Doped cbn particles for improved friability and enhanced grinding

Abstract

A method for manufacturing self-sharpening cubic boron nitride (cBN) particles is provided. The method includes forming a mixture having a plurality of hexagonal boron nitride (hBN) particles and a catalyst material, the catalyst material including at least one of lithium (Li), magnesium (Mg), sodium (Na), potassium (K), barium (Ba), calcium (Ca), tin (Sn), or their nitrides. A niobium foil is placed in a reaction zone adjacent to the mixture comprising the plurality of hBN particles and the catalyst material. Next, the mixture and the niobium foil are reacted under high pressure and high temperature (HPHT) conditions sufficient to form self-sharpening cBN particles. The niobium and the catalyst material are retained in inclusions within the self-sharpening cBN particles, causing microfractures of the self-sharpening cBN particles. Furthermore, a glass-modified cBN grinding wheel incorporating such self-sharpening cBN particles with improved friability doped niobium is proposed, along with a related method for sharpening the glass-modified cBN grinding wheel during the machining of a workpiece.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing self-sharpening cubic boron nitride (cBN) particles doped with a refractory metal, and a glass-modified cBN grinding wheel incorporating such cBN particles doped with a refractory metal, the refractory metal having improved brittleness of the cBN particles and enhanced abrasive material removal performance of the glass-modified cBN grinding wheel. Prior Technology

[0002] Cubic boron nitride (cBN) is typically produced by high-pressure and high-temperature (HPHT) conversion of hexagonal boron nitride (hBN) in the presence of a suitable catalyst. These cBN crystals are then incorporated into glass-enhanced grinding wheels for machining metal alloys. The material removal rate of these cBN grinding wheels depends in part on the properties of the cBN crystals. If improved crystal properties can be demonstrated, the resulting cBN grinding wheels will be able to remove material at an increased rate.

[0003] It has been demonstrated that incorporating trace amounts of heavy refractory metals into the lattice structure of grown cBN crystals can improve the brittleness of cBN crystals. This is achieved by converting hBN to cBN in the presence of such refractory metals and metal catalysts, either as components incorporated into the raw material powder mixture or in other ways contacting the reactants.

[0004] During the conversion of hBN to cBN, refractory metals and catalysts are essentially trapped within the cBN crystals, known as inclusions, resulting in internal growth defects within the cBN crystals. Without being bound by any particular theory, it is believed that these internal growth defects manifest as fracture sites when the cBN crystals are incorporated into a vitrified grinding wheel as the abrasive material. Typically, a delicate balance is required, where it is generally desirable for the cBN crystals to be both robust and tough enough not to wear out quickly. However, when the cBN crystals eventually begin to wear, the preferred cBN crystals fracture, exposing new and fresh cutting surfaces and edges. To the inventors' knowledge, there are currently no other commercially available options for incorporating heavy refractory metals as inclusions into brittle cBN crystals to increase the abrasive performance of cBN grinding wheels due to microfractures in the cBN crystals.

[0005] In view of the above, there is a need for a glassy cBN grinding wheel with cBN particles doped with refractory metals used to improve the brittleness of cBN particles, thereby resulting in enhanced grinding performance of the cBN grinding wheel. Summary of the Invention

[0006] A method for preparing self-sharpening cubic boron nitride (cBN) particles is provided, the method comprising forming a mixture having a plurality of hexagonal boron nitride (hBN) particles and a catalyst. A niobium foil is placed in a reaction zone adjacent to the mixture comprising the plurality of hBN particles and the catalyst. Next, the components of the mixture are reacted with the niobium foil under high pressure and high temperature (HPHT) conditions to form self-sharpening cBN particles. The niobium and the catalyst are retained in inclusions within the self-sharpening cBN particles, causing microfractures in the self-sharpening cBN particles to expose at least one new cutting surface or at least one new cutting edge within the self-sharpening cBN particles.

[0007] Depending on the circumstances, HPHT conditions include an internal tank pressure ranging from approximately 4 gigapascals (GPa) to approximately 8 GPa and an internal tank temperature ranging from approximately 1100°C to approximately 1800°C.

[0008] Depending on the circumstances, the concentration of niobium incorporated into the crystal structure of cBN particles ranges from about 50 parts per million (ppm) to about 200 ppm.

[0009] Depending on the circumstances, the concentration of niobium incorporated into the crystal structure of cBN particles ranges from about 50 ppm to about 100 ppm.

[0010] Depending on the circumstances, the concentration of niobium incorporated into the crystal structure of cBN particles is in the range of about 100 ppm to about 150 ppm.

[0011] Depending on the circumstances, the concentration of niobium incorporated into the crystal structure of cBN particles is in the range of about 150 ppm to about 200 ppm, or about 175 ppm to about 200 ppm.

[0012] Depending on the circumstances, the catalyst may contain at least one of lithium (Li), magnesium (Mg), sodium (Na), potassium (K), barium (Ba), calcium (Ca), tin (Sn), or their nitrides.

[0013] Depending on the circumstances, the method may further include incorporating self-sharpening cBN particles into a vitrified cBN grinding wheel.

[0014] Depending on the circumstances, cBN particles containing niobium inclusions exhibit an improvement in grinding efficiency of up to approximately 13% compared to cBN particles without such niobium inclusions.

[0015] Depending on the situation, cBN particles containing niobium inclusions exhibit an improvement in grinding efficiency of up to approximately 10% compared to cBN particles without such niobium inclusions.

[0016] Depending on the circumstances, cBN particles containing niobium inclusions exhibit an improvement in grinding efficiency of up to approximately 6% compared to cBN particles without such niobium inclusions.

[0017] Depending on the circumstances, cBN particles containing niobium as an inclusion exhibit an improvement in grinding efficiency ranging from about 6% to about 13% compared to cBN particles without niobium inclusions.

[0018] Depending on the circumstances, cBN particles including niobium inclusions exhibit a decrease in toughness index (TI) of approximately 0.8% to approximately 3.6% compared to cBN particles without niobium inclusions, thereby promoting microfractures.

[0019] Depending on the circumstances, cBN particles including niobium inclusions exhibit a decrease in thermal toughness index (TTI) of approximately 4.1% to approximately 5.7% compared to cBN particles without niobium inclusions, thereby promoting microfracture.

[0020] A further provision is provided: a vitrified cBN grinding wheel comprising self-sharpening cBN particles prepared according to the above method.

[0021] A further method is provided for sharpening a glass-modified cBN grinding wheel during the machining of a workpiece, comprising rubbing the self-sharpening cBN particles of the cBN grinding wheel against the workpiece, wherein the glass-modified cBN grinding wheel comprises self-sharpening cBN particles, a catalyst material, and niobium. The catalyst material and niobium are retained in inclusions within the self-sharpening cBN particles. During the rubbing of the self-sharpening cBN particles of the glass-modified cBN grinding wheel against the workpiece, the self-sharpening cBN particles, the catalyst material, and niobium interact, causing micro-fractures in the self-sharpening cBN particles to expose at least one new cutting surface or at least one new cutting edge within the self-sharpening cBN particles.

[0022] Other systems, methods, features, and advantages will or will become apparent to those skilled in the art upon examination of the following drawings and embodiments. All such additional systems, methods, features, and advantages are intended to be included within this specification, falling within the scope of this disclosure, and protected by the appended claims. Nothing in this section should be construed as limiting the claims. Other variations and advantages are discussed below in conjunction with embodiments of this disclosure. It should be understood that the preceding inventive description and the following embodiments are illustrative and intended to provide further explanation of the claimed disclosure. Simple Explanation of the Diagram

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

[0024] [Figure 1A] shows a side view of a cubic boron nitride (cBN) grinding wheel according to the present invention, which contains cBN particles free of niobium inclusions.

[0025] [Figure 1B] shows a side view of a glassy cubic boron nitride (cBN) grinding wheel with cBN particles containing niobium inclusions according to the present invention.

[0026] [Figure 2] shows a cross-sectional view of a portion of the abrasive layer of a glassy cubic boron nitride (cBN) grinding wheel containing cBN particles with niobium inclusions according to the present invention.

[0027] [Figure 3] shows a flowchart illustrating the various process steps in preparing self-sharpening cubic boron nitride (cBN) particles incorporating niobium inclusions according to this standard.

[0028] [Figure 4A] shows the microstructure of the cBN crystal without niobium inclusions according to this specification at 40x magnification, wherein the cBN particles were pressed using a belt press.

[0029] [Figure 4B] shows the microstructure of the cBN crystal containing niobium inclusions according to this specification at 40x magnification, wherein the cBN particles were pressed using a cubic press.

[0030] [Figure 5A] shows a cross-sectional view of the grinding characteristics of the transverse grinding technology according to this specification.

[0031] [Figure 5B] shows a cross-sectional view of the grinding characteristics of the creeping grinding technology according to this specification.

[0032] [Figure 6A] shows the normalized results of slow-feed grinding of M2 steel using glassy cubic boron nitride (cBN) grinding wheels incorporating the following: cBN particles containing niobium inclusions, where the cBN particles are pressed using a cubic press, or cBN particles without niobium inclusions, where the cBN particles are pressed using a belt press. The normalized results show the grinding ratio, power, and surface finish (i.e., 100%) of cBN particles containing niobium inclusions pressed using a cubic press compared to cBN particles without niobium inclusions pressed using a belt press.

[0033] [Figure 6B] shows the normalized results of transverse grinding of 4140 steel using glassy cubic boron nitride (cBN) grinding wheels incorporating the following: cBN particles containing niobium inclusions, where the cBN particles are pressed using a cubic press, or cBN particles without niobium inclusions, where the cBN particles are pressed using a belt press. The normalized results show the grinding ratio, power, and surface finish (i.e., 100%) of cBN particles containing niobium inclusions pressed using a cubic press compared to cBN particles without niobium inclusions pressed using a belt press. Implementation

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter herein belongs.

[0035] When a numerical range is provided, such as a concentration range, percentage range, or ratio range, it should be understood that unless the context explicitly specifies otherwise, each intermediate value to the lower limit of the range, from the upper and lower limits to any other stated or intermediate value within the range, is included within the described object. The upper and lower limits of such smaller ranges may be independently included within those smaller ranges, and such instances are also included within the described object, but are subject to any explicit exclusions from the range. Where the range includes one or both of the included limitations, the range excluding one or both of those included limitations is also included in the described object.

[0036] The following definitions describe the parameters of the target being described.

[0037] As used herein, the term "cBN particle" refers to a discrete cBN body or multiple discrete cBN bodies. As used herein, the term "cBN particle" is also considered to be a cBN crystal or cBN grain, and is therefore used interchangeably with such terms.

[0038] As used herein, the term "vol.%" refers to a given volume percentage based on the total volume of the cBN grinding wheel or powder mixture.

[0039] As used herein, the term "superabrasive superhard material" or simply "superabrasive material" refers to an abrasive material exhibiting excellent hardness and good wear resistance, which can be found below, but is not limited to, B4C diamond composites, SiC-TiN-TiCN diamond composites, crystalline diamond, single-crystal diamond, polycrystalline diamond (PCD), thermally stabilized 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 combination thereof. The term "abrasive" as used herein refers to any superabrasive material used to grind away softer materials.

[0040] As used herein, the term "about" means an average of plus or minus 5% of the numerical values ​​used in the request and in this disclosure. Thus, "about" can be used to provide flexibility for the endpoints of a numerical range, where a given value may be "above" or "below" that given value. Therefore, a value of, for example, 50% can be intended to cover a range that can be defined by, for example, the following instance ranges: 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%-50%. 2.5%, 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%-51.75%, 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%-51.75%, 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.

[0041] Wherever the term is used throughout the invention, it means "typically," "closely," or "within the vicinity or range of."

[0042] As used in this article, the term "friable" or "friability" refers to the tendency of a solid material to break into smaller fragments when bound or in contact (especially by friction).

[0043] As used herein, the term "fracture toughness" (KIc) refers to the ability of a pre-cracked material to resist further fracture propagation when it absorbs energy. Fracture toughness (KIc) is calculated using the following formula: , where A is a constant of 0.0028, HV is the hardness (N / mm2), P is the applied load (N), and ΣL is the sum of the imprinted crack lengths (mm).

[0044] As used in this article, the term "HV30 Vickers hardness" (i.e., 30 kgf load applied) is a measure of a sample's resistance to localized plastic deformation, which is obtained by indenting the sample with a Vickers tip at 30 kgf.

[0045] As used herein, the term "substantially" refers to the extent or degree of completeness or near-completeness of an action, characteristic, nature, state, structure, item, or result.

[0046] As used herein, the term "catalytic material" refers to a material that promotes and actively drives the reaction from hexagonal boron nitride (hBN) to cBN.

[0047] As used herein, the term "inclusion" refers to internal growth defects and specifically to the incorporation, penetration, or insertion of heavy refractory metals (such as niobium) and / or catalysts (such as lithium) within the lattice structure of cBN particles. This occurs during the high-pressure, high-temperature (HPHT) conversion of hBN to cBN, in which foils embedded with niobium, etc., are placed in an HPHT cell within a reaction zone adjacent to the hBN particles and the catalyst. The HPHT cell is placed in a cubic press, and an internal cell pressure, typically from about 4 gigapascals (GPa) to about 8 GPa, and an internal cell temperature, typically from about 1100°C to about 1800°C, are applied to the HPHT cell to convert hBN to cBN.

[0048] As used herein, the term "creepfeed grinding" (Figure 5B) refers to a grinding method used for high-rate material removal, while the conventional transverse grinding (Figure 5A) technique can be used for finishing surfaces. Compared to the conventional transverse grinding technique (Figure 5A), creepfeed grinding (Figure 5B) features a larger depth of cut (ae), a lower workpiece speed (vw), a longer wheel / workpiece contact length (i.e., stroke length), a much higher average contact temperature, a much higher total grinding force, and a finer surface finish.

[0049] As used herein, the term "high-pressure high-temperature (HPHT) conversion" refers to a process in which heating is performed at an internal tank pressure typically ranging from about 4 gigapascals (GPa) to about 8 GPa to minimize the surface area of ​​a cBN-based particulate system. This relates to the formation of bonds between adjacent small cBN particles and the subsequent contraction of the aggregated cBN particles. The cBN particles are compacted and formed into a dense mass by heating them under high pressure. Atoms in the cBN particles diffuse across the boundaries of the cBN particles, thereby fusing the small cBN particles together to form a solid, dense mass. Although many HPHT devices are well known to those skilled in the art, the two most common devices used for HPHT conversion are cubic presses and belt presses.

[0050] As used in this article, the term "facet" refers to a geometrically flat surface defined by the edges surrounding the flat surface.

[0051] As used in this article, the term "blocky" refers to a blocky shape.

[0052] As used herein, the term "reaction zone" refers to the internal region within the HPHT reactor where hBN particles and catalysts undergo a chemical reaction to form cBN particles during HPHT conversion.

[0053] As used herein, the term "adjacent to" means that one thing is directly adjacent to another, or is close to or near but not directly adjacent to it, such as distances from the specific object under discussion of 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, etc. cm, 1.95 cm or 2 cm.

[0054] As used in this article, the term "vitrified bond" refers to a glassy appearance or feature.

[0055] As used in this article, the term "aspect ratio" for an object refers to the ratio defined by its width relative to its height.

[0056] As used herein, the term "environmental conditions" refers to 25°C, 298.15 K, and 101.325 kPa pressure.

[0057] As used herein, the term "workpiece" refers to material that has been cut, ground, or otherwise machined by a glassy cBN grinding wheel. Those skilled in the art will recognize that workpieces typically include composites, metals, alloys, superalloys, and difficult-to-machine materials. It refers to a component or object from which material is typically removed by machining.

[0058] This disclosure presupposes a method for preparing self-sharpening cBN particles and a cBN grinding wheel incorporating trace amounts of a heavy refractory metal, such as niobium, as a metal dopant on the cBN crystal, which improves the fragility of the cBN crystal and enhances the abrasive removal rate of the cBN grinding wheel. Not wishing to be bound by any particular theory, the proposed mechanism for such improvements involves incorporating these large niobium atoms as inclusions into the cBN lattice structure during growth. This may introduce strain into the entire cBN lattice structure, resulting in reduced fracture toughness. This makes the cBN crystal more prone to fracture, thereby creating new sharp cutting edges and surfaces during workpiece grinding operations. In other words, the larger atomic radius of the niobium inclusions imposes additional stress and strain on the cBN lattice structure, effectively making the cBN crystal more susceptible to fracture. This exposes more cutting edges and surfaces, while the cBN wheel wears during workpiece machining. This can be viewed as a self-sharpening cBN grinding wheel, but at the cost of the overall mechanical fracture toughness of the cBN crystal with such heavy niobium inclusions. Without being bound by any particular theory, it is believed that large niobium atoms can substitute on boron, or on nitrogen sites within the cBN lattice structure, or that niobium atoms can be interstitially or substituted.

[0059] cBN particles are typically present at about 60 vol.% to about 80 vol.% of the total volume of the cBN grinding wheel. In some instances, cBN particles are present at about 62 vol.% to about 80 vol.% of the total volume of the cBN grinding wheel. In other instances, cBN particles are present at about 65 vol.% to about 80 vol.% of the total volume of the cBN grinding wheel. In still other embodiments, cBN particles are present at about 67 vol.% to about 80 vol.% of the total volume of the cBN grinding wheel. In still other instances, cBN particles are present at about 69 vol.% to about 80 vol.% of the total volume of the cBN grinding wheel. In even other instances, cBN particles are present at about 71 vol.% to about 80 vol.% of the total volume of the cBN grinding wheel. In further instances, cBN particles are present at approximately 73 vol.% to approximately 80 vol.% of the total volume of the cBN grinding wheel. In other instances, cBN particles are present at approximately 75 vol.% to approximately 80 vol.% of the total volume of the cBN grinding wheel. In still other instances, cBN particles are present at approximately 77 vol.% to approximately 80 vol.% of the total volume of the cBN grinding wheel. In even more instances, cBN particles are present at approximately 78 vol.% to approximately 80 vol.% of the total volume of the cBN grinding wheel.

[0060] cBN particles can also be approximately 60 vol.% to approximately 62 vol.%, 60 vol.% to approximately 65 vol.%, approximately 62 vol.% to approximately 65 vol.%, approximately 65 vol.% to approximately 67 vol.%, approximately 60 vol.% to approximately 67 vol.%, approximately 60 vol.% to approximately 70 vol.%, approximately 60 vol.% to approximately 72 vol.%, approximately 60 vol.% vol.% to approximately 75 vol.%, approximately 67 vol.% to approximately 69 vol.%, approximately 69 vol.% to approximately 71 vol.%, approximately 71 vol.% to approximately 73 vol.%, approximately 67 vol.% to approximately 73 vol.%, approximately 67 vol.% to approximately 75 vol.%, approximately 67 vol.% to approximately 77 vol.%, approximately 70 vol.% to approximately 75 vol.%, approximately 70 vol.% to approximately 77 vol.%, approximately 70 vol.% to approximately 79 vol.%. It exists in vol.%, about 73 vol.% to about 75 vol.%, about 73 vol.% to about 77 vol.%, or about 75 vol.% to about 77 vol.%, based on the total volume of the cBN grinding wheel.

[0061] cBN particles typically have sieve sizes ranging from 1250 mesh (for powders with a particle size of less than about 10 micrometers) to 2500 mesh (for powders with a particle size of less than about 5 micrometers).

[0062] To determine a specific cBN particle size, those skilled in the art typically employ dynamic digital image analysis (DIA), static laser light scattering (SLS) (also known as laser diffraction), or visual measurements using electron microscopy, techniques known as image analysis and light masking. Each method covers a range of characteristic sizes that can be measured. These ranges partially overlap. However, the results of measuring the same sample may differ depending on the specific method used. Those skilled in the art who wish to determine cBN particle size or cBN particle size distribution will readily understand how each of the mentioned methods is typically performed and practiced. Therefore, readers can refer to "Comparison of Methods. Dynamic Digital Image Analysis, Laser Diffraction, Sieve Analysis", Retsch Technology and Kelly et al.'s scientific publication "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, for a more in-depth understanding of each procedure and method.

[0063] The concentration of niobium incorporated into the crystal structure of cBN particles is typically in the range of about 50 parts per million (ppm) to about 200 ppm. In some examples, the concentration of niobium incorporated into the crystal structure of cBN particles is in the range of about 70 ppm to about 200 ppm. In other examples, the concentration of niobium incorporated into the crystal structure of cBN particles is in the range of about 90 ppm to about 200 ppm. In still other examples, the concentration of niobium incorporated into the crystal structure of cBN particles is in the range of about 110 ppm to about 200 ppm. In yet still other examples, the concentration of niobium incorporated into the crystal structure of cBN particles is in the range of about 130 ppm to about 200 ppm. In still other examples, the concentration of niobium incorporated into the crystal structure of cBN particles is in the range of about 150 ppm to about 200 ppm. In even further instances, the concentration of niobium incorporated into the crystal structure of cBN particles ranges from about 170 ppm to about 200 ppm.

[0064] The concentration of niobium incorporated into the lattice structure of cBN particles can also be in the range of about 50 ppm to about 70 ppm, about 70 ppm to about 90 ppm, about 90 ppm to about 110 ppm, about 50 ppm to about 110 ppm, about 70 ppm to about 110 ppm, about 110 ppm to about 130 ppm, about 150 ppm to about 170 ppm, or about 110 ppm to about 170 ppm.

[0065] Referring to Figures 1A and 1B, these figures illustrate two separate scenarios affecting the final configuration of the cBN grinding wheel. Figure 1A shows a side view of a cBN grinding wheel 10 according to the present invention, which has an aluminum or steel core or substrate 11 and an abrasive layer 12 containing cBN particles free of niobium inclusions. Figure 1B shows a side view of a glassy cBN grinding wheel 10A according to the present invention, which has an aluminum or steel core or substrate 11A and an abrasive layer 12A containing cBN particles containing niobium inclusions. Essentially, it is noteworthy that the cBN grinding wheel 10A in Figure 1B is formed by a cutting edge 13A and a cutting surface 13A, and the glassy cBN grinding wheel 10A wears during the machining of the workpiece. As previously stated, the formation of these cutting edges 13A and cutting surfaces 13A is at least due to niobium and / or catalyst inclusions formed in the glassy cBN grinding wheel 10A, as shown in Figure 1B. These inclusions thus cause internal growth defects. These growth defects manifest as common fracture sites, thereby exposing new cutting edges 13A and cutting surfaces 13A during workpiece grinding with the glassy cBN grinding wheel 10A, where the niobium inclusions are absent in the cBN grinding wheel 10 shown in Figure 1A.

[0066] Figure 2 shows a cross-sectional view of a portion of the abrasive layer 12A of the cubic boron nitride (cBN) grinding wheel 10A according to the present invention, wherein the cubic boron nitride (cBN) grinding wheel 10A has cBN particles 28 containing niobium 26 and catalyst material 25 as inclusions. Figure 2 further shows that the cBN abrasive particles 28 and the abrasive layer 12A are held together by a reinforced glass transition bond 24.

[0067] The vitrified bonding material 24 can be composed of, for example, amorphous glasses typically selected from the group consisting of borosilicate glasses, phosphate glasses, and borate glasses, or any desired combination thereof. Alternatively, the vitrified bonding material 24 may further include oxide particles added for the purpose of enhancing the strength of the amorphous glass, and is typically selected from the group consisting of zircon (ZrSiO4), titanium dioxide (TiO2), zirconium oxide (ZrO2), chromium oxide (Cr2O3), and aluminum oxide (Al2O3), or any desired combination thereof. The linear coefficients of thermal expansion of the oxide particles and the amorphous glass are substantially equal to the linear coefficient of thermal expansion of the bonded cBN abrasive particles 28. The linear coefficient of thermal expansion may, for example, be in the range of (3.5±2)×10-6 / C. Under such conditions, the cBN abrasive particles 28, oxide particles, and amorphous glass will not separate or be damaged due to potential temperature fluctuations, thereby maintaining the quality and physical integrity of the cBN grinding wheel 10A.

[0068] The catalysts that can be advantageously utilized can vary depending on the properties of the superabrasive material and the conditions under which microcracks occur. Therefore, any refractory metal and / or catalyst capable of promoting or facilitating microcracks and microfractures should be considered within the scope disclosed herein. In some instances, lithium (Li) is the most typical catalytic material.

[0069] Catalysts are typically used at the following concentrations: from about 10 ppm to about 800 ppm, from about 50 ppm to about 800 ppm, from about 100 ppm to about 800 ppm, from about 150 ppm to about 800 ppm, from about 200 ppm to about 800 ppm, from about 250 ppm to about 800 ppm, from about 300 ppm to about 800 ppm, from about 350 ppm to about 800 ppm, from about 400 ppm to about 800 ppm, from about 450 ppm to about 800 ppm, from about 500 ppm to about 800 ppm, from about 550 ppm to about 800 ppm, from about 600 ppm to about 800 ppm, from about 650 ppm to about 800 ppm, from about 700 ppm to about 800 ppm, from about 750 ppm to about 800 ppm, and from about 10 ppm to about 500 ppm. 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 ppm to about 750 ppm, or across about 600 ppm to about 800 ppm.

[0070] To avoid being bound by a specific theory, microfractures during the machining of the glassy cBN grinding wheel 10A can be caused by internal growth defects that act as fracture sites. These internal growth defects are typically inclusions, single grains with internal defects, cracks, crystal dislocations, and / or polycrystalline grains with weak intergranular boundaries due to niobium infiltration into the cBN lattice structure. Therefore, it is desirable to manufacture a more robust bulk cBN crystal shape to promote more uniform wear of the cBN grinding wheel 10A.

[0071] Toughness index (TI) can be measured under typical environmental conditions. In many cases, generally, the tougher the cBN crystals, the longer the unbroken cBN crystals remain within the matrix of the vitrified cBN grinding wheel 10A. Compared to cBN particles 28 without such niobium inclusions 26, cBN particles 28 including niobium inclusions 26 typically exhibit a reduction in TI of about 0.8% to about 3.6%, resulting in microfractures. In some instances, cBN particles 28 including niobium inclusions 26 exhibit a reduction in TI of about 1.3% to about 3.6% compared to cBN particles 28 without such niobium inclusions 26, resulting in microfractures. In other instances, cBN particles 28 including niobium inclusions 26 exhibit a reduction in TI of about 1.8% to about 3.6% compared to cBN particles 28 without such niobium inclusions 26, resulting in microfractures. In further examples, cBN particles 28 including niobium inclusions 26 exhibit a reduction in TI of approximately 2.3% to approximately 3.6% compared to cBN particles 28 without such niobium inclusions 26, resulting in microfractures. In still other examples, cBN particles 28 including niobium inclusions 26 exhibit a reduction in TI of approximately 2.8% to approximately 3.6% compared to cBN particles 28 without such niobium inclusions 26, resulting in microfractures. In even more other examples, cBN particles 28 including niobium inclusions 26 exhibit a reduction in TI of approximately 3.3% to approximately 3.6% compared to cBN particles 28 without such niobium inclusions 26, resulting in microfractures.

[0072] Compared to cBN particles 28 that do not contain such niobium inclusions 26, cBN particles 28 including niobium inclusions 26 may also exhibit a reduction in TI of about 0.8% to about 1.3%, about 1.3% to about 1.8%, about 1.8% to about 2.3%, about 0.8% to about 1.8%, about 0.8% to about 2.3%, about 1.3% to about 2.3%, about 2.3% to about 2.8%, about 2.3% to about 3.3%, or about 2.8% to about 3.3%, thereby causing microfractures.

[0073] The thermal toughness index (TTI) can be measured after the product has been fired at high temperatures, for example, at approximately 1100°C to approximately 1500°C, approximately 1100°C to approximately 1600°C, approximately 1100°C to approximately 1700°C, approximately 1100°C to approximately 1800°C, approximately 1200°C to approximately 1500°C, approximately 1200°C to approximately 1600°C, approximately 1200°C to approximately 1700°C, approximately 1200°C to approximately 1800°C, approximately 1300°C to approximately 1400°C, and approximately 1300°C to approximately 1400°C. The temperatures range from 0°C to approximately 1500°C, from approximately 1300°C to approximately 1600°C, from approximately 1300°C to approximately 1700°C, from approximately 1300°C to approximately 1800°C, from approximately 1400°C to approximately 1500°C, from approximately 1400°C to approximately 1600°C, from approximately 1500°C to approximately 1600°C, from approximately 1500°C to approximately 1700°C, from approximately 1500°C to approximately 1800°C, from approximately 1600°C to approximately 1800°C, or from approximately 1700°C to approximately 1800°C. Compared to cBN particles 28 without such niobium inclusions 26, cBN particles 28 including niobium inclusions 26 can exhibit a reduction in TTI of approximately 4.1% to approximately 5.7%, thereby causing microfractures. In some instances, cBN particles 28 including niobium inclusions 26 may exhibit a TTI reduction of about 4.5% to about 5.7% compared to cBN particles 28 without such niobium inclusions 26, resulting in microfractures. In other instances, cBN particles 28 including niobium inclusions 26 may exhibit a TTI reduction of about 4.8% to about 5.7% compared to cBN particles 28 without such niobium inclusions 26, resulting in microfractures. In still other embodiments, cBN particles 28 including niobium inclusions 26 may exhibit a TTI reduction of about 5.1% to about 5.7% compared to cBN particles 28 without such niobium inclusions 26, resulting in microfractures. In even other instances, cBN particles 28 including niobium inclusions 26 may exhibit a TTI reduction of about 5.4% to about 5.7% compared to cBN particles 28 without such niobium inclusions 26, resulting in microfractures.

[0074] Compared to cBN particles 28 that do not contain such niobium inclusions 26, cBN particles 28 including niobium inclusions 26 may also exhibit a reduction in TTI of about 4.1% to about 4.5%, about 4.5% to about 4.8%, about 4.8% to about 5.1%, about 4.1% to about 5.1%, about 4.5% to about 5.1%, about 4.5% to about 5.4%, about 4.8% to about 5.4%, or about 5.1% to about 5.4%, thereby causing microfractures.

[0075] The process for manufacturing self-sharpening cubic boron nitride (cBN) particles will now be described. U.S. Patent No. 2,947,617A, incorporated herein by reference in its entirety, describes a conventional process for manufacturing cBN particles that includes first preparing a powder mixture of hBN particles and a suitable catalyst material (such as, for example, lithium, magnesium, sodium, potassium, barium, calcium, tin, or nitrides of such metals). Next, the powder mixture is placed in a high-pressure, high-temperature (HPHT) reactor. High pressure and temperature conditions are then applied at levels suitable for each individual catalyst system. This is typically from about 4 gigapascals (GPa) to about 8 GPa, about 5 GPa to about 8 GPa, about 6 GPa to about 8 GPa, about 7 GPa to about 8 GPa, about 5 GPa to about 6 GPa, about 5 GPa to about 7 GPa, or about 6 GPa to about 7 GPa. Within the GPa range, the internal tank temperature is approximately 1100°C to approximately 1500°C, approximately 1100°C to approximately 1600°C, approximately 1100°C to approximately 1700°C, approximately 1100°C to approximately 1800°C, approximately 1200°C to approximately 1500°C, approximately 1200°C to approximately 1600°C, approximately 1200°C to approximately 1700°C, approximately 1200°C to approximately 1800°C, approximately 1300°C to approximately 1400°C, approximately 1300°C to approximately 1400°C, approximately 1300°C to approximately 1500°C, approximately 1200°C to approximately 1600°C, approximately 1200°C to approximately 1700°C, approximately 1200°C to approximately 18 ...300°C to approximately 1700°C, approximately 1200°C to approximately 1800°C, approximately 1300°C to approximately 1400°C, approximately 1300°C to approximately 1700°C, approximately 1200°C to approximately 1800°C, approximately 1300°C to approximately 170 The temperatures range from 0°C to approximately 1500°C, from approximately 1300°C to approximately 1600°C, from approximately 1300°C to approximately 1700°C, from approximately 1300°C to approximately 1800°C, from approximately 1400°C to approximately 1500°C, from approximately 1400°C to approximately 1600°C, from approximately 1500°C to approximately 1600°C, from approximately 1500°C to approximately 1700°C, from approximately 1500°C to approximately 1800°C, from approximately 1600°C to approximately 1800°C, or from approximately 1700°C to approximately 1800°C. The converted cBN material is recovered, and all remaining non-cBN material is removed by a series of chemical reactions, such as dissolution with a reactive acid, leaving the formed cBN, and specifically dissolving unreacted hBN and unreacted catalyst material. A suitable reactive acid can be selected based on the solubility of hBN and catalyst material present in the formed cBN sample. Examples of such reactive acids typically include, but are not limited to, ferric chloride, copper 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 used.

[0076] In this invention, additional niobium dopant is added to the system to prevent it from catalyzing the hexagonal-to-cubic transformation of boron nitride (BN). This is done to trap trace amounts of niobium dopant within the transformed lattice structure while simultaneously transforming BN from a hexagonal to a cubic form. This can be achieved in several ways, but the most uniform approach is to incorporate the niobium dopant into the original dopant mixture of hBN and the catalyst material. Alternatively, niobium dopant can be added by placing a solid layer of dopant material around the HPHT reactor.

[0077] When all non-cBN materials are reacted, the niobium dopants incorporated into the cBN lattice structure during the conversion from hBN and subsequent cBN crystal growth remain within the cBN lattice. Unbound by any particular theory, it is believed that these niobium dopant atoms, with atomic sizes different from boron and nitrogen atoms, will deform and thereby impose strain on the cBN lattice structure of the cBN grains. This deformation will cause an internal stress field to form around the heavy niobium dopants. When a load is applied to the cBN crystal during the machining of the material, this will act as a weak zone, making the cBN crystal more prone to fracture under lower applied loads.

[0078] The toughness of the cBN crystals manufactured from this specification can be measured using a crystal toughness test known as the Toughness Index (TI) test. To perform this test, the cBN crystals are typically first sorted by size using a series of sieves, and only those cBN crystals of interest are selected, such as those that pass through a 60-mesh sieve but not an 80-mesh sieve. It is worth noting that the sieve mesh number is typically the number of septa per inch, thus causing higher mesh numbers to allow only finer particles to pass through. Once the desired cBN crystal size is determined, a specified weight of cBN crystal is placed in a small tube containing tungsten carbide (WC) spheres. The tube is then agitated for a specific period of time, typically one to ten hours. During this agitation process, the WC spheres fall back and forth, physically impacting the cBN crystals and often causing internal breakage within the individual cBN crystals. After shaking is complete, the cBN crystals are removed from the tube and then passed through a sieve again to specifically measure the amount of broken cBN crystals. TI can then be defined as the percentage of cBN crystals that did not break during the shaking procedure using the WC ball. In the example above, if, for example, 70% of the cBN crystals still did not pass through an 80-mesh sieve after the shaking procedure using the WC ball, then the cBN crystals would be characterized as having a TI of 70.

[0079] Another test for the strength of cBN crystals is the Thermal Toughness Index (TTI) test. This test is performed in the same manner as the TI test. However, before placing the cBN crystals into a tube containing WC spheres, they are heated to a temperature sufficient to cause thermal damage. Typical applied temperatures can be approximately 1100°C to approximately 1500°C, approximately 1100°C to approximately 1600°C, approximately 1100°C to approximately 1700°C, approximately 1100°C to approximately 1800°C, approximately 1200°C to approximately 1500°C, approximately 1200°C to approximately 1600°C, approximately 1200°C to approximately 1700°C, approximately 1200°C to approximately 1800°C, approximately 1300°C to approximately 1400°C, and approximately 1300°C to approximately... The temperatures range from approximately 1500°C to approximately 1300°C to approximately 1600°C, approximately 1300°C to approximately 1700°C, approximately 1300°C to approximately 1800°C, approximately 1400°C to approximately 1500°C, approximately 1400°C to approximately 1600°C, approximately 1500°C to approximately 1600°C, approximately 1500°C to approximately 1700°C, approximately 1500°C to approximately 1800°C, approximately 1600°C to approximately 1800°C, or approximately 1700°C to approximately 1800°C. This test shows the degree of degradation caused by the applied high temperatures. Upon completion of the test, it can be combined with TI tests to provide a reasonable estimate of the toughness of cBN crystals in applications such as, for example, grinding wheels, where the grinding force may generate heat.

[0080] Figure 3 is a flowchart showing the various process steps for preparing self-sharpening cBN particles incorporating niobium inclusions 26 according to the present invention. In step 30, a mixture comprising a plurality of hBN particles and catalyst 25 is first formed. In step 32, a niobium foil is placed in a reaction zone adjacent to the mixture comprising the plurality of hBN particles and catalyst 25. In step 34, the process is finally completed by reacting the components of the mixture with the niobium foil in a cubic press under HPHT conditions sufficient to form self-sharpening cBN particles. Niobium 26 and catalyst 25 are substantially retained in the inclusions within the self-sharpening cBN abrasive particles 28, causing microfractures in the self-sharpening cBN particles 28 to expose at least one new cutting surface or at least one new cutting edge within the self-sharpening cBN particles 28.

[0081] The formed self-sharpening cBN particles 28 can then be used as a functional component of the vitrified cBN grinding wheel 10A. The wheel 10A is sharpened throughout the entire machining cycle of the workpiece. This is accomplished by rubbing the self-sharpening cBN particles 28 of the vitrified cBN grinding wheel 10A against the workpiece to promote the blunting of the cutting surface of the self-sharpening cBN particles 28. The vitrified cBN grinding wheel 10A includes self-sharpening cBN particles 28, catalyst material 25, and niobium 26. The catalyst material 25 and niobium 26 are retained in inclusions within the self-sharpening cBN particles 28. Next, the self-sharpening cBN particles 28, the catalyst material 25, and the niobium 26 interact to cause micro-fractures in the self-sharpening cBN particles 28, thereby exposing at least one new cutting surface or at least one new cutting edge in the self-sharpening cBN particles 28 during the friction of the glassy cBN grinding wheel 10A against the workpiece.

[0082] Those skilled in the art will know in practice how the HPHT conversion from hBN to cBN is typically performed. Therefore, readers may additionally refer to U.S. Patent Nos. 6,814,775B2 and 10,196,314B2 for further understanding of the HPHT conversion procedure and method, which are incorporated herein by reference in their entirety.

[0083] Example

[0084] The following embodiments are provided to give those skilled in the art a complete disclosure and description of how to make and use the described subject matter, but are not intended to limit the scope of what the inventors consider their invention, nor are they intended to represent all or only the experiments conducted. Efforts have been made to ensure the accuracy of the figures used, but some experimental errors and biases should be taken into account.

[0085] Example 1

[0086] Compared to cubic boron nitride (cBN) particles without niobium inclusions, cBN particles containing niobium inclusions exhibit a reduced toughness index (TI) and a reduced thermal toughness index (TTI).

[0087] Table 1 shows the toughness index (TI) and thermal toughness index (TTI) results for cBN particles 28 containing niobium inclusions 26 and those without niobium inclusions 26, respectively.

[0088] [Table 1] Aspect Ratio [Resilience Index ()] [TI] [)] [Thermal toughness index ()] [TTI] [)] [Including niobium] [cBN] 0.770 69.9 66.0 [Including niobium] [cBN] 0.758 71.9 67.1 [customary knowledge] [cBN] 0.741 72.5 70.0

[0089] As shown in Table 1, the TI and TTI results of cBN particles 28 containing niobium inclusions 26 are lower compared to cBN particles 28 without niobium inclusions 26. The TI of cBN particles 28 with niobium inclusions 26 is reduced by approximately 0.8% to approximately 3.6% compared to cBN particles 28 without niobium inclusions 26. Furthermore, the TTI of cBN particles 28 with niobium inclusions 26 is reduced by approximately 4.1% to approximately 5.7% compared to cBN particles 28 without niobium inclusions 26. The reduction in TI and TTI leads to microfractures in the cBN particles 28 containing niobium inclusions 26 during machining of the workpiece. This is due to internal growth defects formed by stress generated within the cBN lattice structure, which manifest as fracture sites caused by niobium inclusions 26 within the cBN lattice structure.

[0090] To further characterize the microstructure of cBN crystals, Figure 4A shows the microstructure of cBN crystals without niobium inclusions at 40x magnification, where the cBN particles were pressed using a belt press according to this standard. In contrast, Figure 4B shows the microstructure of cBN crystals containing niobium inclusions at 40x magnification, where the cBN particles were pressed using a cubic press according to this standard. Microstructure analysis of the cBN crystals reveals that, compared to the cBN crystals without niobium inclusions depicted in Figure 4A, the cBN crystals containing niobium inclusions shown in Figure 4B have a more robust and bulky shape. This will promote more uniform cBN grinding wheel wear, resulting in a more consistent cBN grinding wheel form from the beginning to the end of the cBN grinding wheel's lifespan.

[0091] Example 2

[0092] The use of glassy cBN grinding wheels containing niobium-inclusion cubic boron nitride (cBN) particles for creeping grinding of M2 steel and transverse grinding of 4140 steel showed improved grinding performance compared to grinding wheels containing cBN particles without niobium inclusions.

[0093] Experiments were conducted in which M2 steel was slowly ground using a glassy cBN grinding wheel containing niobium inclusions and cubic boron nitride (cBN) particles, wherein the cBN particles were pressed using a cubic press. Alternatively, M2 steel was slowly ground using a glassy cBN grinding wheel containing niobium-free cBN particles, wherein the cBN particles were pressed using a belt press.

[0094] Further experiments were also conducted, in which 4140 steel was again transversely ground using a glassy cBN grinding wheel containing niobium inclusions, wherein the cBN particles were pressed using a cubic press, or 4140 steel was transversely ground using a glassy cBN grinding wheel containing niobium-free cBN inclusions, wherein the cBN particles were pressed using a belt press.

[0095] The wheel preparation technique was optimized to maximize grinding performance. The grinding test standards included in the experiments are as follows: Wheel run-out (TIR) ​​after dressing was less than 3.0 µm, and wheel balance displacement was less than 0.3 µm. The cBN grinding wheel specifications are as follows: The bonding type is a vitrified cBN bond with a continuous rim. The wheel size is 178 mm D x 6.35 mm W x 3.2 mm rim layer, and the mesh size is B126 (120 / 140 mesh). The wheel has a glass substrate or core, and the applied speed is 60 m / s.

[0096] Table 2 shows the experimental conditions for slow-progress grinding.

[0097] [Table 2] [machine] Blohm 15 hp CNC surface grinder [Grinding Mode] Gradual grinding (upward cutting only) [Wheel speed] [] [(V, s , )] 45 m / s (9,000 SFPM) [Depth of Cut] [] [(a, e , )] 1.02 mm (0.040”) [Workbench Speed] [] [(v, w , )] 508 mm / min (20 ipm) [Cutting width] [] [(b, d , )] 3.2 mm (0.125”) [Arc Contact Length] Arc contact length: 13.44 mm (0.5292”) [Workpiece Material] AISI M2 tool steel (HRC 62) [Cutting length] 102 mm (4.0”) [Material removal rate] [] [(Q / , w , )] 8.6 mm3 / mm / sec (0.80 in3 / in / min) [Coolant] 5% concentration water-soluble oil [Coolant flow rate] 117 liters / min x 10.3 bar (31 gpm x 150 psi) / inlet and outlet nozzles

[0098] Table 3 illustrates the experimental conditions for transverse grinding.

[0099] [Table 3] [machine] Blohm 15 hp CNC surface grinder [Grinding Mode] Lateral grinding (downward cutting only) [Wheel speed] [(V, s , )] 60 m / s (12,000 SFPM) [Depth of Cut] [] [(a, e , )] 0.13 mm (0.0050”) [Workbench Speed] [] [(v, w , )] 5.08 mm / min (200 ipm) [Cutting width] [] [(b, d , )] 4.75 mm (0.187”) [Arc Contact Length] Arc contact length: 13.44 mm (0.5292”) [Workpiece Material] AISI 4140 tool steel (HRC 53) [Cutting length] 305 mm (12.0”) [Material removal rate] [] [(Q / w)] 10.8 mm3 / mm / sec (1.0 in3 / in / min) [Coolant] 5% concentration water-soluble oil [Coolant flow rate] 98 liters / min x 6.9 bar (26 gpm x 100 psi) / inlet and outlet nozzles

[0100] According to this specification, as shown in Figure 5B, creeping grinding is a grinding method used to achieve high material removal rates with a large depth of cut (ae), while the conventional transverse grinding technique of this specification results in a shallower depth of cut (ae) as shown in Figure 5A. Compared with the conventional transverse grinding technique, creeping grinding essentially features a large depth of cut (ae), a low workpiece speed (Vw), a long wheel / workpiece contact length (i.e., a long stroke), a much higher average contact temperature, a much higher total grinding force, and a finer surface finish.

[0101] Table 4 shows the wheel specifications.

[0102] [Table 4] [Wheel Type] 1A1 [Combination Type] Vitrified cBN (continuous rim) [Wheel Size] 178 mm D x 6.35 mm W x 3.2 mm flange layer [Sieve Mesh Size] B126 (120 / 140 mesh) [concentration] 150 [Wheel Core] Glass [Radial] [Feedback] [ / ] [pass] 0.012 mm (0.00005”) [rate] 60 m / s

[0103] Table 5 shows the wheel preparation conditions.

[0104] [Table 5] [Adjustment device] Powder Rotation [Costume Dressing Type] 1A1 Metal-Combined Diamond Wheel [Costume Dressing Wheel Size] 152 mm D x 2.54 mm W (6.0” x 0.100”) [Sieve Mesh Size] 50 / 60 [concentration] 50 [Trim Speed ​​Ratio] +0.4 (one-way) [Radial] [Feedback] [ / ] [pass] 0.012 mm (0.00005”) [Adjusting the guide] [ / ] [Number of revolutions] 0.203 mm (0.008)

[0105] Figure 6A shows the standardized results of slow-feed grinding of M2 steel using glass-modified cBN grinding wheels with the following: cBN particles containing niobium inclusions, where the cBN particles are pressed using a cubic press, or cBN particles without niobium inclusions, where the cBN particles are pressed using a belt press. The standardized results show the grinding ratio, power, and surface finish (i.e., 100%) of cBN particles containing niobium inclusions pressed using a cubic press compared to cBN particles without niobium inclusions pressed using a belt press.

[0106] Figure 6B shows the standardized results of transverse grinding of 4140 steel again using glass-modified cBN grinding wheels with the following: cBN particles containing niobium inclusions, where the cBN particles were pressed using a cubic press, or cBN particles without niobium inclusions, where the cBN particles were pressed using a belt press. The standardized results show the grinding ratio, power, and surface finish (i.e., 100%) of cBN particles containing niobium inclusions pressed using a cubic press compared to cBN particles without niobium inclusions pressed using a belt press.

[0107] As shown in Figures 6A and 6B, the combined results of the slow-forward grinding of M2 steel and the transverse grinding of 4140 steel using a glassy cBN grinding wheel containing niobium inclusions show that, compared with a cBN grinding wheel without niobium inclusions, the grinding efficiency is improved by approximately 6% (results in column 2 of Figure 6B) to approximately 13% (results in column 3 of Figure 6A).

[0108] Importantly, it is noteworthy that the surface finish obtained when using a glassy cBN grinding wheel incorporating niobium-containing cBN particles for the slow-motion grinding of M2 steel and the transverse grinding of 4140 steel is improved compared to a cBN grinding wheel with cBN particles free of inclusions. As shown in Figures 6A and 6B, the achieved surface finish is reduced by approximately 4% to approximately 21%. Without wishing to be bound by any particular theory, these results are likely due to the formation of bulk cBN crystal shapes and the increased aspect ratio of the cBN crystals (whose microstructure incorporates niobium inclusions) compared to cBN crystals free of niobium inclusions, as seen in Table 1.

[0109] Finally, maintaining crystal structure characteristics that contribute to low grinding power is highly advantageous. Results show that, compared to cBN grinding wheels with cBN particles free of niobium inclusions, the grinding power of glassy cBN grinding wheels incorporating cBN particles containing niobium inclusions is generally slightly, but disadvantageously, higher, ranging from approximately 96% to approximately 105%, as shown in Figures 6A and 6B. This is likely due to the higher aspect ratio of the cBN crystals containing niobium inclusions in Table 1.

[0110] Although this disclosure has been described in conjunction with embodiments thereof, those skilled in the art will understand that additions, deletions, modifications and substitutions not specifically described may be made without departing from the spirit and scope of this disclosure as defined in the appended claims.

[0111] Regarding any plural and / or singular terms used substantially herein, those skilled in the art can appropriately convert plural to singular and / or singular to plural depending on the context and / or application. For clarity, various singular / plural substitutions are not explicitly described herein.

[0112] The objects described herein sometimes refer to different components contained in or connected to different other components. It should be understood that the architectures depicted are merely illustrative, and many other architectures can actually be implemented to achieve the same functionality. Conceptually, the configuration of components that achieve the same functionality is effectively "associated" to achieve the desired function. Therefore, any two components combined in this document to achieve a specific function can be considered as "associated" with each other to achieve the desired function, regardless of the architecture or intermediate components. Similarly, any two such associated components can also be considered as "operably connected" or "operably coupled" to each other to achieve the desired function, and any two components that can be suchly associated can also be considered as "operably coupled" to each other to achieve the desired function. Specific examples of operational coupling include, but are not limited to, physically compatible and / or physically interacting components, and / or wirelessly interacting and / or wirelessly interacting components, and / or logically interacting and / or logically interacting components.

[0113] In some contexts, 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, unless the context otherwise requires, such terms (e.g., "configured") generally encompass active state components, and / or inactive state components, and / or standby state components.

[0114] Although specific aspects of the subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based on the teachings herein, changes and modifications may be made without departing from the subject matter and its broader aspects. Therefore, the appended claims will cover, within their scope, all such changes and modifications to the true spirit and scope of the subject matter as described herein. Those skilled in the art will understand that, in general, the terminology used herein, and particularly in the appended claims (e.g., the body of the appended claims), is intended to be "open" terms (e.g., the term "comprising" should be interpreted as "including but not limited to," the term "having" should be interpreted as "at least having," the term "including" should be interpreted as "including but not limited to," etc.).

[0115] Those skilled in the art will further understand that if a specific number of claims is intended to be introduced, such an purpose will be explicitly stated in the claim, and without such a statement, such a purpose does not exist. For example, to aid understanding, the appended claims may contain the introductory phrases “at least one” and “one or more” to introduce claims. However, the use of such phrases should not be construed as implying that a claim introduced by the indefinite article “a (a, an)” limits any particular claim containing such an introduction to a claim containing only one such claim, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a (a, an)” (e.g., “a (a and / or an)” should typically be interpreted as meaning “at least one” or “one or more”); the same applies to the use of definite articles to introduce claims.

[0116] Furthermore, even if the specific number of the claims is clearly stated, those skilled in the art will recognize that such a statement is typically to be interpreted as meaning at least the number stated (e.g., a simple statement of "two statements" without other modifiers typically means at least two statements, or two or more statements).

[0117] Furthermore, in those cases, where the convention is similar to "at least one of A, B, and C, etc.", generally, such wording is intended to be understood by a person skilled in the art in the sense of convention (e.g., "a system having at least one of A, B, and C" includes, but is not limited to, systems having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). In those cases, where the convention is similar to "at least one of A, B, or C, etc.", generally, such wording is intended to be understood by a person skilled in the art in the sense of convention (e.g., "a system having at least one of A, B, or C" includes, but is not limited to, systems having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). Unless the context otherwise requires, those skilled in the art will further understand that, typically whether in a specification, claim, or drawing, separate terms and / or phrases presenting two or more alternative terms should be understood as implying the possibility of including one, one, or both of such terms. For example, the phrase "A or B" will typically be understood as implying the possibility of including "A" or "B" or "A and B".

[0118] Regarding the appended claims, those skilled in the art will understand that the operations described therein can generally be performed in any order. Furthermore, although various operational flows are shown in one or more sequences, it should be understood that various operations can be performed in other orders different from those shown, or can be performed simultaneously. Unless the context otherwise indicates, examples of such alternative orderings may include overlapping, interleaving, discontinuous, reordering, ascending, preparatory, supplementary, simultaneous, reverse, or other variations of ordering. Moreover, unless the context otherwise indicates, terms such as "responsive to," "related to," or other past tense adjectives are generally not intended to exclude such variations.

[0119] Those skilled in the art will understand that the aforementioned specific exemplary processes and / or apparatus and / or techniques represent more general processes and / or apparatus and / or techniques taught elsewhere herein, such as those taught in the claims filed in this application and / or elsewhere.

[0120] Although various embodiments and examples have been disclosed herein, other embodiments and examples will be apparent to those skilled in the art. The various embodiments and examples disclosed herein are for illustrative purposes only and are not intended to be limiting; the true scope and spirit are indicated by the appended claims.

[0121] The illustrative embodiments described in the implementation methods, drawings, and claims are not intended to be limiting. Other examples and changes may be used without departing from the spirit or scope of the subject matter presented herein.

[0122] Where a numerical range is provided, it should be understood that unless the context explicitly specifies otherwise, each intermediate value between the upper and lower limits of the range and one-tenth of the lower limit unit of any other stated or intermediate value within the range is included in this disclosure. The upper and lower limits of such smaller ranges may be independently included within the smaller range and are also included in this disclosure, but are subject to any explicit exclusions from the range. Where the range includes one or both of the included limitations, the range excluding both of those included limitations is also included in this disclosure.

[0123] Those skilled in the art will recognize that the components (e.g., operation), apparatus, purpose, and accompanying discussion described herein are used as examples for clarity of concept, and various configuration modifications are contemplated. Therefore, as used herein, the specific examples illustrated and the accompanying discussions are intended to represent their more general categories. In general, the use of any particular example is intended to represent its category, and the exclusion of a particular component (e.g., operation), apparatus, and purpose should not be considered a limitation.

[0124] Furthermore, any sequence and / or chronological order of sequences in the systems and methods described herein are illustrative and should not be construed as inherently restrictive. Therefore, it should be understood that process steps may be shown and described in sequence or chronological order, but are not necessarily limited to any particular sequence or order. For example, steps in such processes or methods can typically be performed in various different sequences and orders, while still falling within the scope of this disclosure.

[0125] Finally, the applications and / or patents discussed herein are provided only for inventions filed before the date of such application. Nothing in this document should be construed as an admission that the invention is exempt from rights prior to such disclosure due to prior disclosure.

[0126] 10: cBN grinding wheel 10A: Glass-converted cBN grinding wheel 11: Aluminum or steel wheel core or base 11A: Aluminum or steel core or substrate 12: Abrasive layer 12A: Abrasive layer 13A: Cutting edge / cutting surface 24: Vitrification 25: Catalytic materials 26: Niobium 28: cBN particles / cBN abrasive particles / cBN grinding particles 30: Steps 32: Steps 34: Steps ae: Depth of cut vw: Workpiece speed

Claims

1. A method for manufacturing self-sharpening cubic boron nitride (cBN) particles, comprising: forming a mixture comprising a plurality of hexagonal boron nitride (hBN) particles and a catalyst; placing a niobium foil in a reaction zone adjacent to the mixture comprising the plurality of hBN particles and the catalyst; and reacting the components of the mixture with the niobium foil under high pressure and high temperature (HPHT) conditions to form self-sharpening cBN particles; wherein the niobium and the catalyst are retained in inclusions within the self-sharpening cBN particles, causing microfractures in 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.

2. The method for manufacturing self-sharpening cBN particles as claimed in claim 1, wherein the HPHT conditions include an internal tank pressure in the range of 4 gigapascals (GPa) to 8 GPa and an internal tank temperature in the range of 1100°C to 1800°C.

3. The method for manufacturing self-sharpening cBN particles as claimed in claim 1, wherein the concentration of niobium incorporated into the crystal structure of the cBN particles is in the range of 50 to 200 parts per million (ppm).

4. The method for manufacturing self-sharpening cBN particles as claimed in claim 3, wherein the concentration of niobium incorporated into the crystal structure of the cBN particles is in the range of 50 ppm to 100 ppm.

5. The method for manufacturing self-sharpening cBN particles as claimed in claim 3, wherein the concentration of niobium incorporated into the crystal structure of the cBN particles is in the range of 100 ppm to 150 ppm.

6. The method for manufacturing self-sharpening cBN particles as claimed in claim 3, wherein the concentration of niobium incorporated into the crystal structure of the cBN particles is in the range of 150 ppm to 200 ppm.

7. The method for manufacturing self-sharpening cBN particles as claimed in claim 6, wherein the concentration of niobium incorporated into the crystal structure of the cBN particles is in the range of 175 ppm to 200 ppm.

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

9. The method for manufacturing self-sharpening cBN particles as claimed in claim 1, further comprising incorporating the self-sharpening cBN particles into a vitrified cBN grinding wheel.

10. The method for manufacturing self-sharpening cBN particles as claimed in claim 9, wherein the cBN particles containing niobium inclusions exhibit an improvement in grinding efficiency of up to 13% compared to cBN particles without niobium inclusions.

11. The method for manufacturing self-sharpening cBN particles as claimed in claim 10, wherein the cBN particles containing niobium inclusions exhibit an improvement in grinding efficiency of up to 10% compared to cBN particles without niobium inclusions.

12. The method for manufacturing self-sharpening cBN particles as claimed in claim 11, wherein the cBN particles containing niobium inclusions exhibit an improvement in grinding efficiency of up to 6% compared to cBN particles without niobium inclusions.

13. The method for manufacturing self-sharpening cBN particles as claimed in claim 10, wherein the cBN particles containing niobium as an inclusion exhibit an improvement in grinding efficiency in the range of 6% to 13% compared to cBN particles without niobium inclusions.

14. The method for manufacturing self-sharpening cBN particles as claimed in claim 9, wherein the cBN particles containing niobium inclusions exhibit a reduction in toughness index (TI) of 0.8% to 3.6% compared to cBN particles without niobium inclusions.

15. The method for manufacturing self-sharpening cBN particles as claimed in claim 9, wherein the cBN particles containing niobium inclusions exhibit a 4.1% to 5.7% reduction in thermal toughness index (TTI) compared to cBN particles without niobium inclusions.

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

17. A method for sharpening a glass-modified cBN grinding wheel during the machining of a workpiece, comprising: rubbing self-sharpening cBN particles of the glass-modified cBN grinding wheel against the workpiece, the glass-modified cBN grinding wheel comprising the self-sharpening cBN particles; a catalyst material; and niobium; the catalyst material and the niobium being retained in inclusions within the self-sharpening cBN particles; and during the rubbing of the self-sharpening cBN particles of the glass-modified cBN grinding wheel against the workpiece, causing the self-sharpening cBN particles, the catalyst material, and the niobium to interact, resulting in microfractures in the self-sharpening cBN particles to expose at least one new cutting surface or at least one new cutting edge within the self-sharpening cBN particles.

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

19. The method of sharpening a glassy cBN grinding wheel during the machining of a workpiece as claimed in claim 17, wherein the cBN particles containing niobium inclusions exhibit a reduction in toughness index (TI) of 0.8% to 3.6% compared to cBN particles without niobium inclusions.

20. The method of sharpening a glassy cBN grinding wheel during the machining of a workpiece as claimed in claim 17, wherein the cBN particles containing niobium inclusions exhibit a 4.1% to 5.7% reduction in thermal toughness index (TTI) compared to cBN particles without niobium inclusions.

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