Wear-resistant and corrosion-resistant heterostructure hard alloy material and preparation method thereof

Abstract

The invention discloses a wear-resistant and corrosion-resistant heterostructure hard alloy material and a preparation method thereof.The preparation method comprises the steps that firstly, modified WC powder is prepared through liquid-liquid doping, then the modified WC powder and Co powder are subjected to wet grinding and spray drying, WC-Co spherical mixed powder with enough strength is obtained through calcination, then the WC-Co spherical mixed powder, WC powder with different granularities, Fe powder, Ni powder and Co powder are subjected to three-section ball milling, and composite powder is obtained; and finally, the composite powder is sintered, and the hetero-structure hard alloy material is prepared. The wear-resistant and corrosion-resistant heterostructure hard alloy material disclosed by the invention has high hardness, high toughness and high corrosion resistance; under the dual effects of corrosion and abrasion, the material can effectively delay the corrosion process, the service life of the material is remarkably prolonged, and the material is very suitable for the application fields of high-end equipment manufacturing, mining machinery, abrasion-resistant parts and the like; the material has higher adaptability and reliability, and can meet multiple requirements on material performance under complex working conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of cemented carbide material preparation, and specifically relates to a cemented carbide material with a heterogeneous structure and a preparation method thereof, and more specifically relates to a wear-resistant and corrosion-resistant cemented carbide material with a heterogeneous structure and a preparation method thereof. Background Art

[0002] With its excellent hardness, strength and good wear resistance, cemented carbide is widely used in cutting tools, mining machinery, molds and wear-resistant parts. However, with the continuous development of industrial technology and the increasingly harsh complex working conditions, traditional cemented carbide has gradually exposed some limitations during use. Especially under extreme conditions such as high temperature, high pressure and strong corrosion, how to simultaneously meet the high hardness and high toughness of the material has always been a difficult technical bottleneck to overcome. High hardness usually means higher wear resistance, but the increase in hardness is often accompanied by a decrease in toughness, which makes the material prone to brittle cracking or breakage under complex stress conditions. At the same time, in order to cope with the strong corrosive environment in industrial production, the corrosion resistance of the material is also crucial. However, while pursuing high hardness and high toughness, the corrosion resistance is often not effectively guaranteed, which accelerates the failure of the material during service due to the combined effects of chemical corrosion and mechanical wear.

[0003] This performance contradiction severely limits the application scope of traditional cemented carbide, and also forces related fields to make a trade-off between hardness, toughness and corrosion resistance, making it difficult to achieve comprehensive optimization of performance. Therefore, how to break through this technical bottleneck and develop cemented carbide materials with high hardness, high toughness and excellent corrosion resistance has become one of the key technical problems in the field of materials science and related industrial applications. Solving this challenge can not only significantly extend the service life of the material and improve its reliability under complex working conditions, but also provide more ideal key materials for high-end equipment manufacturing and other fields, which has important theoretical significance and practical value. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention aims to provide a wear-resistant and corrosion-resistant heterostructure cemented carbide material and a preparation method thereof. The cemented carbide material has high hardness, high toughness and excellent corrosion resistance, and can be used in complex and harsh working environments.

[0005] The technical solution of the present invention: A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof, comprising the following steps: S1. Dissolve tungstate, vanadate and organic carbon source in an appropriate amount of deionized water, heat and stir at a certain temperature, evaporate to form a precursor precipitate, and then dry it in a drying oven. After drying, grind and sieve to obtain a precursor powder with uniform particle size; S2, calcining the precursor powder, reducing and carbonizing it with hydrogen, and then sieving to obtain modified WC powder; S3, mixing the modified WC powder and the Co powder, wet grinding, spray drying to obtain WC-Co spherical mixed powder, and then calcining the WC-Co spherical mixed powder to ensure that the spherical mixed powder has sufficient strength; S4, placing high-purity Fe powder, Ni powder and Co powder in a ball mill for the first wet grinding, then adding WC powder of different particle sizes for the second wet grinding, and finally adding calcined WC-Co spherical mixed powder for the third wet grinding; S5. Dry and sieve the mixed powder slurry after three wet grindings, and then put it into a graphite mold. First, use a hydraulic press to pre-press the composite powder, and then put it into a vacuum discharge plasma sintering furnace for sintering, so as to obtain a heterogeneous structure cemented carbide material with excellent comprehensive performance.

[0006] Preferably, the tungstate, vanadate and organic carbon source in S1 are ammonium metatungstate, ammonium metavanadate and glucose, respectively, and their addition amounts are calculated based on the contents of WC and VC in the final WC-VC composite powder, the content of VC is 0.5 wt%, and the balance is WC, wherein the carbon content in WC is 6.14%.

[0007] Preferably, in S1, oil bath heating is adopted, and the heating temperature is 120-140° C.; the drying temperature is 120-130° C., and the drying time is 4-8 hours; after drying, the mixture is ground and sieved through a 120-mesh sieve.

[0008] Preferably, in S2, the calcination temperature is 550-650° C., the calcination time is 2-4 h; the carbonization temperature is 1250-1350° C., the carbonization time is 2-4 h, and the hydrogen flow rate is 4-6 L / min.

[0009] Preferably, the medium for wet grinding the modified WC powder and Co powder in S3 is anhydrous ethanol, the ball-to-material ratio is (4-6):1, the ball milling time is 20-26h, and the ball milling speed is 220-280r / min.

[0010] Preferably, the air inlet temperature of the spray drying in S3 is 120-200° C., the feed rate is 60-180 mL / min, and the spray pressure is 0.6-2 MPa.

[0011] Preferably, the calcination temperature in S3 is 900-1200° C., and the calcination time is 1.5-3.5 hours.

[0012] Preferably, in the first wet grinding in S4, the mass ratio of Fe powder, Ni powder and Co powder is 1:2:2, the ball-to-material ratio is (6-10):1, the ball milling time is 26-30h, and the ball milling speed is 250-350r / min.

[0013] Preferably, the WC particle sizes of the second wet grinding in S4 are 8 μm, 4 μm and 2 μm, the ball-to-material ratio is (3-5):1, the ball milling time is 20-26 h, and the ball milling speed is 120-160 r / min.

[0014] Preferably, the ball-to-material ratio of the third wet milling in S4 is (1-2):1, the ball milling time is 6-12 hours, and the ball milling speed is 80-120 r / min.

[0015] Preferably, the drying temperature of the mixed powder slurry in S5 is 75-85°C, the drying time is 4-6h, and the mesh size is 100 mesh; the sintering temperature is 600°C for 5min, 1200-1300°C for 4-8min, the heating rate is 100°C / min, and the sintering pressure is 50MPa.

[0016] Beneficial effects of the present invention: (1) The present invention overcomes the technical bottleneck of traditional cemented carbide that the toughness decreases when the hardness is increased through innovative heterogeneous structure design, and achieves an organic combination of high hardness and high toughness; (2) Through the optimization of special alloy composition and microstructure, the cemented carbide material of the present invention exhibits excellent performance in corrosion resistance, especially under the dual effects of corrosion and wear, the material can effectively delay the corrosion process and significantly improve its service life; (3) The heterogeneous structure cemented carbide material used in the present invention can comprehensively improve the hardness, toughness and corrosion resistance, so that the material has stronger adaptability and reliability in application fields such as high-end equipment manufacturing, mining machinery and wear-resistant parts, and meets the multiple requirements for material performance under complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a morphology diagram of the heterogeneous structure cemented carbide material prepared in Example 1; Figure 2 This is the morphology of the traditional cemented carbide material prepared in Comparative Example 3. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below with reference to specific embodiments.

[0019] Example 1 S1. Dissolve ammonium metatungstate, ammonium metavanadate and glucose in an appropriate amount of deionized water, heat and stir in an oil bath at 130°C, evaporate to form a precursor precipitate, and then dry in a drying oven at a drying temperature of 125°C for 5 hours. After drying, grind through a 120-mesh sieve to obtain a precursor powder with uniform particle size. The mass of ammonium metatungstate, ammonium metavanadate and glucose is calculated based on the WC and VC contents in the final WC-VC composite powder. The VC content is 0.5wt%, the WC content is 99.5%, and the carbon content in WC is 6.14%; S2. The precursor powder is calcined and then reduced and carbonized by hydrogen, and then sieved to obtain modified WC powder. The calcination temperature is 600°C, the calcination time is 3h, the carbonization temperature is 1300°C, the carbonization time is 2.5h, and the hydrogen flow rate is 5L / min.

[0020] S3, the modified WC powder and Co powder were mixed and wet-milled, the ball-to-material ratio was 4:1, the ball milling time was 26h, the ball milling speed was 240r / min, wherein the content of WC powder was 94%, and the content of Co powder was 6%; after the wet milling, the WC-Co spherical mixed powder was obtained by spray drying, the inlet air temperature of the spray drying was 150°C, the feed rate was 100 mL / min, and the spray pressure was 1.5Mpa; then the spherical mixed powder was calcined, the calcination temperature was 1100°C, and the calcination time was 2h to ensure that the spherical mixed powder had sufficient strength; S4, high purity Fe powder, Ni powder and Co powder were placed in a ball mill for the first wet grinding, the mass ratio of Fe:Ni:Co powder was 1:2:2, the ball to material ratio was 8:1, the ball milling time was 28h, and the ball milling speed was 300r / min; then WC powders of different particle sizes were added for the second wet grinding, the ball to material ratio was 4:1 (the total powder mass in the current ball mill), the ball milling time was 24h, the ball milling speed was 150r / min, and the WC particle sizes were 8μm, 4μm and 2μm, the mass ratio is 1:1:1, the content of total WC powder is 90%, the content of FeNiCo powder is 10%, and finally the WC-Co spherical mixed powder calcined in S3 is added for the third wet grinding, the ball-to-material ratio is 1.5:1 (the total powder mass in the current ball mill), the ball milling time is 10h, the ball milling speed is 85r / min, the content of WC-Co spherical mixed powder is 60%, and the rest is WC-FeNiCo mixed powder; S5. Dry and sieve the wet-milled mixed powder slurry at 80°C for 4 hours and with a sieve mesh of 100 meshes. Then put it into a graphite mold, pre-press the composite powder with a hydraulic press, and then sinter it in a vacuum plasma sintering furnace at a heating rate of 100°C / min and a sintering pressure of 50 MPa. First, heat it to 600°C and keep it for 5 minutes, then heat it to 1250°C and keep it for 5 minutes. After the insulation is completed, cool it with the furnace to obtain a heterogeneous structure cemented carbide material with excellent comprehensive performance.

[0021] Example 2 S1. Dissolve ammonium metatungstate and glucose in an appropriate amount of deionized water, heat and stir in an oil bath at 130°C, evaporate to form a precursor precipitate, and then dry it in a drying oven at a drying temperature of 125°C for 5 hours. After drying, grind through a 120-mesh sieve to obtain a precursor powder with uniform particle size. The mass of ammonium metatungstate and glucose is calculated based on the carbon content in the final WC powder, and the carbon content in WC is set to 6.14%; S2, calcining the precursor powder, reducing and carbonizing it with hydrogen, and then sieving to obtain WC powder; the calcination temperature is 600°C, the calcination time is 3h, the carbonization temperature is 1300°C, the carbonization time is 2.5h, and the hydrogen flow rate is 5L / min; S3, wet-grinding WC powder and Co powder, with a ball-to-material ratio of 4:1, a ball-milling time of 26 hours, and a ball-milling speed of 240 r / min, wherein the content of WC powder is 94%, and the content of Co powder is 6%; after wet-grinding, spray drying is performed to obtain WC-Co spherical mixed powder, the inlet air temperature of the spray drying is 150°C, the feed rate is 100 mL / min, and the spray pressure is 1.5 MPa; then the spherical mixed powder is calcined at a calcination temperature of 1100°C and a calcination time of 2 hours to ensure that the spherical mixed powder has sufficient strength; S4, the WC powders of different particle sizes were wet-milled with 1μm Co powder for the first time, with a ball-to-material ratio of 4:1, a ball-milling time of 24h, and a ball-milling speed of 150r / min, wherein the WC particle sizes were 8μm, 4μm, and 2μm, respectively, and the mass ratios were 1:1:1, respectively, the total WC powder content was 90%, and the Co powder content was 10%; after the first ball-milling, the WC-Co spherical mixed powder calcined in S3 was added for the second wet-milling, with a ball-to-material ratio of 1.5:1 (the total powder mass in the current ball-milling jar), a ball-milling time of 10h, and a ball-milling speed of 85r / min, wherein the content of the WC-Co spherical mixed powder was 70%, and the remainder was the WC-Co first ball-milling mixed powder; S5. Dry and sieve the wet-milled mixed powder slurry at 80°C for 4 hours and with a sieve mesh of 100 meshes. Then put it into a graphite mold, pre-press the composite powder with a hydraulic press, and then sinter it in a vacuum plasma sintering furnace at a heating rate of 100°C / min and a sintering pressure of 50 MPa. First, heat it to 600°C and keep it for 5 minutes, then heat it to 1250°C and keep it for 5 minutes. After the insulation is completed, cool it with the furnace to obtain a heterogeneous structure cemented carbide material with excellent comprehensive performance.

[0022] Example 3 S1. Dissolve ammonium metatungstate, ammonium metavanadate and glucose in an appropriate amount of deionized water, heat and stir in an oil bath at 130°C, evaporate to form a precursor precipitate, and then dry in a drying oven at a drying temperature of 125°C for 5 hours. After drying, grind through a 120-mesh sieve to obtain a precursor powder with uniform particle size. The mass of ammonium metatungstate, ammonium metavanadate and glucose is calculated based on the WC and VC contents in the final WC-VC composite powder. The VC content is 0.5wt%, the WC content is 99.5%, and the carbon content in WC is 6.14%; S2, calcining the precursor powder, reducing and carbonizing it with hydrogen, and then sieving to obtain modified WC powder; the calcination temperature is 600°C, the calcination time is 3h, the carbonization temperature is 1300°C, the carbonization time is 2.5h, and the hydrogen flow rate is 5L / min; S3, the modified WC powder and Co powder were mixed and wet-milled, the ball-to-material ratio was 4:1, the ball milling time was 26h, the ball milling speed was 240r / min, wherein the content of WC powder was 94%, and the content of Co powder was 6%; after the wet milling, the WC-Co spherical mixed powder was obtained by spray drying, the inlet air temperature of the spray drying was 150°C, the feed rate was 100 mL / min, and the spray pressure was 1.5Mpa; then the spherical mixed powder was calcined, the calcination temperature was 1100°C, and the calcination time was 2h to ensure that the spherical mixed powder had sufficient strength; S4, placing high-purity Fe powder, Ni powder and Co powder in a ball mill for the first wet grinding, the mass ratio of Fe:Ni:Co powder is 1:2:2, the ball-to-material ratio is 8:1, the ball milling time is 28h, and the ball milling speed is 300r / min, then adding 8μm WC powder for the second wet grinding, the ball-to-material ratio is 4:1 (the total powder mass in the current ball mill), the ball milling time is 24h, the ball milling speed is 150r / min, the total WC powder content is 90%, and the FeNiCo powder content is 10%, and finally adding the calcined WC-Co spherical mixed powder in S3 for the third wet grinding, the ball-to-material ratio is 1.5:1 (the total powder mass in the current ball mill), the ball milling time is 10h, and the ball milling speed is 85r / min, wherein the content of WC-Co spherical mixed powder is 70%, and the remainder is WC-FeNiCo mixed powder; S5. Dry and sieve the wet-milled mixed powder slurry at 80°C for 4 hours and with a sieve mesh of 100 meshes. Then put it into a graphite mold, pre-press the composite powder with a hydraulic press, and then sinter it in a vacuum plasma sintering furnace at a heating rate of 100°C / min and a sintering pressure of 50 MPa. First, heat it to 600°C and keep it for 5 minutes, then heat it to 1250°C and keep it for 5 minutes. After the insulation is completed, cool it with the furnace to obtain a heterogeneous structure cemented carbide material with excellent comprehensive performance.

[0023] Comparative Example 1 S1. The cemented carbide material of this comparative example is prepared by mixing WC powder of different particle sizes and 1μm Co powder through wet grinding, drying, sieving and pre-pressing sintering, wherein the ball-to-material ratio is 4:1, the ball milling time is 24h, the ball milling speed is 150r / min, the WC particle sizes are 8μm, 4μm and 2μm, respectively, the mass ratios are 1:1:1, the total WC powder content is 90%, and the Co powder content is 10%; S2. Dry and sieve the wet-grinded mixed powder slurry at 80°C for 4 hours and with a sieve mesh of 100 meshes; then put it into a graphite mold, pre-press the composite powder with a hydraulic press, and then sinter it in a vacuum plasma sintering furnace at a heating rate of 100°C / min and a sintering pressure of 50Mpa. First, heat it to 600°C and keep it for 5 minutes, then heat it to 1250°C and keep it for 5 minutes, and then cool it with the furnace after the insulation is completed, thereby obtaining a cemented carbide material.

[0024] Comparative Example 2 S1. Place high-purity Fe powder, Ni powder and Co powder in a ball mill for the first wet grinding. The mass ratio of Fe:Ni:Co powder is 1:2:2, the ball-to-material ratio is 8:1, the ball milling time is 28h, and the ball milling speed is 300r / min. Then add WC powder of different particle sizes for the second wet grinding. The ball-to-material ratio is 4:1 (the total powder mass in the current ball mill), the ball milling time is 24h, and the ball milling speed is 150r / min. The WC particle sizes are 8μm, 4μm and 2μm, respectively, and the mass ratio is 1:1:1, respectively. The total WC powder content is 90%, and the FeNiCo powder content is 10%; S2. Dry and sieve the wet-grinded mixed powder slurry at 80°C for 4 hours and with a sieve mesh of 100 meshes; then put it into a graphite mold, pre-press the composite powder with a hydraulic press, and then sinter it in a vacuum plasma sintering furnace at a heating rate of 100°C / min and a sintering pressure of 50Mpa. First, heat it to 600°C and keep it for 5 minutes, then heat it to 1250°C and keep it for 5 minutes, and then cool it with the furnace after the insulation is completed, thereby obtaining a cemented carbide material.

[0025] Comparative Example 3 Referring to Comparative Example 1, the preparation method of this comparative example is the same as that of Comparative Example 1, except that the WC particles in this comparative example are composed of WC of one particle size, and the WC particle size is 4 μm. The cemented carbide material is obtained by mixed wet grinding, drying, sieving and pre-pressing and sintering.

[0026] Performance Test: The hard alloy materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to performance tests, including Vickers hardness, fracture toughness and corrosion current density. The sample area for electrochemical testing was 1 cm 2 , the scanning rate is 5 mV / s, the concentration of sodium chloride aqueous solution is 3.5%, and the results are shown in Table 1: Table 1 Properties of cemented carbide materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 It can be seen from Table 1 that compared with Comparative Examples 1 to 3, the heterogeneous structure cemented carbide materials prepared in Examples 1 to 3 have relatively higher hardness, especially the alloy containing FeNiCo alloy powder has not only higher hardness but also higher fracture toughness and lower corrosion current density.

[0027] Depend on Figure 1 It can be seen that the prepared heterogeneous structure cemented carbide is composed of a variety of WC grains, and the density of the heterogeneous structure cemented carbide is good; the core structure composed of fine WC grains provides high hardness, and the shell structure composed of three coarse WC grains and FeNiCo alloy powder provides high toughness and high corrosion resistance.

[0028] Depend on Figure 2 It can be seen that the prepared cemented carbide is composed of larger coarse WC grains, and the average WC grain size is greater than 2μm; the alloy has good density, but because the alloy has a single homogeneous structure and the bonding phase is only the Co phase, the hardness of the alloy is relatively low and the corrosion resistance is poor.

[0029] From the above analysis, the heterogeneous structure cemented carbide material prepared by the present invention can comprehensively improve the hardness, toughness and corrosion resistance, and can meet the multiple requirements for material performance under complex working conditions.

Claims

1. A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof, characterized in that: The following steps are involved: S1. Dissolve tungstate, vanadate and organic carbon source in an appropriate amount of deionized water, heat and stir at a certain temperature, evaporate to form a precursor precipitate, and then dry it in a drying oven. After drying, grind and sieve to obtain a precursor powder with uniform particle size; S2, calcining the precursor powder, reducing and carbonizing it with hydrogen, and then sieving to obtain modified WC powder; S3, mixing the modified WC powder and the Co powder, wet grinding, spray drying to obtain WC-Co spherical mixed powder, and then calcining the WC-Co spherical mixed powder to ensure that the spherical mixed powder has sufficient strength; S4, placing high-purity Fe powder, Ni powder and Co powder in a ball mill for the first wet grinding, then adding WC powder of different particle sizes for the second wet grinding, and finally adding calcined WC-Co spherical mixed powder for the third wet grinding; S5. Dry and sieve the mixed powder slurry after three wet grindings, and then put it into a graphite mold. First, use a hydraulic press to pre-press the composite powder, and then put it into a vacuum discharge plasma sintering furnace for sintering, so as to obtain a heterogeneous structure cemented carbide material with excellent comprehensive performance.

2. A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof as claimed in claim 1, characterized in that: The tungstate, vanadate and organic carbon source in S1 are ammonium metatungstate, ammonium metavanadate and glucose respectively, and their addition amounts are calculated based on the contents of WC and VC in the final WC-VC composite powder, with the content of VC being 0.5 wt% and the balance being WC, wherein the carbon content in WC is 6.14%.

3. A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof as claimed in claim 1, characterized in that: In the S1, the oil bath is used for heating at a temperature of 120-140° C.; the drying temperature is 120-130° C. and the drying time is 4-8 hours; after drying, the mixture is ground and sieved through a 120-mesh sieve.

4. A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof as claimed in claim 1, characterized in that: In the S2, the calcination temperature is 550-650° C., the calcination time is 2-4 hours; the carbonization temperature is 1250-1350° C., the carbonization time is 2-4 hours, and the hydrogen flow rate is 4-6 L / min.

5. A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof as claimed in claim 1, characterized in that: The medium for wet grinding the modified WC powder and Co powder in S3 is anhydrous ethanol, the ball-to-material ratio is (4-6):1, the ball milling time is 20-26h, and the ball milling speed is 220-280r / min.

6. A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof as claimed in claim 1, characterized in that: In the spray drying process of S3, the air inlet temperature is 120-200° C., the feed rate is 60-180 mL / min, and the spray pressure is 0.6-2 MPa; the calcination temperature is 900-1200° C., and the calcination time is 1.5-3.5 h.

7. A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof as claimed in claim 1, characterized in that: In the first wet grinding in S4, the mass ratio of Fe powder, Ni powder and Co powder is 1:2:2, the ball-to-material ratio is (6-10):1, the ball milling time is 26-30h, and the ball milling speed is 250-350r / min.

8. A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof as claimed in claim 1, characterized in that: The WC particle sizes of the second wet grinding in S4 are 8 μm, 4 μm and 2 μm, the ball-to-material ratio is (3-5):1, the ball milling time is 20-26 h, and the ball milling speed is 120-160 r / min.

9. A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof as claimed in claim 1, characterized in that: The ball-to-material ratio of the third wet grinding in S4 is (1-2):1, the ball milling time is 6-12 hours, and the ball milling speed is 80-120 r / min.

10. A wear-resistant and corrosion-resistant heterogeneous structure cemented carbide and a preparation method thereof as claimed in claim 1, characterized in that: The drying temperature of the mixed powder slurry in S5 is 75-85°C, the drying time is 4-6h, and the mesh size is 100 mesh; the sintering temperature is 600°C for 5min, 1200-1300°C for 4-8min, the heating rate is 100°C / min, and the sintering pressure is 50MPa.

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