Preparation method of synergistically hardened and toughened WC-FeNiCo-CeO2 hard alloy material

Abstract

The application discloses a preparation method of a synergistically hardened and toughened WC-FeNiCo-CeO2 hard alloy material, and specifically comprises the following steps: (1) W-CeO2 composite powder preparation; (2) FeNiCo entropy alloy adhesive preparation; (3) WC-FeNiCo-CeO2 composite powder preparation; and (4) discharge plasma sintering. The application introduces CeO2 as a reinforcing phase through a wet chemical method, ensures uniform distribution of trace additives in the entire composite powder, purifies the grain boundary, improves the wetting performance of the grain boundary and the binder phase, promotes the voids to be filled with liquid phase, and reduces the porosity of the alloy; the FeNiCo entropy alloy adhesive is used to replace Co, thereby reducing the material cost and improving the hardness and the fracture toughness; and the discharge plasma sintering is adopted, so that the hard alloy composite material with high density, uniform grain structure, superior mechanical properties and a more extensive application range is prepared.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cemented carbide strengthening, and particularly relates to a preparation method of a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material. BACKGROUND

[0002] Cemented carbide is an excellent alloy material made of carbides (such as WC and TiC) of high-hardness refractory metals and binder metals (such as Co, Ni and Mo) through advanced powder metallurgy process. This material not only has extremely high hardness and strength, but also has excellent wear resistance and corrosion resistance, and is praised as "industrial tooth". The application range of cemented carbide is extremely wide, covering military industry, aerospace, mechanical processing, metallurgy, oil drilling, mining tools, electronic communication and building, etc. In order to meet the high performance requirements brought by the progress of the times, the comprehensive mechanical properties of cemented carbide need to be further improved.

[0003] Cobalt (Co) is the most widely used binder in the production of cemented carbide, and it is favored because of its excellent comprehensive performance, but its resource scarcity and high cost have become one of the key factors restricting the development of cemented carbide. Fe and Ni can be used as alternative binders because of their similar properties to Co. Ni can form a protective film on the surface due to its passivation characteristics, which helps to improve corrosion resistance. In addition, the addition of Ni can also improve the thermal stability of cemented carbide, so that it can maintain good mechanical properties in high temperature environment. Fe can help to refine WC grains, thereby improving the wear resistance of cemented carbide. Therefore, by accurately controlling the composition ratio and microstructure design of the Fe-Ni-Co ternary system, the overall performance of cemented carbide can be precisely controlled to meet the specific needs of different application scenarios.

[0004] The preparation of WC-FeNiCo by ordinary sintering technology requires long time high temperature sintering, which not only increases the production cycle and cost, but also causes the problems of uneven organization and low density of the sample. Spark plasma sintering (SPS) is a new technology that uses pulse current to directly sinter. Compared with ordinary sintering technology, SPS has the advantages of rapid sintering, low temperature sintering, high uniformity and controllable microstructure, etc. During the sintering process, CeO2 can act as a sintering aid to promote the densification process of the alloy, improve the density and strength of the alloy, and also improve the fracture toughness of the cemented carbide by adding appropriate CeO2. SUMMARY

[0005] In order to solve the problems raised in the background art, the present application aims to provide a preparation method of a synergistically hardened and toughened WC-FeNiCo-CeO2 hard alloy material, which has low material cost and can make the reinforcing phase uniformly distributed in the matrix, and the prepared WC-based hard alloy material has significantly improved mechanical properties and fracture toughness.

[0006] The technical solution of the present application:

[0007] A preparation method of a synergistically hardened and toughened WC-FeNiCo-CeO2 hard alloy material, specifically comprising the following steps:

[0008] (1) Preparation of W-CeO2 composite powder

[0009] A certain amount of ammonium metatungstate ((NH4)2WO4) and cerium nitrate (Ce(NO3)3) are added to deionized water, and after the two reagents are fully dissolved and uniformly mixed, a certain amount of oxalic acid is continuously added to the solution to adjust the pH value of the solution to the required range (pH value is 7~9), then the solution is heated at a certain temperature and continuously stirred until the solution is evaporated and concentrated to form a precursor precipitate; then, the precipitate is placed in a drying oven for drying treatment for several hours until the water in it is completely removed, the dried precipitate is crushed and sieved using a standard screen to ensure that a composite precursor powder with uniform particle size is obtained; finally, the composite precursor powder is placed in a high-purity alumina crucible and placed in a muffle furnace for high-temperature calcination, and then the sample is transferred to a high-temperature tube furnace for high-temperature reduction treatment, and finally the required W-CeO2 composite powder material is prepared;

[0010] (2) Preparation of FeNiCo entropy alloy binder

[0011] High-purity Fe powder, Ni powder and Co powder are weighed and placed in a ball mill jar, hard alloy pellets are added, the ball-to-material ratio is set to 10:1, anhydrous ethanol is added and mixed and milled in a ball mill to obtain a uniformly mixed powder slurry, which is then dried in a drying oven and sieved to obtain the FeNiCo entropy alloy binder;

[0012] (3) Preparation of WC-FeNiCo-CeO2 composite powder

[0013] The W-CeO2 composite powder prepared in step (1) is placed in a ball mill tank with an appropriate amount of carbon black, and hard alloy grinding balls are added. The ball mill tank is assembled under the protection of argon, and then fixed in a planetary ball mill for several hours. Then the ball milled mixture is placed in a high temperature tube furnace for carbonization, thereby obtaining a WC-CeO2 composite powder. Then, the WC-CeO2 composite powder and the FeNiCo powder obtained in step (2) are weighed according to the designed component ratio, and placed in a ball mill tank equipped with hard alloy grinding balls and anhydrous ethanol for mixing and ball milling. Then the ball milled mixture is placed in a drying box for drying treatment for several hours until the water is completely removed. The dried precipitate is crushed and sieved using a standard screen to obtain a WC-FeNiCo-CeO2 composite powder with uniform particle size.

[0014] (4) spark plasma sintering

[0015] The WC-FeNiCo-CeO2 composite powder obtained in step (3) is loaded into a graphite mold. The composite powder is pre-pressed using a hydraulic machine, and then the treated mold is placed in a spark plasma sintering furnace. The furnace chamber is vacuumed at room temperature, heated to 600℃ and kept for 5min to remove residual gas, and then heated to 1200-1300℃ and kept for 5min to complete the sintering. The sample is cooled with the furnace, thereby obtaining a high-performance WC-FeNiCo-CeO2 cemented carbide composite material.

[0016] The mass of ammonium metatungstate ((NH4)2WO4) and cerium nitrate (Ce(NO3)3) in step (1) is calculated according to the content of WC and CeO2 in the WC-FeNiCo-CeO2 cemented carbide. The addition amount of oxalic acid is 39.0% of the sum of the mass of ammonium metatungstate ((NH4)2WO4) and cerium nitrate (Ce(NO3)3). Heating is carried out by oil bath heating, and the heating temperature is 120-150℃.

[0017] The drying box in step (1) is an electric heating constant temperature air drying box, model DHG-9070, temperature setting is 80-100℃, drying time is 8-12h.

[0018] The temperature of the muffle furnace in step (1) is set to 500-600℃, and the time is set to 4-5h.

[0019] The reduction temperature of the composite precursor powder in step (1) to generate W-CeO2 composite powder in a high temperature tube furnace is 800-900℃, the reduction time is 2-3h, and the hydrogen flow rate is 4m 3 / h.

[0020] The mass ratio of Fe powder, Ni powder and Co powder in step (2) is 1:2:2.

[0021] The ball mill in step (2) is a Nan Da instrument QM-QX4 omnidirectional planetary ball mill, the rotation speed (rotation speed) of the ball mill is 350 rpm, the ball-to-material ratio is set to 10:1, the ball milling time is set to 30 h, and the ball tank and the ball milling medium small balls are made of hard alloy.

[0022] The drying oven in step (2) is an electric heating constant temperature air drying oven, the model is DHG-9070, the temperature is set to 80-100℃, and the drying time is 8-12h.

[0023] The addition amount of carbon black in step (3) is configured according to 6.14% of the total mass of W-CeO2 composite powder, the dry mixing time in the planetary ball mill is 4-8h, the rotation speed is set to 300-400r / min, and the ball-to-material ratio is set to 10:1.

[0024] The temperature for high-temperature carbonization of the tungsten-carbon composite powder in step (3) is 1400-1550℃ in the high-temperature tube atmosphere furnace, the reaction time is 2-3h, the hydrogen flow rate is 4m 3 / h, after cooling in the furnace, the composite powder is ground and sieved to 80 mesh, thereby obtaining WC-CeO2 composite powder.

[0025] The addition amount of FeNiCo powder in step (3) is configured according to 10% of the total mass of WC-FeNiCo-CeO2 composite powder, wet grinding in the planetary ball mill for 30-40h, the rotation speed is set to 350 r / min, and the ball-to-material ratio is set to 10:1.

[0026] The drying oven in step (3) is an electric heating constant temperature air drying oven, the model is DHG-9070, the temperature is set to 80-100℃, and the drying time is 8-12h.

[0027] In step (4), the graphite mold has a diameter of 25 mm, and carbon paper is used to isolate the WC-FeNiCo-CeO2 final processing composite powder from the graphite mold, which facilitates sampling and demolding after sintering.

[0028] In step (4), the pre-compaction pressure is 20 MPa, and infrared temperature measurement is used for sintering, and the infrared detector is aimed at the temperature measurement hole of the graphite mold.

[0029] The step (4) discharges the plasma sintering furnace model LaboxTM-300, and the setting program is as follows: increasing to 600 DEG C at the rate of 100 DEG C / min, sintering pressure is 20 MPa, and holding for 5 min; then increasing to 1230 DEG C at the rate of 100 DEG C / min, in the process, the pressure is increased from 20 MPa to 40 MPa, holding for 5 min, and cooling with the furnace.

[0030] The beneficial effects of the present application are: (1) the present application introduces CeO2 as a reinforcing phase by wet chemical method, realizes the uniform mixing of additives and matrix at the molecular level, ensures the uniform distribution of trace additives in the entire composite powder, thereby maximizing the function of additives, at the same time, the method can also purify the grain boundary, improve the wetting performance of the grain boundary and the binder phase, promote the voids to be filled with liquid phase, and reduce the porosity of the alloy; using FeNiCo entropy alloy adhesive instead of Co can not only reduce the cost of the material, but also improve the hardness and fracture toughness; finally, using the spark plasma sintering technology, a new WC-FeNiCo-CeO2 cemented carbide composite material with high density, uniform grain structure, superior mechanical properties and more extensive application range is prepared; (2) the new cemented carbide prepared by the present application exhibits excellent performance, the hardness reaches 1647 HV, and the fracture toughness is 20.38 MPa·m 1 / 2 , which is significantly improved compared with the traditional cemented carbide using only Co as the binder (hardness is 1483 HV, and fracture toughness is 12.15 MPa·m 1 / 2 ), in addition, the density of the new cemented carbide is also improved, which indicates that the microstructure is more compact, which means better mechanical properties and service life, such progress is of great significance for application fields requiring high hardness and good toughness (such as cutting tools, die manufacturing, etc.). BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The SEM image of the WC-10%FeNiCo-1.2%CeO2 new cemented carbide material prepared in Example 2.

[0032] Figure 2 The EDS image of the WC-10%FeNiCo-1.2%CeO2 new cemented carbide material prepared in Example 2.

[0033] Figure 3 The indentation image of the WC-10%FeNiCo-1.2%CeO2 new cemented carbide material prepared in Example 2. DETAILED DESCRIPTION

[0034] The present application is further described below in combination with the drawings and specific examples.

[0035] Example 1

[0036] The rare earth oxide and medium-entropy alloy adhesive synergistically toughened WC hard alloy material in this embodiment is prepared by high-temperature carbonization, medium-entropy alloy adhesive ball milling and spark plasma sintering on the basis of modifying tungsten powder by composite salt additives. The WC-FeNiCo-CeO2 composite powder is composed of the following components in mass percentage, including the following components (WC: 89.4%, FeNiCo: 10%, CeO2: 0.6%).

[0037] The preparation method of the WC-FeNiCo-CeO2 material in this embodiment is as follows:

[0038] (1) Preparation of W-CeO2 composite powder

[0039] First, ammonium metatungstate ((NH4)2WO4) and cerium nitrate (Ce(NO3)3) are dissolved in deionized water according to the component ratio of this embodiment. After the two reagents are fully dissolved and uniformly mixed, a proper amount of oxalic acid is added to the solution, and the addition amount of oxalic acid is 39.0% of the sum of the mass of ammonium metatungstate ((NH4)2WO4) and cerium nitrate (Ce(NO3)3) to adjust the pH value of the solution to the required range (pH value is 7~9). Subsequently, the solution is heated to 120℃ in an oil bath and continuously stirred until the solution is evaporated and concentrated to form a precursor precipitate. Then, the precipitate is placed in a forced air drying oven for drying treatment at a temperature of 80℃ for 8h. The dried precipitate is crushed and sieved using an 80-mesh standard sieve to ensure that a uniform particle size composite precursor powder is obtained. Finally, the composite precursor powder is placed in a high-purity alumina crucible and calcined at 550℃ in a muffle furnace for 4h, and then the sample is transferred to a high-temperature tube furnace for reduction at 800℃ for 3h to finally prepare the required W-CeO2 composite powder material;

[0040] (2) Preparation of FeNiCo medium-entropy alloy adhesive

[0041] High-purity Fe powder, Ni powder and Co powder with a mass ratio of 1:2:2 are weighed and placed in a ball mill jar. Hard alloy balls are added with a ball-to-material ratio of 10:1, and anhydrous ethanol is added for mixing and ball milling at a speed of 350r / min for 30h to obtain a uniformly mixed powder slurry. Then, the slurry is dried in an electrically heated constant temperature air drying oven at 80℃ for 8h, and sieved using an 80-mesh standard sieve to obtain the FeNiCo medium-entropy alloy adhesive.

[0042] (3) Preparation of WC-FeNiCo-CeO2 composite powder

[0043] The W-CeO2 mixed powder obtained in step (1) is placed in a ball mill tank with an appropriate amount of carbon black, the addition amount of carbon black is 6.14% of the total mass of the W-CeO2 composite powder, hard alloy grinding balls are added, the ball-to-material ratio is 10:1, the ball mill tank is assembled under the protection of argon, after assembly, the ball mill tank is fixed in a planetary ball mill and ball milled for 6h at a speed of 350r / min, and then it is placed in a high-temperature tube atmosphere furnace for carbonization, the carbonization temperature is set to 1500℃, the reaction time is 2h, and the hydrogen flow rate is 4m 3 / h, thereby obtaining a WC-CeO2 composite powder; then the WC-CeO2 composite powder and the FeNiCo powder obtained in step (2) are weighed according to the designed component ratio and placed in a ball mill tank provided with hard alloy grinding balls and anhydrous ethanol for mixing and ball milling, the ball-to-material ratio is 10:1, the ball milling time is 30h, and the speed is 350r / min; then the ball-milled mixed powder slurry is placed in a forced air drying oven for drying at 80℃ for 8h, the dried precipitate is crushed, and 80 mesh standard sieve is used for sieving to obtain a WC-FeNiCo-CeO2 composite powder with uniform particle size;

[0044] (4) spark plasma sintering

[0045] The WC-FeNiCo-CeO2 composite powder obtained in step (3) is loaded into a graphite mold, the composite powder is pre-pressed using a hydraulic machine, and then the treated mold is placed in a spark plasma sintering furnace, and the furnace chamber is vacuumed at room temperature. The heating rate is 100℃ / min, first heated to 600℃ and kept for 5min, the pressure is 20MPa, so that the residual gas can be discharged, then heated to 1230℃, pressurized to 40MPa, kept for 5min, and then sintering is completed, and the sample is cooled with the furnace, thereby obtaining a high-performance WC-FeNiCo-CeO2 cemented carbide composite material.

[0046] Example 2

[0047] The rare earth oxide and medium-entropy alloy adhesive synergistically toughened WC cemented carbide material in this embodiment is prepared by high-temperature carbonization of modified tungsten powder obtained by composite salt addition, ball milling of medium-entropy alloy adhesive, and spark plasma sintering, and the components in the WC-FeNiCo-CeO2 composite powder are composed of the following components (WC: 88.8%, FeNiCo: 10%, CeO2: 1.2%).

[0048] The preparation method of the WC-FeNiCo-CeO2 material in this embodiment is as follows:

[0049] (1) Preparation of W-CeO2 composite powder

[0050] First, according to the component ratio of the present embodiment, ammonium metatungstate ((NH4)2WO4) and cerium nitrate (Ce(NO3)3) are dissolved in deionized water, after the two reagents are fully dissolved and uniformly mixed, an appropriate amount of oxalic acid is added to the solution, the addition amount of oxalic acid is 39.0% of the sum of the mass of ammonium metatungstate ((NH4)2WO4) and cerium nitrate (Ce(NO3)3), to adjust the pH value of the solution to the required range (pH value is 7~9), then, the solution is heated to 120℃ in an oil bath and continues to stir until the solution is evaporated and concentrated to form a precursor precipitate; then, the precipitate is placed in a forced air drying oven for drying treatment, the temperature is 80℃, and the duration is 8h, the dried precipitate is crushed and sieved using an 80 mesh standard sieve to ensure that the composite precursor powder with uniform particle size is obtained; finally, the composite precursor powder is placed in a high-purity alumina crucible and placed in a muffle furnace at 550℃ for 4h, and then the sample is transferred to a high-temperature tube furnace for 3h at 800℃, and the desired W-CeO2 composite powder material is finally prepared;

[0051] (2) Preparation of FeNiCo entropic alloy adhesive

[0052] Respectively, high-purity Fe powder, Ni powder and Co powder with a mass ratio of 1:2:2 are placed in a ball mill pot, hard alloy balls are added, the ball-to-material ratio is set to 10:1, and anhydrous ethanol is added for mixing and ball milling, the rotation speed is 350r / min, and the ball milling time is 30h to obtain a uniformly mixed powder slurry, then it is placed in a drying oven at 80℃ for 8h, and sieved using an 80 mesh standard sieve to obtain the FeNiCo entropic alloy adhesive;

[0053] (3) Preparation of WC-FeNiCo-CeO2 composite powder

[0054] The W-CeO2 mixed powder obtained in step (1) and an appropriate amount of carbon black are placed in a ball mill pot, the addition amount of carbon black is 6.14% of the total mass of the W-CeO2 composite powder, hard alloy grinding balls are added, the ball-to-material ratio is 10:1, the ball mill pot is assembled under the protection of argon, after assembly, the ball mill pot is fixed in a planetary ball mill and ball milled for 6h at a rotation speed of 350r / min, then it is placed in a high-temperature tube furnace for carbonization, the carbonization temperature is set to 1500℃, the reaction time is 2h, the hydrogen flow rate is 4m 3 / h, thereby obtaining the WC-CeO2 composite powder; then, the WC-CeO2 composite powder and the FeNiCo powder obtained in step (2) are weighed according to the designed component ratio, and are mixed and ball milled in a ball mill tank provided with hard alloy grinding balls and anhydrous ethanol, with a ball-to-material ratio of 10:1, a ball milling time of 30 h, and a rotating speed of 350 r / min; then, the mixed powder slurry ball milled is placed in a blast drying oven for drying at 80℃ for 8 h, the precipitate obtained by drying is crushed, and is sieved using an 80-mesh standard sieve to obtain the WC-FeNiCo-CeO2 composite powder with uniform particle size;

[0055] (4) spark plasma sintering

[0056] The WC-FeNiCo-CeO2 composite powder obtained in step (3) is loaded into a graphite mold, the composite powder is pre-pressed using a hydraulic machine, and then the treated mold is placed in a spark plasma sintering furnace, and the furnace cavity is vacuum-extracted at room temperature. The heating rate is 100℃ / min, first heated to 600℃ and kept for 5 min, the pressure is 20 MPa, so that the residual gas can be discharged, then heated to 1230℃, and the pressure is increased to 40 MPa, kept for 5 min, and then the sintering is ended, and the sample is cooled with the furnace, thereby obtaining the high-performance WC-FeNiCo-CeO2 cemented carbide composite material.

[0057] Example 3

[0058] The rare earth oxide and medium-entropy alloy adhesive synergistically toughened WC cemented carbide material in this embodiment is prepared by high-temperature carbonization of the modified tungsten powder obtained by composite salt addition, ball milling of the medium-entropy alloy adhesive, and spark plasma sintering. The components in the WC-FeNiCo-CeO2 composite powder are composed of the following components (WC: 88.2%, FeNiCo: 10%, CeO2: 1.8%).

[0059] The preparation method of the WC-FeNiCo-CeO2 material in this embodiment is as follows:

[0060] (1) Preparation of W-CeO2 composite powder

[0061] First, according to the component ratio of the present embodiment, ammonium metatungstate ((NH4)2WO4) and cerium nitrate (Ce(NO3)3) are dissolved in deionized water, after the two reagents are fully dissolved and uniformly mixed, an appropriate amount of oxalic acid is added to the solution, the addition amount of oxalic acid is 39.0% of the sum of the mass of ammonium metatungstate ((NH4)2WO4) and cerium nitrate (Ce(NO3)3), to adjust the pH value of the solution to the required range (pH value is 7~9), then, the solution is heated to 120℃ in an oil bath and continues to stir until the solution is evaporated and concentrated to form a precursor precipitate; then, the precipitate is placed in a forced air drying oven for drying treatment, the temperature is 80℃, and the duration is 8h, the dried precipitate is crushed and sieved using an 80 mesh standard sieve to ensure that the composite precursor powder with uniform particle size is obtained; finally, the composite precursor powder is placed in a high-purity alumina crucible and placed in a muffle furnace at 550℃ for 4h, and then the sample is transferred to a high-temperature tube furnace for 3h at 800℃, and the desired W-CeO2 composite powder material is finally prepared;

[0062] (2) Preparation of FeNiCo entropic alloy adhesive

[0063] Respectively, high-purity Fe powder, Ni powder and Co powder with a mass ratio of 1:2:2 are placed in a ball mill pot, hard alloy balls are added, the ball-to-material ratio is set to 10:1, and anhydrous ethanol is added for mixing and ball milling, the rotation speed is 350r / min, and the ball milling time is 30h to obtain a uniformly mixed powder slurry, then it is placed in a drying oven at 80℃ for 8h, and sieved using an 80 mesh standard sieve to obtain the FeNiCo entropic alloy adhesive;

[0064] (3) Preparation of WC-FeNiCo-CeO2 composite powder

[0065] The W-CeO2 mixed powder obtained in step (1) and an appropriate amount of carbon black are placed in a ball mill pot, the addition amount of carbon black is 6.14% of the total mass of the W-CeO2 composite powder, hard alloy grinding balls are added, the ball-to-material ratio is 10:1, the ball mill pot is assembled under the protection of argon, after assembly, the ball mill pot is fixed in a planetary ball mill and ball milled for 6h at a rotation speed of 350r / min, then it is placed in a high-temperature tube furnace for carbonization, the carbonization temperature is set to 1500℃, the reaction time is 2h, and the hydrogen flow rate is 4m 3 / h, thereby obtaining the WC-CeO2 composite powder; then the WC-CeO2 composite powder and the FeNiCo powder obtained in step (2) are weighed according to the designed component ratio, and are mixed and ball milled in a ball mill tank provided with hard alloy grinding balls and anhydrous ethanol, the ball-to-material ratio is 10:1, the ball milling time is 30 h, and the rotation speed is 350 r / min; then the ball milled mixed powder slurry is placed in a blast drying oven for drying at 80℃ for 8 h, the dried precipitate is crushed, and is sieved using an 80 mesh standard sieve to obtain the WC-FeNiCo-CeO2 composite powder with uniform particle size;

[0066] (4) spark plasma sintering

[0067] The WC-FeNiCo-CeO2 composite powder obtained in step (3) is loaded into a graphite mold, the composite powder is pre-pressed using a hydraulic machine, and then the treated mold is placed in a spark plasma sintering furnace, and the furnace cavity is vacuumed at room temperature. The heating rate is 100℃ / min, first heated to 600℃ and kept for 5 min, the pressure is 20 MPa, so that the residual gas can be discharged, then heated to 1230℃, and pressurized to 40 MPa, kept for 5 min, and then the sintering is ended, and the sample is cooled with the furnace, thereby obtaining the high-performance WC-FeNiCo-CeO2 cemented carbide composite material.

[0068] Comparative Example 1

[0069] The WC-Co material in the present comparative example is processed by high-energy ball milling and spark plasma sintering, wherein the mass fraction of Co is pre-set to 10%, and the rest is WC.

[0070] The preparation method of the WC-Co material in the present comparative example is as follows:

[0071] (1) Preparation of WC-Co composite powder

[0072] The WC powder and the Co powder are weighed according to the component ratio and are loaded into a ball mill tank, the ball milling medium is anhydrous ethanol, the ball milling time is set to 30 h, the ball-to-material ratio is 10:1, and the ball milling rotation speed is set to 350 r / min. The obtained slurry is transferred to a blast drying oven, wherein the drying temperature is 80℃, and the drying time is 6 h. The dried precipitate is crushed, and is sieved using an 80 mesh standard sieve to ensure that the WC-Co composite powder with uniform particle size is obtained;

[0073] (2) Spark plasma sintering

[0074] The above-mentioned WC-10Co composite powder was added to a graphite mold wrapped with carbon paper, and then the graphite mold was placed in the spark plasma sintering furnace chamber; the infrared was aligned with the temperature measuring hole of the graphite mold; the chamber door was closed and the furnace chamber was vacuum treated. After the furnace chamber reached the vacuum level, the program was set for sintering. The sintering program was as follows: the temperature was raised to 600°C at a rate of 100°C / min, kept warm for 5 minutes, then raised to 1230°C and kept warm for 5 minutes. After the holding period, the temperature was cooled with the furnace. The pressure during sintering was 40 MPa. After the sintering was completed, a WC-10%Co cemented carbide composite material was obtained.

[0075] Comparative Example 2

[0076] The WC-FeNiCo material in this comparative example is made by high-energy ball milling and spark plasma sintering, wherein the mass fraction of FeNiCo is preset to 10%, and the rest is WC.

[0077] (1) Preparation of FeNiCo medium entropy alloy adhesive

[0078] High-purity Fe powder, Ni powder, and Co powder in a mass ratio of 1:2:2 were weighed and placed in a ball mill, and cemented carbide balls were added. The ball-to-material ratio was set to 10:1, and anhydrous ethanol was added for mixed ball milling at a speed of 350 r / min. The mixed powder slurry was obtained by ball milling for 30 h. The mixed powder slurry was then dried at 80°C in a drying oven for 8 h and sieved using an 80-mesh standard sieve to obtain a FeNiCo medium-entropy alloy adhesive.

[0079] (2) Preparation of WC-FeNiCo composite powder

[0080] According to the designed component ratio, an appropriate amount of WC powder and the FeNiCo powder obtained in step (2) are added to a ball mill, and hard alloy balls are added. The ball-to-material ratio is set to 10:1, and anhydrous ethanol is added for mixed ball milling. The ball milling time is 30 hours and the speed is 350 r / min; a uniformly mixed powder slurry is obtained, which is then placed in a blast drying oven for drying at 80°C for 8 hours, and sieved using an 80-mesh standard sieve to obtain a WC-FeNiCo composite powder with uniform particle size;

[0081] (3) Spark plasma sintering

[0082] The WC-FeNiCo composite powder obtained in step (2) is loaded into a graphite mold, the composite powder is pre-pressed by using a hydraulic machine, then the treated mold is placed into a spark plasma sintering furnace, and the furnace cavity is vacuum-extracted at room temperature. The heating rate is 100℃ / min, first heated to 600℃ and kept for 5min, the pressure is 20MPa, so that the residual gas can be discharged, then heated to 1230℃, pressurized to 40MPa, kept for 5min, and then the sintering is ended, and the sample is cooled with the furnace, thereby obtaining a high-performance WC-10%FeNiCo cemented carbide composite material.

[0083] The cemented carbide composite materials prepared in Examples 1-3 and Comparative Examples 1-2 are tested for performance, and the test results are shown in Table 1:

[0084] Table 1 Comparison of hardness and fracture toughness test results of cemented carbide composite materials of Examples 1-3 and Comparative Examples 1-2

[0085]

[0086] As can be seen from Table 1, by introducing CeO2 as a reinforcing phase by wet chemical method, the uniform mixing of the additive and the matrix at the molecular level is realized, and the uniform distribution of the trace additive in the entire composite powder is ensured, so that the function of the additive is maximized; using FeNiCo entropy alloy adhesive instead of Co can not only reduce the cost of the material, but also improve the hardness and fracture toughness; finally, using the spark plasma sintering method to prepare the bulk material, a new type of WC-FeNiCo-CeO2 cemented carbide composite material with high density, uniform grain structure, superior mechanical properties and wider application range is prepared. It is found that the addition of appropriate CeO2 can also improve the fracture toughness of the cemented carbide. In general, the hardness and fracture toughness of the cemented carbide composite material prepared by the composition design and preparation process of the present application are good, and when the CeO2 addition amount is 1.2%, the hardness and fracture toughness of the cemented carbide composite material are increased to the maximum value, which are 1647HV and 20.38MPa·m 1 / 2 , respectively. At the same time, the density of the material is also improved.

[0087] From the SEM images of the cross-section of the cemented carbide composite material prepared in Example 3, it can be seen that the grain size of the cemented carbide composite material is uniform and small, and no defects and impurities are found. Figure 1

[0088] From the SEM images of the cross-section of the cemented carbide composite material prepared in Example 3, it can be seen that the grain size of the cemented carbide composite material is uniform and small, and no defects and impurities are found. Figure 2 It can be seen from the energy spectrum analysis that the element distribution is uniform, indicating that the reinforcing phase is uniformly distributed in the WC matrix and is tightly combined with the interface of the WC matrix. Such structure not only improves the overall strength of the material, but also enhances the wear resistance and crack resistance.

[0089] From the SEM images of the cross-section of the cemented carbide composite material prepared in Example 3, it can be seen that the grain size of the cemented carbide composite material is uniform and small, and no defects and impurities are found.​Figure 3 It can be seen that there is no crack around the indentation of WC-10%FeNiCo-1.2%CeO2, indicating that the material has very good toughness.

[0090] The above-described embodiments are merely illustrative of the specific implementation of the present disclosure, but the implementation of the present disclosure is not limited by the above. Any change, modification, replacement, combination, simplification made without materially departing from the spirit and principles of the inventive concept of the present disclosure shall be an equivalent replacement manner and shall be included in the protection scope determined by the claims.

Claims

1. A method for preparing a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material, characterized by: The specific steps include: (1) Preparation of W-CeO2 composite powder Add an appropriate amount of ammonium metatungstate and cerium nitrate to deionized water. After the two reagents are fully dissolved and evenly mixed, continue to add an appropriate amount of oxalic acid to the solution to adjust the pH value of the solution to 7-9. Subsequently, heat the solution at a certain temperature and continue stirring until the solution evaporates and concentrates to form a precursor precipitate. After that, place the precursor precipitate in a drying oven for drying for several hours until the water therein is completely removed. The dried precipitate is crushed and sieved with a standard sieve to ensure that a composite precursor powder with uniform particle size is obtained. Finally, the composite precursor powder is placed in an alumina crucible, and the alumina crucible is placed in a muffle furnace for calcination at 500-600°C. The sample is then transferred to a high-temperature tubular atmosphere furnace for reduction treatment at 800-900°C to finally prepare the desired W-CeO2 composite powder. (2) Preparation of FeNiCo medium entropy alloy adhesive High-purity Fe powder, Ni powder, and Co powder were weighed separately and placed in a ball mill. Carbide balls were added with a ball-to-material ratio of 10:

1. After adding anhydrous ethanol, the mixture was mixed and milled in a ball mill to obtain a uniformly mixed powder slurry, which was then dried in a drying oven and sieved to obtain a FeNiCo medium-entropy alloy binder. (3) Preparation of WC-FeNiCo-CeO2 composite powder The W-CeO2 composite powder obtained in step (1) and an appropriate amount of carbon black are placed in a ball mill, carbide grinding balls are added, and the ball mill is assembled under the protection of argon. After the assembly is completed, the ball mill is fixed in a planetary ball mill and ball milled for several hours, and then placed in a high-temperature tubular atmosphere furnace for carbonization to obtain a WC-CeO2 composite powder; then the WC-CeO2 composite powder and the FeNiCo medium entropy alloy adhesive obtained in step (2) are weighed according to the designed component ratio, and placed in a ball mill equipped with carbide grinding balls and anhydrous ethanol for mixed ball milling, and then the ball-milled mixed powder slurry is placed in a drying oven for drying for several hours until the moisture therein is completely removed, the dried precipitate is crushed, and sieved using a standard sieve to obtain a WC-FeNiCo-CeO2 composite powder with uniform particle size; (4) Spark plasma sintering The WC-FeNiCo-CeO2 composite powder obtained in step (3) is loaded into a graphite mold, and the WC-FeNiCo-CeO2 composite powder is first pre-pressed using a hydraulic press, and then the treated mold is placed in a spark plasma sintering furnace, and the furnace cavity is vacuum-extracted at room temperature, and the temperature is raised to 600°C and kept warm for 5 minutes to allow residual gas to be discharged, and then the temperature is raised to 1200-1300°C, and the sintering is terminated after keeping warm for 5 minutes. The sample is cooled with the furnace, thereby obtaining a WC-FeNiCo-CeO2 cemented carbide composite material.

2. A method for preparing a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material according to claim 1, characterized in that: The mass of ammonium metatungstate and cerium nitrate in step (1) is calculated based on the content of WC and CeO2 in the WC-FeNiCo-CeO2 cemented carbide, and the amount of oxalic acid added is 39.0% of the sum of the mass of ammonium metatungstate and cerium nitrate. The heating is carried out in an oil bath at a temperature of 120-150°C.

3. The method for preparing a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material according to claim 1, characterized in that: The drying oven in step (1) is an electric constant temperature blast drying oven, model DHG-9070, with a temperature setting of 80-100°C and a drying time of 8-12 hours. The time of the muffle furnace in step (1) is set to 4-5 hours.

4. The method for preparing a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material according to claim 1, characterized in that: In step (1), the composite precursor powder is reduced in a high-temperature tubular atmosphere furnace to generate W-CeO2 composite powder. The reduction time is 2 to 3 hours, and the hydrogen flow rate is 4m 3 / h.

5. The method for preparing a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material according to claim 1, characterized in that: In step (2), the mass ratio of high-purity Fe powder, Ni powder and Co powder is 1:2:

2.

6. A method for preparing a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material according to claim 1, characterized in that: The ball mill in step (2) is a QM-QX4 all-round planetary ball mill produced by Nanjing University of Science and Technology. The rotation speed of the ball mill is 350 rpm, the ball-to-material ratio is set to 10:1, the ball milling time is set to 30 h, the ball tank and the ball milling medium are made of cemented carbide, and the drying oven in step (2) is an electric constant temperature blast drying oven, model DHG-9070, with a temperature set to 80~100°C and a drying time of 8~12 h.

7. The method for preparing a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material according to claim 1, characterized in that: The amount of carbon black added in step (3) is configured according to 6.14% of the total mass of the W-CeO2 composite powder. The dry mixing time in the planetary ball mill is 4 to 8 hours, the speed is set to 300 to 400 r / min, the ball-to-material ratio is set to 10:1, the carbonization temperature in step (3) is 1400 to 1550°C, the carbonization reaction time is 2 to 3 hours, and the hydrogen flow rate is 4m 3 / h, and after cooling in the furnace, grind the composite powder and sieve it through 80 mesh to obtain WC-CeO2 composite powder. The amount of entropy alloy binder added in FeNiCo in step (3) is configured according to 10% of the total mass of WC-FeNiCo-CeO2 composite powder. Wet grind it in a planetary ball mill for 30~40h, set the speed to 350 r / min, and set the ball-to-material ratio to 10:

1.

8. The method for preparing a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material according to claim 1, characterized in that: The drying oven in step (3) is an electric constant temperature blast drying oven, model DHG-9070, with a temperature setting of 80-100°C and a drying time of 8-12 hours.

9. The method for preparing a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material according to claim 1, characterized in that: In step (4), the diameter of the graphite mold is 25 mm. Carbon paper is used to isolate the WC-FeNiCo-CeO2 composite powder from the graphite mold to facilitate sampling and demoulding after sintering. The pre-pressing pressure in step (4) is 20 MPa. Infrared temperature measurement is used during sintering, and the infrared detector is aligned with the temperature measuring hole of the graphite mold.

10. The method for preparing a synergistically hardened and toughened WC-FeNiCo-CeO2 cemented carbide material according to claim 1, characterized in that: The spark plasma sintering furnace setting procedure in step (4) is as follows: increase the temperature to 600°C at a rate of 100°C / min, the sintering pressure is 20 MPa, and the temperature is kept at this temperature for 5 minutes; then increase the temperature to 1230°C at a rate of 100°C / min, during which the pressure is increased from 20 MPa to 40 MPa, and the temperature is kept at this temperature for 5 minutes before cooling with the furnace.

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