Fine-grain tungsten-nickel-iron composite material and low-temperature sintering preparation method thereof

Abstract

The invention discloses a fine-grain tungsten-nickel-iron composite material and a low-temperature sintering preparation method thereof. The composite material takes W as a hard phase, Ni and Fe as binding phases, Y2O3 as a particle reinforcement phase and a grain growth inhibitor, and Sn as an alloy element and a sintering fluxing agent. The preparation method comprises the following steps: 1, carrying out carbon heat and hydrogen reduction on WO3, NiO, Fe2O3 and nano carbon black to obtain composite powder; 2, carrying out wet grinding with Sn and Y2O3 powder, and drying; 3, compression molding; 4, degreasing and pre-sintering treatment; and 5, low-temperature liquid-phase sintering. According to the composite material, low-temperature liquid-phase sintering is achieved by introducing the Sn element and the Y2O3, the wettability and the interface bonding force between W crystal grains and a bonding phase are improved, and the composite material with uniform components and refined crystal grains is obtained; the preparation method improves the tensile strength, microhardness and room temperature plasticity of the composite material, and is suitable for the fields of aerospace, national defense and military industry, nuclear industry, electronic information, metallurgy and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of metal matrix composites, and particularly relates to a fine-grained tungsten-nickel-iron composite material and a method for preparing the same by low-temperature sintering. Background Art

[0002] Tungsten-nickel-iron alloy is a two-phase alloy with W as the matrix and low-melting-point elements such as Ni, Fe, Cu, and Co added. It has a series of excellent properties, such as: high density, high strength and high hardness, low coefficient of expansion, good plasticity, good electrical and thermal conductivity, and excellent corrosion resistance, etc. Relying on these excellent properties, tungsten-nickel-iron alloy is widely used in key fields such as aerospace, national defense, nuclear industry, electronic information, and metallurgy, and has become an important type of material indispensable for the development of the national economy.

[0003] At present, the preparation of tungsten-nickel-iron alloy still adopts the high-temperature liquid-phase sintering method, with a sintering temperature of about 1500 °C. The sintering temperature is high and the holding time is long, and the obtained W grain size is between 40 μm and 50 μm. The tungsten-nickel-iron alloy prepared by this method has poor organizational structure uniformity and coarse grain size, resulting in the deterioration of material properties. With the rapid development of science and technology and the extreme service environment, higher requirements are put forward for the properties of tungsten-nickel-iron alloy materials and their advanced preparation technologies. Numerous studies have shown that fine-grained tungsten-nickel-iron materials have great advantages in performance improvement. To meet the demand for high-mechanical-property tungsten-nickel-iron alloy, inhibiting the growth of W grains and preparing fine-grained tungsten-nickel-iron alloy is an important development trend.

[0004] The sintering process largely determines the organizational structure and properties of the subsequent alloy. The solid-phase sintered tungsten-nickel-iron alloy sintered below 1500 °C, due to the absence of a liquid-phase bonding phase, cannot achieve the rearrangement of W grains, resulting in uneven distribution of W grains and the bonding phase, and the comprehensive mechanical properties of the alloy are relatively low. Therefore, it is necessary to solve the problem of low-temperature liquid-phase sintering of tungsten-nickel-iron alloy to control the W grain size, distribution, and its connection degree with the bonding phase, and obtain a tungsten-nickel-iron alloy with high mechanical properties. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a fine-grained tungsten-nickel-iron composite material in view of the deficiencies of the above-mentioned prior art. In this fine-grained tungsten-nickel-iron composite material, the liquid-phase sintering temperature of the alloy system is reduced by adding a trace amount of low-melting-point Sn element, and combined with the introduction of rare-earth oxide Y 2 O 3 , the interfacial bonding force between W grains and the bonding phase is enhanced, effectively inhibiting the growth of W grains during sintering, and playing a dual strengthening role of refining the grain structure and dispersion strengthening of the alloy, obtaining a fine-grained tungsten-nickel-iron composite material with excellent comprehensive mechanical properties, and solving the problems of coarse grain size, poor organizational structure uniformity, and poor mechanical properties of tungsten-nickel-iron alloy in the prior art.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A fine-grained tungsten-nickel-iron composite material, characterized in that W is used as the hard phase, Ni and Fe are used as the binder phases, and Y 2 O 3 is used as the particle reinforcement phase and grain growth inhibitor, and Sn is used as the alloying element and sintering flux.

[0007] In the fine-grained tungsten-nickel-iron composite material of the present invention, by adding a trace amount of low-melting-point Sn element (232 °C), the liquid-phase sintering temperature of the alloy system is greatly reduced (usually 200 °C to 300 °C), thereby realizing the low-temperature liquid-phase sintering of tungsten-nickel-iron alloy, improving the material density, and having good chemical compatibility with both Ni and Fe. Combining with the introduction of rare-earth oxide Y 2 O 3 , making it disperse in the form of second-phase particles at the interface between W grains and the binder phase, improving the wettability between W grains and the binder phase, significantly enhancing the interfacial bonding force between W grains and the binder phase, and at the same time effectively inhibiting the growth of W grains during sintering, playing a dual role of refining the grain structure and dispersion strengthening of the alloy, and obtaining a fine-grained tungsten-nickel-iron composite material with excellent comprehensive mechanical properties.

[0008] For the above-mentioned fine-grained tungsten-nickel-iron composite material, it is characterized in that the average size of W grains in the composite material is less than 10 μm. This grain refinement size is much smaller than the average size of 40 μm to 50 μm of W grains in tungsten-nickel-iron composite materials prepared by traditional high-temperature liquid-phase sintering, which helps to improve the mechanical properties of tungsten-nickel-iron composite materials.

[0009] For the above-mentioned fine-grained tungsten-nickel-iron composite material, it is characterized in that the composite material is composed of the following components by mass percentage: Y 2 O 3 0.5% to 1%, Sn 0.5% to 1%, Ni 4.9% to 7%, Fe 2.1% to 3%, and the balance is W and unavoidable impurities. Usually, the mass ratio of Ni to Fe in the composite material is controlled to be 7:3, and the contents of Y 2 O 3 and Sn should not be too much to prevent the formation of brittle intermetallic compounds from deteriorating the mechanical properties of tungsten-nickel-iron composite materials.

[0010] At the same time, the present invention also discloses a low-temperature sintering preparation method of the above-mentioned fine-grained tungsten-nickel-iron composite material, which is characterized in that the method includes the following steps:

[0011] Step 1. Preparation of W-Ni-Fe composite powder: Mix WO 3 , NiO and Fe 2 O 3Mix with the reducing agent nano-carbon black, and then put it into a tube-type reduction furnace equipment for carbothermal reduction and hydrogen reduction to obtain a W-Ni-Fe composite powder; the WO 3 , NiO, Fe 2 O 3 and the mass purity of nano-carbon black are all not less than 99%;

[0012] Step Two: Wet milling and powder mixing: Put the W-Ni-Fe composite powder obtained in Step One, Sn, and Y 2 O 3 powder into a ball milling tank, add anhydrous ethanol as a process control agent, and add stearic acid as a molding agent for wet milling. After drying, obtain a W-Ni-Fe-Sn-Y 2 O 3 composite powder; the mass purity of the Sn and Y 2 O 3 powder are all not less than 99%;

[0013] Step Three: Compression molding: Put the W-Ni-Fe-Sn-Y 2 O 3 composite powder into a tungsten carbide mold, put it into a uniaxial hydraulic press, apply pressure and hold the pressure to obtain a green compact A;

[0014] Step Four: Debinding and pre-sintering: Put the green compact A obtained in Step Three into a tube furnace and carry out debinding and pre-sintering treatment in a hydrogen atmosphere to obtain a green compact B;

[0015] Step Five: Low-temperature liquid-phase sintering: Put the green compact B obtained in Step Four into a tube furnace for low-temperature liquid-phase sintering to prepare a fine-grained tungsten-nickel-iron composite material.

[0016] In the present invention, first, WO 3 , NiO, and Fe 2 O 3 are used as tungsten source, nickel source, and iron source, and nano-carbon black is used as a reducing agent and nucleating agent. Through carbothermal reduction treatment and subsequent deep hydrogen reduction treatment, high-purity and ultrafine W-Ni-Fe composite powder is prepared, providing a basis for the subsequent uniform mixing with Sn powder and Y 2 O 3 powder; then, in the present invention, the W-Ni-Fe composite powder is wet-milled and mixed with Sn and Y 2 O 3 powder, improving the powder mixing uniformity, and the ultrafine Y 2 O 3The particles are uniformly dispersed in the matrix, avoiding the coarsening and agglomeration of W grains during the subsequent sintering process, significantly improving the stability of W grains. At the same time, the low-melting-point Sn element plays an alloying role, providing the necessary conditions for low-temperature liquid-phase sintering and effectively controlling the growth rate of W grains. Finally, the high-purity, ultrafine (average grain size remains below 1 μm) W-Ni-Fe-Sn-Y 2 O 3 composite powder has high sintering activity and can be formed at a lower sintering temperature to form a Y 2 O 3 particle-dispersion-strengthened tungsten-nickel-iron composite material, greatly improving the mechanical properties of the tungsten-nickel-iron composite material and solving the problem that it is difficult to control the non-uniformity of W grain size, the connectivity between W grains, the size and distribution of the second-phase particles in the preparation process of traditional high-temperature liquid-phase sintered tungsten-nickel-iron alloy, resulting in poor mechanical properties.

[0017] The above-mentioned low-temperature sintering preparation method is characterized in that the particle size of WO 3 in step one is 40 μm to 50 μm, the particle size of NiO is 0.5 μm to 1 μm, and the Fe 2 O 3 has a particle size of 0.5 μm to 1 μm, and the particle size of the nano carbon black is 20 nm to 50 nm.

[0018] The above-mentioned low-temperature sintering preparation method is characterized in that the reduction temperature of the carbothermal reduction in step one is 600 °C to 650 °C and 1050 °C to 1100 °C, the reduction time is 2 h to 4 h respectively, and the atmosphere is argon; the reduction temperature of the hydrogen reduction is 800 °C to 900 °C, the time is 2 h to 4 h, and the atmosphere is hydrogen. The present invention adopts segmented carbothermal reduction treatment and limits the temperature of each segment, effectively improving the solid solution degree and compositeness of the W-Ni-Fe composite powder. Usually, the thickness of the powder bedding for hydrogen reduction treatment is less than 30 mm, and this preferred bedding thickness is conducive to the discharge of the water vapor generated during the hydrogen reduction treatment, improving the dispersibility and stability of the W-Ni-Fe composite powder.

[0019] The above-mentioned low-temperature sintering preparation method is characterized in that the rotation speed of the wet grinding in step two is 200 rpm to 250 rpm, the ball-to-material ratio is 10 to 15:1, and the time is 2 h to 4 h; the particle size of Sn is 2 μm to 5 μm, and the Y 2 O 3 has a particle size of 0.2 μm to 0.5 μm. Usually, the molding agent in step two can also adopt PVP and PEG, and the ball milling equipment used is made of stainless steel ball milling material. The present invention controls Sn and Y 2 O 3The particle size is convenient for its dispersion in the W-Ni-Fe composite powder.

[0020] The above low-temperature sintering preparation method is characterized in that in step three, the pressure of the die pressing is 200 MPa to 300 MPa, and the pressure holding time is 5 min to 10 min. Generally, the die pressing method is uniaxial pressure or cold isostatic pressing.

[0021] The above low-temperature sintering preparation method is characterized in that in step four, the process of the degreasing pre-sintering treatment is: heating to 300°C to 400°C in a hydrogen atmosphere and holding for 1 h to 2 h, then continuing to heat to 800°C to 1000°C and holding for 2 h to 4 h. Generally, the heating rate to 300°C to 400°C and the heating rate to 800°C to 1000°C are not greater than 2.5°C / min and 5°C / min, and the atmosphere used can also be vacuum. This preferred multi-stage degreasing pre-sintering treatment completely removes the molding agent in the green compact A, while effectively strengthening its strength, providing a basis for further sintering treatment.

[0022] The above low-temperature sintering preparation method is characterized in that in step five, the process of the low-temperature liquid-phase sintering is: first heating to 300°C at a rate of 10°C / min in a hydrogen atmosphere, then heating to 1200°C to 1300°C at a rate of 5°C / min and holding for 1 h to 2 h, then cooling to 800°C at a rate of 5°C / min, and then cooling with the furnace. Generally, the low-temperature liquid-phase sintering uses conventional pressureless sintering, SPS sintering or hot isostatic pressing, the atmosphere used is hydrogen or vacuum, and the sintering temperature does not exceed 1300°C; in the obtained fine-grained tungsten-nickel-iron composite material, rare earth oxide Y 2 O 3 particles are distributed at the interface between the W grains and the binder phase. Compared with the tungsten-nickel-iron composite material with coarsened oxide particles distributed at the phase boundary prepared by traditional high-temperature liquid-phase sintering, this fine-grained tungsten-nickel-iron composite material is more conducive to the smooth progress of dislocation transfer during the stress loading process, effectively delaying premature failure caused by stress concentration, and thus making the tungsten-nickel-iron composite material have more excellent mechanical properties.

[0023] The present invention has the following advantages compared with the prior art:

[0024] 1. In the fine-grained tungsten-nickel-iron composite material of the present invention, by introducing a low-melting-point Sn element and rare earth oxide Y 2 O 3, it greatly reduces the liquid-phase sintering temperature of the alloy system, realizes the low-temperature liquid-phase sintering of tungsten-nickel-iron alloy, improves the wettability and interfacial bonding force between W grains and the binder phase, and plays a dual role of grain refinement and dispersion strengthening, obtaining a fine-grained tungsten-nickel-iron composite material with uniform composition, refined grains and near-density, avoiding the drawbacks of grain coarsening, poor microstructure uniformity and performance deterioration caused by the existing high-temperature liquid-phase sintering preparation process, providing a new idea for the preparation of fine-grained tungsten-nickel-iron composite materials, and having high industrial application value.

[0025] 2. The low-melting-point Sn powder and Y used in the present invention 2 O 3 The rare earth oxide powder has a wide source, low price and simple preparation process, and is easy to be applied in engineering.

[0026] 3. The present invention prepares high-purity and ultrafine W-Ni-Fe composite powder through carbothermal reduction and hydrogen reduction, and wet-mills and mixes it with Sn and Y 2 O 3 powders to promote dispersion, avoiding the coalescence coarsening and agglomeration of W grains during the subsequent sintering process, and using the alloying effect of Sn element to control the growth rate of W grains, improving the sintering activity of the composite powder, so as to form and prepare a fine-grained tungsten-nickel-iron composite material with uniform structure, fine grains and uniformly dispersed ultrafine Y 2 O 3 particles at a lower sintering temperature. Compared with the coarse-grained tungsten-nickel-iron alloy prepared by the existing high-temperature liquid-phase sintering method, the tensile strength and microhardness of the fine-grained tungsten-nickel-iron composite material are greatly improved, and the room-temperature plasticity is also significantly improved.

[0027] 4. The preparation process flow of the present invention is simple, with low cost and high efficiency, and it is a method for efficiently preparing fine-grained tungsten-nickel-iron composite materials

[0028] The technical solution of the present invention will be further described in detail below through the drawings and examples. Description of the Drawings

[0029] Figure 1 It is a process flow diagram of the method for preparing the fine-grained tungsten-nickel-iron composite material in the present invention.

[0030] Figure 2 It is the SEM diagram of the W-Ni-Fe-Sn-Y 2 O 3 composite powder prepared in Example 1 of the present invention.

[0031] Figure 3 It is the SEM diagram of the fine-grained tungsten-nickel-iron composite material prepared in Example 1 of the present invention.

[0032] Figure 4EDS diagram of the fine-grained tungsten-nickel-iron composite material prepared in Example 1 of the present invention. Detailed implementation manners

[0033] Example 1

[0034] In this example, the fine-grained tungsten-nickel-iron composite material uses W as the hard phase, Ni and Fe as the binder phases, Y 2 O 3 as the particle reinforcement phase and grain growth inhibitor, and Sn as the alloying element and sintering flux; the composite material is composed of the following components by mass percentage: Y 2 O 3 0.5%, Sn 0.5%, Ni 7%, Fe 3%, and the balance is W and inevitable impurities

[0035] As Figure 1 shown, the preparation method of the fine-grained tungsten-nickel-iron composite material in this example includes the following steps:

[0036] Step 1, Preparation of W-Ni-Fe composite powder: Mix WO 3 , NiO and Fe 2 O 3 with the reducing agent nano carbon black, and then put it into a tube reduction furnace equipment for staged carbothermal reduction and hydrogen reduction to obtain W-Ni-Fe composite powder; the mass purities of WO 3 , NiO, Fe 2 O 3 and nano carbon black are all not less than 99%; the particle size of WO 3 is 40μm, the particle size of NiO is 0.5μm, the particle size of Fe 2 O 3 is 0.5μm, and the particle size of nano carbon black is 20nm;

[0037] The staged carbothermal reduction is as follows: First, heat it at a heating rate of 5°C / min to 650°C and keep it warm for 2h, then heat it at a heating rate of 5°C / min to 1050°C and keep it warm for 2h, and the atmosphere used is argon with a mass purity greater than 99.99%;

[0038] The hydrogen reduction is as follows: Heat it at a heating rate of 5°C / min to 800°C and keep it warm for 2h, and the atmosphere used is hydrogen with a mass purity greater than 99.99%;

[0039] Step 2, Wet grinding and powder mixing: Mix the W-Ni-Fe composite powder obtained in Step 1 with Sn, Y 2 O 3The powder was loaded into a ball milling jar, anhydrous ethanol was added as a process control agent, and stearic acid was added as a molding agent for wet milling. Stainless steel balls were used as the grinding medium, the ball-to-material ratio was 10:1, the ball milling speed was 200 rpm, and the time was 2 h. After drying, W-Ni-Fe-Sn-Y 2 O 3 composite powder was obtained; the mass purity of the Sn and Y 2 O 3 powders was not less than 99%, the particle size of the Sn was 2 μm, and the particle size of the Y 2 O 3 was 0.2 μm;

[0040] Step 3, die pressing: The W-Ni-Fe-Sn-Y 2 O 3 composite powder obtained in Step 2 was loaded into a tungsten carbide mold and placed in a uniaxial hydraulic press. It was kept under pressure for 5 min at a uniaxial pressure of 200 MPa to obtain a green compact A;

[0041] Step 4, debinding and pre-sintering: The green compact A obtained in Step 3 was placed in a tube furnace and subjected to debinding and pre-sintering treatment in a hydrogen atmosphere to obtain a green compact B; the process of the debinding and pre-sintering treatment was as follows: first, it was heated to 300 °C at a heating rate of 2.5 °C / min and kept warm for 1 h, then it was heated to 800 °C at a heating rate of 5 °C / min and kept warm for 2 h. The atmosphere used was hydrogen with a mass purity greater than 99.99%;

[0042] Step 5, low-temperature liquid-phase sintering: The green compact B obtained in Step 4 was placed in a tube furnace for low-temperature liquid-phase sintering to prepare a fine-grained tungsten nickel iron composite material; the process of the low-temperature liquid-phase sintering was as follows: in a hydrogen atmosphere, it was first heated to 300 °C at a rate of 10 °C / min, then heated to 1200 °C at a rate of 5 °C / min and kept warm for 1 h, then cooled to 800 °C at a rate of 5 °C / min, and then cooled with the furnace.

[0043] After testing, the density of the fine-grained tungsten nickel iron composite material prepared in this example was 99.6%, and the average grain size of the W grains was 3 μm; the tensile strength of the fine-grained tungsten nickel iron composite material reached 768 MPa, the elongation reached 17.9%, and the microhardness reached 426 HV 1 .

[0044] Figure 2 is the SEM image of the W-Ni-Fe-Sn-Y 2 O 3 composite powder prepared in this example. It can be seen from Figure 2 that the composite powder has good dispersibility, the particle size is 0.1 μm to 1 μm, providing good conditions for the preparation of the fine-grained tungsten nickel iron composite material.

[0045] Figure 3 SEM image of the fine-grained tungsten-nickel-iron composite material prepared in this example. From Figure 3 it can be seen that the microstructure of this composite material is relatively uniform, and Y 2 O 3 particles are dispersed, and the average size of W grains is 3 μm.

[0046] Figure 4 EDS image of the fine-grained tungsten-nickel-iron composite material prepared in this example. From Figure 4 it can be seen that there are a large number of fine Y 2 O 3 particles at the interface between W grains and the binder phase in this composite material ( Figure 4 A in).

[0047] The rare earth oxide in step three of this example can also be replaced by La 2 O 3 , the molding agent can also be replaced by PVP or PEG; the low-temperature liquid-phase sintering method in step five can also be SPS sintering or hot isostatic pressing sintering.

[0048] Example 2

[0049] The fine-grained tungsten-nickel-iron composite material of this example uses W as the hard phase, Ni and Fe as the binder phase, Y 2 O 3 as the particle reinforcement phase and grain growth inhibitor, and Sn as the alloying element and sintering flux; the composite material is composed of the following components by mass percentage: Y 2 O 3 0.5%, Sn 1%, Ni 7%, Fe 3%, and the balance is W and unavoidable impurities

[0050] As Figure 1 shown, the preparation method of the fine-grained tungsten-nickel-iron composite material of this example includes the following steps:

[0051] Step 1, Preparation of W-Ni-Fe composite powder: Mix WO 3 , NiO and Fe 2 O 3 with the reducing agent nano-carbon black, and then put it into a tube-type reduction furnace equipment for staged carbothermal reduction and hydrogen reduction to obtain W-Ni-Fe composite powder; the mass purity of WO 3 , NiO, Fe 2 O 3 and nano-carbon black is not less than 99%; the particle size of WO 3 is 40 μm, the particle size of NiO is 0.5 μm, the particle size of Fe 2 O 3 is 1 μm, and the particle size of nano-carbon black is 30 nm;

[0052] The segmented carbothermal reduction is as follows: First, heat at a heating rate of 5 °C / min to 600 °C and hold for 2 h, then heat at a heating rate of 5 °C / min to 1050 °C and hold for 2 h. The atmosphere used is argon with a mass purity greater than 99.99%.

[0053] The hydrogen reduction is as follows: Heat at a heating rate of 5 °C / min to 800 °C and hold for 2 h. The atmosphere used is hydrogen with a mass purity greater than 99.99%.

[0054] Step 2: Wet milling and powder mixing: Put the W-Ni-Fe composite powder obtained in Step 1, Sn, and Y 2 O 3 powders into a ball milling tank, add absolute ethanol as a process control agent, and add stearic acid as a molding agent for wet milling. Use stainless steel balls as the grinding medium, with a ball-to-powder ratio of 10:1, a ball milling speed of 200 rpm, and a time of 4 h. After drying, obtain the W-Ni-Fe-Sn-Y 2 O 3 composite powder; The mass purities of the Sn and Y 2 O 3 powders are both not less than 99%. The particle size of the Sn is 2 μm, and the particle size of Y 2 O 3 is 0.3 μm.

[0055] Step 3: Compression molding: Put the W-Ni-Fe-Sn-Y 2 O 3 composite powder into a tungsten carbide mold, place it in a uniaxial hydraulic press, and hold the pressure at 300 MPa for 5 min to obtain a green compact A.

[0056] Step 4: Debinding and pre-sintering: Put the green compact A obtained in Step 3 into a tube furnace and perform debinding and pre-sintering treatment in a hydrogen atmosphere to obtain a green compact B; The process of the debinding and pre-sintering treatment is as follows: First, heat at a heating rate of 2.5 °C / min to 400 °C and hold for 2 h, then heat at a heating rate of 5 °C / min to 1000 °C and hold for 4 h. The atmosphere used is hydrogen with a mass purity greater than 99.99%.

[0057] Step 5: Low-temperature liquid-phase sintering: Put the green compact B obtained in Step 4 into a tube furnace for low-temperature liquid-phase sintering to prepare a fine-grained tungsten-nickel-iron composite material; The process of the low-temperature liquid-phase sintering is as follows: In a hydrogen atmosphere, first heat at a rate of 10 °C / min to 300 °C, then heat at a rate of 5 °C / min to 1200 °C and hold for 1 h, then cool at a rate of 5 °C / min to 800 °C, and then cool with the furnace.

[0058] After testing, the density of the fine-grained tungsten-nickel-iron composite material prepared in this example is 99.8%, the average size of the W grains is 4 μm; the tensile strength of the fine-grained tungsten-nickel-iron composite material reaches 741 MPa, the elongation rate reaches 19.8%, and the microhardness reaches 409 HV 1 .

[0059] Example 3

[0060] The fine-grained tungsten-nickel-iron composite material of this example uses W as the hard phase, Ni and Fe as the binder phases, Y 2 O 3 as the particle reinforcement phase and grain growth inhibitor, and Sn as the alloying element and sintering flux; the composite material is composed of the following components by mass percentage: Y 2 O 3 0.5%, Sn 0.5%, Ni 4.9%, Fe 2.1%, and the balance is W and unavoidable impurities

[0061] As Figure 1 shown, the preparation method of the fine-grained tungsten-nickel-iron composite material of this example includes the following steps:

[0062] Step 1. Preparation of W-Ni-Fe composite powder: Mix WO 3 , NiO and Fe 2 O 3 with the reducing agent nano carbon black, and then put it into a tube reduction furnace equipment for staged carbothermal reduction and hydrogen reduction to obtain a W-Ni-Fe composite powder; the mass purities of WO 3 , NiO, Fe 2 O 3 and nano carbon black are all not less than 99%; the particle size of WO 3 is 50 μm, the particle size of NiO is 0.5 μm, the particle size of Fe 2 O 3 is 1 μm, and the particle size of nano carbon black is 40 nm;

[0063] The staged carbothermal reduction is: first heat it at a heating rate of 5 °C / min to 650 °C and hold for 2 h, then heat it at a heating rate of 5 °C / min to 1100 °C and hold for 4 h, and the atmosphere used is argon with a mass purity greater than 99.99%;

[0064] The hydrogen reduction is: heat it at a heating rate of 5 °C / min to 800 °C and hold for 2 h, and the atmosphere used is hydrogen with a mass purity greater than 99.99%;

[0065] Step 2. Wet grinding and powder mixing: Mix the W-Ni-Fe composite powder obtained in Step 1 with Sn, Y 2 O 3The powder is loaded into a ball milling jar, anhydrous ethanol is added as a process control agent, and stearic acid is added as a molding agent for wet milling. Stainless steel balls are used as the grinding medium, the ball-to-material ratio is 15:1, the ball milling speed is 250 rpm, the time is 2 h, and after drying, W-Ni-Fe-Sn-Y 2 O 3 composite powder is obtained; the mass purity of the Sn and Y 2 O 3 powders are both not less than 99%, the particle size of the Sn is 4 μm, and the particle size of Y 2 O 3 is 0.5 μm;

[0066] Step 3, die pressing: The W-Ni-Fe-Sn-Y 2 O 3 composite powder obtained in Step 2 is loaded into a tungsten carbide mold and placed in a uniaxial hydraulic press. It is kept under pressure at a uniaxial pressure of 250 MPa for 8 min to obtain a green compact A;

[0067] Step 4, debinding and pre-sintering: The green compact A obtained in Step 3 is placed in a tubular furnace and subjected to debinding and pre-sintering treatment in a hydrogen atmosphere to obtain a green compact B; the process of the debinding and pre-sintering treatment is as follows: first, it is heated to 400 °C at a heating rate of 2.5 °C / min and kept warm for 2 h, then it is heated to 1000 °C at a heating rate of 5 °C / min and kept warm for 2 h. The atmosphere used is hydrogen with a mass purity greater than 99.99%;

[0068] Step 5, low-temperature liquid-phase sintering: The green compact B obtained in Step 4 is placed in a tubular furnace for low-temperature liquid-phase sintering to prepare a fine-grained tungsten-nickel-iron composite material; the process of the low-temperature liquid-phase sintering is as follows: in a hydrogen atmosphere, it is first heated to 300 °C at a rate of 10 °C / min, then heated to 1200 °C at a rate of 5 °C / min and kept warm for 2 h, and then cooled to 800 °C at a rate of 5 °C / min, and then cooled with the furnace.

[0069] After testing, the density of the fine-grained tungsten-nickel-iron composite material prepared in this example is 99.2%, the average grain size of the W grains is 5 μm; the tensile strength of the fine-grained tungsten-nickel-iron composite material reaches 806 MPa, the elongation reaches 16.8%, and the microhardness reaches 453 HV 1 .

[0070] Example 4

[0071] The fine-grained tungsten-nickel-iron composite material in this example uses W as the hard phase, Ni and Fe as the binder phases, Y 2 O 3 as the particle reinforcement phase and grain growth inhibitor, and Sn as the alloying element and sintering flux; the composite material is composed of the following components by mass percentage: Y 2 O3 1%, Sn 1%, Ni 4.9%, Fe 2.1%, the balance being W and unavoidable impurities

[0072] As Figure 1 shown, the preparation method of the fine-grained tungsten-nickel-iron composite material of this embodiment includes the following steps:

[0073] Step 1, preparation of W-Ni-Fe composite powder: Mix WO 3 , NiO and Fe 2 O 3 with the reducing agent nano-carbon black, and then put it into a tube-type reduction furnace equipment for staged carbothermal reduction and hydrogen reduction to obtain W-Ni-Fe composite powder; the mass purities of the WO 3 , NiO, Fe 2 O 3 and nano-carbon black are all not less than 99%; the particle size of the WO 3 is 50 μm, the particle size of NiO is 0.5 μm, the particle size of Fe 2 O 3 is 1 μm, and the particle size of nano-carbon black is 50 nm;

[0074] The staged carbothermal reduction is: first heat it to 650 °C at a heating rate of 5 °C / min and then hold for 2 h, and then heat it to 1100 °C at a heating rate of 5 °C / min and hold for 2 h. The atmosphere used is argon with a mass purity greater than 99.99%;

[0075] The hydrogen reduction is: heat it to 900 °C at a heating rate of 5 °C / min and hold for 4 h. The atmosphere used is hydrogen with a mass purity greater than 99.99%;

[0076] Step 2, wet grinding and mixing of powders: Put the W-Ni-Fe composite powder obtained in Step 1, Sn, and Y 2 O 3 powder into a ball milling tank, add anhydrous ethanol as a process control agent, and add stearic acid as a molding agent for wet grinding. Use stainless steel balls as the grinding medium, with a ball-to-material ratio of 15:1, a ball milling speed of 250 rpm, and a time of 2 h. After drying, obtain W-Ni-Fe-Sn-Y 2 O 3 composite powder; the mass purities of the Sn and Y 2 O 3 powders are all not less than 99%, the particle size of the Sn is 5 μm, and the particle size of Y 2 O 3 is 0.5 μm;

[0077] Step 3, molding by die pressing: The W-Ni-Fe-Sn-Y 2 O3 The composite powder is loaded into a tungsten carbide mold and placed in a uniaxial hydraulic press. It is kept under pressure for 10 min at a uniaxial pressure of 250 MPa to obtain a green compact A.

[0078] Step 4, debinding and pre-sintering: The green compact A obtained in Step 3 is placed in a tubular furnace and subjected to debinding and pre-sintering treatment in a hydrogen atmosphere to obtain a green compact B. The process of the debinding and pre-sintering treatment is as follows: First, it is heated to 400 °C at a heating rate of 2.5 °C / min and held for 2 h, then heated to 1000 °C at a heating rate of 5 °C / min and held for 2 h. The atmosphere used is hydrogen with a mass purity greater than 99.99%.

[0079] Step 5, low-temperature liquid-phase sintering: The green compact B obtained in Step 4 is placed in a tubular furnace for low-temperature liquid-phase sintering to prepare a fine-grained tungsten-nickel-iron composite material. The process of the low-temperature liquid-phase sintering is as follows: In a hydrogen atmosphere, it is first heated to 300 °C at a rate of 10 °C / min, then heated to 1300 °C at a rate of 5 °C / min and held for 1 h, and then cooled to 800 °C at a rate of 5 °C / min, and then cooled with the furnace.

[0080] After testing, the density of the fine-grained tungsten-nickel-iron composite material prepared in this example is 99.2%, the average size of the W grains is 7 μm; the tensile strength of the fine-grained tungsten-nickel-iron composite material reaches 768 MPa, the elongation rate reaches 17.5%, and the microhardness reaches 429 HV. 1 。

[0081] The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change, and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A fine-grained tungsten-nickel-iron composite material, characterized in that: W is used as the hard phase, Ni and Fe are used as the bonding phase, Y2O3 is used as the particle reinforcement phase and grain growth inhibitor, and Sn is used as the alloy element and sintering flux.

2. A fine-grained tungsten-nickel-iron composite material according to claim 1, characterized in that: The average size of W grains in the composite material is less than 10 μm.

3. A fine-grained tungsten-nickel-iron composite material according to claim 1, characterized in that: The composite material consists of the following components by mass percentage: Y2O3 0.5%-1%, Sn 0.5%-1%, Ni 4.9%-7%, Fe 2.1%-3%, and the remainder is W and unavoidable impurities.

4. A low temperature sintering method for preparing a fine-grained tungsten-nickel-iron composite material according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: Step 1, preparation of W-Ni-Fe composite powder: WO3, NiO and Fe2O3 are mixed with reducing agent nano carbon black, and then placed in a tubular reduction furnace for carbon thermal reduction and hydrogen reduction to obtain W-Ni-Fe composite powder; the mass purity of the WO3, NiO, Fe2O3 and nano carbon black is not less than 99%; Step 2, wet grinding and mixing powder: the W-Ni-Fe composite powder obtained in step 1 is put into a ball mill with Sn and Y2O3 powders, anhydrous ethanol is added as a process control agent, and stearic acid is added as a molding agent for wet grinding, and W-Ni-Fe-Sn-Y2O3 composite powder is obtained after drying; the mass purity of the Sn and Y2O3 powders is not less than 99%; Step 3: Compression molding: The W-Ni-Fe-Sn-Y2O3 composite powder obtained in step 2 is loaded into a tungsten steel mold, placed in a uniaxial hydraulic press, and pressure is applied and maintained to obtain a compact A; Step 4: Degreasing and pre-sintering: placing the compact A obtained in step 3 into a tubular furnace, and performing degreasing and pre-sintering treatment under a hydrogen atmosphere to obtain a compact B; Step 5: Low-temperature liquid phase sintering: The compact B obtained in step 4 is placed in a tubular furnace for low-temperature liquid phase sintering to prepare a fine-grained tungsten-nickel-iron composite material.

5. The low temperature sintering preparation method according to claim 4, characterized in that: In step 1, the particle size of WO3 is 40 μm to 50 μm, the particle size of NiO is 0.5 μm to 1 μm, the particle size of Fe2O3 is 0.5 μm to 1 μm, and the particle size of nano carbon black is 20 nm to 50 nm.

6. The low temperature sintering preparation method according to claim 4, characterized in that: The reduction temperature of the carbon thermal reduction in step 1 is 600°C to 650°C and 1050°C to 1100°C, the reduction time is 2h to 4h respectively, and the atmosphere is argon; the reduction temperature of the hydrogen reduction is 800°C to 900°C, the time is 2h to 4h, and the atmosphere is hydrogen.

7. The low temperature sintering preparation method according to claim 4, characterized in that: The rotation speed of the wet grinding in step 2 is 200rpm~250rpm, the ball-to-material ratio is 10~15:1, and the time is 2h~4h; the particle size of the Sn is 2μm~5μm, and the particle size of the Y2O3 is 0.2μm~0.5μm.

8. The low temperature sintering preparation method according to claim 4, characterized in that: The compression molding pressure in step 3 is 200 MPa to 300 MPa, and the holding time is 5 min to 10 min.

9. The low temperature sintering preparation method according to claim 4, characterized in that: The process of the debinding pre-sintering treatment in step 4 is: heating to 300°C-400°C in a hydrogen atmosphere and keeping it warm for 1h-2h, and then continuing to heat up to 800°C-1000°C and keeping it warm for 2h-4h.

10. The low temperature sintering preparation method according to claim 4, characterized in that: The process of low-temperature liquid phase sintering in step five is: first heat up to 300°C at a rate of 10°C / min in a hydrogen atmosphere, then heat up to 1200°C~1300°C at a rate of 5°C / min and keep warm for 1h~2h, then cool down to 800°C at a rate of 5°C / min, and then cool down with the furnace.

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