including the main matrix material and design of the tool into which the coated particle is to be incorporated. However, in one aspect, the metallic overcoat may include at least one metal selected from the group consisting of Co, Cu, Fe, Ni, and mixtures thereof. As will be recognized, one or more overcoats may be utilized to achieve a desired total coating thickness for the coated particle. In one aspect, the total coating thickness achieved around the superabrasive particle may be greater than the diameter of the superabrasive particle.
In addition to the metallic overcoat, a number of various other materials may be applied as an overcoat on the protective material and/or braze alloy coating. Referring to FIGS. 1 a-1 c, there are shown various embodiments of superabrasive particles 10 coated with a solidified liquid braze coating 15 in accordance with the present invention. As can be seen, FIG. 1 c additionally shows the bonding of smaller particles 20 to the exterior of the coating. In some aspects, such particles may be materials of various constitution, with the proviso that such particulates each have a size that is smaller than the coated superabrasive particle. Examples of specific types include without limitation, metallic particulates, metallic alloy particulates, such as carbides, or superabrasive particulates. Examples of specific carbide particulates include without limitation, SiC, WC, and Ti coated cBN. In one aspect, such particles may be diamonds or other superabrasive particles that have a smaller size than the coated superabrasive particle. Such coatings have been found to further increase the retention strength of the superabrasive particle. Specifically, coatings of these types effect a gradual or “gradient” transition between the outside of the reactive metal alloy coating, and the matrix material of the tool into which the coated superabrasive particle is incorporated. Thus, the weak interface created by a sharper transition between two materials is eliminated.
In one aspect of the present invention, the molten braze alloy may wet at least about 40% of the surface of the superabrasive particle. In another aspect, the alloy may wet at least about 50% of the surface of the superabrasive particle. In yet another aspect, the alloy may wet at least about 60% of the surface of the superabrasive particle. In some aspects, at least about 80% or greater of the surface of the superabrasive particle may be wetted by the braze alloy.
It should be noted that a single molten braze or protective material coated particle can act as a tool precursor for incorporation into a tool. Further, in accordance with the present invention, a plurality of coated particles may be metallurgically bonded together into various one, two, and three dimensional configurations and used as tool precursors. In some aspects, the tool precursors may consist essentially of the superabrasive particles and the solidified molten braze alloy. For example, referring now to FIG. 2, there is shown one embodiment of a one dimensional tool precursor 30 in accordance with the present invention. The tool precursor includes a plurality of superabrasive particles 10, each coated with, and metallurgically bonded together, by metal matrix coatings 15. The superabrasive particles are aligned in a single row forming a one dimensional needle-type structure. Further, FIG. 3 shows a two dimensional tool precursor 40 that is made by metallurgically bonding a plurality of one dimensional structures as shown in FIG. 2 together. In yet another embodiment of the present invention, a plurality of two dimensional tool precursors, such as plates, sticks, or rods, such as shown in FIG. 2, can be metallurgically bonded together to form a three dimensional structure (not shown). It should be noted that while the particles of the tool precursors shown in FIGS. 2 and 3 are arranged in accordance with a predetermined pattern, in some aspects, the particle positioning may be random.
The present invention additionally encompasses various methods of making and using superabrasive tools, including various components thereof such as the coated superabrasive particles and tool precursors as described herein. Such methods may employ the materials, structures, dimensions, and other parameters disclosed for the device above, as well as equivalents thereof as recognized by one of ordinary skill in the art. In one aspect, the present invention includes a method of chemically bonding a superabrasive particle to a reactive metal alloy coating. Such a method may include the steps of covering the superabrasive particle with the braze alloy in a molten liquid state and solidifying the liquid braze alloy around the superabrasive particle, such that the reactive metal alloy becomes chemically bonded with the superabrasive particle. In another aspect of the present invention, a method is provided for protecting the superabrasive particles from over bonding during the chemical bonding process. Such a method may include providing superabrasive particles coated with a protective material which moderates chemical bonding between the superabrasive particles and the metal matrix to a degree which is sufficient to retain the superabrasive particles in the metal matrix but minimize the conversion of the superabrasive particles to a different material. Accordingly, incorporating the superabrasive particles into the superabrasive tool may include chemically bonding at least a portion of each superabrasive particle to the metal matrix.
Those of ordinary skill in the art will recognize a number of ways to cover the superabrasive particle with the metal matrix, such as by dipping the particles in the alloy, and dripping the alloy onto the particles, among other application techniques. However, in one aspect of the invention, the step of covering may further include the steps of coating the superabrasive particle with an organic binder material, adhering a powdered form of braze alloy to the superabrasive particle with the organic binder material, and heating the reactive metal alloy to a temperature sufficient to cause the alloy to melt and coat and chemically bond to the superabrasive particle.
A variety of organic binders will be recognized as suitable for use in this context by those of ordinary skill in the art. However, in one aspect, the binder material may be a member selected from the group consisting of: polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyethylene glycol (PEG), paraffin, phenolic resin, wax emulsions, and acrylic resins. In another aspect, the binder may be PEG. Further, applying the powdered form of the reactive metal alloy to the binder coated particle for the purposes of adhering the alloy thereto may be accomplished by various methods, such as rolling, dipping, or tumbling the binder coated particles with the powder. Further, such application may be accomplished by various methods of spraying, showering, projecting, or otherwise directing the powder onto the superabrasive particles to form the desired coating. One example of such a method is by the use of a fluidized bed stream. Other methods of adhering the powder to the binder coated particles will be recognized by those of ordinary skill in the art.
A variety of ways for heating the powder coated superabrasive particles may be employed as recognized by those of ordinary skill in the art. No particular limitation is placed on the specific heating mechanism employed, other than the ability to reach a temperature sufficient to melt the powdered braze alloy into a molten liquid state. Once melted, the liquid alloy will wet the superabrasive particles and form the desired chemical bonds at the interface thereof. Further, other mechanisms in addition to heat may be used to facilitate the melting and liquefaction of the alloy, such as by adding a flux, or other methods as will be recognized by those of ordinary skill in the art, so long as such methods do not hinder or prevent the wetting of the superabrasive particles and the formation of the desired chemical bonds.
Under some circumstances, it may be desirable to first coat or “pre-treat” the superabrasive particle with certain materials, prior to covering it with the metal matrix. Such undercoating materials may be used with any superabrasive particle, but are especially advantageous with certain superabrasive particles, such as cBN, which are extremely inert. The high inertness of such materials may make it difficult to create chemical bonds with the metal matrix. Therefore, in one aspect of the present invention, the superabrasive particle may be conditioned by forming a pre-treatment, or undercoating layer of a reactive material on the superabrasive particle. Such undercoating layers may typically be formed by conventional methods, such as the solid state and vapor deposition techniques discussed above. In one aspect, the pre-treatment layer may be a reactive material selected from the group consisting of: chromium, silicon, titanium, tungsten, and mixtures thereof, including carbides, nitrides, and alloys. In another aspect, the reactive material may be titanium. In another aspect, the reactive material may be tungsten carbide. In another aspect, the reactive material may be silicon carbide. In yet another aspect, the reactive material may be chromium. In yet another aspect, the superabrasive particle may be pre-coated with an undercoat including a reactive material admixed with the protective material. Those of ordinary skill in the art will recognize other suitable materials that may be first deposited on the superabrasive particle, including materials formed in multiple layers, in order to facilitate or enhance the formation of chemical bonding with the molten braze alloy.
As a practical matter, it may often be the case that a plurality of superabrasive particles are simultaneously coated with the metal matrix in a single processing event. In such instances, according to certain aspects of the present invention, it may be desirable to prevent coated particles from fusing or joining together. As such, in one aspect, the heating may include distributing the superabrasive particles in a separator that allows separation of the particles during heating, heating the reactive metal alloy to a temperature sufficient to cause the alloy to melt and wet and chemically bond to the superabrasive particle, and removing the superabrasive particles from the separator. A variety of separating methods and devices may be employed. The specific selection of a particular separator may be dictated by factors such as speed, economy, and quality of result achieved. However, in one aspect, the separator may be a powder which does not react with the braze alloy, and which can tolerate high temperatures. Examples of such materials include without limitation, oxide powders, such as Al₂O₃, SiO₂, or ZrO₂, and nitride powders, such as BN, AlN. Other non-reactive powdered materials will be recognized by those of ordinary skill in the art.
In another aspect, the separator may be a plate with a plurality of apertures therein. The specific size and placement of the apertures may be determined in part by the size and shape of the superabrasive particles being coated. However, as a general procedure, a single superabrasive particle may be placed in each aperture of the plate, in either a coated or uncoated state. Excess particles are swept off the plate, and the apertures are then filled with a braze powder. The plate containing the particles and braze alloy is then subjected to a sufficient amount of heat to melt the braze alloy and cause the wetting of the particles and the formation of chemical bonds. In the case where particles have not been pre-coated prior to deposition in the apertures, powdered coating may then be placed in, or over, the aperture, and will cover and attach to the superabrasive particle when melted by a sufficient amount of heat.
After the melted braze alloy has bonded to the superabrasive particles, the particles are allowed to cool, and the braze alloy solidifies. Once the alloy has solidified, the coated superabrasive particles are removed from the separator and may be either subjected to additional processing steps as alluded to above, such as by applying one or more overcoats, or by bonding additional smaller particles thereto. Alternatively, the coated superabrasive particles may be directly incorporated into a tool by coupling the particles to a tool body, for example, by impregnating the coated particles into a matrix, or in some aspects, by simply coupling a plurality of particles together.
Alternatively, in some aspects of the invention it may be desirable to have the superabrasive particles coated simultaneously in a manner that also allows them to metallurgically bond together in the same step. For example, when a one, two, or three dimensional tool precursor is desired, it may be convenient to simply arrange the particles in the desired configuration, for example, by placing the particles into a tray with a specified shape, or by individual placement of the particles as recited above, and then coat the particles en mass with the molten braze alloy. Upon solidification of the alloy, the particles not only become chemically bonded thereto, but the metal matrix coatings of the particles become metallurgically bonded to one another. In one aspect, the braze material may be provided as a powder. In another aspect, the braze material may be provided as a sheet or foil of amorphous brazing alloy.
Once the coated superabrasive particle or tool precursor is complete, it may be incorporated into a tool by metallurgically bonding the particle or precursor to a support matrix. A number of tools may find use for such coated superabrasive particles, including without limitation, saw blades, drill bits, grinding wheels, wire saws, chain saws, circular saws, frame saws, profile wheels, hole saws, and chemical mechanical polishing pad dressers, among others. A number of ways of incorporating the coated particle into such tools will be recognized by one of ordinary skill in the art, and the specific method of integration may be determined by a number of factors, such as the other materials in the tool, tool configuration, tool purpose, type of support matrix, etc.
Moreover, the arrangement of such particles may be in accordance with a predetermined pattern or specific configuration. Examples of specific methods of effecting such patterns or configurations of superabrasive particles may be found in U.S. Pat. Nos. 4,925,457, 5,380,390, 6,039,641, and 6,286,498, each of which is incorporated herein by reference. Additionally, in many cases, the tool precursors themselves may be suitable for certain uses as a tool. Moreover, a number of uses for individually coated particles not incorporated into a tool will be recognized by those of ordinary skill in the art as loose abrasives.
Those of ordinary skill in the art will readily recognize a number of ways of creating specifically desired configurations, such as by using a mold, etc. Once in a mold, additional brazing or metal particulate material may be added to the assembly in order to add substance to the forming body. Additionally, superabrasive particles of different sizes may be assembled in order to reduce the amount of interstitial spaces between particles, and provide a rigid and durable polycrystalline body. Other techniques of reducing interstitial space may also be applied to the superabrasive agglomerate while in a mold, such as shaking, vibrating, etc., if desired.
The consolidated coated superabrasive particles may additionally be infiltrated with a number of specific materials aimed at attaining a specific purpose. For example, molten Si may be infiltrated through the superabrasive agglomerate during the formation of the tool body in order to create a tool capable of dissipating heat, such as a heat spreader. A number of other specific tools that can be created using the present technology will be recognized by those of ordinary skill in the art, such as drill bits, saws, and other cutting tools.
When used, the support matrix, to which the coated particles and tool precursors are bonded, may be selected from a wide variety of materials that will be recognized by those of ordinary skill in the art. Metal powders which can be consolidated, and solid metal substrates are exemplary.
Referring now to FIG. 4, there is shown a perspective view of one embodiment of a superabrasive tool 50 in accordance with the present invention. The tool has a support matrix 55 of consolidated metal powder, and a plurality of one dimensional tool precursors 30 each having a plurality of superabrasive particles 10 bonded by a solidified braze coating 15 which is further metallurgically bonded to the support matrix. As can be seen, the tool precursors have been arranged in the matrix support material such that the superabrasive particles are each held as specific locations in accordance with a predetermined pattern. However, it is to be noted that such patterns while desirable are optional. For example, as shown in FIG. 5, superabrasive particles 10 coated with solidified molten braze alloy 15 are held randomly in the support matrix 55.
Additionally, while the matrix support material in FIG. 4 is shown as a consolidated powder, it is to be understood that the present invention may alternatively utilize a solid metal support matrix. In such a case, the support matrix would be configured with slots or grooves that can accommodate the tool precursors, or a plurality of coated particles. Further, for some tools with a solid metal support matrix, it may be desirable to simply bond the abrasive particles to the surface of the matrix, as will be discussed in greater detail below. As such, the metal matrix may serve as the substrate.
Referring to FIG. 5, there is shown yet another embodiment of a superabrasive tool 50 in accordance with the present invention. Most notably, the support matrix 55 is porous, containing a plurality of pores 60. It has been discovered that such pores are advantageous for the purposes of improving tool performance, especially when the tool is one utilized for the purpose of material removal. Specifically, the pores and spacers may facilitate the chipping and breaking of material from the workpiece. Further, the pores may act as a conduit for passing and holding a liquid coolant. In this manner, the tool may remove material from the workpiece at a faster rate without a significant increase in temperature. Such pores may be implemented into a tool in a variety of manners. For example, air may be bubbled through a powdered matrix material during the consolidation thereof, grains that disintegrate during the heating step may be used, or the pores may result to some degree simply from the consolidation processing procedure, such as sintering. Further, in some aspects, the pores may result from placement and joining of the coated superabrasive particles, and may occur in accordance with a predetermined pattern.
One reason why a porous support matrix is feasible is because of the fact that the superabrasive particles are chemically bonded with the metal matrix and thus tenaciously held in the matrix. As a result, a reduced amount of mechanical support for each particle is acceptable. Moreover, the chemical bonding allows for softer, less expensive materials to be used as the matrix support, such as Cu, Fe, steel, etc.
In addition to metallurgically bonding the coated superabrasive particles to a support matrix, in some aspects, the coated particles may be attached to the matrix with an adhesive or organometallic binder. As discussed in U.S. Pat. No. 6,915,796, which is incorporated herein by reference, a wide variety of organic and organometallic binders are known to those of ordinary skill in the art and may be used. Organometallic coupling agents can include at least one reactive moiety which chemically reacts with metal to form a chemical bond and at least one reactive moiety which reacts with the organic binder to form a chemical bond. In this way, the organometallic coupling agent acts as a bridge to form bonds between the organic binder and the metal surface of the coated superabrasive particles. In one aspect of the present invention, the organometallic coupling agent can be a titanate, zirconate, silane, or mixture thereof. These materials can contain hydrolyzable groups which react with hydroxyl groups and thereby chemically bond to the metal surface. Additionally, these materials can also contain non-hydrolyzable groups which chemically react with the organic binder. Such organometallic coupling agents are described in U.S. Pat. Nos. 4,620,933, 5,558,705, 5,571,296, and 6,579,931, which are each incorporated by reference.
Specific non-limiting examples of silanes suitable for use in the present invention include: 3-glycidoxypropyltrimethoxy silane (available from Dow Corning as Z-6040); γ-methacryloxy propyltrimethoxy silane (available from Union Carbide Chemicals Company as A-174); β-(3,4-epoxycyclohexyl)ethyltrimethoxy silane, γ-aminopropyltriethoxy silane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxy silane (available from Union Carbide, Shin-etsu Kagaku Kogyo K.K., etc.); and additional examples of suitable silane coupling agents can be found in U.S. Pat. Nos. 4,795,678, 4,390,647, and 5,038,555, which are each incorporated herein by reference.
Specific non-limiting examples of titanate coupling agents include: isopropyltriisostearoyl titanate, di(cumylphenylate)oxyacetate titanate, 4-aminobenzenesulfonyldodecylbenzenesulfonyl titanate, tetraoctylbis (ditridecylphosphite) titanate, isopropyltri(N-ethylamino-ethylamino) titanate (available from Kenrich Petrochemicals. Inc.), neoalkyoxytitanates such as LICA-01, LICA-09, LICA-28, LICA-44 and LICA-97 (also available from Kenrich), and the like.
Specific non-limiting examples of aluminum coupling agents include acetoalkoxy aluminum diisopropylate (available from Ajinomoto K.K.), and the like.
Specific non-limiting examples of zirconate coupling agents include: neoalkoxy zirconates, LZ-01, LZ-09, LZ-12, LZ-38, LZ-44, LZ-97 (all available from Kenrich Petrochemicals, Inc.), and the like. Other known organometallic coupling agents, e.g., thiolate based compounds, can be used in the present invention and are considered within the scope of the present invention.
The amount of organometallic coupling agent used depends on the coupling agent and on the surface area of the metal matrix coating the superabrasive particles. Typically, 0.05% to 10% by weight of the organic binder layer is sufficient.
As noted above, the methods of the present invention may be used in the production of a wide variety of superabrasive tools. Referring now to FIG. 6, there is shown a saw segment for use in a saw, such as a reciprocating or circular saw. The saw segment 65 has a plurality of stacked and metallurgically bonded layers 70 of support matrix 55 and tool precursors 30. The tool precursor is metallurgically bonded to one or more support matrix to form a layer, and the layers are effectively metallurgically bonded together. Additionally, because of the spacing of the superabrasive particles 10 within each layer, and because of the amount and application of the brazing alloy 15, a plurality of pores 60 occur. Again, these pores may provide all of the advantages as recited above.
In the embodiment shown in FIG. 6, the brazing alloy 15 utilized to make the tool precursors 30 is a sheet or foil of amorphous brazing alloy. However, it is to be noted that another form of brazing alloy, such as a powdered form may be used. In one aspect of fabrication, sheets may be adhered to each side of a support matrix 55, and then the superabrasive particles 10 adhered to the exposed surface of one or both sheets to form a layer. Notably, the superabrasive particles may be adhered either randomly, or in accordance with a predetermined pattern. Multiple layers are then assembled by stacking and heated to a temperature sufficient to melt the sheets of brazing alloy and coat the superabrasive particles. The assembly is then cooled and the brazing alloy solidifies and chemically bonds to the particles, and metallurgically bonds to the support matrices, effectively bonding the layers together. The saw segment may then be attached to the blade of a saw.
Various methods of affixing superabrasive particles to a substrate are contemplated. In one example, a template having apertures may be placed upon a sheet of brazing alloy. In one aspect of the present invention, the sheet may be a rolled sheet of continuous amorphous brazing alloy. In another aspect, the sheet may be a brazing alloy powder that is held together with a binder material. In an additional aspect, the brazing alloy powder may include other metallic powders, and such other powders may constitute a majority of the material in the brazing sheet. In yet another aspect, the sheet may be sufficient to act as a substrate. The use of the template allows controlled placement of each abrasive particle at a specific location by designing the template with apertures in a desired pattern.
After the template has been placed on the brazing alloy sheet, the apertures are filled with superabrasive particles. The apertures have a predetermined size, so that only one abrasive particle will fit in each. Any size of abrasive particle or grit is acceptable, however in one aspect of the invention, the particle sizes may be from about 100 to about 350 micrometers in diameter.
In another aspect of the invention, the size of the apertures in the template may be customized in order to obtain a pattern of abrasive particles having a size within a uniform size range. In one embodiment, the apertures of the template are sufficient to select only particles within a size range having a variance no greater than 50 micrometers. In the case of CMP pad dressers, this uniformity of particle size contributes to the uniformity of CMP pad grooming, as the work load of each abrasive particle is evenly distributed. In turn, the even work load distribution reduces the stress on individual superabrasive particles, and extends the effective life of the CMP pad dresser.
After the apertures of the template are all filled, any excess particles are removed and a flat surface is applied to the superabrasive particles. The flat surface may be of a strong, rigid material, so that it is capable of pushing superabrasive particles down into the brazing alloy sheet. Such materials typically include, but are not limited to steel, iron, alloys thereof, etc.
Because a flat surface is used to press the superabrasive particles into the brazing alloy, the particles will extend away from the substrate to a predetermined, uniform height. This uniform height will be determined by the thickness of template. As such, each superabrasive particle grooms to substantially the same depth on the CMP pad. However, it is to be understood that in certain applications, particle height may not be desired to be uniform. As such, those of ordinary skill in the art will recognize that particle patterns of varied height may be provided by so configuring the template and the surface that presses down on the particles to provide such a design. For example, in one aspect, such a surface may have a concave shape so as to press the peripherally located particles further down than the centrally located particles. Such a concave shape will provide a slope for the superabrasive particles which begins at a low point with the working ends of the peripherally located particles and slopes up to a high point at the working ends of the centrally located particles.
In an alternative embodiment, rather than pressing the superabrasive particles into the brazing alloy sheet, they may be fixed in the templated position by disposing an adhesive on the surface of the brazing alloy sheet. In this manner, the particles remain fixed in place when the template is removed, and during heat processing. In yet another embodiment of the invention, the template may be laid upon a transfer sheet having a thin adhesive film thereon. In this case, the particles become adhered to the transfer sheet using the template procedure specified above. The template is then removed, and the transfer sheet is laid onto the brazing sheet with abrasive particles facing the sheet. Disposed upon the brazing sheet is the afore-mentioned adhesive layer, which is more strongly adhesive than the adhesive on the transfer sheet. Therefore, the superabrasive particles are transferred to the sheet of brazing alloy in the pattern dictated by the template.
After the superabrasive particles are at least partially embedded in, or adhered to, the brazing alloy sheet, the sheet may be affixed to a substrate. Alternatively, in some embodiments, the sheet of brazing alloy may be first affixed to the substrate, and the superabrasive particles subsequently added thereto using the template procedure described herein.
Because the superabrasive particles are firmly held in, or on the brazing alloy sheet, the surface tension of the liquid brazing alloy is insufficient to cause particle clustering. Additionally, braze thickening occurs to a much lesser degree and few or no “mounds” are formed. Rather, the braze forms a slightly concave surface between each abrasive particle, which provides additional structural support. In one embodiment, the thickness of the brazing alloy sheet is predetermined to allow at least about 10 to 90% of each superabrasive particle to protrude above the outer, or working, surface of brazing material.
As a result of the methods for maintaining the superabrasive particles in a fixed position during processing, even spaces may be created between superabrasive particles. Additionally, the particles may extend to a uniform height or distance above the substrate, and thus when applied to a CMP pad they will protrude to a uniform depth within the pad fibers. The even spacing and uniform protrusion causes the CMP to be dressed or groomed evenly, which in turn increases the polishing efficiency of the CMP pad and extends its useful life. In addition to the specific methods of embedding, or adhering the superabrasive particles to the brazing alloy, those skilled in the art will recognize suitable alternative procedures, such as fixing the superabrasive particles to the substrate and then placing the braze thereon. In this case, the particles may be positioned on the substrate using the template method recited above, and held in place by a glue, or other suitable binder. The braze material is then showered, or placed on the substrate around the abrasive particles, and the overlay material may be added.
Additional details regarding CMP pad dressers can be found in U.S. Pat. Nos. 6,884,155 and 6,413,987, each of which is incorporated herein by reference in their entirety.
As an alternative to being bonded to a matrix support, the coated particles of the present invention may include a plurality of spacer particles which are mixed with and become chemically bonded to the metal matrix. Referring now to FIG. 7, there is shown a sectional of a tool made in accordance with another embodiment of the present invention. As can be seen, a plurality of superabrasive particles 10 coated with a solidified molten braze alloy 15 are metallurgically bonded together into a porous tool containing pores 60. Additionally, the tool contains a plurality of spacer particles 75 which are chemically bonded to the brazing alloy. The spacer particles may themselves be coated with a solidified molten braze alloy prior to incorporation into the tool, or may be uncoated. It is also to be understood that while the superabrasive and spacer particles are depicted in FIG. 7 in a random placement, that the placement thereof may be in accordance with a predetermined pattern, and the pores may also occur in accordance with a predetermined pattern. Those of ordinary skill in the art will recognize a number of suitable materials for the spacer particles, and the specific selection of a material may be based on a number of considerations, such as the type of tool, brazing alloy, etc. However, in one aspect, the material may be SiC.
The following examples present various methods for making the coated superabrasive particles of the present invention. Such examples are illustrative only, and no limitation on present invention is meant thereby.

EXAMPLES

Example 1

Diamond particles of 40/50 mesh were covered with a thin film of an acrylic binder.
The binder covered diamond was then mixed with a powdered metallic alloy containing B, Ni, Cr, Si, having an average particle size of about 325 mesh, and sold under the trade name NICHROBRAZ LM® (Wall Colomnoy). The result was a braze powder wrapped diamond. These coated particles were then mixed with fine powder of Al₂O₃. The mixture was heated in a vacuum furnace held at 10⁻⁵torr to a maximum temperature of about 1005° C. for approximately 17 minutes to assure that the metallic alloy coating became molten and liquefied and flowed around the diamond particles wetting them. The mixture was then cooled and retrieved from the furnace. After separating the diamond particles from Al₂O₃, a number of coated particles were mixed with a cobalt powder and sintered in a hot press to form rectangular segments. Some of these segments were broken by bending with pliers. The fractured surface was then viewed under a microscope. It was observed that the fracture plane propagated through the coated diamond particles rather than deviating around the interface between the diamond particle and the coating, as is typical of sintered diamond particles without the braze coating described above.

Example 2

The same procedure as outlined in Example 1 was followed, but the Al₂O₃separator powder was replaced with diamond particles having an average mesh size of from about 325 to about 400 mesh. During the heating process, the smaller diamond particles were wetted by the braze alloy coating, and became chemically bonded to the outside of the coated diamond particle. Thus, coated diamond particles having a chemically bonded metallic alloy shell with smaller diamond particles further bonded to the outside of the shell were produced. These “spiky” coated particles were incorporated into a cobalt matrix and fracture tested as above with similar results achieved.

Example 3

The process of Example 2 was followed, but the smaller diamond particles were replaced with particles of SiC. The process yielded a coated diamond particle having ceramic particles bonded to the outside of the metallic coating similar to the diamond particles of Example 2. Moreover, the fracture testing yielded results similar to that of Examples 1 and 2.

Example 4

Diamond particles were coated with a powdered braze alloy as in Example 1, and then lined up in a groove carved on an Al₂O₃plate. A small amount of braze powder was packed in between the coated particles, and the assembly was heated in a furnace as in Example 1. The resultant “needle” was fracture tested as in the previous examples, and revealed fracture across a diamond particle, rather than fracture around the diamond particle at the interface of the diamond and the metal alloy coating, or between diamond particles.

Example 5

The same procedure was followed as in Example 4, however, diamond coated particles were spread out on the Al₂O₃plate. Braze powder was then packed between the coated particles and the assembly was heated as in the previous examples. The resultant diamond plate of diamond particles bonded by the brazing alloy was then fracture tested as in previous examples. Analysis of the fracture plains revealed random fractures that included fractures through various diamond particles, rather than a pattern of fractures following the diamond particle arrangement and falling primarily at the diamond particle/metallic coating interfaces.

Example 6

The procedure of Examples 4 and 5 was again followed, only the interstices between coated diamond particles were filled with a mixture of WC and the braze powder used to coat the diamond particles. Heating in accordance with the prior examples was again conducted, and a tile of the composite materials was obtained. The tile was fracture tested, and the results proved to be consistent with those obtained for the above-recited examples.

Example 7

40/50 mesh MBS-950 diamond particles were coated with either Ti (0.4 micron), Cr (0.4 micron), Cu (10 microns), Cu (30 microns), Cu(50 microns), or multiple coatings of Ti/Cr (1 micron) plus Cu (10 microns). They were mixed with Nicrobraz LM powder (90 wt %), copper powder (10%), and an acrylic binder (3 wt % of the total powder) and were cold pressed to form rectangular segments. These segments were heated to 1010 C for 10 minutes under vacuum (10ˆ−5 torr). After heating, the Nicrobraz LM melted and infiltrated to bond the copper powder and the diamond. The copper powder was used to block the flow of molten LM so the segment shape could be maintained. Without the copper powder, the molten Nicrobraz LM will coalesce to form a ball due to surface tension. These segments were dissolved in aqua regia to free the diamond particles. Diamond particles so formed were tested for impact strength. It was found that the relative strength was ranked as follows: Cu (50 micron)>Cu (30 micron)>Cu+Ti/Cr>Cu (10 micron)>Cr>Ti>virgin diamond heated with LM and copper powder.
Of course, it is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements. Thus, while the present invention has been described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred embodiments of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein.

Claims

1. A method of making a superabrasive tool having improved retention of superabrasive particles in a metal matrix, comprising:

providing a substrate;

providing superabrasive particles;

chemically bonding the superabrasive particles with the metal matrix to a degree which holds the superabrasive particles in the metal matrix without substantially degrading the superabrasive particles; and

metallurgically bonding the superabrasive particles to the substrate with the metal matrix.

2. The method of claim 1, wherein without substantially degrading the superabrasive particles further includes protecting the superabrasive particles from over-bonding during the chemical bonding process.

3. The method of claim 2, wherein protecting the superabrasive particles from over-bonding further comprises:

moderating chemical bonding between the superabrasive particles and the metal matrix to a degree that is sufficient to retain the superabrasive particles in the metal matrix while minimizing superabrasive particle degradation.

4. The method of claim 3, wherein superabrasive particle degradation includes conversion of the superabrasive particles to a different material.

5. The method of claim 4, wherein the different material is a member selected from the group consisting of non-diamond forms of carbon, carbides, nitrides, borides, and combinations thereof.

6. The method of claim 4, wherein moderating chemical bonding further includes moderating a relative amount of a reactive element in the metal matrix.

7. The method of claim 4, wherein moderating chemical bonding further includes diluting the metal matrix with a protective material which moderates chemical bonding between the superabrasive particles and the metal matrix.

8. The method of claim 7, wherein diluting the metal matrix further comprises coating the superabrasive particles with the protective material prior to chemically bonding with the metal matrix.

9. The method of claim 7, wherein diluting the metal matrix further comprises admixing the protective material with the metal matrix prior to chemically bonding to the superabrasive particles.

10. The method of claim 7, wherein the protective material includes a member selected from the group consisting of copper, silver, zinc, tin, titanium, silicon, chromium, tungsten, zirconium, and mixtures thereof.

11. The method of claim 10, wherein the protective material is copper.

12. The method of claim 10, wherein the protective material is silver.

13. The method of claim 10, wherein the protective material is zinc.

14. The method of claim 10, wherein the protective material includes a member selected from the group consisting of titanium, chromium, silicon, tungsten, and mixtures thereof

15. The method of claim 7, wherein the protective material is substantially less reactive with the superabrasive particles than the metal matrix with the superabrasive particles during the chemical bonding of the metal matrix to the superabrasive particles.

16. The method of claim 7, further comprising pre-coating the superabrasive particles with a reactive material.

17. The method of claim 16, wherein pre-coating the superabrasive particles includes admixing the reactive material with the protective material.

18. The method of claim 17, wherein the reactive material is selected from the group consisting of chromium, silicon, titanium, tungsten, and mixtures thereof, including carbides, nitrides, and alloys.

19. The method of claim 1, wherein providing superabrasive particles includes providing superabrasive particles coated with a protective material which moderates chemical bonding between the superabrasive particles and the metal matrix to a degree that is sufficient to retain the superabrasive particles in the metal matrix but minimize superabrasive particle degradation.

20. The method of claim 1, wherein the superabrasive particles include a member selected from the group consisting of diamond, polycrystalline diamond, cubic boron nitride, polycrystalline cubic boron nitride, and combinations thereof.

21. The method of claim 20, wherein the superabrasive particles include diamond.

22. The method of claim 20, wherein the superabrasive particles include cubic boron nitride.

23. The method of claim 1, wherein the metal matrix is a braze alloy.

24. The method of claim 23, wherein the braze alloy includes a nickel alloy having a chromium content of at least about 2 wt %.

25. A superabrasive tool, comprising:

a substrate; and

a plurality of superabrasive particles metallurgically bonded to the substrate with a metal matrix, at least a portion of each of the plurality of superabrasive particles being chemically bonded to the metal matrix as recited in claim 1.

26. The superabrasive tool of claim 25, wherein the metal matrix includes a protective material which provides improved strength and retention to the superabrasive particles as compared with the metal matrix alone.

27. The superabrasive tool of claim 25, wherein the plurality of superabrasive particles includes a member selected from the group consisting of diamond, polycrystalline diamond, cubic boron nitride, polycrystalline cubic boron nitride, and combinations thereof.

28. The superabrasive tool of claim 26, wherein the protective material is selected from the group consisting of copper, silver, zinc, tin, titanium, silicon, chromium, tungsten, zirconium, and mixtures thereof, including carbides, nitrides, and alloys.

29. The superabrasive tool of claim 28, wherein the protective material is copper.

30. The superabrasive tool of claim 28, wherein the protective material is tin.

31. The superabrasive tool of claim 28, wherein the protective material is zinc.

32. The superabrasive tool of claim 25, wherein the substrate is the metal matrix.

33. The superabrasive tool of claim 25, wherein the plurality of superabrasive particles are arranged in accordance with a predetermined pattern.

34. The superabrasive tool of claim 25, wherein the tool is a member selected from the group consisting of CMP pad dressers, wire saws, chain saws, saw blades, circular saws, frame saws, profile wheels, grinding wheels, drill bits, hole saws, and combinations thereof.

35. The superabrasive tool of claim 34, wherein the tool is a CMP pad dresser.