Ultrahigh-pressure-resistant and high-temperature-resistant tungsten carbide anvil cell and ceramic assembly

Abstract

The invention discloses an ultrahigh-pressure-resistant and high-temperature-resistant tungsten carbide anvil cell and a ceramic assembly, and belongs to the technical field of metal powder processing and high temperature and high pressure. The preparation method of the tungsten carbide anvil cell comprises the following steps: grinding cobalt powder, rhodium powder and tungsten carbide powder for 24 hours, drying for 2 hours, pressing into a block blank under 50-100 MPa, carrying out vacuum sintering, cutting into a cubic block, and polishing a triangular cut corner with the side length of 3 mm at one corner. The assembly comprises a cubic tungsten carbide anvil (1), an octahedral pressure transmitting medium (2) and a pyrophyllite sealing edge (3), the octahedral pressure transmitting medium (2) comprises a regular octahedron (201), a sample bin (202), a first pair of plugs (203), a second pair of plugs (204), a third pair of plugs (205) and the like. The tungsten carbide alloy sintered by the method disclosed by the invention has ultrahigh Vickers hardness and transverse breaking strength. The designed assembly can generate an ultrahigh-pressure high-temperature environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluid pressure technology, and particularly relates to a method for preparing a tungsten carbide anvil resistant to ultra-high pressure and high temperature environments by using cobalt powder, rhodium powder and tungsten carbide powder, and a pressure unit assembly resistant to ultra-high pressure and high temperature environments composed of the tungsten carbide anvil. Background Art

[0002] A tungsten carbide anvil is a high-performance material made of tungsten carbide (WC) and a binder alloy, and is known for its high strength, high hardness, wear resistance, toughness and excellent thermal stability. It is widely used in high-pressure devices such as large chamber presses and is a key component of high-pressure synthesis technology, mainly used in fields such as superhard material synthesis, geological research, simulation of the deep earth environment and exploration of new materials. In large chamber ultra-high pressure and high temperature devices, tungsten carbide anvils and their ceramic assemblies are essential and key materials to achieve extreme pressure and temperature conditions, and their performance directly determines whether the device can stably and efficiently generate an ultra-high pressure and high temperature extreme environment. However, the existing technology still faces bottlenecks. For example, the cobalt content of traditional tungsten carbide anvils is relatively high, resulting in a low ultimate pressure and easy plastic deformation; the control of WC grain size and microstructure is unreasonable, which limits its performance under high temperature and high pressure conditions; the preparation process of high-performance anvils is complex, which restricts their large-scale application. In addition, the Kawai-type large volume press (KLVP) has become one of the commonly used devices in high-pressure scientific research due to its user-friendliness. Although traditional KLVPs using conventional anvils and commercial assemblies can generate temperatures above 1500 K, their pressure generating capacity is usually limited to 25 GPa. Chinese Patent ZL2024102183848 (previous research results of this research group) discloses a method for improving the pressure boosting efficiency of a large chamber press based on the principle of large mass support. By using a diamond plug, the pressure boosting efficiency is improved, and a higher pressure can be generated inside the chamber under a lower oil pressure, and the ultimate pressure can reach about 27 GPa. However, this method still cannot meet the requirements of some high-pressure tests (above 30 GPa) at room temperature, and cannot perform temperature rising operations, and can only generate high pressure at room temperature, which limits its application in experimental scenarios where high temperature and higher pressure coexist, and further restricts the research on the deep lower mantle of the earth and new materials under extreme high pressure. Therefore, it is crucial to develop high-strength, tough and high-hardness tungsten carbide anvils and high-efficiency ceramic assemblies. By optimizing the material composition (such as reducing the cobalt content and increasing more favorable metal materials) and optimizing the structural design of the assembly, the ultimate pressure, thermal fatigue resistance and pressure transfer efficiency of the anvil can be significantly improved, thereby achieving higher pressure and temperature limits and improving the operating stability and service life of the device. In summary, high-strength, tough and high-hardness tungsten carbide anvils and high-efficiency ceramic assemblies are the prerequisites for generating ultra-high pressure and high temperature extreme environments in large chambers, and are of great significance for promoting the development of ultra-high pressure and high temperature technologies. Summary of the Invention

[0003] The object of the present invention is to overcome the deficiencies existing in the background art and provide a method for preparing a tungsten carbide anvil resistant to ultra-high pressure and high temperature environments using cobalt powder, rhodium powder and tungsten carbide powder, as well as a tungsten carbide anvil ceramic assembly resistant to ultra-high pressure and high temperature for a Kawai-type press.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A method for preparing a tungsten carbide anvil resistant to ultra-high pressure and high temperature, comprising the following steps: First, put cobalt powder, rhodium powder and tungsten carbide powder into a ball mill and grind for 24 h, where the mass fraction of cobalt powder is 3-5 wt%, the mass fraction of rhodium powder is 1-3 wt%, and the balance is tungsten carbide powder. After grinding, take it out and dry it in a vacuum drying furnace for 2 h. Then, press the mixed powder into a block blank under a pressure of 50-100 MPa by a powder briquetting machine, put it into a vacuum sintering furnace, evacuate, raise the temperature to 1500-1900 °C and hold for 0.5-1 h to obtain a low-cobalt microcrystalline hard tungsten carbide alloy. Cut it into a cubic block with a side length of 25.4 mm with a diamond wire saw, and grind a triangular cut with a side length of 3 mm at one corner of the cubic block to obtain a cubic tungsten carbide anvil resistant to ultra-high pressure and high temperature.

[0006] A tungsten carbide anvil ceramic assembly resistant to ultra-high pressure and high temperature, the structure comprising eight cubic tungsten carbide anvils 1, an octahedral pressure transmitting medium 2 and a pyrophyllite sealing edge 3; the structure of the octahedral pressure transmitting medium 2 comprises a regular octahedron 201 and a sample chamber 202, the sample chamber 202 being located at the center of the regular octahedron 201, the side length of the regular octahedron 201 being 8 mm, the distance between opposite faces being 6.3 mm, the sample chamber 202 being cylindrical in shape, with an outer diameter of 1.6 mm, an inner diameter of 0.8 mm and a height of 1.5 mm, and on both ends of the sample chamber 202, there are symmetrically distributed in sequence from the inside out a first pair of cylindrical plugs 203, a second pair of disc-shaped plugs 204 and a third pair of cylindrical plugs 205, wherein the bottom diameter of the first pair of plugs 203 is 0.8 mm, and the height of each plug is 0.5 mm; the bottom diameter of the second pair of plugs 204 is 1.6 mm, and the thickness of each plug is 0.25 mm; the bottom diameter of the third pair of plugs 205 is 1.6 mm, and the height of each plug is 1.9 mm; there is a pair of inner cylinders 206 between the second pair of plugs 204 and the sample chamber 202, the outer diameter of each inner cylinder 206 being 1.6 mm, the inner diameter being 0.8 mm and the height being 0.25 mm, a middle cylinder 207 is sleeved outside the sample chamber 202, the inner diameter of the middle cylinder 207 being 1.6 mm, the outer diameter being 1.8 mm and the height being 6.3 mm, an outer cylinder 208 is sleeved outside the middle cylinder 207, the outer diameter of the outer cylinder 208 being 3.7 mm, the inner diameter being 1.8 mm and the height being 6.3 mm, a thermocouple 209 is located on one side of the third pair of plugs 205, and the sample chamber 202, the first pair of plugs 203, the second pair of plugs 204, the third pair of plugs 205, the inner cylinders 206, the middle cylinder 207 and the outer cylinder 208 are coaxial; the regular octahedron 201 is a material of magnesium oxide doped with 5 wt% chromium trioxide, the sample chamber 202 is a hard alumina material, the first pair of plugs 203 is a boron-doped diamond material, the second pair of plugs 204 is a hard alumina material, the third pair of plugs 205 is a hard magnesium oxide material, the inner cylinders 206 are boron nitride materials, the middle cylinder 207 is a rhenium metal material, the outer cylinder 208 is a zirconia material, the thermocouple 209 is a tungsten-rhenium type thermocouple, and the middle of the sample chamber 202 is used to fill the sample 210, and the height of the sample 210 is 1.0 mm;

[0007] The pyrophyllite 3 is fixed after truncating the corners of each cubic tungsten carbide anvil 1, and the eight cubic tungsten carbide anvils 1 are combined to form an octahedral cavity for placing the octahedral pressure transmitting medium 2, thereby forming a tungsten carbide anvil ceramic assembly resistant to ultra-high pressure and high temperature.

[0008] Further, the pyrophyllite sealing edge 3 is in the shape of a frustum of a square pyramid and is divided into two sizes. One is the long pyrophyllite sealing edge, with specific dimensions: the length of the long side is 14.5 mm, the length of the short side is 7.9 mm, the distance between the long side and the short side is 3.4 mm, and the thickness is 2.4 mm; the other is the short pyrophyllite sealing edge, with specific dimensions: the length of the long side is 11.3 mm, the length of the short side is 4.7 mm, the distance between the long side and the short side is 3.4 mm, and the thickness is 2.4 mm.

[0009] Beneficial effects:

[0010] 1. The low-cobalt microcrystalline hard tungsten carbide alloy sintered by the method of the present invention has a Vickers hardness of 1800 HV and a transverse rupture strength of 2050 Mpa.

[0011] 2. The tungsten carbide anvil and the ceramic ultra-high pressure and high temperature assembly of the present invention reach an ultra-high pressure of 50 GPa and achieve a high temperature exceeding 1900 K ( Figure 6 ), and operate stably for 12 h, simulating the temperature and pressure environment in the lower part of the lower mantle, and obtaining bridgmanite existing in this environment ( Figure 7 ). In the traditional large chamber press combined with the traditional tungsten carbide anvil assembly, the above-mentioned temperature and pressure have not been achieved simultaneously before.

[0012] 3. The tungsten carbide anvil and the ceramic assembly of the present invention are not damaged after being heated for 12 hours and then depressurized to normal pressure, and can be recycled. Description of the drawings

[0013] Figure 1 is the electron micrograph of the ultra-high pressure and high temperature resistant hard tungsten carbide alloy prepared in Example 1.

[0014] Figure 2 is the schematic diagram of the external structure of the ultra-high pressure and high temperature resistant tungsten carbide anvil ceramic assembly in Example 2.

[0015] Figure 3 is the schematic diagram of the internal structure of the ultra-high pressure and high temperature resistant tungsten carbide anvil ceramic assembly in Example 2.

[0016] Figure 4 is the schematic diagram of the octahedral pressure transmitting medium of the Kawai-type press.

[0017] Figure 5 is the internal assembly schematic diagram of the octahedral pressure transmitting medium.

[0018] Figure 6 is the temperature change curve following the adjusted power in the ultra-high pressure and high temperature experiment in Example 3.

[0019] Figure 7It is the backscattered image after polishing of aluminous bridgmanite obtained in Example 3 under the conditions of 50 GPa and 1900 K with heat preservation for 12 h. Specific implementation mode

[0020] Example 1 Preparation of tungsten carbide anvils resistant to ultra-high pressure and high temperature

[0021] Weigh tungsten carbide (WC) powder with a particle size of 0.5 μm by a balance, add 4 wt% of cobalt (Co) and 1 wt% of rhodium (Rh). After weighing, put it into a grinding jar and prepare uniform powder particles through ball milling. The ball-to-material ratio is 10:1, the parameter is adjusted to 300 revolutions per minute. Every 1 hour of grinding, stop for 20 minutes, and the total duration is 20 hours. Cold-press the mixed initial alloy powder into a large-size bulk powder blank by a cold press, with the pressure around 50 Mpa. After demolding, put it into a vacuum sintering furnace. When the vacuum degree reaches 10 -3 ~10 -5 Pa, then raise the temperature with the parameter of 10 °C / min until the temperature reaches 1700 °C. After heat preservation for half an hour, cool down at 10 °C / min. After cooling to room temperature, obtain a sintered dense cemented carbide blank. Cut the sintered blank with a diamond wire saw into a cubic tungsten carbide block with a side length of 25.4 mm, and the cutting parameter is 1000 revolutions per minute and the feed rate is 5 mm / min. Then use a precision grinding machine to grind a truncated corner with a side length of 3 mm at one of the vertex positions, with the grinding wheel speed of 10000 revolutions per minute and the feed rate of 0.5 mm / min. Prepare 8 tungsten carbide anvils resistant to ultra-high pressure and high temperature by the above method, Figure 1 It is the electron microscope photo at the fracture, with its Vickers hardness reaching 1800 HV and the transverse rupture strength reaching 2050 MPa.

[0022] Example 2 Preparation of tungsten carbide anvil ceramic assembly resistant to ultra-high pressure and high temperature

[0023] Figure 2 It is the schematic diagram of the tungsten carbide anvil ceramic assembly resistant to ultra-high pressure and high temperature of the present invention. Figure 3 It is the schematic diagram of its internal structure, specifically including 8 cubic tungsten carbide anvils 1 prepared by the method of Example 1; the octahedral pressure transmission medium 2 is a regular octahedron of a conventional Kawai-type press (such as Figure 4 shown), and the unique internal structure is as shown in Figure 5As shown in the figure; and the pyrophyllite sealing edge 3. The specific method is as follows: Drill a through hole with a diameter of 3.7 mm at the center of the regular octahedron 201. Use a carving machine to cut zirconia into a cylinder with an outer diameter of 3.7 mm, an inner diameter of 1.8 mm, and a height of 6.3 mm, and place it into the through hole of the regular octahedron 201 to obtain the outer cylinder 208. Roll a rhenium metal sheet into a cylinder with an outer diameter of 1.8 mm, an inner diameter of 1.6 mm, and a height of 6.3 mm, and place it into the outer cylinder 208 to obtain the middle cylinder 207. After preparation, assemble the remaining parts from bottom to top. First, place one of the magnesium oxides (one of the third pair of plugs 205) with a height of 1.9 mm and a diameter of 1.6 mm processed by the carving machine at the bottom of the middle cylinder 207. Then place an alumina wafer (one of the second pair of plugs 204) with a height of 0.25 mm and a diameter of 1.6 mm processed by the carving machine. Next, place a boron nitride cylinder (one of the inner cylinders 206) with a height of 0.25 mm, an outer diameter of 1.6 mm, and an inner diameter of 0.8 mm processed by the carving machine. Place a boron-doped diamond (one of the first pair of plugs 203) with a diameter of 0.8 mm and a height of 0.5 mm processed by a laser cutting machine inside the inner cylinder 206. Then place an alumina sample chamber 2 with a height of 1.5 mm, an outer diameter of 1.6 mm, and an inner diameter of 0.8 mm processed by the carving machine. Then place the sample 210 inside the sample chamber 2. Regarding sample preparation: Weigh the oxide powders of Al2O3, MgO, and SiO2 with a purity of 99.9% using a balance according to a molar ratio of 1:1:1, place them in a mortar, and grind and mix them thoroughly by adding alcohol for two hours. After mixing, put them into an oven and dry them in a vacuum at 100°C for 12 h to obtain the MgAl2SiO4 oxide powder. After placing the sample 210, place the other one of the first pair of plugs 203, then place the other one of the inner cylinders 206, and then place the other one of the second pair of plugs 204. Drill two through holes with a diameter of 0.2 mm and a spacing of 0.7 mm from the upper bottom surface to the lower bottom surface of the magnesium oxide cylinder for the other one of the processed third pair of plugs 205. Tie the thermocouple 209 and place it into the through holes. Then place the magnesium oxide cylinder at the top of the inner cylinder 207 and seal the surface with magnesium oxide powder. So far, the ultra-high pressure and high-temperature resistant ceramic assembly is ready. The pyrophyllite sealing edge 3 is processed into a frustum of a pyramid shape by a carving machine, and there are two sizes. One of them is: the long side length is 14.5 mm, the short side length is 7.9 mm, the spacing between the long side and the short side is 3.4 mm, and the thickness is 2.4 mm; the other one is: the long side length is 11.3 mm, the short side length is 4.7 mm, the spacing between the long side and the short side is 3.4 mm, and the thickness is 2.4 mm. Use white glue to fix it behind the truncated corner of the cubic tungsten carbide anvil 1. The short side of the pyrophyllite is parallel to the truncated corner edge, and the long side pyrophyllite and the short side pyrophyllite are alternately matched so that when they are spliced together, it is exactly the shape of a hollow octahedron. Then place the assembled octahedral pressure-transmitting medium 2 on Figure 3In the cavity formed by the four tungsten carbide anvils 1 and the pyrophyllite sealing edges 3 shown, and place another four identical cubic tungsten carbide anvils 1 on Figure 3 above the structure shown, thus forming a cubic-shaped tungsten carbide anvil ceramic assembly resistant to ultra-high pressure and high temperature (as Figure 2 shown).

[0024] Example 3 Ultra-high pressure and high temperature generation experiment

[0025] Place the assembled tungsten carbide anvil ceramic assembly resistant to ultra-high pressure and high temperature in a Kawai press to increase the pressure at a rate of 0.5 MN / h until the pressure reaches 6.4 MN. After reaching the target pressure, start heating. As Figure 6 shown, by increasing the power to 340 W and reading the corresponding temperature inside the assembly through a thermocouple as 1900 K, maintain the temperature for 10 h to allow MgAl2SiO4 to fully react and reach chemical equilibrium completely. Then, quench to room temperature within 10 s by directly adjusting the power to 0 W. After quenching, release the pressure to atmospheric pressure to obtain the sample. MgAl2SiO4 will form two crystalline minerals under high temperature and high pressure: bridgmanite (MgSiO3) and corundum (Al2O3). Among them, bridgmanite will dissolve part of Al2O3 in its crystal structure as the pressure and temperature increase. By measuring the content of Al2O3 in bridgmanite after high temperature and high pressure quenching and substituting it into the equation of state X = -52 + 1.19*P - 0.008*P 2 + 0.023*(T - 300), the actual pressure inside the cavity under high temperature and high pressure can be obtained, where X represents the molar percentage of Al2O3 in bridgmanite, T represents the temperature (unit K), and P represents the pressure (unit GPa). Polish the sample with a 0.5-micron diamond polishing disc and then conduct electron probe testing on it. Figure 7 is the backscattered imaging photo taken during the testing process. The electron probe analysis results show that the content of Al2O3 in bridgmanite is 24.4 ± 0.23 mol%. Substitute the temperature and the content of Al2O3 into the above equation of state to obtain a pressure of 50 ± 1 GPa. Thus, it is determined that the assembly of the present invention can reach a pressure of 50 GPa at a high temperature of 1900 K. And no failure phenomena such as blasting occurred in multiple experiments, enabling the tungsten carbide anvils to be reused, saving costs. This has never been achieved in using a traditional Kawai press with traditional tungsten carbide anvils.

[0026] As can be seen from Example 3, the tungsten carbide anvil and ceramic assembly of the present invention that are resistant to ultra-high pressure and high temperature can stably operate at a super-high pressure of 50 GPa at a high temperature of 1900 K for 12 h, which is a super-high pressure record that has never been achieved before using a traditional Kawai press with a tungsten carbide anvil. This is mainly attributed to the tungsten carbide anvil ceramic assembly of the present invention that is resistant to ultra-high pressure and high temperature.

Claims

1. A preparation method of a tungsten carbide anvil resistant to ultra-high pressure and high temperature, comprising the following steps: First, put cobalt powder, rhodium powder and tungsten carbide powder into a ball mill and grind for 24 h, where the mass fraction of cobalt powder is 3-5 wt%, the mass fraction of rhodium powder is 1-3 wt%, and the balance is tungsten carbide powder. After grinding, take it out and dry it in a vacuum drying furnace for 2 h. Then, press the mixed powder into a blank of a block at 50-100 MPa through a powder pressing machine, put it into a vacuum sintering furnace. After evacuating, raise the temperature to 1500-1900 °C and keep it warm for 0.5-1 h to obtain a low-cobalt microcrystalline hard tungsten carbide alloy. Cut it into a cube with a side length of 25.4 mm by a diamond wire saw, and grind a triangular truncated corner with a side length of 3 mm at one corner of the cube to obtain a cubic tungsten carbide anvil resistant to ultra-high pressure and high temperature.

2. A tungsten carbide anvil ceramic assembly resistant to ultra-high pressure and high temperature, the structure comprising eight cubic tungsten carbide anvils (1), an octahedral pressure transmitting medium (2) and a pyrophyllite sealing edge (3); characterized in that, The cubic tungsten carbide anvil (1) is prepared by the method according to Claim 1. The structure of the octahedral pressure transmitting medium (2) includes a regular octahedron (201) and a sample chamber (202). The sample chamber (202) is located at the center of the regular octahedron (201). The side length of the regular octahedron (201) is 8 mm, and the distance between two opposite faces is 6.3 mm. The sample chamber (202) is in a cylindrical shape, with an outer diameter of 1.6 mm, an inner diameter of 0.8 mm, and a height of 1.5 mm. At both ends of the sample chamber (202), a first pair of cylindrical plugs (203), a second pair of disc-shaped plugs (204), and a third pair of cylindrical plugs (205) are symmetrically distributed from the inside to the outside in sequence. The bottom diameter of the first pair of plugs (203) is 0.8 mm, and the height of each plug is 0.5 mm; the bottom diameter of the second pair of plugs (204) is 1.6 mm, and the thickness of each plug is 0.25 mm; the bottom diameter of the third pair of plugs (205) is 1.6 mm, and the height of each plug is 1.9 mm; there is a pair of inner cylinders (206) between the second pair of plugs (204) and the sample chamber (202). The outer diameter of each inner cylinder (206) is 1.6 mm, the inner diameter is 0.8 mm, and the height is 0.25 mm. The middle cylinder (207) is sleeved outside the sample chamber (202). The inner diameter of the middle cylinder (207) is 1.6 mm, the outer diameter is 1.8 mm, and the height is 6.3 mm. The outer cylinder (208) is sleeved outside the middle cylinder (207). The outer diameter of the outer cylinder (208) is 3.7 mm, the inner diameter is 1.8 mm, and the height is 6.3 mm. The thermocouple (209) is located on one side of the third pair of plugs (205). The sample chamber (202), the first pair of plugs (203), the second pair of plugs (204), the third pair of plugs (205), the inner cylinders (206), the middle cylinder (207), and the outer cylinder (208) are coaxial. The regular octahedron (201) is made of a material with 5 wt% chromium sesquioxide doped with magnesia. The sample chamber (202) is made of hard alumina material. The first pair of plugs (203) is made of boron-doped diamond material. The second pair of plugs (204) is made of hard alumina material. The third pair of plugs (205) is made of hard magnesia material. The inner cylinders (206) are made of boron nitride material. The middle cylinder (207) is made of rhenium metal material. The outer cylinder (208) is made of zirconia material. The thermocouple (209) is a tungsten-rhenium type thermocouple. The middle of the sample chamber (202) is used to fill the sample (210), and the height of the sample (210) is 1.0 mm; The pyrophyllite (3) is fixed to each truncated cubic tungsten carbide anvil (1), and then eight cubic tungsten carbide anvils (1) are combined to form an octahedral cavity for placing the octahedral pressure transmitting medium (2), thereby forming a tungsten carbide anvil ceramic assembly resistant to ultra-high pressure and high temperature.

3. A tungsten carbide anvil ceramic assembly resistant to ultra-high pressure and high temperature according to claim 2, characterized in that, The pyrophyllite sealing edge (3) is in the shape of a frustum of a square pyramid and is divided into two sizes. One is the long pyrophyllite sealing edge, and the specific dimensions are as follows: the length of the long side is 14.5 mm, the length of the short side is 7.9 mm, the distance between the long side and the short side is 3.4 mm, and the thickness is 2.4 mm. The other is the short pyrophyllite sealing edge, and the specific dimensions are as follows: the length of the long side is 11.3 mm, the length of the short side is 4.7 mm, the distance between the long side and the short side is 3.4 mm, and the thickness is 2.4 mm.

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