Patent Description:
Abrasives used in machining applications typically include bonded abrasive articles and coated abrasive articles. Coated abrasive articles are generally layered articles having a backing and an adhesive coat to fix abrasive grains to the backing, the most common example of which is sandpaper. Bonded abrasive tools consist of rigid, and typically monolithic, three-dimensional, abrasive composites in the form of wheels, discs, segments, mounted points, hones and other tool shapes, which can be mounted onto a machining apparatus, such as a grinding or polishing apparatus.

Bonded abrasive tools usually have at least two phases including abrasive grains and bond material. Certain bonded abrasive articles can have an additional phase in the form of porosity. Bonded abrasive tools can be manufactured in a variety of 'grades' and 'structures' that have been defined according to practice in the art by the relative hardness and density of the abrasive composite (grade) and by the volume percentage of abrasive grain, bond, and porosity within the composite (structure).

Some bonded abrasive tools may be particularly useful in grinding and shaping certain types of workpieces, including for example, metals, ceramics and crystalline materials, used in the electronics and optics industries. In other instances, certain bonded abrasive tools may be used in shaping of superabrasive materials for use in industrial applications. In the context of grinding and shaping certain workpieces with metal-bonded abrasive articles, generally the process involves a significant amount of time and labor directed to maintaining the bonded abrasive article. That is, generally, metal-bonded abrasive articles require regular truing and dressing operations to maintain the grinding capabilities of the abrasive article.

<CIT> describes abrasive articles possessing a highly open (porous) structure and uniform abrasive grit distribution. <CIT> describes an abrasive article including from about <NUM> to about <NUM> volume percent interconnected porosity. <CIT> describes abrasive tools suitable for precision grinding of hard brittle materials.

The industry continues to demand improved methods and articles capable of grinding.

According to the present invention, an abrasive article includes a body having abrasive grains contained within a bond material comprising a metal or metal alloy, wherein the body comprises a ratio of VP/VBM of at least about <NUM>, wherein VP is the volume percent of particulate material including abrasive grains and fillers within the total volume of the body and VBM is the volume percent of bond material within the total volume of the body, wherein the body comprises greater than <NUM> vol% porosity and not greater than <NUM>% vol porosity. The bond material has an average fracture toughness (K1c) of not greater about <NUM> MPa m<NUM>.

The following is generally directed to bonded abrasive articles incorporating abrasive grains within a three-dimensional matrix of material. Bonded abrasive articles utilize a volume of abrasive grains secured within a three-dimensional matrix of bond material. Moreover, the following includes description related to methods of forming such bonded abrasive articles and applications for such bonded abrasive articles.

In accordance with an embodiment, the process for forming an abrasive article can be initiated by forming a mixture containing abrasive grains and bond material. The abrasive grains can include a hard material. For example, the abrasive grains can have a Mohs hardness of at least about <NUM>. In other abrasive bodies, the abrasive grains can have a Mohs hardness of at least <NUM>, or even at least <NUM>.

In particular instances, the abrasive grains can be made of an inorganic material. Suitable inorganic materials can include carbides, oxides, nitrides, borides, oxycarbides, oxyborides, oxynitrides, and a combination thereof. Particular, examples of abrasive grains include silicon carbide, boron carbide, alumina, zirconia, alumina-zirconia composite particles, silicon nitride, SiAlON, and titanium boride. In certain instances, the abrasive grains can include a superabrasive material, such as diamond, cubic boron nitride, and a combination thereof. In particular instances, the abrasive grains can consist essentially of diamond. In other embodiments, the abrasive grains can consist essentially of cubic boron nitride.

The abrasive grains can have an average grit size of not greater than about <NUM> microns. In other embodiments, the abrasive grains can have an average grit size of not greater than about <NUM> microns, such as not greater than about <NUM> microns, not greater than about <NUM> microns, not greater than about <NUM> microns, or even not greater than about <NUM> microns. In particular instances, the abrasive grains of embodiments herein can have an average grit size, within a range between about <NUM> micron and about <NUM> microns, such as between about <NUM> micron and <NUM> microns, or even between about <NUM> microns and <NUM> microns.

In further reference to the abrasive grains, the morphology of the abrasive grains can be described by an aspect ratio, which is a ratio between the dimensions of length to width. It will be appreciated that the length is the longest dimension of the abrasive grit and the width is the second longest dimension of a given abrasive grit. In accordance with embodiments herein, the abrasive grains can have an aspect ratio (length:width) of not greater than about <NUM>:<NUM> or even not greater than about <NUM>:<NUM>. In particular instances, the abrasive grains can be essentially equiaxed, such that they have an aspect ratio of approximately <NUM>:<NUM>.

The abrasive grains can include other features, including for example, a coating. The abrasive grains can be coated with a coating material which may be an inorganic material. Suitable inorganic materials can include a ceramic, a glass, a metal, a metal alloy, and a combination thereof. In particular instances, the abrasive grains can be electroplated with a metal material and, more particularly, a transition metal composition. Such coated abrasive grains may facilitate improved bonding (e.g., chemical bonding) between the abrasive grains and the bond material.

In certain instances, the mixture can include a particular distribution of abrasive grains. For example, the mixture can include a multi-modal distribution of grit sizes of abrasive grains, such that a particular distribution of fine, intermediate, and coarse grit sizes are present within the mixture. In one particular instance the mixture can include a bimodal distribution of abrasive grains including fine grains having a fine average grit size and coarse abrasive grains having a coarse average grit size, wherein the coarse average grit size is significantly greater than the fine average grit size. For instance, the coarse average grit size can be at least about <NUM>% greater, at least about <NUM>%, at least about <NUM>%, or even at least about <NUM>% greater than the fine average grit size (based on the fine abrasive grit size). It will be appreciated that the mixture can include other multi-modal distribution of abrasive grains, including for example, a trimodal distribution or a quad-modal distribution.

It will also be appreciated that abrasive grains of the same composition can have various mechanical properties, including for example, friability. The mixture, and the final-formed bonded abrasive body, can incorporate a mixture of abrasive grains, which may be the same composition, but having varying mechanical properties or grades. For example, the mixture can include abrasive grains of a single composition, such that the mixture includes only diamond or cubic boron nitride. However, the diamond or cubic boron nitride can include a mixture of different grades of diamond or cubic boron nitride, such that the abrasive grains having varying grades and varying mechanical properties.

The abrasive grains can be provided in the mixture in an amount such that the finally-formed abrasive article contains a particular amount of abrasive grains. For example, the mixture can include a majority content (e.g., greater than <NUM> vol%) of abrasive grains.

In accordance with an embodiment, the bond material can be a metal or metal alloy material. For example, the bond material can include a powder composition including at least one transition metal element. In particular instances, the bond material can include a metal selected from the group including copper, tin, silver, molybdenum, zinc, tungsten, iron, nickel, antimony, and a combination thereof. In one particular embodiment, the bond material can be a metal alloy including copper and tin. The metal alloy of copper and tin can be a bronze material, which may be formed of a <NUM>:<NUM> by weight composition of copper and tin, respectively.

According to a particular embodiment, the metal alloy of copper and tin can include a certain content of copper, such that the final-formed bonded abrasive article has suitable mechanical characteristics and grinding performance. For example, the copper and tin metal alloy can include not greater than about <NUM>% copper, such as not greater than about <NUM>% copper, not greater than about <NUM>% not greater than about <NUM>% copper, not greater than about <NUM>% copper, or even not greater than about <NUM>% copper. In particular instances, the amount of copper is within a range between about <NUM>% and about <NUM>%, and more particularly, between about <NUM>% and about <NUM>%.

Certain metal alloys of copper and tin can have a minimum amount of tin. For example, the metal alloy can include at least about <NUM>% tin of the total amount of the composition. In other instances, the amount of tin can be greater, such as at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, or even at least about <NUM>%. Certain bond materials can include a copper and tin metal alloy having an amount of tin within a range between about <NUM>% and about <NUM>%, between about <NUM>% and about <NUM>%, or even between about <NUM>% and about <NUM>%.

In an alternative embodiment, the bond material can be a tin-based material, wherein tin-based materials include metal and metal alloys comprising a majority content of tin versus other compounds present in the material. For example, the bond material can consist essentially of tin. Still, certain-tin-based bond materials may be used that include not greater than about <NUM>% of other alloying materials, particularly metals.

The mixture can contain an equal portion of abrasive grains to bond. However, in certain embodiments, the mixture can be formed such that the amount of bond material can be less than the amount of abrasive grains within the mixture. Such a mixture facilitates a bonded abrasive article having certain properties, which are described in more detail herein.

In addition to the abrasive grains and bond material, the mixture can further include an active bond composition precursor. The active bond composition precursor includes a material, which can be added to the mixture that later facilitates a chemical reaction between certain components of the bonded abrasive body, including for example, particulate material (e.g., abrasive grains and/or fillers) and bond material. The active bond composition precursor can be added to the mixture in minor amounts, and particularly, in amounts less than the amount of the abrasive grains present within the mixture.

In accordance with an embodiment, the active bond composition precursor can include a composition including a metal or metal alloy. More particularly, the active bond composition precursor can include a composition or complex including hydrogen. For example, the active bond composition precursor can include a metal hydride, and more particularly, can include a material such as titanium hydride. In one embodiment, the active bond composition precursor consists essentially of titanium hydride.

The mixture generally includes a minor amount of the active bond composition precursor. For example, the mixture can include not greater than about <NUM> wt% of the active bond composition precursor of the total weight of the mixture. In other embodiments, the amount of the active bond composition precursor within the mixture can be less, such as not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, or even not greater than about <NUM> wt%. In particular instances, the amount of active bond composition precursor within the mixture can be within a range between about <NUM> wt% and about <NUM> wt%, such as between about <NUM> wt% and about <NUM> wt%, between about <NUM> wt% and about <NUM> wt%, between about <NUM> wt% and about <NUM> wt%, or even between about <NUM> wt %, and about <NUM> wt%.

The mixture can further include a binder material. The binder material may be utilized to provide suitable strength during formation of the bonded abrasive article. Certain suitable binder materials can include an organic material. For example, the organic material can be a material such as a thermoset, thermoplastic, adhesive and a combination thereof. In one particular instance, the organic material of the binder material includes a material such as polyimides, polyamides, resins, aramids, epoxies, polyesters, polyurethanes, acetates, celluloses, and a combination thereof. In one embodiment, the mixture can include a binder material utilizing a combination of a thermoplastic material configured to cure at a particular temperature. In another embodiment, the binder material can include an adhesive material suitable for facilitating attachment between components of the mixture. The binder can be in the form of a liquid, including for example, an aqueous-based or non-aqueous-based compound.

Generally, the binder material can be present in a minor amount (by weight) within the mixture. For example, the binder can be present in amount significantly less than the amount of the abrasive grains, bond material, or the active bond composition precursor. For example, the mixture can include not greater than about <NUM> wt% of binder material for the total weight of the mixture. In other embodiments, the amount of binder material within the mixture can be less, such as not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, not greater than about <NUM> wt%, or even not greater than about <NUM> wt%. In particular instances, the amount of binder material within the mixture can be within a range between about <NUM> wt% and about <NUM> wt%, such as between about <NUM> wt% and about <NUM> wt%, between about <NUM> wt% and about <NUM> wt%, between about <NUM> wt% and about <NUM> wt%, or even between about <NUM> wt % and about <NUM> wt%.

The mixture can further include a certain amount of fillers. The fillers can be a particulate material, which may be substituted for certain components within the mixture, including for example, the abrasive grains. Notably, the fillers can be a particulate material that may be incorporated in the mixture, wherein the fillers substantially maintain their original size and shape in the finally-formed bonded abrasive body. Examples of suitable fillers can include oxides, carbides, borides, silicides, nitrides, oxynitrides, oxycarbides, silicates, graphite, silicon, inter-metallics, ceramics, hollow-ceramics, fused silica, glass, glass-ceramics, hollow glass spheres, natural materials such as shells, and a combination thereof.

Notably, certain fillers can have a hardness that is less than the hardness of the abrasive grains. Additionally, the mixture can be formed such that the fillers are present in an amount of not greater than about <NUM> vol% of the total volume of the mixture. Volume percent is used to describe the content of fillers as fillers can have varying density depending upon the type of particulate, such as hollow spheres versus heavy particulate. In other embodiments, the amount of filler within the mixture can be not greater than about <NUM> vol%, such as not greater than about <NUM> vol%, not greater than about <NUM> vol%, not greater than about <NUM> vol%, not greater than about <NUM> vol%, not greater than about <NUM> vol%, or even not greater than about <NUM> vol%.

Certain forming processes may utilize a greater amount of filler material than the amount of abrasive grains. For example, nearly all of the abrasive grains can be substituted with one or more filler materials. In other instances, a majority content of the abrasive grains can be substituted with filler material. In other embodiments, a minor portion of the abrasive grains can be substituted with filler material.

Moreover, the fillers can have an average particulate size that is significantly less than the average grit size of the abrasive grains. For example, the average particulate size of the fillers can be at least about <NUM>% less, such as at least about <NUM>% less, such as at least about <NUM>% less, at least about <NUM>% less, or even at least about <NUM>% less than the average grit size of the abrasive grains based on the average grit size of the average grit size of the abrasive grains.

In certain other embodiments, the fillers can have an average particulate size that is greater than the abrasive grains, particularly in the context of fillers that are hollow bodies.

In particular instances, the filler material can have a fracture toughness (K1c) of not greater than about <NUM> MPa m<NUM>, as measured by a nano-indentation test via standardized test of ISO <NUM> utilizing a diamond probe available from CSM Indentation Testers, Inc. , Switzerland or similar companies. In other embodiments, the filler can have a fracture toughness (K1c) of not greater than about <NUM> MPa m<NUM>, such as not greater than about <NUM> MPa m<NUM>, or even not greater than about <NUM> MPa m<NUM>. Still, the average fracture toughness of the fillers can be within a range between about <NUM> MPa m<NUM> about <NUM> MPa m<NUM>, such as within a range between about <NUM> MPa m<NUM> about <NUM> MPa m<NUM>, or even within a range between about <NUM> MPa m<NUM> about <NUM> MPa m<NUM>.

After forming the mixture, the process of forming the bonded abrasive article continues by shearing the mixture such that it has proper rheological characteristics. For example, the mixture can be sheared until it has a particular viscosity, such as at least about <NUM> Centipoise, and can have a consistency that is semi-liquid (e.g., a mud-like consistency). In other instances, it could be of much lower viscosity such as a paste.

After shearing the mixture, the process can continue by forming agglomerates from the mixture. Process of forming agglomerates can initially include a process of drying the mixture. In particular the drying process may be conducted at a temperature suitable to cure an organic component (e.g., thermoset) within the binder contained within the mixture, and remove a portion of certain volatiles (e.g., moisture) within the mixture. Thus, upon suitable curing the organic material within the binder material, the mixture can have a hardened or semi-hardened form. Particularly suitable drying temperatures can be not greater than about <NUM>, and more particularly, within a range between about <NUM> and about <NUM>.

After drying the mixture at a suitable temperature, the process of forming agglomerates can continue by crushing the hardened form. After crushing the hardened form, the crushed particles include agglomerates of the components contained within the mixture, including the abrasive grains and bond material. The process of forming the agglomerates can then include sieving of the crushed particulate to obtain a suitable distribution of agglomerate sizes.

After forming the agglomerates, the process can continue by shaping the agglomerates into a desirable shape of the finally-formed bonded abrasive article. One suitable shaping process includes filling a mold with the agglomerated particles. After filling the mold, the agglomerates can be pressed to form a green (i.e., unsintered) body having the dimensions of the mold. In accordance with one embodiment, pressing can be conducted at a pressure of at least about <NUM> kPa (about <NUM> ton/in<NUM>) of the area of the bonded abrasive article. In other embodiments, the pressure can be greater, such as on the order of at least about <NUM> kPa (about <NUM> tons/in<NUM>), at least about <NUM> MPa (about <NUM> tons/in<NUM>), at least about <NUM> MPa (about <NUM> ton/in<NUM>), or even at least about <NUM> MPa (about <NUM> tons/in<NUM>). In one particular embodiment pressing is completed at a pressure within a range between about <NUM> kPa (about <NUM> ton/in<NUM>) and about <NUM> MPa (about <NUM> tons/in<NUM>), or more particularly, within a range between about <NUM> MPa (about <NUM> tons/in<NUM>) and about <NUM> MPa (about <NUM> tons/in<NUM>).

After shaping the mixture to form the green article, the process can continue by treating the green article. Treating can include heat treating the green article, and particularly sintering of the green article. In one particular embodiment, treating includes liquid phase sintering to form the bonded abrasive body. Notably, liquid phase sintering includes forming a liquid phase of certain components of the green article, particularly, the bond material, such that at the sintering temperature at least a portion of the bond material is present in liquid phase and free-flowing. Notably, liquid phase sintering is not a process generally used for formation of bonded abrasives utilizing a metal bond material.

In accordance with an embodiment, treating the green article includes heating the green article to a liquid phase sintering temperature of at least <NUM>. In other embodiments, the liquid phase sintering temperature can be greater, such as at least <NUM>, at least about <NUM>, at least about <NUM>, or even at least about <NUM>. In particular instances, the liquid phase sintering temperature can be within a range between about <NUM> and about <NUM>, such as between about <NUM>, and about <NUM>, and more particularly, within a range between about <NUM> and <NUM>.

Treating, and particularly sintering, can be conducted for a particular duration. Sintering at the liquid phase sintering temperature can be conducted for a duration of at least about <NUM> minutes, at least about <NUM> minutes, at least about <NUM> minutes, or even at least about <NUM> minutes. In particular embodiments, the sintering at the liquid phase sintering temperature can last for a duration within a range between about <NUM> minutes and about <NUM> minutes, such as between about <NUM> minutes and <NUM> minutes, or even between about <NUM> minutes and about <NUM> minutes.

Treating the green article can further include conducting a liquid phase sintering process in a particular atmosphere. For example, the atmosphere can be a reduced pressure atmosphere having a pressure of not greater than about <NUM>-<NUM> Torr. In other embodiments, the reduce pressure atmosphere can have a pressure of not greater than about <NUM>-<NUM> Torr, not greater than about <NUM>-<NUM> Torr, such as not greater than about <NUM>-<NUM> Torr, or even not greater than about <NUM>-<NUM> Torr. In particular instances, the reduced pressure atmosphere can be within a range between about <NUM>-<NUM> Torr and about <NUM>-<NUM> Torr.

Additionally, during treating the green article, and particularly during a liquid phase sintering process, the atmosphere can be a non-oxidizing (i.e., reducing) atmosphere. Suitable gaseous species for forming the reducing atmosphere can include hydrogen, nitrogen, noble gases, carbon monoxide, dissociated ammonia, and a combination thereof. In other embodiments, an inert atmosphere may be used during treating of the green article, to limit oxidation of the metal and metal alloy components.

After completing the treating process, a bonded abrasive article incorporating abrasive grains within a metal bond material is formed. In accordance with an embodiment, the abrasive article can have a body having particular features. For example, in accordance with one embodiment, the bonded abrasive body can have a significantly greater volume of abrasive grains than the volume of bond material within the body. The bonded abrasive body can have a ratio of VAG/VBM of at least about <NUM>, wherein VAG represents a volume percent of abrasive grains within the total volume of the bonded abrasive body, and VBM represents the volume percent of bond material within the total volume of the bonded abrasive body. In accordance with another embodiment, the ratio of VAG/VBM can be at least about <NUM>, such as at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or even at least about <NUM>. In other embodiments, the bonded abrasive body can be formed such that the ratio of VAG/VBM is within a range between about <NUM> and about <NUM>, such as between about <NUM> and about <NUM>, such as between about <NUM> and about <NUM>, such as between about <NUM> and about <NUM>, between about <NUM> and about <NUM>, between about <NUM> and about <NUM>, between about <NUM> and about <NUM>, or even between about <NUM> and about <NUM>.

In more particular terms, the bonded abrasive body can include at least about <NUM> vol% abrasive grains for the total volume of the bonded abrasive body. In other instances, the content of abrasive grains is greater, such as at least about <NUM> vol%, at least about <NUM> vol%, at least about <NUM> vol%, at least about <NUM> vol%, or even at least about <NUM> vol%. In particular embodiments, the bonded abrasive body comprises between about <NUM> vol% and about <NUM> vol%, such as between about <NUM> vol% and about <NUM> vol%, between about <NUM> vol% and about <NUM> vol%, or even between about <NUM> vol% and about <NUM> vol% abrasive grains for the total volume of the bonded abrasive body.

The bonded abrasive body can include not greater than about <NUM> vol% bond material for the total volume of the bonded abrasive body. According to certain embodiments, the content of bond material is less, such not greater than about <NUM> vol%, not greater than about <NUM> vol%, not greater than about <NUM> vol%, not greater than about <NUM> vol%, or even not greater than about <NUM> vol%. In particular embodiments, the bonded abrasive body comprises between about <NUM> vol% and about <NUM> vol%, such as between about <NUM> vol% and about <NUM> vol%, between about <NUM> vol% and about <NUM> vol%, or even between about <NUM> vol% and about <NUM> vol% bond material for the total volume of the bonded abrasive body.

In accordance with another embodiment, the bonded abrasive body herein can include a certain amount of porosity. The bonded abrasive body can have at least about <NUM> vol%, at least about <NUM> vol%, even at least about <NUM> vol% porosity for the total volume of the body. The bonded abrasive body can have not greater than <NUM> vol% porosity for the total volume of the body. It will be appreciated that the porosity can fall within a range between any of the minimum and maximum values listed herein.

The bonded abrasive body can be formed such that a certain content of the porosity within the bonded abrasive body is interconnected porosity. Interconnected porosity defines a network of interconnected channels (i.e., pores) extending through the volume of the bonded abrasive body. For example, a majority of the porosity of the body can be interconnected porosity. In fact, in particular instances, the bonded abrasive body can be formed such that at least <NUM>%, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, or even at least about <NUM>% of the porosity present within the bonded abrasive body is interconnected porosity. In certain instances, essentially all of the porosity present within the body is interconnected porosity. Accordingly, the bonded abrasive body can be defined by a continuous network of two phases, a solid phase defined by the bond and abrasive grains and a second continuous phase defined by the porosity extending between the solid phase throughout the bonded abrasive body.

In accordance with another embodiment, the bonded abrasive body can have a particular ratio of particulate material (VP), which includes abrasive grains and fillers, as compared to the bond material (VBM) for the total volume of the bonded abrasive body. It will be appreciated that the amounts of the particulate material and the bond material are measured in volume percent of the component as part of the total volume of the body According to the present invention, the bonded abrasive body of embodiments herein has a ratio (VP/VBM) of at least about <NUM>. In other embodiments, the ratio (VP/VBM) can be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or even at least about <NUM>. In particular instances, the ratio (VP/VBM) can be within a range between <NUM> and about <NUM>, such as between about <NUM> and <NUM>, such as between about <NUM> and about <NUM>, between about <NUM> and about <NUM>, between about <NUM> and about <NUM>, between about <NUM> and about <NUM>, or even between about <NUM> and about <NUM>. As such, the bonded abrasive body can incorporate a higher content of particulate material including fillers and abrasive grains than bond material.

According to one embodiment, the abrasive body can include an amount (vol%) of fillers that can be less than, equal to, or even greater than the amount (vol%) of abrasive grains present within the total volume of the bonded abrasive body. Certain abrasive articles can utilize not greater than about <NUM> vol% fillers for the total volume of the bonded abrasive body. According to certain embodiments, the content of fillers in the body can be not greater than about <NUM> vol%, not greater than about <NUM> vol%, not greater than about <NUM> vol%, not greater than about <NUM> vol%, or even not greater than about <NUM> vol%. In particular embodiments, the bonded abrasive body comprises between about <NUM> vol% and about <NUM> vol%, such as between about <NUM> vol% and about <NUM> vol%, between about <NUM> vol% and about <NUM> vol%, or even between about <NUM> vol% and about <NUM> vol% fillers for the total volume of the bonded abrasive body. In one instance, the bonded abrasive body can be essentially free of fillers.

The bonded abrasive bodies of embodiments herein can have a particular content of active bond composition. As will be appreciated the active bond composition can be a reaction product formed from a reaction between the active bond composition precursor and certain components of the bonded abrasive body, including for example, abrasive grains, fillers, and bond material. The active bond composition can facilitate chemical bonding between the particulates (e.g., abrasive grains or filler) within the body and the bond material, which may facilitate retention of particulates within the bond material.

In particular, the active bond composition can include distinct phases, which can be disposed in distinct regions of the bonded abrasive body. Moreover, the active bond composition can have a particular composition depending upon the location of the composition. For example, the active bond composition can include a precipitated phase and an interfacial phase. The precipitated phase can be present within the bond material and can be dispersed as a distinct phase throughout the volume of the bond material. The interfacial phase can be disposed at the interface between the particulate material (i.e., abrasive grains and/or fillers) and the bond material. The interfacial phase can extend around a majority of the surface area of the particulate material of the body. While not completely understood, it is theorized that the distinct phases and differences in the composition of the active bond composition are due to the forming processes, particularly liquid phase sintering.

Accordingly, the bond material can be a composite material including a bond phase and a precipitated phase, which are separate phases. The precipitated phase can be made of a composition including at least one element of the active bond composition and at least one element of the bond material. Notably, the precipitated phase can include at least one metal element originally provided in the mixture as the bond material. The precipitated phase can be a metal or metal alloy compound or complex. In particular embodiments, the precipitated phase can include a material selected from the group of materials consisting of titanium, vanadium, chromium, zirconium, hafnium, tungsten, and a combination thereof. In more particular instances, the precipitated phase includes titanium, and may consist essentially of titanium and tin.

The bond phase of the bond material can include a transition metal element, and particularly a metal element included in the original bond material used to form the mixture. As such, the bond phase can be formed of a material selected from the group of metals consisting of copper, tin, silver, molybdenum, zinc, tungsten, iron, nickel, antimony, and a combination thereof. In particular instances, the bond phase can include copper, and may be a copper-based compound or complex. In certain embodiments, the bond phase consists essentially of copper.

The interfacial phase can include at least one element of the active bond composition. Moreover, the interfacial phase can include at least one element of the particulate material. As such, the interfacial phase can be a compound or complex formed through a chemical reaction between the active bond composition and the particulate. Certain interfacial phase materials include carbides, oxides, nitrides, borides, oxynitrides, oxyborides, oxycarbides and a combination thereof. The interfacial phase can include a metal, and more particularly, may be a compound incorporating a metal, such as a metal carbide, metal nitride, metal oxide, metal oxynitride, metal oxyboride, or metal oxycarbide. According to one embodiment, the interfacial phase consists essentially of a material from the group of titanium carbide, titanium nitride, titanium boronitride, titanium aluminum oxide, and a combination thereof.

Moreover, the interfacial phase can have an average thickness of at least about <NUM> microns. However, and more particularly, the interfacial phase can have a varying thickness depending upon the size of the particulate material the interfacial phase overlies. For example, with regard to abrasive grains and/or fillers having an average size of less than <NUM> microns, the interfacial phase can have a thickness within a range between about <NUM>% to <NUM> of the average size of the particulate. For particulate material having an average size within a range between about <NUM> microns and about <NUM> microns, the interfacial phase can have a thickness within a range between about <NUM>% to about <NUM>% of the average size of the particulate. For particulate material having an average size within a range between about <NUM> microns and about <NUM> microns, the interfacial phase can have a thickness within a range between about <NUM>% to about <NUM>% of the average size of the particulate. For particulate material having an average size of greater than about <NUM> microns, the interfacial phase can have a thickness within a range between about <NUM>% to about <NUM>% of the average size of the particulate.

<FIG> include magnified images of the microstructure of a bonded abrasive body in accordance with an embodiment. <FIG> includes a scanning electron microscope image (operated in backscatter mode) of a cross-section of a portion of a bonded abrasive body including abrasive grains <NUM> and bond material <NUM> extending between the abrasive grains <NUM>. As illustrated, the bond material <NUM> includes two distinct phases of material, a preciptated phase <NUM> represented by a lighter color and extending through the volume of the bond material <NUM>, and a bond phase <NUM> represented by a darker color and extending through the volume of the bond material <NUM>.

<FIG> include magnified images of the same area of the bonded abrasive body of <FIG>, using microprobe analysis to identify select elements present in certain regions of the body. <FIG> includes a microprobe image of the region of <FIG> in a mode set to identify regions high in copper, such that the lighter regions indicate regions where copper is present. According to an embodiment, the bond material <NUM> can include a metal alloy of copper and tin. According to a more particular embodiment, the bond phase <NUM> of the bond material <NUM>, which is one of at least two distinct phases of the bond material <NUM>, can have a greater amount of copper present than the precipitated phase <NUM>.

<FIG> includes a magnified image of the region of <FIG> and <FIG>, using microprobe analysis to identify select elements present in certain regions of the bonded abrasive body. <FIG> uses a microprobe in a mode set to identify regions having tin present, such that the lighter regions indicate regions where tin is more prevalent. As illustrated, the precipitated phase <NUM> of the bond material <NUM> has a greater content of tin than the bond phase <NUM>.

<FIG> includes a magnified image of the region of <FIG>, using microprobe analysis. In particular, <FIG> uses a microprobe in a mode set to identify regions having titanium present, such that the lighter regions indicate regions where titanium is more prevalent. As illustrated, the precipitated phase <NUM> of the bond material <NUM> has a greater content of titanium than the bond phase <NUM>. <FIG> also provides evidence of the interfacial phase <NUM> at the interface of the abrasive grains <NUM> and the bond material <NUM>. As evidenced by <FIG>, the interfacial phase <NUM> includes a particularly high content of titanium, indicating that the titanium of the active bond composition precursor may preferentially migrate to the interface of the particulate (i.e., abrasive grains <NUM>) and chemically react with the abrasive grains to form an interracial phase compound as described herein.

<FIG> provide evidence of an unexpected phenomenon. While it is not completely understood, the original bond material comprising copper and tin is separated during processing, which is theorized to be due to the liquid phase sintering process. The tin and copper become distinct phases; the precipitated phase <NUM> and the bond phase <NUM>, respectively. Moreover, the tin preferentially combines with the titanium, present in the active bond composition precursor material to form the precipitated phase <NUM>.

In accordance with an embodiment, the bonded abrasive body can include at least about <NUM> vol% of the active bond composition, which includes all phases of the active bond composition, such as the interfacial phase and the precipitate phase, for the total volume of the bond material. In other instances, the amount of active bond composition within the bond can be greater, such at least about <NUM> vol%, at least about <NUM> vol%, at least about <NUM> vol%, at least about <NUM> vol%, at least about <NUM> vol%, at least about <NUM> vol%, or even at least about <NUM> vol%. In particular instances, the bond material contains an amount of active bond composition within the range between about <NUM> vol% and about <NUM> vol%, such as between about <NUM> vol% and <NUM> vol%, between about <NUM> vol% and about <NUM> vol%, between about <NUM> vol% and about <NUM> vol%, or between about <NUM> vol% and about <NUM> vol%. In some instances, the amount of active bond composition is within a range between about <NUM> vol% and about <NUM> vol%, between about <NUM> vol% and about <NUM> vol%, or even between about <NUM> vol% and about <NUM> vol% of the total volume of the bond material.

The bonded abrasive body is formed such that the bond material has a particular fracture toughness (K1c). The toughness of the bond material may be measured via a micro-indentation test or nano-indentation test. Micro-indentation testing measures the fracture toughness through a principle of generating cracks on a polished sample through loading an indentor at a particular location within the material, including for example in the present instance, in the bond material. For example, a suitable micro-indentation test can be conducted according to the methods disclosed in "<NPL>. In accordance with the present invention. the bonded abrasive body has a bond material having an average fracture toughness (K1c) of not greater than about <NUM> MPa m<NUM>. In other embodiments, the average fracture toughness (K1c) of the bond material can be not greater about <NUM> MPa m<NUM>, such as not greater about <NUM> MPa m<NUM>, not greater about <NUM> MPa m<NUM>, not greater about <NUM> MPa m<NUM>, not greater about <NUM> MPa m<NUM>, or even not greater about <NUM> MPa m<NUM>. The average fracture toughness of the bond material can be within a range between about <NUM> MPa m<NUM> about <NUM> MPa m<NUM>, such as within a range between about <NUM> MPa m<NUM> about <NUM> MPa m<NUM>, or even within a range between about <NUM> MPa m<NUM> about <NUM> MPa m<NUM>.

The abrasive articles of the embodiments herein may have particular properties. For example, the bonded abrasive body can have a modulus of rupture (MOR) of at least about <NUM> MPa (about <NUM> psi), such as at least about <NUM> MPa (about <NUM> psi), and more particularly, at least about <NUM> MPa (about <NUM> psi).

The bonded abrasive bodies of the embodiments herein demonstrate particular properties when used in certain grinding operations. In particular, the bonded abrasive wheels can be used in non-dressed grinding operations, wherein the bonded abrasive body does not require a dressing operation after the body has undergone a truing operation. Traditionally, truing operations are completed to give the abrasive body a desired contour and shape. After truing, the abrasive body is dressed, typically with an equally hard or harder abrasive element to remove worn grit and expose new abrasive grains. Dressing is a time consuming and necessary process for conventional abrasive articles to ensure proper operation of the abrasive article. The bonded abrasive bodies of the embodiments herein have been found to require significantly less dressing during use and have performance parameters that are significantly improved over conventional abrasive articles.

For example, in one embodiment, during a non-dressed grinding operation, the bonded abrasive body of an embodiment, can have a power variance of not greater than about <NUM>%, wherein power variance is described by the equation [(Po - Pn)/Po] x <NUM>%. Po represents the grinding power (Hp or Hp/in) to grind a workpiece with the bonded abrasive body at an initial grinding cycle and Pn represents the grinding power (Hp or Hp/in) to grind the workpiece for a nth grinding cycle, wherein n≥<NUM>. Accordingly, the power variance measures the change in grinding power from an initial grinding cycle to a subsequent grinding cycle, wherein at least <NUM> grinding cycles are undertaken.

In particular, the grinding cycles can be completed in a consecutive manner, which means no truing or dressing operations are conducted on the bonded abrasive article between the grinding cycles. The bonded abrasive bodies of the embodiments herein can have a power variance of not greater than about <NUM>% during certain grinding operations. In still other embodiments, the power variance of the bonded abrasive body can be not greater than about <NUM>%, such as not greater than about <NUM>%, or even not greater than about <NUM>%. The power variance of certain abrasive bodies can be within a range between about <NUM>% and about <NUM>%, such as between about <NUM>% and about <NUM>%, or even between about <NUM>% and about <NUM>%.

In further reference to the power variance, it will be noted that the change in grinding power between the initial grinding cycle (Po) and the grinding power used to grind the workpiece at an nth grinding cycle (Pn) can be measured over a number of grinding cycles wherein "n" is greater than or equal to <NUM>. In other instances, "n" can be greater than or equal to <NUM> (i.e., at least <NUM> grinding cycles), greater than or equal to <NUM>, or even greater than or equal to <NUM>. Moreover, it will be appreciated that the nth grinding cycle can represent consecutive grinding cycles, wherein dressing is not completed on the abrasive article between the grinding cycles.

In accordance with an embodiment, the bonded abrasive body can be used in grinding operations, wherein the material removal rate (MRR') is at least about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in). In other embodiments, a grinding operation using a bonded abrasive body of embodiments herein, can be conducted at a material removal rate of at least about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in), such as at least about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in), at least about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in), or even at least about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in). Certain grinding operations utilizing the bonded abrasive bodies of embodiments herein can be conducted at a material removal rate (MRR') within a range between about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in) and about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in), within a range between about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in) and about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in), within a range between about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in) and about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in), or even within a range between about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in) and about <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in).

Moreover, the bonded abrasive body can be utilized in grinding operations wherein the bonded abrasive body is rotated at particular surface speeds. Surface speed refers to the speed of the wheel at the point of contact with the work piece. For example, the bonded abrasive body can be rotated at a speed of at least <NUM>/s (<NUM> surface feet per minute (sfpm)), such as at least about <NUM>/s (<NUM> sfpm), such as at least about <NUM>/s (<NUM> sfpm), at least about <NUM>/s (<NUM> sfpm), at least about <NUM>/s (<NUM> sfpm), or even at least <NUM>/s (<NUM> sfpm). In particular instances, the bonded abrasive body can be rotated at a speed within a range between about <NUM>/s (<NUM> sfpm) and about <NUM>/s (<NUM> sfpm), such as between about <NUM>/s (<NUM> sfpm) and <NUM>/s (<NUM> sfpm).

The bonded abrasive body may be suitable for use in various grinding operations including for example plunge grinding operations, creep feed grinding operations, peel grinding operations, flute grinding operations, and the like. In one particular instance, the bonded abrasive body is suitable for use in end mill grinding applications. In other instances, the bonded abrasive body may be useful in thinning of hard and brittle workpieces, including for example, sapphire and quartz materials.

Furthermore, the bonded abrasive bodies of embodiments herein may be utilized in grinding operations, wherein after grinding, the workpiece has an average surface roughness (Ra) that is not greater than about <NUM> microns (about <NUM> microinches). In other instances, the average surface roughness of the workpiece can be not greater than about <NUM> micron (about <NUM> microinches), or even not greater than about about <NUM> microns (<NUM> microinches).

In other embodiments, during grinding with bonded abrasive articles of embodiments herein, the average surface roughness variance for at least three consecutive grinding operations can be not greater than about <NUM>%. It should be noted that consecutive grinding operations are operations wherein a truing operation is not conducted between each of the grinding operations. The variance in the average surface roughness can be calculated as a standard deviation of the measured average surface roughness (Ra) of the workpiece at each of the locations on the workpiece, where each separate grinding operation is conducted. In accordance with certain embodiments, the average surface roughness variance for at least three consecutive grinding operations can be not greater than about <NUM>%, not greater than about <NUM>%, not greater than about <NUM>%, not greater than about <NUM>%, or even not greater than about <NUM>%.

In accordance with other embodiments, the bonded abrasive article can have a G-ratio of at least about <NUM>. The G-ratio is the volume of material removed from the workpiece divided by the volume of material lost from the bonded abrasive body through wear. In accordance with another embodiment, the bonded abrasive body can have a G-ratio of at least about <NUM>, such as at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or even at least about <NUM>. In certain instances, the G-ratio of the bonded abrasive body can be within a range between about <NUM> and about <NUM>, such as between about <NUM> and about <NUM>, or even between about <NUM> and about <NUM>. The G-ratio values noted herein can be achieved at the material removal rates noted herein. Moreover, the G-ratio values described can be achieved on a variety of workpiece material types described herein.

In other terms, the bonded abrasive article can have a G-ratio that is significantly improved over conventional abrasive articles, particularly metal-bonded abrasive articles. For instance, the G-ratio of the bonded abrasive bodies according to embodiments herein can be at least about <NUM>% greater than the G-ratio of a conventional abrasive article. In other instances, the improvement in G-ratio can be greater, such as at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, or even at least about <NUM>%. Particular embodiments of the bonded abrasive article demonstrate an increase in G-ratio as compared to a conventional bonded abrasive within a range between about <NUM>% and about <NUM>%, between about <NUM>% and about <NUM>%, between about <NUM>% and about <NUM>%, between about <NUM>% and about <NUM>%, between about <NUM>% and about <NUM>% or even between about <NUM>% and about <NUM>%.

Certain bonded abrasive bodies demonstrate an initial grinding power that is sufficiently close to a steady state grinding power. Generally, the steady state grinding power is significantly different from an initial grinding power for conventional metal-bonded abrasive articles. As such, the increase in the grinding power from an initial grinding power is particularly low for the bonded abrasive bodies of embodiments herein as compared to conventional metal-bonded abrasive articles. For example, the bonded abrasive bodies of the embodiments herein can have an increase in the initial grinding power of not greater than about <NUM>% as defined by the equation [(Pn - Po)/Po] x <NUM>%. In the equation, Po represents the initial grinding power (Hp or Hp/in) to grind the workpiece with the bonded abrasive body at an initial grinding cycle and Pn represents the grinding power (Hp or Hp/in) to grind the workpiece with the bonded abrasive body at a nth grinding cycle, wherein n≥<NUM>. It will be appreciated that the grinding cycles can be consecutive grinding cycles, wherein no truing or dressing of the bonded abrasive body is conducted.

According to one embodiment, during a grinding operation using the bonded abrasive article of embodiments herein, the increase in the initial grinding power is not greater than about <NUM>%, such as not greater than about <NUM>%, not greater than about <NUM>%, not greater than about <NUM>%, not greater than about <NUM>%, not greater than about <NUM>%, not greater than about <NUM>%, not greater than about <NUM>%, or even not greater than about <NUM>%. In particular instances, the bonded abrasive body is capable of conducting grinding operations wherein the increase in the initial grinding power can be within a range between about <NUM>% and about <NUM>%, such as within a range between about <NUM>% and about <NUM>%, within a range between about <NUM>% and about <NUM>%, within a range between about <NUM>% and about <NUM>%, or even within a range between about <NUM>% and about <NUM>%.

In other embodiments, the bonded abrasive bodies demonstrate an increase in the initial grinding power of not greater than about <NUM>% for a grinding time of at least <NUM> seconds at a minimum feed rate of about <NUM>/min (<NUM> inches/min). The increase in initial grinding power can be defined by the equation [(P<NUM> - Po)/Po] x <NUM>%, wherein Po represents the initial grinding power (Hp or Hp/in) to initially grind the workpiece with the bonded abrasive body at a first grinding cycle and P<NUM> represents the grinding power (Hp or Hp/in) to grind the workpiece with the bonded abrasive body after <NUM> seconds of grinding. In certain other grinding operations, the bonded abrasive body can have an increase in the initial grinding power of not greater than about <NUM>%, such as not greater than about <NUM>%, such as not greater than about <NUM>%, or even not greater than about <NUM>% for a grinding time of at least <NUM> seconds at a minimum feed rate of about <NUM>/min (<NUM> inches/min). In particular grinding applications, the bonded abrasive body demonstrates an increase in the initial grinding power within a range between about <NUM>% and about <NUM>%, such as between about <NUM>% and about <NUM>%, such as between about <NUM>% and about <NUM>%, or even between about <NUM>% and about <NUM>%, for a grinding time of at least <NUM> seconds at a minimum feed rate of about <NUM>/min (<NUM> inches/min).

The bonded abrasive bodies of embodiments herein can have a particular grinding performance, wherein the increase in initial grinding power is not greater than about <NUM>% for a grinding time of at least about <NUM> seconds at a minimum feed rate of at least <NUM>/min (<NUM> inches/min). The increase in initial grinding power for such applications can be defined by the equation [(P<NUM> - Po)/Po] x <NUM>%, wherein Po represents the initial grinding power (Hp or Hp/in) to initially grind the workpiece with the bonded abrasive body at a first grinding cycle and P<NUM> represents the grinding power (Hp or Hp/in) to grind the workpiece with the bonded abrasive body after <NUM> seconds of grinding. Still, for certain bonded abrasive articles of embodiments herein, the increase in initial grinding power can be less, such as not greater than about <NUM>%, not greater than about <NUM>%, or even not greater than about <NUM>% over a time of at least <NUM> seconds at a minimum feed rate of <NUM>/min (<NUM> inches/min). The bonded abrasive bodies herein can have an increase in the initial grinding power within a range between about <NUM>% and about <NUM>%, such as between about <NUM>% and about <NUM>%, such as between about <NUM>% and about <NUM>%, or even between about <NUM>% and about <NUM>%, for a grinding time of at least <NUM> seconds at a minimum feed rate of about <NUM>/min (<NUM> inches/min). Such properties may be particularly suitable for functioning of the bonded abrasive body when grinding hard or superhard workpieces.

In accordance with another embodiment, the bonded abrasive body can have a limited increase in initial grinding power for a grinding time of at least <NUM> seconds at a minimum feed rate of at least about <NUM>/min (<NUM> inches/min). For example, the increase in initial grinding power can be not greater than about <NUM>%, such as not greater than about <NUM>%, not greater than about <NUM>%, or even not greater than about <NUM>%, for a grinding time of at least <NUM> seconds at a minimum feed rate of about <NUM>/min (<NUM> inches/min). Such properties may be particularly suitable for functioning of the bonded abrasive body when grinding hard or superhard workpieces.

The bonded abrasive bodies of the embodiments herein may be suitable for grinding certain workpieces, such as particularly hard workpieces. For example, workpieces can have an average Vickers hardness of at least <NUM> GPa. In other instances, the average Vickers hardness of the workpieces can be at least about <NUM> GPa or even at least about <NUM> GPa.

The workpieces can be made of metals, metal alloys, nitrides, borides, carbides, oxides, oxynitrites, oxyborates, oxycarbides, in a combination thereof. In particular instances, the workpieces can be metal carbides, including for example, tungsten carbide. In exemplary conditions where grinding is conducted on workpieces made of tungsten carbide, the amount of cobalt within the tungsten carbide workpiece can be within a range between about <NUM>% and about <NUM>% by weight.

In conducting certain grinding operations, for example, on particularly hard materials, the bonded abrasive body can be operated at a rate of at least <NUM>/s (<NUM> sfpm). In other instances, the bonded abrasive body can be rotated at a rate of at least <NUM>/s (<NUM> sfpm), at least about <NUM>/s (<NUM> sfpm), or even at least <NUM>/s (<NUM> sfpm). In particular instances, the bonded abrasive body can be rotated at a rate within a range between about <NUM>/s (<NUM> sfpm) and about <NUM>/s (<NUM> sfpm), more particularly, within a range between about <NUM>/s (<NUM> sfpm) and about <NUM>/s (<NUM> sfpm) during grinding operations.

Additionally, the bonded abrasive articles of embodiments herein are suitable for certain grinding operations, such as, for example, on particularly hard workpieces at certain feed rates. For example, the feed rate can be at least about <NUM>/min (<NUM> inches/min). In other instances, the feed rate can be greater, such as at least about <NUM>/min (<NUM> inches/min), at least about <NUM>/min (<NUM> inches/min), or at least about <NUM>/min (<NUM> inches/min). Particular embodiments may utilize the bonded abrasive body in a grinding operation wherein the feed rate is within a range between about <NUM>/min (<NUM> inches/min) and about <NUM>/min (<NUM> inches/min), such as between about <NUM>/min (<NUM> inches/min) and about <NUM>/min (<NUM> inches/min).

In yet another embodiment, the bonded abrasive body can be used in a grinding operation wherein after truing the bonded abrasive body with an abrasive truing wheel, the bonded abrasive body is capable of grinding a workpiece having an average Vickers hardness of at least <NUM> GPa for at least <NUM> consecutive grinding cycles without exceeding the maximum spindle power of the grinding machine. As such, the bonded abrasive bodies demonstrate an improved working lifetime particularly in the context of grinding workpieces of hard material. In fact, the bonded abrasive body is capable of conducting at least about <NUM> consecutive grinding cycles, at least about <NUM> consecutive grinding cycles, or at least about <NUM> consecutive grinding cycles before a truing operation is utilized. It will be appreciated that reference to consecutive grinding cycles is reference to grinding cycles conducted in a continuous manner without truing or dressing of the bonded abrasive body between grinding cycles.

In comparison of the bonded abrasive bodies of embodiments herein to conventional bonded abrasive bodies, generally, conventional bonded abrasive articles conduct not greater than about <NUM> consecutive grinding cycles on comparatively hard workpieces before requiring a truing operation for resharpening and resurfacing. As such, the bonded abrasive bodies of embodiments herein demonstrate an improvement of operable grinding time over conventional metal-bonded, bonded abrasives, as measured by the number of consecutive grinding cycles conducted before a truing operation is necessary or the grinding power exceeds the power capabilities of the grinding machine.

Another noteworthy improvement in grinding performance as measured in the industry is parts/dress, which is a measure of the number of parts that can be machined by a particular abrasive article before the abrasive article requires dressing to maintain performance. According to one embodiment, the bonded abrasive bodies of the embodiments herein can have an increase in grinding efficiency on a workpiece, as measured by parts/dress, of at least about <NUM>% compared to a conventional metal-bonded abrasive article. According to another embodiment, the increase in grinding efficiency is at least about <NUM>%, such as at least about <NUM>%, at least about <NUM>%, or even at least about <NUM>% as compared to conventional metal-bonded abrasive articles. Notably, such conventional metal-bonded abrasive articles can include state of the art articles such as G-Force and Spector brand abrasive articles available from Saint-Gobain Corporation. In particular instances, the increase in grinding efficiency as measured by parts/dress can be within a range between about <NUM>% and about <NUM>%, such as on the order of between about <NUM>% and about <NUM>%, between about <NUM>% and about <NUM>%, or even between about <NUM>% and about <NUM>%. It will be appreciated, that such improvements can be achieved on workpieces described herein under the grinding conditions described herein.

Additionally, the bonded abrasive articles of embodiments herein can have an improvement in grinding performance as measured in the industry by wear rate, which is a measure of the wear an abrasive article experiences during grinding. According to one embodiment, the bonded abrasive bodies of the embodiments herein can have an improvement in wear rate, such that the abrasive article wears at a rate that is at least <NUM>% less than the wear rate of a conventional metal-bonded abrasive article. According to another embodiment, the wear rate is at least about <NUM>% less, such as at least about <NUM>%, at least about <NUM>%, or even at least about <NUM>% as compared to conventional metal-bonded abrasive articles. In particular instances, the improvement in wear rate can be within a range between about <NUM>% and about <NUM>%, such as on the order of between about <NUM>% and about <NUM>%, between about <NUM>% and about <NUM>%, or even between about <NUM>% and about <NUM>%. It will be appreciated, that such improvements can be achieved on workpieces described herein under the grinding conditions described herein.

Another noteworthy improvement in grinding performance as measured in the industry is wear rate, which is a measure of the wear an abrasive article experiences during grinding. According to one embodiment, the bonded abrasive bodies of the embodiments herein can have an improvement in wear rate, such that the abrasive article wears at a rate that is at least <NUM>% less than the wear rate of a conventional metal-bonded abrasive article. According to another embodiment, the wear rate is at least about <NUM>% less, such as at least about <NUM>%, at least about <NUM>%, or even at least about <NUM>% as compared to conventional metal-bonded abrasive articles. In particular instances, the improvement in wear rate can be within a range between about <NUM>% and about <NUM>%, such as on the order of between about <NUM>% and about <NUM>%, between about <NUM>% and about <NUM>%, or even between about <NUM>% and about <NUM>%. It will be appreciated, that such improvements can be achieved on workpieces described herein under the grinding conditions described herein.

Another noted improvement in grinding performance demonstrated by the abrasive articles of the embodiments herein includes an increase in useable grinding rate. Grinding rate is the speed at which a workpiece can be shaped without sacrificing the surface finish or exceeding the grinding power of the machine or bonded abrasive article. According to one embodiment, the bonded abrasive bodies of the embodiments herein can have an improvement in grinding rate, such that the abrasive article can grind at a rate that is at least <NUM>% faster than a conventional metal-bonded abrasive article. In other instances, the grinding rate can be greater, such as at least about <NUM>% less, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, or even at least about <NUM>% as compared to conventional metal-bonded abrasive articles. For certain bonded abrasive articles herein, the improvement in grinding rate can be within a range between about <NUM>% and about <NUM>%, such as on the order of between about <NUM>% and about <NUM>%, between about <NUM>% and about <NUM>%, or even between about <NUM>% and about <NUM>%. It will be appreciated, that such improvements can be achieved on workpieces described herein under the grinding conditions described herein.

Notably, such improvements in the grinding rate can be achieved while maintaining other grinding parameters noted herein. For example, improvements in grinding rate can be achieved while also having limited increase in initial grinding power as noted herein, limited variance in the surface finish as noted herein, and limited wear rate as noted herein.

<FIG> includes a magnified image of a bonded abrasive body according to an embodiment. As illustrated, the bonded abrasive body includes abrasive grains <NUM> contained within and surrounded by a bond material <NUM> including a metal or metal alloy material. As further illustrated, the bonded abrasive body has a substantially open structure, including pores <NUM> extending between the abrasive grains <NUM> and bond material <NUM>. As evident from <FIG>, the bonded abrasive body includes a significant amount (vol%) of abrasive grains <NUM>, such that the structure contains primarily abrasive grains <NUM> which are bonded together by the bond material <NUM>. Moreover, the abrasive grains <NUM> are in close proximity to each other, and little bond material <NUM> separates the abrasive grains <NUM>, demonstrating the high ratio of abrasive grains <NUM> to bond material <NUM>.

A first bonded abrasive sample is made into a <NUM>" diameter wheel having a 1A1 shape as understood in the industry. Forming of the sample includes creating a mixture including <NUM> grams of bronze powder (i.e., <NUM>:<NUM> by weight of coppertin) having a size of <NUM> U. mesh obtained from Connecticut Engineering Associate Corporation located at <NUM> Philo Curtis Road, Sandy Hook, CT <NUM>, USA. The bronze powder is dry blended with <NUM> grams of titanium hydride of same size purchased from Chemetall Chemical Products, New Providence New Jersey, USA. Abrasive grains of cubic boron nitride having a US mesh size -<NUM>/+<NUM> are also mixed with the bronze powder and titanium hydride. The abrasive grains are from Saint-Gobain Ceramics and Plastics, Worcester, MA and commercially available as CBN-V.

After adding the abrasive grains, <NUM> grams of organic binder is added to the mixture and the mixture is sheared to a consistency of mud. The organic binder includes a thermoplastic resin sold under the brand name S-binder by Wall Colmonoy Co. and a K424 binder from Vitta Corporation. The mixture is then oven dried to remove moisture. The dried mixture is crushed and sieved to obtain agglomerates. The agglomerates are placed into a steel mold having an annular shape and defining an outside nominal diameter of <NUM> (<NUM> inches) and an inside diameter of <NUM> (<NUM> inches). The agglomerates are pressed at <NUM> MPa (<NUM> tons/in<NUM>) to form a green article. The green article is sintered at <NUM> for <NUM> minutes in a reducing atmosphere having a pressure of approximately <NUM>-<NUM> Torr. The finally-formed bonded abrasive has a ratio (VAG/VBM) of <NUM> and an amount of porosity (<NUM>% interconnected porosity) of <NUM> volume percent of the total volume of the body.

A steel core is attached to the bonded abrasive body using epoxy and further finished, balanced and speed tested to complete the wheel manufacturing process. The wheel was marked Sample <NUM> for identification.

Sample <NUM> is used to grind a workpiece of <NUM> bearing steel, originally hardened to <NUM>-<NUM> HRC, in an external cylindrical plunge grinding mode on a Bryant OD/ID grinder. The workpieces are in the form of <NUM> steel disks, <NUM> (<NUM> inches) in diameter, and the grinding operation is an external cylindrical plunge grind. Initially, before grinding, Sample <NUM> is mounted on the machine spindle and trued with a BPR diamond roll, commercially available from Saint-Gobain Abrasives, Arden, NC, as BPR roll. The truing parameters are shown in Table <NUM>.

Sample <NUM> is not dressed with an abrasive stick after truing, as the abrasive grit are sufficiently exposed, reading the abrasive bodies for a non-dressed grinding operation. The grinding parameters are given in Table <NUM>.

<FIG> includes a plot of grinding power (HP/in) versus number of grinding cycles for Sample <NUM> under the grinding conditions provided in Table <NUM> at two different material removal rates (MRR') (i.e., <NUM><NUM>/sec/mm (<NUM> in3/min/in) and <NUM><NUM>/sec/mm (<NUM> in3/min/in)). As demonstrated, plot <NUM> demonstrates that Sample <NUM> is capable of grinding the workpiece at a MRR' of <NUM><NUM>/sec/mm (<NUM> in3/min/in) at an initial grinding power of <NUM> W/µm (<NUM> Hp/in) and a grinding power after <NUM> consecutive grinding cycles of <NUM> W/µm (<NUM> Hp/in). Plot <NUM> shows that Sample <NUM> is capable of grinding the workpiece at a MRR' of <NUM><NUM>/sec/mm (<NUM> in3/min/in) at an initial grinding power of <NUM> W/µm (<NUM> Hp/in) and a grinding power after <NUM> consecutive grinding cycles of <NUM> W/µm (<NUM> Hp/in). The power variance for Sample <NUM> in grinding the workpiece at a MRR' of <NUM><NUM>/sec/mm (<NUM> in3/min/in) was <NUM>% and the power variance for Sample <NUM> in grinding the workpiece at a MRR' of <NUM><NUM>/sec/mm (<NUM> in3/min/in) was <NUM>%. Accordingly, Sample <NUM> demonstrates little variance between an initial grinding power and a steady state grinding power after <NUM> consecutive grinding operations. The workpiece had a width of approximately <NUM> (<NUM>. <NUM> inches(and the abrasive wheel samples were formed to have a width of <NUM> (<NUM> inches). The width used to calculate MRR' was <NUM> (<NUM> inches); the width of the workpiece.

<FIG> further includes two plots of grinding power (HP/in) versus number of grinding cycles for a conventional metal bonded abrasive article (Sample NMS1) commonly available as G-Force wheel B181-75UP061 from Saint-Gobain Corporation. As demonstrated, plot <NUM> demonstrates that Sample MBS1 is capable of grinding the workpiece at an initial grinding power of <NUM> W/µm (<NUM> Hp/in) at a MRR' of <NUM><NUM>/sec/mm (<NUM> in3/min/in). After <NUM> consecutive grinding cycles Sample MBS1 grinds at a power of <NUM> W/µm (<NUM> Hp/in) for a MRR' of <NUM><NUM>/sec/mm (<NUM> in3/min/in). Sample MBS1 demonstrates a power variance in a non-dressed grinding operation of <NUM>%.

Plot <NUM> demonstrates that Sample MBS1 is capable of grinding the workpiece at an initial grinding power of <NUM> W/µm (<NUM> Hp/in) at a MRR' of <NUM><NUM>/sec/mm (<NUM> in3/min/in). After <NUM> consecutive grinding cycles Sample MBS grinds at a power of <NUM> W/µm (<NUM> Hp/in) for a MRR' of <NUM><NUM>/sec/mm (<NUM> in3/min/in). Sample MBS1 demonstrates a power variance in a non-dressed grinding operation of <NUM>%. Clearly, in a non-dressed grinding operation the bonded abrasive articles of the embodiments herein demonstrate significantly improved performance of grinding power variance over the state-of-the-art abrasive wheels.

<FIG> includes a plot of surface finish or surface roughness (Ra) versus number of grinding cycles for Sample <NUM> under the grinding conditions provided in Table <NUM> at the two different material removal rates (MRR') (i.e., <NUM><NUM>/sec/mm (<NUM> in3/min/in) and <NUM><NUM>/sec/mm (<NUM> in3/min/in)). As demonstrated, Sample , represented by plots <NUM> and <NUM>, provides a surface finish (Ra) on the workpiece after consecutive grinding cycles of not greater than about <NUM> (<NUM> microinches) at both material removal rates. Moreover, the variance (i.e., the standard deviation of all measurements) of all measured surface finish values between the initial grinding operation and the fifth grinding cycle does not vary by more than <NUM>.

<FIG> further includes surface finish (Ra) versus number of grinding cycles for Sample BMS1 under the grinding conditions provided in Table <NUM> at the two different material removal rates (MRR') (i.e., <NUM><NUM>/sec/mm (<NUM> in3/min/in) and <NUM><NUM>/sec/mm (<NUM> in3/min/in)). As demonstrated by the plots <NUM> and <NUM>, representing the surface finish achieved by Sample MBS1 at both material removal rates, was initially <NUM> (<NUM> microinches) at both material removal rates, and rose significantly upon further consecutive grinding to values of <NUM> (<NUM> microinches) and about <NUM> (<NUM> microinches) at the material removal rates of <NUM><NUM>/sec/mm (<NUM> in3/min/in) and <NUM><NUM>/sec/mm (<NUM> in3/min/in), respectively. The average surface finish for Sample MBS1 at both material removal rates was approximately <NUM> microinches and the variance in surface finish (standard deviation) was approximately <NUM> at both material removal rates. Clearly, Sample <NUM> is capable of providing superior surface finish on the workpiece after consecutive grinding cycles as compared to Sample MBS1.

Sample <NUM> is created using the same process as Sample <NUM> provided herein. Sample <NUM> included an amount of fused silica filler material, which was substituted for <NUM>% of the abrasive grain material. The fused silica was of size -<NUM>/+<NUM> U. mesh and procured from Washington Mills. The finally-formed bonded abrasive has a ratio (VP/VBM) of <NUM> and an amount of porosity (<NUM>% interconnected porosity) of <NUM>% volume percent of the total volume of the body.

For comparison, a vitrified CBN wheel of specification B126-M160VT2B was also included in the test as Sample C1. Such a grinding wheel is commonly available from Saint-Gobain Corporation as B126-M160VT2B abrasive wheel.

<FIG> includes a plot of grinding power (HP/in) versus number of grinding cycles for Sample <NUM> as plot <NUM>, Sample <NUM> as plot <NUM>, and Sample C1 as plot <NUM>, under the grinding conditions provided in.

Table <NUM>. A material removal rate of <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in) is used during grinding. As demonstrated by plot <NUM>, Sample <NUM> is capable of grinding the workpiece at an initial grinding power of <NUM> W/µm (<NUM> Hp/in) and a grinding power after <NUM> consecutive grinding cycles of <NUM> W/µm (<NUM> Hp/in), for a power variance of approximately <NUM>%. Plot <NUM> shows that Sample <NUM> was capable of grinding the workpiece at an initial grinding power of <NUM> W/µm (<NUM> Hp/in) and a grinding power after <NUM> consecutive grinding cycles of <NUM> W/µm (<NUM> Hp/in), for a power variance of approximately <NUM>%. By comparison, as shown by plot <NUM>, the conventional, vitrified bonded abrasive sample had the same change in power as Sample <NUM>, and a power variance of approximately <NUM>%. As such, and quite unexpectedly, Samples <NUM> and <NUM>, despite being metal-bonded abrasive articles, behave more like a vitrified bonded abrasive article with a brittle bond component and low power variance.

A third sample (Sample <NUM>) was made using the same forming processes as Sample <NUM>. The initial mixture is formed using <NUM> grams of a metal bond composition of <NUM>/<NUM> copper/tin, <NUM> grams of an active bond composition precursor of titanium hydride, <NUM> grams of abrasive grains of CBN-V of size B181, <NUM> grams of filler available as 38A alumina of size <NUM> mesh from Saint-Gobain Grains and Powders, and <NUM> grams of the binder used in Example <NUM>. Sample <NUM> has a ratio (VP/VBM) of <NUM> and porosity of approximately <NUM> vol%.

Sample <NUM> is used in a peel grinding operation on an outside diameter of a workpiece made of <NUM> steel in the shape of a round bar having a diameter of <NUM> (<NUM> inches) and a length of <NUM> (<NUM> inches). The workpiece is hardened to <NUM>-<NUM> HRC. Sample <NUM> is compared to a conventional, vitrified CBN wheel commercially available from Saint Gobain Abrasives as B150-M150-VT2B (Sample C2).

Sample <NUM> is formed into a large bonded abrasive wheel, mounted on the periphery of a steel disk to form a <NUM> (<NUM> inch) diameter wheel. Sample <NUM> is trued using a diamond roll and used to grind the workpiece without any subsequent dressings to expose the grit. Truing conditions are shown in Table <NUM> below. The grinding conditions are shown in Table <NUM>.

The results are summarized in <FIG> and <FIG>. <FIG> includes a bar graph of grinding power (Hp) versus two different material removal rates (i.e., <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in) and <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in)). Bar <NUM> represents the grinding power used during grinding of the workpiece by Sample <NUM> after an initial pass at a material removal rate of <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in). Bar <NUM> represents the grinding power of Sample <NUM> during grinding of the workpiece after <NUM> consecutive grinding cycles (i.e., passes) on the workpiece at the material removal rate of <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in). As illustrated, Sample <NUM> demonstrates a very small change in the grinding power over <NUM> consecutive grinding cycles without undergoing a truing operation. In fact, the change in grinding power is estimated to be less than about <NUM>%.

Bars <NUM> and <NUM> demonstrate the grinding power used during grinding of Sample C2 and after <NUM> consecutive grinding cycles (i.e., passes) on the workpiece at the material removal rate of <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in). In a comparison of Sample <NUM> with Sample C2, it is noted that Sample <NUM> behaves more like a vitrified bonded abrasive article than conventional metal bonded abrasive articles.

Bar <NUM> represents the grinding power used during grinding of the workpiece by Sample <NUM> after an initial pass at a material removal rate of <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in). Bar <NUM> represents the grinding power of Sample <NUM> during grinding of the workpiece after <NUM> consecutive grinding cycles (i.e., passes) on the workpiece at the material removal rate of <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in). Again, Sample <NUM> demonstrates a very small change in the grinding power over <NUM> consecutive grinding cycles without undergoing a truing operation. In fact, the change in grinding power is estimated to be less than about <NUM>%.

Bars <NUM> and <NUM> demonstrate the grinding power used during grinding of the workpiece by Sample C2 and at an initial pass and after <NUM> consecutive grinding cycles (i.e., passes) on the workpiece at the material removal rate of <NUM> in<NUM>/min/in. In a comparison of Sample <NUM> with Sample C2, it is noted that Sample <NUM> behaves more like a vitrified bonded abrasive article than conventional metal bonded abrasive articles.

<FIG> includes a bar graph of grinding ratio (G-ratio) versus two different material removal rates (i.e., <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in) and <NUM><NUM>/sec/mm (<NUM> in<NUM>/min/in)) for Sample <NUM> and Sample C2. As illustrated, at both material removal rates, Sample <NUM> has a G-ratio that is significantly greater than Sample C2. In fact, while the spindle power and surface finish were virtually the same for Sample <NUM> as compared to Sample C2, the G-ratio of the Sample <NUM> is <NUM>% to <NUM>% greater than the G-ratio of Sample C1 at both material removal rates.

A fourth sample (Sample <NUM>) is created according to the processes provided in Example <NUM>. The initial mixture is formed from <NUM> grams of a metal bond composition of <NUM>/<NUM> copper-tin, <NUM> grams of titanium hydride as an active bond component precursor, <NUM> grams of the organic binder of Example <NUM>, and <NUM> grams of diamonds available from Saint-Gobain Ceramics and Plastics as RB <NUM>/<NUM> U. mesh, diamond grits. Sample <NUM> has a ratio (VAG/VBM) of <NUM> and porosity of approximately <NUM> vol%.

The grinding operation includes fluting of a tungsten carbide workpiece of <NUM> inches in diameter and <NUM>% by weight of cobalt as binder. The grinding performance of Sample <NUM> was tested against a state-of-the-art metal bonded wheel (G-Force Abrasive available from Saint-Gobain Corporation) having <NUM> vol% abrasive grains, <NUM> vol% bond, diamond abrasive grains of type RB <NUM>/<NUM> U.

Both samples were trued and dressed off-line before use. The samples were mounted on a steel arbor and balanced. The sample is trued with a silicon carbide wheel of <NUM> grit, H grade and vitrified bond, commonly used for such processes. The sample is rotated at about <NUM>/<NUM> the surface speed of the silicon carbide wheel that is run at approximately <NUM>/s (<NUM> sfpm). While the sample wheel is rotating, it is trued at <NUM>" depth of cut and <NUM>/min (<NUM> in/min). traverse rate until the wheel is considered true. Each sample is also dressed with a silicon carbide wheel of <NUM> mesh to expose the grit for grinding. Dressing with the stick is completed at the beginning of all grinds to start from same reference point.

The results of the grinding test are provided in <FIG> includes a plot of spindle power (Hp) versus grinding time (sec) for Sample <NUM> under three different conditions and Sample C2 in one condition. Sample C2 is represented by plot <NUM> and grinding was conducted at a wheel speed of <NUM> rpm and a grinding rate of <NUM>/min (<NUM> inches/min). As illustrated, Sample C2 experienced a significant increase in grinding power necessary for consecutive grinding cycles. The initial grinding power is approximately <NUM> kW (<NUM> Hp) and increases dramatically to <NUM> kW (<NUM> Hp) over <NUM> grinding cycles for a duration of approximately <NUM> seconds. Sample C2 experienced an increase in grinding power from the threshold grinding power of at least <NUM>%.

By contrast, Sample <NUM> demonstrated significantly less increase in initial grinding power for various grinding conditions. Plot <NUM> demonstrates the grinding power of Sample <NUM> on the workpiece at <NUM> rpm and a grinding rate of <NUM>/min (<NUM> inches/min). The conditions are identical to the grinding conditions used to test Sample C2. As illustrated by plot <NUM>, Sample <NUM> has an initial grinding power of approximately <NUM> kW (<NUM> Hp) and a final grinding power <NUM> kW (<NUM> Hp) after <NUM> consecutive grinding cycles at nearly <NUM> seconds. Sample <NUM> demonstrates an increase in the threshold power of only <NUM>%. Sample <NUM> demonstrates a significantly improved operable grinding lifetime as compared to Sample C2.

Plot <NUM> demonstrates the grinding power of Sample <NUM> on the workpiece at <NUM> rpm and a grinding rate of <NUM>/min (<NUM> inches/min). As illustrated by plot <NUM>, Sample <NUM> has a initial grinding power of approximately <NUM> kW (<NUM> Hp) and a final grinding power of <NUM> kW (<NUM> Hp) after <NUM> consecutive grinding cycles over <NUM> seconds. Sample <NUM> demonstrates effectively no increase in the threshold power for all of the grinding cycles demonstrating a significantly improved operable grinding lifetime as compared to Sample C2.

Plot <NUM> demonstrates the grinding power of Sample <NUM> on the workpiece at <NUM> rpm and a grinding rate of <NUM>/min (<NUM> inches/min). As illustrated by plot <NUM>, Sample <NUM> has an initial grinding power of approximately <NUM> kW (<NUM> Hp) and a final grinding power of <NUM> kW (<NUM> Hp) after <NUM> consecutive grinding cycles at approximately <NUM> seconds. Sample <NUM> demonstrates effectively no increase in the threshold power for all of the grinding cycles demonstrating a significantly improved operable grinding lifetime as compared to Sample C2.

In addition to the noted above difference in grinding performance, the bonded abrasive body of Sample <NUM> (plots <NUM> and <NUM>) was able to continue grinding <NUM> flutes in total, which corresponds to <NUM> parts, before dressing. By contrast, Sample C2 was capable of grinding <NUM> flutes total, which corresponds to <NUM> parts total before needing dressing. As such, Sample <NUM> demonstrates an improvement in grinding efficiency, as measured by parts/dress of approximately <NUM>% over the conventional Sample C2.

Moreover, in a comparison of plots <NUM> and <NUM>, it is demonstrated that Sample <NUM> is capable of improved grinding rate over the conventional Sample C2. Under the grinding conditions of plot <NUM>, Sample <NUM> demonstrated a capability to grind the same number of parts (<NUM> total) in approximately <NUM> seconds, as compared to Sample C2, which needed approximately <NUM> seconds. Accordingly, Sample <NUM> demonstrated an improvement in grinding time of <NUM> seconds, corresponding to an improvement of approximately <NUM>% over the conventional Sample C2. Furthermore, based on the feed rate conditions for plots <NUM> and <NUM>, Sample <NUM> demonstrated an improvement in grinding rate of <NUM>% (using inches/min) as compared to the conventional Sample C2. Moreover, Sample <NUM> achieved improved grinding rates while maintaining substantially the same grinding power, while Sample C2 demonstrated a rapid and unsatisfactory increase in grinding power.

Sample <NUM> and Sample C2 are used in a flute grinding operation on a workpiece of <NUM> (<NUM> inch) diameter tungsten carbide with <NUM>% cobalt. This type of work material is harder to grind than the workpiece of Example <NUM> due to higher tungsten carbide content (<NUM> vs <NUM>%) as evidenced by the difference between plots <NUM> and <NUM>. Plot <NUM> represent the grinding power for Sample C2 on a workpiece of tungsten carbide having <NUM>% cobalt binder at <NUM> rpm and a grinding rate of <NUM>/min (<NUM> inches/min) for a grinding time of <NUM> seconds. In fact, plot <NUM> is the same as plot <NUM> of <FIG>. Plot <NUM> represent the grinding power for Sample C2 on a workpiece of tungsten carbide having <NUM>% cobalt binder, at <NUM> rpm and a grinding rate of <NUM> inches/min for a grinding time of <NUM> seconds. As illustrated, the power needed to grind the workpiece having <NUM>% cobalt is significantly less than the power needed to grind the workpiece made of tungsten carbide with only <NUM>% cobalt for Sample C2.

By comparison, plot <NUM> represents the grinding power of Sample <NUM> conducting a grinding operation on a workpiece of tungsten carbide having only <NUM>% cobalt, at a speed of <NUM> rpm at a grinding rate of <NUM>/min (<NUM> inches/min) for a grinding time of less than <NUM> seconds. As illustrated, in a comparison of plots <NUM> and <NUM>, Sample <NUM> is capable of grinding a greater amount of the tungsten carbide workpiece at a greater rate and more efficiently. That is, Sample <NUM> experiences significantly less change in grinding power throughout the consecutive grinding cycles as compared to Sample C2.

In further comparison of plots <NUM> and <NUM> representing the grinding performance of Sample <NUM> and Sample C2, respectively, it is noted that Sample <NUM> also demonstrated improvements in grinding rate. Notably, with little to no increase in the grinding power, Sample <NUM> required only about <NUM> seconds to grind the same number of parts as required by Sample C2, which required approximately <NUM> seconds. Accordingly, Sample <NUM> achieved an increase in grinding rate of approximately <NUM>% as compared to the conventional Sample C2. Moreover, faster than the time required to grind the same number of parts by Sample C2.

The bonded abrasive bodies herein demonstrate compositions and grinding properties that are distinct from conventional metal-bonded abrasive articles. The grinding properties of the abrasive articles of the embodiments herein are more akin to vitreous bonded abrasive articles than state of the art metal-bonded abrasive articles. The bonded abrasive bodies of the embodiments herein demonstrate improved lifetime of effective grinding, require significantly less dressing than other conventional metal-bonded abrasive bodies, and have improved wear properties as compared to state-of-the-art metal-bonded abrasive bodies. In particular, the bonded abrasive body may not require a separate dressing operation after undergoing a truing operation, which is distinct from conditioning operations of conventional metal-bonded, bonded abrasive articles. That is, it is a typical procedure within the industry to utilize a truing wheel in combination with a dressing stick for resurfacing and sharpening bonded abrasive bodies utilizing metal bond materials. Accordingly, the bonded abrasive bodies of embodiments herein are capable of grinding a greater number of parts per dress, resulting in greater efficiency and longer life as compared to state-of-the-art metal bonded abrasive articles.

Furthermore, particular aspects of the forming process for the bonded abrasive bodies herein are thought to be responsible for certain compositions and microstructural features. The bonded abrasive bodies of embodiments herein include a combination of features, which may be attributed to the forming process and facilitate improved grinding performance, including for example, an active bond composition, particular phases of the active bond composition and particular locations of such phases, type and amount of porosity, type and amount of abrasive grains, type and amount of fillers, ratios of particulate to bond, ratios of abrasive to bond, and mechanical properties (e.g., fracture toughness) of certain components.

Claim 1:
An abrasive article comprising:
a body comprising abrasive grains contained within a bond material comprising a metal, wherein the body comprises a ratio of VP/VBM of at least about <NUM>, wherein VP is a volume percent of particulate material including abrasive grains and fillers within a total volume of the body and VBM is a volume percent of bond material within the total volume of the body, wherein the body comprises greater than <NUM> vol% porosity and not greater than <NUM> vol% porosity and wherein the bond material comprises an average fracture toughness (K1c) of not greater about <NUM> MPa m<NUM>.