Sintered polycrystalline cubic boron nitride material

Abstract

To develop viable alternative materials for tooling operations that perform well under extreme conditions.SOLUTION: The present disclosure relates to a polycrystalline cubic boron nitride material that includes cBN particles in a metal matrix containing zirconium nitride and / or vanadium nitride precipitates or grains.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a sintered polycrystalline cubic boron nitride material and a method for manufacturing such a material.

Background Art

[0002] Polycrystalline superhard materials such as polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) can be used as a variety of tools for cutting, turning, drilling, or grinding hard materials or abrasives such as rocks, metals, ceramics, composite materials, and wood-containing materials. Abrasive compacts are widely used in cutting, turning, grinding, lapping, drilling, and other abrasive operations. They typically contain superhard abrasive particles dispersed in a second-phase matrix. The matrix can be a metal, ceramic, or cermet. The superhard abrasive particles can be diamond, cubic boron nitride (cBN), silicon carbide, or silicon nitride, etc. These particles can bond to each other during the high-pressure and high-temperature compact manufacturing process to form a polycrystalline mass, or bond through the matrix of the second-phase material(s) to form a sintered polycrystalline body. Such substances are usually known as polycrystalline diamond or polycrystalline cubic boron nitride, in which case they contain diamond or cBN as the superhard abrasive, respectively. U.S. Patent No. 4,334,928 teaches a sintered body for use as a tool, which consists essentially of 20 to 80% by volume of cubic boron nitride and the balance which is a matrix of at least one matrix composite selected from the group consisting of carbides, nitrides, carbonitrides, borides, and silicides of Group IVa or Va transition metals of the periodic table, mixtures thereof, and solid solution compounds thereof. The matrix forms a continuous bonding structure with high-pressure boron nitride scattered in the continuous matrix in the sintered body. All of the methods outlined in this patent require combining the desired materials using mechanical grinding / mixing techniques such as ball milling and mortar. Sintered polycrystals can be "back processed" by shaping them on a substrate. Cemented carbides can be used to form a suitable substrate, for example, formed from carbide particles / grains of tungsten carbide and cobalt mixed together and then heated and solidified, from dispersed carbide particles in a cobalt matrix. To form a cutting element having a hard material layer such as PCD or PCBN, diamond particles or grains or CBN grains are placed adjacent to the cemented carbide body in a refractory metal housing such as a niobium housing and subjected to high pressure and high temperature so that intergranular bonding occurs between the diamond grains or CBN grains, forming a polycrystalline diamond or polycrystalline CBN layer.

[0003] In some cases, the substrate is fully hardened before being bonded to the hard material layer, while in other cases, the substrate can be green (not fully hardened material). In the latter case, the substrate can be fully hardened during the HTHP sintering process. The substrate may be in powder form or may solidify during the sintering process used to sinter the hard material layer. Figure 1 shows an exemplary method for manufacturing a sintered PCBN material. The following numbering corresponds to that in Figure 1: S1. The matrix precursor powder is premixed. Examples of matrix precursor powders include carbides and / or nitrides of titanium and aluminum. The typical average particle size of the matrix precursor powder is 1 μm to 10 μm. S2. The matrix precursor powder is heat-treated at over 1000 °C for at least 1 hour to initiate a preliminary reaction between the matrix precursor particles and form a "cake". S3. The cake is crushed and sieved to obtain the desired particle size fraction. S4. Cubic boron nitride (cBN) particles with an average particle size of 0.5 μm to 15 μm are added to the sieved matrix precursor powder. S5. The resulting mixed powder is crushed by ball milling until the matrix precursor powder reaches the desired size (usually 50 nm to 700 nm), and the precursor powder and cBN particles are homogeneously mixed. This step may take several hours and requires a grinding medium such as tungsten carbide balls. S6. The obtained pulverized powder is dried at a temperature exceeding 60°C under vacuum or reduced pressure to remove the solvent, and then oxygen is slowly introduced into the system to passivate the metal surface such as aluminum, thereby bringing it into an appropriate state. S7. The dried powder is sieved to produce a pre-composite construct. S8. The pre-composite construct is heat-treated at a temperature exceeding 700°C to remove adsorbed water or gas. S9. The gas-evolving pre-composite construct is incorporated into a capsule suitable for sintering. S10. The capsule is sintered in a high-pressure high-temperature (HPHT) process at at least 1250°C and at least 4 GPa to form a sintered PCBN material.

[0004] Both tungsten (W) and cobalt (Co) are classified as critical raw materials (CRMs) in Europe. CRMs are raw materials that are considered economically and strategically important for the European economy. In principle, they are associated with high risks regarding their supply, are extremely important for major sectors of the European economy such as household appliances, environmental technologies, automotive, aerospace, defense, health, and steel, and furthermore, there are no (realistic) substitutes for them. Both tungsten and cobalt are major components of two important classes of hard materials, sintered carbides / WC-Co, and PCD / diamond-Co. Summary of the Invention

[0005] One object of the present invention is to develop a feasible alternative material for tool work that functions well under extreme conditions. In one aspect of the present invention, a polycrystalline cubic boron nitride (PCBN) material is provided, the material comprising 30 to 90 volume % of cubic boron nitride (cBN) particles; a matrix material having a content of 10 volume % to 70 volume % of the PCBN material in which the cBN particles are dispersed therein; the matrix material comprising either a titanium compound and an aluminum compound, or a mixture thereof; the matrix material comprising precipitates and / or grains containing zirconium and / or vanadium, and optionally further comprising tungsten and / or titanium; the precipitates and / or grains being substantially spherical, platelet-like or needle-like, and the precipitates and / or grains having an average maximum length dimension of 1 μm or less. The precipitates and / or grains may comprise nitrides, carbides, carbonitrides and / or diborides. Optionally, the zirconium-containing precipitates and / or grains, and / or the vanadium-containing precipitates and / or grains, comprise 10 volume % to 25 volume % of the PCBN material. Optionally, the zirconium-containing precipitates and / or grains, and / or the vanadium-containing precipitates and / or grains, comprise 10 volume %, or 17.5 volume %, or 25 volume % of the PCBN material. The zirconium-containing precipitates and / or grains, and / or the vanadium-containing precipitates and / or grains, may have an average maximum length dimension of 0.50 μm or less. Alternatively, the zirconium-containing precipitates and / or grains, and / or the vanadium-containing precipitates and / or grains, may have an average maximum length dimension of 0.20 μm or less. The matrix material may comprise any one of titanium carbonitride, titanium carbide, titanium nitride, titanium diboride, aluminum nitride and aluminum oxide. The PCBN material may comprise 10 volume % to 25 volume % of titanium carbide, TiC or titanium nitride, TiN. The PCBN material may further comprise 5 volume % of aluminum, Al, or a compound thereof. Preferably, the PCBN material comprises 60 volume % of cubic boron nitride (cBN). As one option, the cBN particles have an average size of 0.5 μm to 15 μm. Preferably, the PCBN material has a Vickers microhardness of 26 GPa to 34 GPa.

[0006] In a second aspect of the present invention, a method for manufacturing a polycrystalline cubic boron nitride (PCBN) material is provided, the method comprising: The step of grinding the following precursor powders together: Cubic boron nitride (cBN), Vanadium-containing powder and / or zirconium-containing powder, and Powder containing either aluminum or titanium, The step of compressing the ground precursor powders to form a green compact, Sintering the green compact at a temperature of 1800 °C to 2300 °C and a pressure of 7.0 GPa to 8.5 GPa to form a sintered PCBN material, The sintered PCBN material contains cubic boron nitride (cBN) particles dispersed in a matrix material containing zirconium-containing precipitates and / or vanadium-containing precipitates, and optionally tungsten-containing precipitates and / or titanium-containing precipitates, and the precipitates have an average maximum length dimension of 1 μm or less. As one option, the temperature is 1800 °C to 1900 °C. Optionally, the step of grinding the precursor powders together includes the following two sub-steps: The step of grinding the vanadium-containing powder and / or zirconium-containing powder over a certain period of time, The step of adding cubic boron nitride powder and aluminum and / or titanium-containing powder, The step of grinding all the precursor powders together for a further certain period of time. The method may further include dividing the green compact into several parts before the sintering step.

[0007] In a third aspect of the present invention, a tool comprises a PCBN material according to the first aspect of the present invention. Preferably, the tool is a tool for cutting, turning, grinding, milling, drilling, or other abrasive applications. Non-limiting embodiments are described hereinafter with reference to the accompanying drawings for illustrative purposes.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying Out the Invention

[0009] The composition of the material shown in the SEM photograph of the above figure was confirmed using transmission electron microscope (TEM) analysis. Figure 2 is a flow diagram showing exemplary steps. The following numbering corresponds to that of Figure 2. S1. The precursor powders of zirconium-containing powder and / or vanadium-containing powder, and the powder containing carbides and / or nitrides of titanium and aluminum are ground together to form a homogeneous mixture and obtain a desired particle size. The precursor powder mixing was carried out using ball milling technology in an organic solvent and drying by a rotary evaporator. S2. The ground powders are dry-pressed together to form a green compact having a strength suitable for handling during processing. Specifically, after drying, the powders are filled into a soft mold and pressed using a cold isostatic press to compress the powders and form a green compact. The formed body is then cut into different heights so as to be accommodated in a high pressure high temperature (HPHT) capsule. S3. The dry-pressed green compact is then sintered in a high temperature vacuum heat treatment and in an HPHT capsule at a temperature of at least 1800 °C (for example, 1800 °C, 1900 °C, 2000 °C, and 2200 °C) and a pressure of about 8 GPa for a certain period of at least 30 seconds. The sintering temperature was calibrated up to 1800 °C using an S-type thermocouple. S4. After sintering, the obtained sintered product is cooled to room temperature. The cooling rate is uncontrolled. Cooling results in the desired precipitation of VN-containing precipitates and / or ZrN-containing precipitates and optionally W and / or Ti-containing precipitates.

Example

[0010] Table 1 lists all the PCBN compositions included in this study together with a TiC reference sample (i.e., a sample that does not use ZrN or VN in the binder).

Table 1

[0011] Visual inspection after sintering Figures 3, 4, 5, 6, and 7 show SEM photographs of different PCBN grades sintered at 1800°C. They are all homogeneous. In these images, the color contrast is due to differences in atomic weight. The cBN component is the lightest and stands out as a very dark / black color in these images. The ceramic component (such as VN or ZrN) appears as a gray phase in the SEM images, and the heaviest metal component (such as WC contamination from ball milling) stands out as bright / white particles. The results have revealed that the powder mixing method results in a homogeneous distribution of the cBN and ceramic components.

[0012] Hardness Inspection after Sintering The next step was to understand the influence of the sintering conditions on the properties of the materials. These materials were tested by indentation using the 1 Kg Vickers indentation method, the hardness results were calculated, and summarized in Table 2. The indentations were made with a Wolpert 572 indenter, and the indentations were measured in the SEM to improve the accuracy (since the indentations were on the order of 20 microns in size).

Table 2

[0013] Application Screening Tests Next, samples were selected for the application screening tests. These samples are shown in Table 3.

Table 3

Table 4

[0014] The chemical composition of the material Ovako 677 by the manufacturer is shown in Table 5. The balance is iron. Briefly speaking, it is 67CrSi4.

Table 5

Table 6

[0015] Microstructure Analysis A more detailed inspection of the microstructure revealed the presence of specific precipitates in the binder microstructure, which can be characterized as being substantially spherical, platelet - like, or needle - shaped. These are summarized in Table 7.

Table 7

[0016] Definitions As used herein, "PCBN" means a type of superhard material comprising grains of cBN dispersed within a matrix comprising metal or ceramic. PCBN is an example of a superhard material. As used herein, "matrix material" is understood to mean a matrix material that completely or partially fills the pore, crack or interstitial regions in a polycrystalline structure. The term "matrix precursor powder" is used to mean a powder that becomes the matrix material when subjected to a high-pressure high-temperature sintering process. A multimodal particle size distribution of a large number of particles is understood to mean particles having a particle size distribution in which the particles have two or more peaks, with each peak corresponding to a respective "mode". A multimodal polycrystal can be produced by providing a plurality of particles of two or more origins, each origin including particles having a substantially different average particle size, and mixing together the particles or grains from that origin. In one embodiment, the PCBN material can include cBN grains having a multimodal distribution.

[0017] The claims refer to the average particle size. This is measured using the equivalent circular diameter (ECD) technique. The ECD distribution of a plurality of loose, unbound and non-aggregated particles can be measured by laser diffraction, in which case the particles are randomly placed in the path of the incident light and the diffraction pattern resulting from the diffraction of the light by the particles is measured. That diffraction pattern is mathematically interpreted as if it were generated by a plurality of spherical particles, its diameter distribution is calculated and reported as an ECD. The interpretation of the particle size distribution can be expressed in terms of various statistical characteristics using various terms and symbols. Specific examples of such terms include the mean, median and mode. The particle size distribution can be considered as a series of values Di corresponding to each size channel, where each Di is the geometric mean ECD value corresponding to the respective channel i, and i is an integer in the range from 1 to the number n of channels used.

[0018] While the invention has been shown and described in detail with reference to embodiments, it will be understood by those skilled in the art that various changes in form and detail can be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A polycrystalline cubic boron nitride (PCBN) material comprising: 30 to 90% by volume of cubic boron nitride (cBN) particles; A matrix material in which the cBN particles are dispersed internally, wherein the content of the matrix material is 10% to 70% by volume of the PCBN material, The matrix material contains either a titanium compound and an aluminum compound, or a mixture thereof; The matrix material further contains zirconium and / or vanadium, and optionally, precipitates and / or grains containing tungsten and / or titanium; The precipitates and / or grains have a shape that is substantially spherical, platelet-like, or needle-like; The precipitates and / or grains have an average maximum length dimension of 1 μm or less, a PCBN material.

2. The PCBN material according to claim 1, wherein the precipitates and / or grains contain nitrides, carbides, carbonitrides, and / or diborides.

3. The PCBN material according to claim 1 or 2, wherein zirconium-containing precipitates and / or grains, and / or vanadium-containing precipitates and / or grains are contained in the PCBN material at 10% to 25% by volume.

4. The PCBN material according to claim 1, 2, or 3, wherein zirconium-containing precipitates and / or grains, and / or vanadium-containing precipitates and / or grains are contained in the PCBN material at 10% by volume, or 17.5% by volume, or 25% by volume.

5. The PCBN material according to any one of claims 1 to 4, wherein zirconium-containing precipitates and / or grains, and / or vanadium-containing precipitates and / or grains have an average maximum length dimension of 0.50 μm or less.

6. The PCBN material according to any one of claims 1 to 5, wherein zirconium-containing precipitates and / or grains, and / or vanadium-containing precipitates and / or grains have an average maximum length dimension of 0.20 μm or less.

7. The PCBN material according to any one of claims 1 to 6, wherein the matrix material contains any one of titanium carbonitride, titanium carbide, titanium nitride, titanium diboride, aluminum nitride, and aluminum oxide.

8. The PCBN material according to claim 7, containing 10% to 25% by volume of titanium carbide (TiC) or titanium nitride (TiN).

9. The PCBN material according to any one of claims 1 to 8, further containing 5% by volume of aluminum (Al) or a compound thereof.

10. The PCBN material according to any one of claims 1 to 9, comprising 60% by volume of cubic boron nitride (cBN).

11. The PCBN material according to any one of claims 1 to 10, wherein the cBN particles have an average size of 0.5 μm to 15 μm.

12. The PCBN material according to any one of claims 1 to 11, wherein the PCBN material has a Vickers microhardness of 26 GPa to 34 GPa.

13. A method for manufacturing a polycrystalline cubic boron nitride (PCBN) material, comprising: grinding the following precursor powders together: cubic boron nitride (cBN), a vanadium-containing powder and / or a zirconium-containing powder, and a powder containing either aluminum or titanium; compressing the ground precursor powders to form a green compact; sintering the green compact at a temperature of 1800°C to 2300°C and a pressure of 7.0 GPa to 8.5 GPa to form a sintered PCBN material, wherein the PCBN material comprises particles of cubic boron nitride (cBN) dispersed in a matrix material containing zirconium and / or vanadium, and optionally tungsten and / or titanium-containing precipitates and / or grains, and the precipitates and / or grains have an average maximum length dimension of 1 μm or less.

14. The method according to claim 13, wherein the temperature is 1800°C to 1900°C.

15. The method for manufacturing a PCBN material according to claim 13 or 14, wherein the step of grinding the precursor powders together comprises the following two sub-steps: grinding the vanadium-containing powder and / or the zirconium-containing powder for a certain period of time, adding the cubic boron nitride powder and the aluminum and / or titanium-containing powder, and grinding all the precursor powders together for a further certain period of time.

16. The method for manufacturing a PCBN material according to claim 13, 14 or 15, further comprising the step of dividing the green compact into several parts before the sintering step.

17. A tool comprising the PCBN material according to any one of claims 1 to 12.

18. The tool according to claim 17, which is a tool for cutting, turning, grinding, milling, drilling, or other polishing applications.

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