WO2025158253A1 - Doped cbn particles for improved friability and enhanced grinding - Google Patents

Abstract

Provided is a method for making self-sharpening cubic boron nitride (cBN) particles. The method includes forming a mixture having a plurality of hexagonal boron nitride (hBN) particles, and a catalytic material including at least one of lithium (Li), magnesium (Mg), sodium (Na), potassium (K), barium (Ba), calcium (Ca), tin (Sn), or nitrides thereof. A niobium-foil is placed within a reaction zone adjacent to the mixture including the plurality of hBN particles, and the catalytic material. Next, the mixture is reacted with the niobium- foil at high-pressure-high-temperature (HPHT) conditions sufficient to form the self-sharpening cBN particles. Niobium and the catalytic material are retained in inclusions within the self-sharpening cBN particles to cause microfracturing of the self-sharpening cBN particles. Further presented is a vitrified cBN grinding wheel incorporating such self-sharpening cBN particles doped with niobium with improved friability, and associated methods of sharpening a vitrified cBN grinding wheel during machining of a workpiece.

Description

DOPED CBN PARTICLES FOR IMPROVED FRIABILITY AND ENHANCED GRINDING

FIELD OF THE DISCLOSURE

[0001] The present disclosure relates to a method for making self-sharpening cubic boron nitride (cBN) particles doped with refractory metals, and vitrified cBN grinding wheels incorporating such cBN particles doped with refractory metals with improved friability of the cBN particles, and enhanced grinding material removal performance of the vitrified cBN grinding wheels.

BACKGROUND

[0002] Cubic boron nitride (cBN) is typically made by a high-pressure and high temperature (HPHT) conversion on hexagonal boron nitride (hBN) in the presence of a suitable catalyst material. These cBN crystals are then incorporated into a vitrified grinding wheel, and used to machine metallic alloys. The material removal rate of these cBN grinding wheels is partly dependent on the properties of these cBN crystals. If improved crystal properties can be demonstrated, the resulting cBN grinding wheels would be able to remove material at an increased rate.

[0003] The incorporation of trace amounts of heavy refractory metals into the crystal lattice structure of the grown cBN crystals has been shown to improve the friability of the cBN crystals. This is achieved by converting hBN into cBN in the presence of these refractory metals and metal catalysts, either as a component blended into the raw powder mix, or otherwise in contact with the reacting material.

[0004] During conversion of hBN to cBN, the refractory metals and the catalysts get inherently trapped within the cBN crystals as what is known as inclusions, thus resulting in intrinsic growth defects in the cBN crystals. Without being bound by a particular theory, it is believed that these intrinsic growth defects behave as fracture-sites when the cBN crystal acts as a grinding material, after having been incorporated into a vitrified grinding wheel. There is typically a delicate balancing act of generally wanting the cBN crystals to be strong, and tough enough without wearing away quickly. However, when the cBN crystals do eventually start to wear away, it is preferred that the cBN crystals fracture, thus exposing new, and fresh cutting-surfaces and cutting-edges. To the best of the inventor’s knowledge, currently there is no other friable cBN crystal in the market that incorporates heavy refractory metals as inclusions to increase the grinding performance of cBN grinding wheels due to microfracturing of the cBN crystals.

[0005] In view of the foregoing, there is a need for vitrified cBN grinding wheels having cBN particles doped with refractory metals for improved friability of the cBN particles, thus leading to enhanced grinding performance of the cBN grinding wheels.

SUMMARY

[0006] Provided is a method for preparing self-sharpening cubic boron nitride (cBN) particles, which includes forming a mixture having a plurality of hexagonal boron nitride (hBN) particles, and a catalytic material. A niobium-foil is placed within a reaction zone adjacent to the mixture including the plurality of hBN particles, and the catalytic material. Next, constituents of the mixture are reacted with the niobium-foil at high- pressure-high-temperature (HPHT)-conditions to form the self-sharpening cBN particles. Niobium and the catalytic material are retained in inclusions within the self-sharpening cBN particles to cause microfracturing of the self-sharpening cBN particles to expose at least one new cutting surface or at least one new cutting edge in the self-sharpening cBN particles.

[0007] Optionally, the HPHT conditions include internal cell pressures in a range of from about 4 gigapascal (GPa) to about 8 GPa, and internal cell temperatures in a range of from about 1100°C to about 1800°C.

[0008] Optionally, the concentration of the niobium incorporated into a crystalstructure of the cBN particles ranges from about 50 parts per million (ppm) to about 200 ppm.

[0009] Optionally, the concentration of the niobium incorporated into the crystalstructure of the cBN particles ranges from about 50 ppm to about 100 ppm. [0010] Optionally, the concentration of the niobium incorporated into the crystalstructure of the cBN particles ranges from about 100 ppm to about 150 ppm.

[0011] Optionally, the concentration of the niobium incorporated into from the crystal-structure of the cBN particles ranges from about 150 ppm to about 200 ppm, or from about 175 ppm to about 200 ppm.

[0012] Optionally, the catalytic material comprises at least one of lithium (Li), magnesium (Mg), sodium (Na), potassium (K), barium (Ba), calcium (Ca), tin (Sn), or nitrides thereof.

[0013] Optionally, the method further includes incorporating the self-sharpening cBN particles into a vitrified cBN grinding wheel.

[0014] Optionally, the cBN particles comprising niobium inclusions demonstrates an improvement in grinding efficiency of up to about 13% compared to cBN particles excluding such niobium inclusions.

[0015] Optionally, the cBN particles comprising niobium inclusions demonstrates an improvement in grinding efficiency of up to about 10% compared to cBN particles excluding such niobium inclusions.

[0016] Optionally, the cBN particles comprising niobium inclusions demonstrates an improvement in grinding efficiency of up to about 6% compared to cBN particles excluding such niobium inclusions.

[0017] Optionally, the cBN particles comprising niobium as inclusions demonstrate an improvement in grinding efficiency in a range of from about 6% to about 13% compared to cBN particles excluding niobium inclusions.

[0018] Optionally, the cBN particles including niobium inclusions demonstrate a decrease in toughness index (Tl) from about 0.8% to about 3.6% compared to cBN particles excluding niobium inclusions thus facilitating the microfracturing. [0019] Optionally, the cBN particles including niobium inclusions demonstrate a decrease in thermal toughness index (TTI) from about 4.1 % to about 5.7% compared to cBN particles excluding niobium inclusions thus facilitating the microfracturing.

[0020] Further provided is a vitrified cBN grinding wheel including self-sharpening cBN particles prepared according to the foregoing method.

[0021] Further provided is a method of sharpening a vitrified cBN grinding wheel during machining of a workpiece, which includes abrading a self-sharpening cBN particle of the cBN grinding wheel against the workpiece, in which, the vitrified cBN grinding wheel includes the self-sharpening cBN particle, a catalytic material, and niobium. The catalytic material, and the niobium are retained in inclusions within the self-sharpening cBN particles. The self-sharpening cBN particle, the catalytic material, and the niobium are interacted to cause microfracturing of the self-sharpening cBN particle to expose at least one new cutting surface or at least one new cutting edge in the self-sharpening cBN particle during the abrading of the self-sharpening cBN particle of the vitrified cBN grinding wheel against the workpiece.

[0022] Other systems, methods, features and advantages will be, or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the present disclosure, and be protected by the following claims. Nothing in this section should be taken as a limitation on those claims. Further aspects and advantages are discussed below in conjunction with the examples of the disclosure. It is to be understood that both the foregoing general description and the following detailed description of the present disclosure are examples and explanatory and are intended to provide further explanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are included to provide a further understanding of the subject matter and are incorporated in and constitute a part of this specification, illustrate implementations of the subject matter and together with the description serve to explain the principles of the disclosure.

[0024] FIG. 1A shows a side view of a cubic boron nitride (cBN) grinding wheel having cBN particles without niobium inclusions in accordance with the current subject matter.

[0025] FIG. 1B shows a side view of a vitrified cubic boron nitride (cBN) grinding wheel having cBN particles with niobium inclusions in accordance with the current subject matter.

[0026] FIG. 2 shows a sectional view of a part of an abrasive layer of a vitrified cubic boron nitride (cBN) grinding wheel having cBN particles with niobium inclusions in accordance with the current subject matter.

[0027] FIG. 3 shows a flow diagram showing the individual process steps of preparing self-sharpening cubic boron nitride (cBN) particles incorporating niobium inclusions in accordance with the current subject matter.

[0028] FIG. 4A shows a microstructure at a 40x magnification of cBN crystals without niobium inclusions, in which, cBN particles were pressed with a belt press in accordance with the current subject matter.

[0029] FIG. 4B shows a microstructure at a 40x magnification of cBN crystals with niobium inclusions, in which, cBN particles were pressed with a cubic press in accordance with the current subject matter.

[0030] FIG. 5A shows a sectional view of grinding characteristics of a traverse grinding technique in accordance with the current subject matter.

[0031] FIG. 5B shows a sectional view of grinding characteristics of a creepfeed grinding technique in accordance with the current subject matter.

[0032] FIG. 6A shows normalized results of a creepfeed grinding of an M2 steel with a vitrified cubic boron nitride (cBN) grinding wheel incorporating cBN particles with niobium inclusions, in which, cBN particles were either pressed with a cubic press, or cBN particles without niobium inclusions, in which, cBN particles were pressed with a belt press. The normalized results show the grinding ratio, the power, and the finish of cBN particles with niobium inclusions pressed with the cubic press taken relative to cBN particles without niobium inclusions pressed with the belt press (i.e., 100%).

[0033] FIG. 6B shows normalized results of a traverse grinding of a 4140 steel with a vitrified cubic boron nitride (cBN) grinding wheel incorporating cBN particles with niobium inclusions, in which, cBN particles were either pressed with a cubic press, or cBN particles without niobium inclusions, in which, cBN particles were pressed with a belt press. The normalized results show the grinding ratio, the power, and the finish of cBN particles with niobium inclusions pressed with the cubic press taken relative to cBN particles without niobium inclusions pressed with the belt press (i.e., 100%).

[0034] DETAILED DESCRIPTION

[0035] Unless defined otherwise all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the presently described subject matter pertains.

[0036] Where a range of values is provided, for example, concentration ranges, percentage ranges, or ratio ranges, it is understood that each intervening value, to the tenth of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the described subject matter. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and such examples are also encompassed within the described subject matter, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the described subject matter.

[0037] The following definitions set forth the parameters of the described subject matter. [0038] As used herein this disclosure, the term “cBN particle” refers to a discrete cBN body, or discrete cBN bodies. As used herein this disclosure, the term “cBN particle” is also considered to be a cBN crystal, or a cBN grain, and as such, is used interchangeably with such terms.

[0039] As used herein, the term “vol.%” refers to a given volume percent based on a total volume of a cBN grinding wheel, or a powder mixture.

[0040] As used herein, the term “superabrasive ultrahard material”, or simply “superabrasive material” refers to an abrasive material demonstrating a superior hardness, and a great wear resistance, which may be found in the following, but not limited to B4C-diamond composites, SiC-TiN-TiCN-diamond composites, crystal diamond, monocrystalline diamond, polycrystalline diamond (PCD), thermally stable PCD, chemical vapor deposition (CVD) diamond, metal matrix diamond composites, ceramic matrix diamond composites, nanodiamond, cubic boron nitride (cBN), polycrystalline cubic boron nitride (PcBN), or any such combinations thereof. The term “abrasive”, as used herein, refers to any superabrasive material used to wear away a softer material.

[0041] As used herein, the term “about” is meant to mean plus or minus 5% of the numerical value of the number with which it is being used in the claims and herein this disclosure. Thus, “about” may be used to provide flexibility to a numerical range endpoint, in which, a given value may be “above” or “below” the given value. As such, for example a value of 50% may be intended to encompass a range, which may be defined by for example ranges like 47.5%-52.25%, 47.5%-52.5%, 47.75%-50%, 50%-52.5%, 48%- 48.5%, 48%-48.75%, 48%-49%, 48%-49.5%, 48%-49.75%, 48%-50%, 48%-50.25%, 48%-50.5%, 48%-50.75%, 48%-51 %, 48%-51.5%, 48%-51.75%, 48%-52%, 48%- 52.25%, 48%-52.5%, 48.25%-48.5%, 48.25%-48.75%, 48.25%-49%, 48.25%-49.5%, 48.25%-49.75%, 48.25%-50%, 48.25%-50.25%, 48.25%-50.5%, 48.25%-50.75%, 48.25%-51 %, 48.25%-51 .25%, 48.25%-51 .5%, 48.25%-51 .75%, 48.25%-52%, 48.25%- 52.25%, 48.25%-52.5%, 48.5%-48.75%, 48.5%-49%, 48.5%-49.5%, 48.5%-49.75%, 48.5%-50%, 48.5%-50.25%, 48.5%-50.5%, 48.5%-50.75%, 48.5%-51 %, 48.5%-51 .25%, 48.5%-51.5%, 48.5%-51.75%, 48.5%-52%, 48.5%-52.25%, 48.5%-52.5%, 49%-49.25%, 49%-49.5%, 49%-49.75%, 49%-50%, 49%-50.25%, 49%-50.5%, 49%-50.75%, 49%- 51 %, 49%-51.25%, 49%-51.5%, 49%-51.75%, 49%-52%, 49%-52.25%, 49%-52.5% 49.5%-49.75%, 49.5%-50%, 49.5%-50.25%, 49.5%-50.5%, 49.5%-50.75%, 49.5%-51 %, 49.5%-51.5%, 49.5%-51 .75%, 49.5%-52%, 49.5%-52.25%, 49.5%-52.5%, 49.75%-50%, 49.75%-50.25%, 49.75%-50.5%, 49.75%-50.75%, 49.75%-51 %, 49.75%-51 .25%, 49.75%-51 .5%, 49.75%-51.75%, 49.75%-52%, 49.75%-52.25%, 49.75%-52.5%, 50%- 50.25%, 50%-50.5%, 50%-50.75%, 50%-51%, 50%-51.25%, 50%-51.5%, 50%-52%, 50%-52.25%, 50%-52.5% etc.

[0042] Wherever used throughout the disclosure, the term “generally” has the meaning of “typically” or “closely” or “within the vicinity or range of.”

[0043] As used herein, the term “friable” or “friability” refers to the tendency of a solid substance to break into smaller pieces under duress, or contact especially by rubbing.

[0044] As used herein, the term “fracture toughness” i.e. , (Kic), refers to the ability of a material with pre-cracks to resist further fracture propagation upon absorbing energy.

Fracture fracture toughness (Kic) is calculated according to:

Kic = where A is a constant of 0.0028, HV is the hardness (N/mm²), P is the applied load (N), and ZL is the sum of crack lengths (mm) of imprints.

[0045] As used herein, the term “HV30 Vickers hardness” (i.e. applying a 30 kgf load) is a measure of the resistance of a sample to localized plastic deformation, which is obtained by indenting the sample with a Vickers tip at 30 kgf.

[0046] As used herein, the term “substantially” refers to the complete or nearly complete extent or degree of an action, characteristic, property, state, structure, item, or result. [0047] As used herein this disclosure, the term “catalytic material” refers to a material that promotes and positively drives a reaction forming cBN from hexagonal boron nitride (hBN).

[0048] As used herein, the term “inclusion” causes intrinsic growth defects, and refers to the incorporation, the infiltration, or the insertion of heavy refractory metals like niobium, and/or catalytic material like lithium within the crystal lattice structure of cBN particles. This happens during a high-pressure high temperature (HPHT) conversion of hBN to cBN, when a foil embedded with for instance niobium is placed in an HPHT-cell within a reaction zone adjacent to hBN particles, and the catalytic material. The HPHT- cell is placed in a cubic press, and internal cell pressures from typically about 4 gigapascal (GPa) to about 8 GPa, and internal cell temperatures typically from about 1100°C to about 1800°C are applied to the HPHT-cell for converting hBN to cBN.

[0049] As used herein, the term “creepfeed grinding” (FIG. 5B) refers to a grinding methodology technique used for high rates of material removal, while a conventional traverse grinding (FIG. 5A) technique may be used to finish surfaces. In creepfeed grinding (FIG. 5B), there is a great depth of cut (a_e), low workpiece velocity (v_w), high wheel/workpiece contact length (i.e., length of stroke), the average contact temperature is much higher, the total grinding forces are much higher, and the surface quality is finer, compared to a conventional traverse grinding technique (FIG. 5A).

[0050] As used herein, the term “high pressure high temperature (HPHT) conversion” refers to a process, where heating under internal cell pressures typically ranging from about 4 gigapascal (GPa) to about 8 GPa, is conducted to minimize the surface of a oBN-based particulate system. This is associated with generation of bonds between neighboring small cBN particles, and shrinkage of the subsequently aggregated cBN particles. Compacting and forming a dense bulk mass is performed by heating the cBN particles under a high pressure. The atoms in the cBN particles diffuse across the boundaries of the cBN particles, thus fusing the small cBN particles together, thereby creating one solid dense bulk piece. Although a number of HPHT apparatuses are generally known to one having ordinary skill in the art, the two most common apparatuses for HPHT conversion are the cubic presses and beit presses.

[0051] As used herein, the term “facet” refers to a flat face on geometric shapes, which is defined by edges around the flat face.

[0052] As used herein, the term “blocky” refers to a shape as a block.

[0053] As used herein, the term “reaction zone” refers to an internal area in an

HPHT reaction-cell, where the hBN particles, and the catalytic material chemically react to form the cBN particles during the HPHT conversion.

[0054] As used herein, the term “adjacent to” refers to something directly abutting something else, or alternatively being close to, near to, however without directly abutting it, such as for example being 0.1 cm, 0.15 cm, 0.2 cm, 0.25 cm, 0.3 cm, 0.35 cm, 0.4 cm, 0.45 cm, 0.5 cm, 0.55 cm, 0.6 cm, 0.65 cm, 0.7 cm, 0.75 cm, 0.8 cm, 0.85 cm, 0.9 cm, 0.95 cm, 1 cm, 1.05 cm 1.1 cm, 1.15 cm, 1.2 cm, 1.25 cm, 1.3 cm, 1.35 cm, 1.4 cm, 1.45 cm, 1 .5 cm, 1 .55 cm, 1 .6 cm, 1 .65 cm, 1 .7 cm, 1 .75 cm, 1 .8 cm, 1 .85 cm, 1 .9 cm, 1 .95 cm, or 2 cm away from the specific object in question.

[0055] As used herein, the term “vitrified bonds” refers to glasslike appearance or characteristics.

[0056] As used herein, the term “aspect ratio” of an object refers to a ratio defined by its width taken relative to its height.

[0057] As used herein, the term “ambient conditions” refer to 25° C, 298.15 K and a pressure of 101 .325 kPa.

[0058] As used herein this disclosure, the term “workpiece” refers to a material that is cut, ground, or otherwise machined by a vitrified cBN grinding wheel. A person having ordinary skill in the art would know that a workpiece can typically include composites, metals, alloys, super-alloys, difficu It-to-cut materials etc. It refers to parts, or objects, from which, material is removed typically by machining. [0059] The current disclosure stems from the premise of presenting a method for preparing self-sharpening cBN particles, and a cBN grinding wheel incorporating cBN crystals with trace amounts of heavy refractory metals, such as e.g. niobium used as a metal dopant on the cBN crystals with improved friability of the cBN crystals, and enhanced grinding material removal rates of the cBN grinding wheel. Without wishing to be bound by a particular theory, the proposed mechanism for this improvement is the incorporation of these large niobium atoms as inclusions within the cBN crystal lattice structure during growth. This may impart a strain on the overall cBN crystal lattice structure, thus resulting in a decreased fracture toughness. This allows the cBN crystal to fracture more easily, which creates new sharp cutting-edges and cutting-surfaces during the grinding operation of a workpiece. In other words, the larger atomic radius of the niobium inclusions puts additional stress and strain on the cBN crystal lattice structure, thus effectively allowing the cBN crystals to fracture more easily. This exposes more cutting-edges and cutting-surfaces, while the cBN wheel is wearing during the machining of a workpiece. This can be viewed much like a self-sharpening cBN grinding wheel, at the cost of the overall mechanical fracture toughness of the cBN crystals having incorporated such heavy niobium inclusions. Without wishing to be bound by any specific theory, it is believed that the large niobium atoms may substitute on the boron, or on the nitrogen sites within the cBN crystal lattice structure, or alternatively, the niobium atoms may be i nterstitial ly , or substitutional ly located.

[0060] The cBN particle may typically be present from about 60 vol.% to about 80 vol.% based on the total volume of the cBN grinding wheel. In some examples, the cBN particle is present from about 62 vol.% to about 80 vol.% based on the total volume of the cBN grinding wheel. In other examples, the cBN particle is present from about 65 vol.% to about 80 vol.% based on the total volume of the cBN grinding wheel. In yet other examples, the cBN particle is present from about 67 vol.% to about 80 vol.% based on the total volume of the cBN grinding wheel. In still other examples, the cBN particle is present from about 69 vol.% to about 80 vol.% based on the total volume of the cBN grinding wheel. In even other examples, the cBN particle is present from about 71 vol.% to about 80 vol.% based on the total volume of the cBN grinding wheel. In further other examples, the cBN particle is present from about 73 vol.% to about 80 vol.% based on the total volume of the cBN grinding wheel. In other examples, the cBN particle is present from about 75 vol.% to about 80 vol.% based on the total volume of the cBN grinding wheel. In still other examples, the cBN particle is present from about 77 vol.% to about 80 vol.% based on the total volume of the cBN grinding wheel. In even other examples, the cBN particle is present from about 78 vol.% to about 80 vol.% based on the total volume of the cBN grinding wheel.

[0061] The cBN particle may also be present from about 60 vol.% to about 62 vol.%, 60 vol.% to about 65 vol.%, from about 62 vol.% to about 65 vol.%, from about 65 vol.% to about 67 vol.%, from about 60 vol.% to about 67 vol.%, from about 60 vol.% to about 70 vol.%, from about 60 vol.% to about 72 vol.%, from about 60 vol.% to about 75 vol.%, from about 67 vol.% to about 69 vol.%, from about 69 vol.% to about 71 vol.%, from about 71 vol.% to about 73 vol.%, from about 67 vol.% to about 73 vol.%, from about 67 vol.% to about 75 vol.%, from about 67 vol.% to about 77 vol.%, from about 70 vol.% to about 75 vol.%, from about 70 vol.% to about 77 vol.%, from about 70 vol.% to about 79 vol.%, from about 73 vol.% to about 75 vol.%, from about 73 vol.% to about 77 vol.%, or from about 75 vol.% to about 77 vol.% based on the total volume of the cBN grinding wheel.

[0062] The cBN particles may typically have a mesh size ranging from 1250-mesh (a mesh screen passing through a powder having a particle size less than about 10 micron) to 2500-mesh (a mesh screen passing through a powder having a particle size less than about 5 micron).

[0063] For determining a specific cBN particle size, one having ordinary skill in the art may typically employ either dynamic digital image analysis (DIA), static laser light scattering (SLS) also known as laser diffraction, or visual measurement by electron microscopy, a technique known as image analysis and light obscuration. Each method covers a characteristic size range within which measurement is possible. These ranges partly overlap. However, the results for measuring the same sample may vary all depending on the particular method that is used. A skilled artisan who wants to determine cBN particle sizes, or cBN particle size distributions would readily know how each mentioned method is commonly performed and practiced. Thus, the reader may be directed to “Comparison of Methods. Dynamic Digital Image Analysis, Laser Diffraction, Sieve Analysis”, Retsch Technology and the scientific publication by Kelly et al., “Graphical comparison of image analysis and laser diffraction particle size analysis data obtained from the measurements of particle systems”, AAPS PharmSciTech. 2006 Aug 18; Vol.7(3):69, to gain further insight into each procedure and methodology.

[0064] A concentration of the niobium incorporated into a crystal lattice structure of the cBN particles may typically range from about 50 parts per million (ppm) to about 200 ppm. In some examples, a concentration of the niobium incorporated into the crystalstructure of the cBN particles ranges from about 70 parts ppm to about 200 ppm. In other examples, a concentration of the niobium incorporated into the crystal-structure of the cBN particles ranges from about 90 ppm to about 200 ppm. In still other examples, a concentration of the niobium incorporated into the crystal-structure of the cBN particles ranges from about 110 ppm to about 200 ppm. In yet other examples, a concentration of the niobium incorporated into the crystal-structure of the cBN particles ranges from about 130 ppm to about 200 ppm. In further other examples, a concentration of the niobium incorporated into the crystal-structure of the cBN particles ranges from about 150 ppm to about 200 ppm. In even further other examples, a concentration of the niobium incorporated into the crystal-structure of the cBN particles ranges from about 170 ppm to about 200 ppm.

[0065] A concentration of the niobium incorporated into the crystal lattice structure of the cBN particles may also range from about 50 ppm to about 70 ppm, from about 70 ppm to about 90 ppm, from about 90 ppm to about 110 ppm, from about 50 ppm to about 110 ppm, from about 70 ppm to about 110 ppm, from about 110 ppm to about 130 ppm, from about 150 ppm to about 170 ppm, or from about 110 ppm to about 170 ppm.

[0066] With reference to FIG. 1A and FIG. 1B, these figures show two separate scenarios impacting the final configuration of a cBN grinding wheel. FIG. 1A shows a side view of a cBN grinding wheel 10 with an aluminum or steel wheel core or base 11, and with an abrasive layer 12 having cBN particles without niobium inclusions in accordance with the current subject matter. FIG. 1B shows a side view of a vitrified cBN grinding wheel 10A with an aluminum or steel core or base 11A and with an abrasive layer 12A having cBN particles with niobium inclusions in accordance with the present subject matter. Essentially, what is noteworthy in the cBN grinding wheel 10A in FIG. 1B is the formation of cutting-edges 13A and cutting-surfaces 13A, while the vitrified cBN grinding wheel 10A is wearing during the machining of a workpiece. As previously described, the formation of these cutting-edges 13A and cutting surfaces 13A is attributed at least to the niobium, and/or catalytic material inclusions that are formed in the vitrified cBN grinding wheel 10A as seen in FIG. 1B. Consequently, these inclusions lead to intrinsic growth defects. These growth defects behave as common fracture-sites, thus exposing fresh cutting-edges 13A and cutting-surfaces 13A during the grinding of the workpiece by the vitrified cBN grinding wheel 10A, which niobium inclusions, being deficient in the cBN grinding wheel 10 shown in FIG. 1A.

[0067] FIG. 2 shows a sectional view of a part of the abrasive layer 12A of a cubic boron nitride (cBN) grinding wheel 10A having cBN particles 28 with niobium 26, and catalytic material 25 as inclusions in accordance with the current subject matter. FIG. 2 further shows cBN abrasive particles 28, and the abrasive layer 12A is held together by way of reinforcing vitrified bonds 24.

[0068] The reinforcing vitrified bond 24 material may be composed of for example amorphous glass generally selected from the group consisting of borosilicate glass, phosphate glass, and borate glass, or any desired combinations thereof. The vitrified bond 24 material may further alternatively include at least an oxide particle added for the purpose of reinforcing intensity of the amorphous glass and may typically be selected from the group consisting of zircon (ZrSiC ), titania (TiO2), zirconia (ZrC>2), chromia (CT2O3), and aluminum oxide (AI2O3), or any desired combinations thereof. Each of the coefficients of linear thermal expansion of the oxide particle and the amorphous glass may substantially be equal to the coefficient of linear thermal expansion of the cBN grinding particles 28 after being bonded. The coefficient of linear thermal expansion may for example be within a range of (3.5±2) x 10’⁶/C. Under such conditions, the cBN grinding particles 28, the oxide particles and the amorphous glass are not separated, or damaged caused by potential temperature fluctuations, thus maintaining the quality, and the physical integrity of the cBN grinding wheel 10A.

[0069] Catalysts that can beneficially be utilized may vary depending on the nature of the superabrasive material and the conditions, under which, microfracturing will occur. As such, any refractory metal, and/or catalyst capable of facilitating, or contributing to microcracking and microfracturing should be considered to be within the present scope disclosed herein. In some examples, the catalytic material is most typically lithium (Li).

[0070] The catalytic material may typically be used in a concentration spanning from about 10 ppm to about 800 ppm, spanning from about 50 ppm to about 800 ppm, spanning from about 100 ppm to about 800 ppm, spanning from about 150 ppm to about 800 ppm, spanning from about 200 ppm to about 800 ppm, spanning from about 250 ppm to about 800 ppm, spanning from about 300 ppm to about 800 ppm, spanning from about 350 ppm to about 800 ppm, spanning from about 400 ppm to about 800 ppm, spanning from about 450 ppm to about 800 ppm, spanning from about 500 ppm to about 800 ppm, spanning from about 550 ppm to about 800 ppm, spanning from about 600 ppm to about 800 ppm, spanning from about 650 ppm to about 800 ppm, spanning from about 700 ppm to about 800 ppm, spanning from about 750 ppm to about 800 ppm, spanning from about 10 ppm to about 50 ppm, spanning from about 20 ppm to about 50 ppm, spanning from about 30 ppm to about 50 ppm, spanning from about 40 ppm to about 50 ppm, spanning from about 50 ppm to about 60 ppm, spanning from about 50 ppm to about 70 ppm, spanning from about 50 ppm to about 80 ppm, spanning from about 50 ppm to about 90 ppm, spanning from about 50 ppm to about 100 ppm, spanning from about 50 ppm to about 125 ppm, spanning from about 50 ppm to about 150 ppm, spanning from about 50 ppm to about 175 ppm, spanning from about 50 ppm to about 200 ppm, spanning from about 150 ppm to about 300 ppm, spanning from about 300 ppm to about 500 ppm, spanning from about 500 ppm to about 750 ppm, spanning from about 500 ppm to about 800 ppm, spanning from about 300 ppm to about 500 ppm, spanning from about 600 ppm to about 750 ppm, spanning from about 650 ppm to about 750 ppm, or spanning from about 600 ppm to about 800 ppm. [0071] Without wishing to be bound by a particular theory, the microfracturing during the machining of the vitrified cBN grinding wheel 10A may be caused by intrinsic growth defects behaving as fracture-sites. These intrinsic growth defects are typically the result of inclusions, monogrits with an internal defect, flaws, crystal dislocations, and/or polygrits with weak intergranular boundaries due to niobium infiltration into the cBN crystal lattice structure. Thus, it would be desirable to produce more robust blockier cBN crystalshapes to promote a more uniform cBN grinding wheel 10A wear.

[0072] Toughness index (Tl) may be measured at typically ambient conditions. In many cases, generally the tougher the cBN crystal is, the longer the preservation of the non-fractured cBN crystal within the matrix of the vitrified cBN grinding wheel 10A. The cBN particles 28 including niobium inclusions 26 may typically demonstrate a decrease in Tl from about 0.8% to about 3.6% compared to the cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing. In some examples, the cBN particles 28 including niobium inclusions 26 demonstrate a decrease in Tl from about 1.3% to about 3.6% compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing. In other examples, the cBN particles 28 including niobium inclusions 26 demonstrate a decrease in Tl from about 1.8% to about 3.6% compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing. In still other examples, the cBN particles 28 including niobium inclusions 26 demonstrate a decrease in Tl from about 2.3% to about 3.6% compared to cBN particles 28 devoid of niobium inclusions 26 thus causing the microfracturing. In yet other examples, the cBN particles 28 including niobium inclusions 26 demonstrate a decrease in Tl from about 2.8% to about 3.6% compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing. In even other examples, the cBN particles 28 including niobium inclusions 26 demonstrate a decrease in Tl from about 3.3% to about 3.6% compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing.

[0073] The cBN particles 28 including niobium inclusions 26 may also demonstrate a decrease in Tl from about 0.8% to about 1.3%, from about 1.3% to about 1.8%, from about 1.8% to about 2.3%, from about 0.8% to about 1.8%, from about 0.8% to about 2.3%, from about 1 .3% to about 2.3%, from about 2.3% to about 2.8%, from about 2.3% to about 3.3%, or from about 2.8% to about 3.3%, compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing.

[0074] Thermal toughness index (TTI) may be measured after the product has been fired at high temperatures, for example at temperatures ranging from about 1100°C to about 1500°C, from about 1100°C to about 1600°C, from about 1100°C to about 1700°C, from about 1100°C to about 1800°C, from about 1200°C to about 1500°C, from about 1200°C to about 1600°C, from about 1200°C to about 1700°C, from about 1200°C to about 1800°C, from about 1300°C to about 1400°C, from about 1300°C to about 1500°C, from about 1300°C to about 1600°C, from about 1300°C to about 1700°C, from about 1300°C to about 1800°C, from about 1400°C to about 1500°, from about 1400°C to about 1600°C, from about 1500°C to about 1600°C, from about 1500°C to about 1700°C, from about 1500°C to about 1800°C, from about 1600°C to about 1800°C, or from about 1700°C to about 1800°C. The cBN particles 28 including niobium inclusions 26 may demonstrate a decrease in TTI from about 4.1 % to about 5.7% compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing. In some examples, the cBN particles 28 including niobium inclusions 26 may demonstrate a decrease in TTI from about 4.5% to about 5.7% compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing. In other examples, the cBN particles 28 including niobium inclusions 26 may demonstrate a decrease in TTI from about 4.8% to about 5.7% compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing. In still other examples, the cBN particles 28 including niobium inclusions 26 may demonstrate a decrease in TTI from about 5.1 % to about 5.7% compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing. In even other examples, the cBN particles 28 including niobium inclusions 26 may demonstrate a decrease in TTI from about 5.4% to about 5.7% compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing.

[0075] The cBN particles 28 including niobium inclusions 26 may also demonstrate a decrease in TTI from about 4.1 % to about 4.5%, from about 4.5% to about 4.8%, from about 4.8% to about 5.1 %, from about 4.1 % to about 5.1 %, from about 4.5% to about 5.1 %, from about 4.5% to about 5.4%, from about 4.8% to about 5.4%, or from about 5.1 % to about 5.4%, compared to cBN particles 28 devoid of such niobium inclusions 26 thus causing the microfracturing.

[0076] The process for making self-sharpening cubic boron nitride (cBN) particles will be described next. With US Patent document No. 2,947,617A incorporated herein by reference in its entirety, the conventional process of producing cBN particles includes first preparing a powder mixture of hBN particles with a suitable catalyst material, such as e.g. lithium, magnesium, sodium, potassium, barium, calcium, tin, or nitrides of these metals. Next, the powder mixture is placed into a high-pressure high temperature (HPHT) reaction cell. High pressure, and temperature conditions are thereafter applied at a temperature, and at a pressure level appropriate for each individual catalyst system. This may typically range from about 4 gigapascal (GPa) to about 8 GPa, from about 5 GPa to about 8 GPa, from about 6 GPa to about 8 GPa, from about 7 GPa to about 8 GPa, from about 5 GPa to about 6 GPa, from about 5 GPa to about 7 GPa, or from about 6 GPa to about 7 GPa, with an internal cell temperature ranging from about 1100°C to about 1500°C, from about 1100°C to about 1600°C, from about 1100°C to about 1700°C, from about 1100°C to about 1800°C, from about 1200°C to about 1500°C, from about 1200°C to about 1600°C, from about 1200°C to about 1700°C, from about 1200°C to about 1800°C, from about 1300°C to about 1400°C, from about 1300°C to about 1500°C, from about 1300°C to about 1600°C, from about 1300°C to about 1700°C, from about 1300°C to about 1800°C, from about 1400°C to about 1500°, from about 1400°C to about 1600°C, from about 1500°C to about 1600°C, from about 1500°C to about 1700°C, from about 1500°C to about 1800°C, from about 1600°C to about 1800°C, or from about 1700°C to about 1800°C. The resulting converted cBN material is recovered, and all remaining non-cBN material is removed with a series of chemical reactions such as e.g. dissolution by reactive acids, which leave the formed cBN, and particularly dissolve unreacted hBN, and unreacted catalyst materials. Suitable reactive acids may be selected based on the solubility of the hBN and the catalyst material that are present in the sample of the formed cBN. Examples of such reactive acids may typically include, for example and without limitation, ferric chloride, cupric chloride, nitric acid, hydrochloric acid, hydrofluoric acid, aqua regia, or solutions, or mixtures thereof. The specific dissolution steps will again depend on the particular catalyst system, which is used.

[0077] In the present subject matter, an additional niobium dopant is added to the system with the intention of not acting catalytically in the hexagonal to the cubic transition of boron nitride (BN). This is done to have trace amounts of the niobium dopant trapped within the converting crystal lattice structure, while the conversion takes place from the hexagonal to the cubic form of BN. This can be achieved in a number of ways, but most uniformly by blending the niobium dopant within the original blend of the hBN, and the catalyst material. Alternatively, the niobium dopant can be added by placing a solid layer of the dopant material around the HPHT reaction cell.

[0078] When reacting away all the non-cBN material, the niobium dopant which is incorporated into the cBN crystal lattice structure upon conversion from hBN and subsequent growth of the cBN crystals, remains in the cBN crystal lattice structure. Without being bound by any specific theory, it is believed that these niobium dopant atoms, which have a different atom size than boron atoms and the nitrogen atoms, will distort and thereby impart a strain on the cBN crystal lattice structure of the cBN grain. The distortion will lead to an internal stress field formed around the heavy niobium dopants. When an applied load is placed on the cBN crystal during use in machining of a material, this will function as a weak zone, thereby allowing the cBN crystal to fracture more easily at lower applied loads.

[0079] The toughness of the cBN crystals produced by the present subject matter can be measured with a crystal toughness test referred to as a Toughness Index (Tl) test. To perform this test, first the cBN crystals are sorted by size typically by using a series of sieves, and only selecting the cBN crystals of interest, such as e.g. those which pass through a 60-mesh sieve, but do not pass through an 80-mesh sieve. It is of note that the mesh number of a sieve is generally the number of partitions per inch, thus resulting in higher mesh numbers allowing only finer particles to pass through the sieve. Once the desired cBN crystal size is determined, a specified weight of the cBN crystals is placed in a small tube with tungsten carbide (WC) balls. The tube is then shaken for a specific period of time. Typical time periods are on the order of one hour to ten hours. During this shaking process, the WC balls fall back and forth, thereby physically impacting the cBN crystals, and frequently leading to fracture within the individual cBN crystals. After the shaking is complete, the cBN crystals are unloaded from the tube, and subsequently run through a sieve station once again to particularly measure the amount of fractured cBN crystals. The Tl can then be defined as the percentage of cBN crystals, which do not fracture during the shaking procedure with the WC balls. In the above example, if for instance, 70% of the cBN crystals after the shaking procedure with the WC balls still do not pass through the 80-mesh sieve, the cBN crystals will then be characterized as having a Tl of 70.

[0080] Another test of the strength of the cBN crystals is the thermal toughness index (TTI) test. The test is performed in the same manner as the Tl test. However, prior to placing the cBN crystals into the tube with the WC balls, they are heated to a temperature sufficient to impart thermal damage. Typically applied temperatures may be from about 1100°C to about 1500°C, from about 1100°C to about 1600°C, from about 1100°C to about 1700°C, from about 1100°C to about 1800°C, from about 1200°C to about 1500°C, from about 1200°C to about 1600°C, from about 1200°C to about 1700°C, from about 1200°C to about 1800°C, from about 1300°C to about 1400°C, from about 1300°C to about 1500°C, from about 1300°C to about 1600°C, from about 1300°C to about 1700°C, from about 1300°C to about 1800°C, from about 1400°C to about 1500°, from about 1400°C to about 1600°C, from about 1500°C to about 1600°C, from about 1500°C to about 1700°C, from about 1500°C to about 1800°C, from about 1600°C to about 1800°C, or from about 1700°C to about 1800°C. This test shows the degree of degradation due to applied high temperatures. When the test is complete, it can give a reasonable estimate in conjunction with the Tl test, of how tough the cBN crystals will be in an application, such as e.g. in use in a grinding wheel, where grinding forces are likely to generate heat.

[0081] FIG. 3 is a flow diagram showing individual process-steps for preparing the self-sharpening cBN particles incorporating niobium inclusions 26 in accordance with the current subject matter. In step 30, a mixture including a plurality of hBN particles, and a catalytic material 25 is first formed. In step 32, a niobium-foil is placed within a reaction zone adjacent to the mixture including the plurality of hBN particles, and the catalytic material 25. In step 34, the process is finally concluded by reacting constituents of the mixture with the niobium-foil at HPHT conditions in a cubic press sufficient to form the self-sharpening cBN particles. The niobium 26, and the catalytic material 25 are essentially retained in inclusions within the self-sharpening cBN abrasive particles 28 to cause microfracturing of the self-sharpening cBN particles 28 to expose at least one new cutting surface or at least one new cutting edge in the self-sharpening cBN particles 28.

[0082] The formed self-sharpening cBN particles 28 can thereafter be used as functional components of a vitrified cBN grinding wheel 10A. The wheel 10A is sharpened during the entire cycle of the machining of a workpiece. This is done by abrading the selfsharpening cBN particle 28 of the vitrified cBN grinding wheel 10A against the workpiece to facilitate dulling of a cutting surface of the self-sharpening cBN particle 28. The vitrified cBN grinding wheel 10A includes the self-sharpening cBN particle 28, the catalytic material 25, and the niobium 26. The catalytic material 25, and the niobium 26 are retained in inclusions within the self-sharpening cBN particle 28. Next, the selfsharpening cBN particle 28, the catalytic material 25, and the niobium 26 are interacted to cause microfracturing of the self-sharpening cBN particle 28 to expose at least one new cutting surface or at least one new cutting edge in the self-sharpening cBN particle 28 during the abrading of the self-sharpening cBN particle 28 of the vitrified cBN grinding wheel 10A against the workpiece.

[0083] A skilled artisan would in practice know how an HPHT conversion of hBN to cBN is commonly performed. Thus, the reader is additionally directed to US Patent document No. 6,814,775B2, and US Patent No. 10,196,314B2 to further gain insight into HPHT conversion procedures and methodologies, which US patent documents, are hereby incorporated herein by reference in their entirety.

[0084] EXAMPLES

[0085] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the described subject matter and is not intended to limit the scope of what the inventors regard as their disclosure, and nor are they intended to represent that the experiments below are all, or the only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used, but some experimental errors and deviations should be accounted for.

[0086] EXAMPLE 1

[0087] CUBIC BORON NITRIDE (CBN) PARTICLES WITH NIOBIUM INCLUSIONS DEMONSTRATE A DECREASED TOUGHNESS INDEX (Tl), AND A DECREASED THERMAL TOUGHNESS INDEX (TTI) COMPARED TO CBN PARTICLES WITHOUT NIOBIUM INCLUSIONS

[0088] TABLE 1 shows toughness index (Tl), and thermal toughness index (TTI) results for cBN particles 28 respectively with niobium inclusions 26, and without niobium inclusions 26.

[0089] [TABLE 1]

[0090] As seen in TABLE 1 , both the Tl and the TTI results for the incorporated cBN particles 28 with niobium inclusions 26 were lower compared to cBN particles 28 without the niobium inclusions. The cBN particles 28 having niobium inclusions 26 demonstrated a decrease in Tl from about 0.8% to about 3.6% compared to cBN particles 28 without the niobium inclusions 26. Furthermore, the cBN particles 28 having niobium inclusions 26 demonstrated a decrease in TTI from about 4.1 % to about 5.7% compared to cBN particles 28 without the niobium inclusions 26. The decrease of the Tl, and the TTI leads to microfracturing of the cBN particles 28 doped with the niobium particles 26 during machining of a workpiece. This is due to formation of intrinsic growth defects as a result of developed stress within the cBN crystal lattice structure, which growth defects thus behave as fracture-sites caused by the niobium inclusions 26 within the cBN crystal lattice structure.

[0091] To further characterize the shape of the microstructure of the cBN crystals, FIG. 4A shows the microstructure at a 40x magnification of cBN crystals without niobium inclusions, in which, cBN particles were pressed with a belt press in accordance with the current subject matter. In contrast, FIG. 4B shows the microstructure at a 40x magnification of cBN crystals with niobium inclusions, in which, cBN particles were pressed with a cubic press in accordance with the current subject matter. The microstructure analysis of the cBN crystals revealed a more robust, and a blockier shape for the cBN crystals with niobium inclusions shown in FIG. 4B in contrast to cBN crystals without niobium inclusions depicted in FIG. 4A. This would promote a more uniform cBN grinding wheel wear to obtain a more consistent cBN grinding wheel form from the start to the end of a cBN grinding wheel life cycle.

[0092] EXAMPLE 2

[0093] CREEPFEED GRINDING OF M2 STEEL, AND TRAVERSE GRINDING OF 4140 STEEL WITH A VITRIFIED CUBIC BORON NITRIDE (CBN) GRINDING WHEEL HAVING CBN PARTICLES WITH NIOBIUM INCLUSIONS DEMONSTRATE AN IMPROVED GRINDING PERFORMANCE COMPARED TO A GRINDING WHEEL HAVING CBN PARTICLES WITHOUT NIOBIUM INCLUSIONS

[0094] Experiments were performed, where creepfeed grinding of M2 steel was done with a vitrified cubic boron nitride (cBN) grinding wheel incorporating cBN particles with niobium inclusions, in which, cBN particles were either pressed with a cubic press, or cBN particles without niobium inclusions, in which, cBN particles were pressed with a belt press.

[0095] Further experiments were also performed, where traverse grinding of 4140 steel was done with a vitrified cBN grinding wheel incorporating cBN particles with niobium inclusions again, in which, cBN particles were either pressed with a cubic press, or cBN particles without niobium inclusions, in which, cBN particles were pressed with a belt press.

[0096] Wheel preparation techniques were optimized to maximize grinding performance. Grinding test criteria included in the experiments were the following. Wheel run-out (TIR) following truing was less than 3.0 pm, and wheel balance was less than 0.3 pm displacement. The cBN grinding wheel specifications were the following. The bondtype was a vitrified cBN bonding with a continuous rim. The wheel size was 178 mm D x 6.35 mm Wx 3.2 mm rim layer, and the mesh-size was B126 (120/140 mesh). The wheel had a glass base or core, and the speed applied was 60 m/s.

[0097] TABLE 2 shows the creepfeed grinding experiment conditions.

[0098] [TABLE 2]

[0099] TABLE 3 illustrates the traverse grinding experiment conditions.

[00100] [TABLE S]

[00101] Creepfeed grinding shown in FIG. 5B in accordance with the current subject matter refers to a grinding methodology used for high rates of material removal with a great depth of cut (a_e), while a conventional traverse grinding technique results in a shallower depth of cut (a_e) shown in FIG. 5A in accordance with the present subject matter. In creepfeed grinding, there is basically a great depth of cut (a_e), low workpiece velocity (V_w), great wheel/workpiece contact length (i.e., long length of stroke), the average contact temperature is much higher, the total grinding forces are equally much higher, and the surface quality is finer, compared to the conventional traverse grinding technique.

[00102] TABLE 4 shows wheel specifications.

[00103] [TABLE 4]

[00104] TABLE 5 shows wheel preparation conditions. [00105] [TABLE 5]

[00106] FIG. 6A shows normalized results of creepfeed grinding of M2 steel with the vitrified cBN grinding wheel incorporating cBN particles with niobium inclusions, in which, cBN particles were either pressed with a cubic press, or cBN particles without niobium inclusions, in which, cBN particles were pressed with a belt press. The normalized results show the grinding ratio, the power, and the finish of the cBN particles with niobium inclusions pressed with the cubic press taken relative to the cBN particles without niobium inclusions pressed with the belt press (i.e., 100%).

[00107] FIG. 6B shows normalized results of traverse grinding of 4140 steel with the vitrified cBN grinding wheel incorporating cBN particles with niobium inclusions again, in which, cBN particles were either pressed with a cubic press, or cBN particles without niobium inclusions, in which, the cBN particles were pressed with a belt press. The normalized results show the grinding ratio, the power, and the finish of the cBN particles with niobium inclusions pressed with the cubic press taken relative to the cBN particles without niobium inclusions pressed with the belt press (i.e., 100%). [00108] As seen in FIG. 6A and FIG. 6B, the combined results of the creepfeed grinding of the M2 steel, and the traverse grinding of the 4140 steel with the vitrified cBN grinding wheel incorporating cBN particles with niobium inclusions demonstrated an improvement in the grinding efficiency in a range of from about 6% (FIG. 6B 2^nd column results) to about 13% (FIG. 6A 3^rd column results), when compared to a cBN grinding wheel devoid of niobium inclusions.

[00109] Importantly, what is noteworthy was the improved finish that was obtained when subjecting the M2 steel to creepfeed grinding, and the 4140 steel to traverse grinding with the vitrified cBN grinding wheel incorporating cBN particles with niobium inclusions in comparison to a cBN grinding wheel having cBN particles devoid of niobium inclusions. As demonstrated in FIG. 6A and FIG. 6B, the achieved finish was reduced by a range of from about 4% to about 21 %. Without wishing to be bound by any particular theory, these results were likely due to the formation of blockier cBN crystal-shapes, and the increase in the aspect ratio for the cBN crystals seen in TABLE 1 , whose microstructures had incorporated niobium inclusions, versus those cBN crystals with no niobium inclusions.

[00110] Finally, maintaining crystal structure characteristics that contribute to a low grinding power would be highly advantageous. The results showed that the grinding power was generally slightly, however, unfavorably higher ranging from about 96% to about 105% for the vitrified cBN grinding wheel incorporating cBN particles with niobium inclusions in comparison to a cBN grinding wheel having cBN particles devoid of niobium inclusions as seen in FIG. 6A and FIG. 6B. This was more than likely driven by the higher aspect ratio for the cBN crystals with niobium inclusions seen in TABLE 1.

[00111] Although the present disclosure has been described in connection with examples thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departure from the spirit and scope of the disclosure as defined in the appended claims.

[00112] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/pl ural permutations are not expressly set forth herein for sake of clarity.

[00113] The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures may be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable,” to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components, and/or wirelessly interactable, and/or wirelessly interacting components, and/or logically interacting, and/or logically interactable components.

[00114] In some instances, one or more components may be referred to herein as “configured to,” “configured by,” “configurable to,” “operable/operative to,” “adapted/adaptable,” “able to,” “conformable/conformed to,” etc. Those skilled in the art will recognize that such terms (e.g., “configured to”) can generally encompass activestate components and/or inactive-state components and/or standby-state components, unless context requires otherwise.

[00115] While particular aspects ofthe present subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from the subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of the subject matter described herein. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.).

[00116] It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations.

[00117] In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations).

[00118] Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “ a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “ a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that typically a disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase “A or B” will be typically understood to include the possibilities of “A” or “B” or “A and B.”

[00119] With respect to the appended claims, those skilled in the art will appreciate that recited operations therein may generally be performed in any order. Also, although various operational flows are presented in a sequence(s), it should be understood that the various operations may be performed in other orders than those which are illustrated or may be performed concurrently. Examples of such alternate orderings may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise. Furthermore, terms like “responsive to,” “related to,” or other past-tense adjectives are generally not intended to exclude such variants, unless context dictates otherwise.

[00120] Those skilled in the art will appreciate that the foregoing specific exemplary processes and/or devices and/or technologies are representative of more general processes and/or devices and/or technologies taught elsewhere herein, such as in the claims filed herewith and/or elsewhere in the present application.

[00121] While various aspects and examples have been disclosed herein, other aspects and examples will be apparent to those skilled in the art. The various aspects and examples disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

[00122] The illustrative examples described in the detailed description, drawings, and claims are not meant to be limiting. Other examples may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. [00123] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the disclosure. The upper and lower limits of these smaller ranges which can independently be included in the smaller ranges is also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits ranges excluding either both of those included limits are also included in the disclosure.

[00124] One skilled in the art will recognize that the herein described components (e.g., operations), devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken as limiting.

[00125] Additionally, for example any sequence(s) and/or temporal order of sequence of the system and method that are described herein this disclosure are illustrative and should not be interpreted as being restrictive in nature. Accordingly, it should be understood that the process steps may be shown and described as being in a sequence or temporal order, but they are not necessarily limited to being carried out in any particular sequence or order. For example, the steps in such processes or methods generally may be carried out in various different sequences and orders, while still falling within the scope of the present disclosure.

[00126] Finally, the discussed application publications and/or patents herein are provided solely for their disclosure prior to the filing date of the described disclosure. Nothing herein should be construed as an admission that the described disclosure is not entitled to antedate such publication by virtue of prior disclosure.

Claims

What is claimed is:

1. A method for making self-sharpening cubic boron nitride (cBN) particles, comprising: forming a mixture comprising a plurality of hexagonal boron nitride (hBN) particles and a catalytic material; placing a niobium-foil within a reaction zone adjacent to the mixture comprising the plurality of hBN particles and the catalytic material; and reacting constituents of the mixture with the niobium-foil at high-pressure-high- temperature (HPHT) conditions to form the self-sharpening cBN particles, wherein niobium and the catalytic material are retained in inclusions within the selfsharpening cBN particles to cause microfracturing of the self-sharpening cBN particles to expose at least one new cutting surface or at least one new cutting edge in the selfsharpening cBN particles.

2. The method for making self-sharpening cBN particles of claim 1 , wherein the HPHT conditions comprise internal cell pressures in a range of from about 4 gigapascal (GPa) to about 8 GPa and internal cell temperatures in a range of from about 1100°C to about 1800°C.

3. The method for making self-sharpening cBN particles of claim 1 , wherein a concentration of the niobium incorporated into a crystal-structure of the cBN particles ranges from about 50 parts per million (ppm) to about 200 ppm.

4. The method for making self-sharpening cBN particles of claim 3, wherein the concentration of the niobium incorporated into the crystal-structure of the cBN particles ranges from about 50 ppm to about 100 ppm.

5. The method for making self-sharpening cBN particles of claim 3, wherein the concentration of the niobium incorporated into the crystal-structure of the cBN particles ranges from about 100 ppm to about 150 ppm.

6. The method for making self-sharpening cBN particles of claim 3, wherein the concentration of the niobium incorporated into from the crystal-structure of the cBN particles ranges from about 150 ppm to about 200 ppm.

7. The method for making self-sharpening cBN particles of claim 6, wherein the concentration of the niobium incorporated into the crystal-structure of the cBN particles ranges from about 175 ppm to about 200 ppm.

8. The method for making self-sharpening cBN particles of claim 1 , wherein the catalytic material comprises at least one of lithium (Li), magnesium (Mg), sodium (Na), potassium (K), barium (Ba), calcium (Ca), tin (Sn), or nitrides thereof.

9. The method for making self-sharpening cBN particles of claim 1 , further comprising incorporating the self-sharpening cBN particles into a vitrified cBN grinding wheel.

10. The method for making self-sharpening cBN particles of claim 9, wherein the cBN particles comprising niobium inclusions demonstrate an improvement in grinding efficiency of up to about 13% compared to cBN particles excluding niobium inclusions.

11 . The method for making self-sharpening cBN particles of claim 10, wherein the cBN particles comprising niobium inclusions demonstrate an improvement in grinding efficiency of up to about 10% compared to cBN particles excluding niobium inclusions.

12. The method for making self-sharpening cBN particles of claim 11 , wherein the cBN particles comprising niobium inclusions demonstrate an improvement in grinding efficiency of up to about 6% compared to cBN particles excluding niobium inclusions.

13. The method for making self-sharpening cBN particles of claim 10, wherein the cBN particles comprising niobium as inclusions demonstrate an improvement in grinding efficiency in a range of from about 6% to about 13% compared to cBN particles excluding niobium inclusions.

14. The method for making self-sharpening cBN particles of claim 9, wherein the cBN particles comprising niobium inclusions demonstrate a decrease in toughness index (Tl) from about 0.8% to about 3.6% compared to cBN particles excluding niobium inclusions.

15. The method for making self-sharpening cBN particles of claim 9, wherein the cBN particles comprising niobium inclusions demonstrate a decrease in thermal toughness index (TTI) from about 4.1 % to about 5.7% compared to cBN particles excluding niobium inclusions.

16. A vitrified cBN grinding wheel, comprising self-sharpening cBN particles prepared by a method of claim 1 .

17. A method of sharpening a vitrified cBN grinding wheel during machining of a workpiece, comprising: abrading a self-sharpening cBN particle of the vitrified cBN grinding wheel against the workpiece, the vitrified cBN grinding wheel comprising the self-sharpening cBN particle; a catalytic material; and niobium, the catalytic material and the niobium being retained in inclusions within the self-sharpening cBN particle; and interacting the self-sharpening cBN particle, the catalytic material and the niobium to cause microfracturing of the self-sharpening cBN particle to expose at least one new cutting surface or at least one new cutting edge in the self-sharpening cBN particle during the abrading of the self-sharpening cBN particle of the vitrified cBN grinding wheel against the workpiece.

18. The method of sharpening a vitrified cBN grinding wheel during machining of a workpiece of claim 17, wherein the catalytic material comprises at least one of lithium (Li), magnesium (Mg), sodium (Na), potassium (K), barium (Ba), calcium (Ca), tin (Sn), or nitrides thereof.

19. The method of sharpening a vitrified cBN grinding wheel during machining of a workpiece of claim 17, wherein the cBN particle comprising niobium inclusions demonstrates a decrease in toughness index (Tl) from about 0.8% to about 3.6% compared to a cBN particle excluding niobium inclusions thus causing the microfracturing.

20. The method of sharpening a vitrified cBN grinding wheel during machining of a workpiece of claim 17, wherein the cBN particle comprising niobium inclusions demonstrates a decrease in thermal toughness index (TTI) from about 4.1 % to about 5.7% compared to a cBN particle excluding niobium inclusions thus causing the microfracturing.