Disclosure of Invention
In view of the above, the invention aims to provide a novel WC-based cermet composite shielding material and a preparation process thereof, and solves the problems of insufficient mechanical property and poor shielding capability of the conventional WC-based cermet composite.
Aiming at the requirements of simplifying small-pile shielding design and reducing the volume of shielding materials of compact small-pile, the invention provides a novel high-strength, high-hardness, high-wear-resistance and corrosion-resistance comprehensive shielding material for a small nuclear reactor and a preparation process thereof.
The technical scheme of the invention is realized as follows:
The first object of the invention is to disclose a novel WC-based cermet composite shielding material, wherein the composite shielding material is prepared from WC-based ceramic powder and high-entropy alloy powder through ball milling mixing, prepressing forming and high-temperature high-pressure sintering treatment, and the mass ratio of the high-entropy alloy powder in the composite shielding material is 2% -10%.
Further, the chemical component content (wt%) of the WC-based ceramic is more than or equal to 99.5%, and the chemical component content (at%) of the high-entropy alloy is composed of, by weight, 13-18% of Al, 13-18% of Co, 13-18% of Cr, 13-18% of Fe, 13-18% of Ni and 13-18% of Cu.
Further, the WC ceramic powder has a particle size of 0.4-1.0 μm and the high-entropy alloy AlCoCrFeNiCu has a powder particle size of 3-18 μm.
Another object of the present invention is to disclose a process for preparing a novel WC-based cermet composite shielding material according to any one of claims 1 to 3 comprising the following specific steps:
S1, preparing WC ceramic powder and high-entropy alloy powder;
S2, ball milling and mixing WC ceramic powder and high-entropy alloy powder;
s3, pre-pressing treatment is carried out;
And S4, performing high-temperature high-pressure sintering treatment.
Further, in step S2, the specific steps of ball-milling and mixing are as follows:
S21, weighing raw material powder in proportion, and then adding the raw material powder into a hard alloy ball milling tank;
S22, adding hard alloy grinding balls, and performing ball milling mixing and refining on raw material powder by using a planetary ball mill;
and S23, after ball milling is finished, taking out the mixed slurry, placing the mixed slurry into a distillation flask, and removing ball milling media in the mixed slurry by means of a rotary evaporator to obtain dry mixed powder.
In step S21, the raw material powder is weighed in proportion by using an electronic balance with an accuracy of 0.01mg, and the ball milling pot and the grinding ball are made of WC cemented carbide.
Further, in step S22, the ball-to-material ratio is set to (3-7): 1, the ball milling rotation speed is set to 250-350rpm, and the forward and reverse rotation mode is adopted, namely, the ball milling tank rotates clockwise for 25-35min, then rotates anticlockwise for 25-35min after resting for 7-13min, and the process is repeated. The ball milling time is 15-50h.
Further, in step S23, in the ball milling and powder mixing process, absolute ethanol is selected as a ball milling medium to improve the ball milling efficiency and prevent powder oxidation.
Further, in step S3, a graphite mold is used for pre-pressing, and the mixed powder is placed in the graphite mold for pre-pressing molding.
Further, in the step S4, the SPS furnace is adopted for high-temperature high-pressure sintering treatment, the sintering pressure is 20-60MPa, the sintering temperature is 1000-1600 ℃, the heating speed is 40-60 ℃ per minute, and the sintering heat preservation time is 3-13 minutes.
Compared with the prior art, the novel WC-based metal ceramic composite shielding material and the preparation process thereof have the following advantages:
1. The novel comprehensive shielding material with high strength, high hardness, high wear resistance and corrosion resistance is prepared by the ultra-temperature high-pressure sintering process, so that the environment adaptability of the shielding material is improved, the material volume is reduced, and the shielding design is optimized.
2. The high-strength, high-hardness, high-wear-resistance and corrosion-resistance comprehensive shielding material is mainly used for comprehensive shielding protection of small nuclear reactors, can effectively shield radiation potential, has good wear resistance, corrosion resistance and strength, and has important engineering application value. Compared with the existing shielding material, the shielding material has the characteristics of good mechanical property, good shielding property, ageing resistance and the like.
Detailed Description
In order to facilitate understanding of the technical means, objects and effects of the present invention, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
It should be noted that all terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inner", "outer", "top", "low", "lateral", "longitudinal", "center", etc. used in the present invention are merely used to explain the relative positional relationship, connection, etc. between the components in a specific state, and are merely used for convenience of describing the present invention, and do not require that the present invention must be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated.
In the description of the present invention, unless explicitly stated and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected, mechanically connected, directly connected, indirectly connected via an intermediate medium, or communicating between the two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The first purpose of the invention is to disclose a novel WC-based cermet composite shielding material, which is prepared from WC-based ceramic powder and high-entropy alloy powder through ball milling mixing, prepressing forming and high-temperature high-pressure sintering treatment.
The high-entropy alloy has good conductivity and magnetism, can effectively shield electromagnetic waves, the WC-based ceramic provides structural support, the overall performance of the material is enhanced, the plasticity of the composite material can be improved by compounding the high-entropy alloy with the WC-based ceramic, the high-entropy alloy can keep good ductility at high temperature, high hardness and high wear resistance can be realized, the electromagnetic shielding performance is improved, the high-temperature stability of the material is also improved, and the high-entropy alloy has excellent corrosion resistance.
The arrangement combines the advantages of high-entropy alloy and WC-based ceramic, realizes high-performance electromagnetic shielding, excellent mechanical property, good high-temperature resistance and excellent corrosion resistance, and can be widely applied to the fields of aerospace, military, industry and the like.
Specifically, the mass ratio of the high-entropy alloy powder in the composite shielding material is 2% -10%.
The mass ratio of the high-entropy alloy powder is 2% -10%, so that the mechanical property and corrosion resistance of the material can be optimized while the electromagnetic shielding property is ensured, and the comprehensive balance of the properties is realized.
Preferably, the mass ratio of the high-entropy alloy powder in the composite shielding material is 2-10%.
As shown in tables 1-2, specifically, the chemical component content (wt%) of the WC-based ceramic is more than or equal to 99.5%, and the chemical component content (at%) of the high-entropy alloy is composed of, by weight, 13-18% of Al, 13-18% of Co, 13-18% of Cr, 13-18% of Fe, 13-18% of Ni and 13-18% of Cu.
TABLE 1 chemical composition and particle size of WC ceramic powder
| Composition of the components | WC | Impurity(s) |
| Content (wt%) | ≥99.5 | ≤0.5 |
TABLE 2AlCoCrFeNiCu chemical composition of high entropy alloy powder
| Composition of the components | Al | Co | Cr | Fe | Ni | Cu |
| Content (at%) | 13-18 | 13-18 | 13-18 | 13-18 | 13-18 | 13-18 |
The WC-based ceramic provides structural support, enhances the overall performance of the material, combines elements such as Al, co, cr, fe, ni, cu and the like to ensure that the material has broadband electromagnetic shielding capability and excellent high-temperature stability, can realize high hardness and high wear resistance by compounding the elements, improves the electromagnetic shielding capability, reduces the atom diffusivity and improves the high-temperature stability of the material, and the addition of the high-entropy alloy improves the plasticity of the composite material so that the composite material keeps better ductility at high temperature, and can form a stable passivation film on the surface to further improve the corrosion resistance.
The arrangement combines the advantages of high-entropy alloy and high-purity WC-based ceramic, and realizes high-performance electromagnetic shielding, excellent mechanical properties, good high-temperature resistance and excellent corrosion resistance.
Specifically, the compactness of the WC-AlCoCrFeNiCu composite material reaches more than 99.5%, the Rockwell hardness is more than 93HRA, the bending strength is more than 1300MPa, the volume abrasion rate is only 1/6 of 316L, no obvious corrosion is seen in 720h neutral salt fog, after 1.5 x 107 Gy irradiation test, the hardness and the bending strength of the material are not obviously reduced, the attenuation ratio Ky reaches 3.66, and the attenuation coefficient is 0.6486 mu/cm-1.
The addition of the high-entropy alloy obviously improves the electromagnetic shielding performance of the material, the attenuation ratio and the attenuation coefficient show that the material has wide-band electromagnetic shielding capability, electromagnetic waves with different frequencies can be effectively shielded, the material has excellent wear resistance and impact resistance due to high hardness and high bending strength, the material has excellent wear resistance due to low volume wear rate, the material has excellent corrosion resistance, the material is stable in a corrosive environment, and the material has stable performance in a high-radiation environment due to good irradiation stability.
The WC-AlCoCrFeNiCu composite material has very high compactness, excellent mechanical property, wear resistance and corrosion resistance, simultaneously has excellent electromagnetic shielding and irradiation stability, the material combines the advantages of high-entropy alloy and WC-based ceramic, and realizes high-performance electromagnetic shielding, excellent mechanical properties, good high-temperature resistance and excellent corrosion resistance.
The second purpose of the invention is to disclose a preparation process of a novel WC-based metal ceramic composite shielding material, which comprises the following specific steps:
s1, preparing WC ceramic powder and high-entropy alloy powder;
S2, ball milling and mixing WC ceramic powder and high-entropy alloy powder;
s3, pre-pressing treatment is carried out;
And S4, performing high-temperature high-pressure sintering treatment.
The powder after mixing is pressed into a preform with a certain shape and density through pre-pressing treatment, a foundation is provided for subsequent sintering, and the preform is subjected to solid phase reaction and liquid phase sintering at high temperature through high-pressure sintering, so that the interface reaction between WC ceramic and high-entropy alloy is promoted, a good bonding interface is formed, and a compact composite material is formed.
The high-purity WC-based ceramic and the high-entropy alloy are compounded through the steps of ball milling mixing, pre-pressing treatment, high-temperature high-pressure sintering and the like, the uniformity and compactness of the material are guaranteed by forming the composite material with unique properties, the plasticity of the composite material is improved, the composite material keeps good ductility at high temperature, the diffusion rate of atoms is reduced, the high-temperature stability of the material is improved, a stable passivation film can be formed on the surface by the high-entropy alloy, the corrosion resistance is further improved, and the comprehensive performance of the material is integrally improved.
Specifically, in step S1, WC ceramic powder has a particle size of 0.4-1.0 μm and the high-entropy alloy AlCoCrFeNiCu has a powder particle size of 3-18 μm.
As shown in tables 3 to 4, the WC ceramic powder has a particle size of preferably 0.6 to 0.8. Mu.m, and the high-entropy alloy AlCoCrFeNiCu has a particle size of 5 to 15. Mu.m.
TABLE 3WC ceramic powder particle size
| Powder | Particle size distribution/. Mu.m |
| WC | 0.6-0.8 |
TABLE 4AlCoCrFeNiCu high entropy alloy powder particle size
| Powder | Particle size distribution/. Mu.m |
| AlCoCrFeNiCu | 5-15 |
In the sintering process, fine particles are easier to fill gaps, the porosity is reduced, the compactness of the material is improved, the contact area between the particles can be increased, a tighter structure is formed, the hardness and the wear resistance of the material are improved, the fine WC particles are easier to uniformly mix with other powder, the uniform and consistent performance of the composite material is ensured, the particle size of the high-entropy alloy powder is relatively large, good mixing uniformity can be formed between the high-entropy alloy powder and the fine WC particles, the particle size of the high-entropy alloy powder is relatively large, the fine WC particles can be embedded between the large high-entropy alloy particles to form the uniform composite material, the large high-entropy alloy particles can provide a certain supporting effect in the sintering process, the fine WC particles are prevented from being excessively sintered, the microstructure of the material is maintained, the large high-entropy alloy particles can provide more conductive paths, and the electromagnetic shielding performance of the material is improved.
The arrangement can obviously improve the compactness of the material, reduce the porosity, improve the mechanical property and corrosion resistance of the material, obviously improve the hardness and wear resistance of the material, is suitable for occasions needing high hardness and high wear resistance, and can ensure the uniformity of mixing by fine WC particles and improve the performance consistency of the material.
Specifically, in step S2, the specific steps of ball-milling and mixing are as follows:
S21, weighing raw material powder in proportion, and then adding the raw material powder into a hard alloy ball milling tank;
S22, adding hard alloy grinding balls, and performing ball milling mixing and refining on raw material powder by using a planetary ball mill;
and S23, after ball milling is finished, taking out the mixed slurry, placing the mixed slurry into a distillation flask, and removing absolute ethyl alcohol in the mixed slurry by means of a rotary evaporator to obtain dry mixed powder.
The method has the advantages that the raw material powder can be accurately weighed, the composite material performance of each batch can be ensured to be consistent, performance fluctuation caused by improper proportion is avoided, the cemented carbide ball milling tank and the planetary ball mill can ensure uniform mixing of WC ceramic powder and high-entropy alloy powder, local aggregation is avoided, powder particles can be further refined in the ball milling process, compactness and performance after sintering are improved, absolute ethyl alcohol can be effectively removed by the rotary evaporator, drying of mixed powder is ensured, subsequent pre-pressing and sintering treatment is avoided due to overlarge humidity, and meanwhile, the mixed powder is purer.
The arrangement can improve compactness and performance after sintering, ensure performance consistency of materials, avoid influence of residual solvents on the performance of the materials, and ensure purity and performance stability of the materials.
Specifically, in step S21, raw material powder is weighed in proportion by using an electronic balance with an accuracy of 0.01mg, and both the ball milling tank and the grinding balls are made of WC cemented carbide.
The setting ensures the accurate weighing of the raw material powder, avoids weighing errors, improves the repeatability and the reliability of experiments, and simultaneously ensures the wear resistance and the chemical stability of the ball milling tank and the grinding balls due to the high hardness and the wear resistance of WC hard alloy, avoids polluting the raw material powder, and ensures the purity and the uniformity of the raw material powder.
Specifically, in step S22, the ball-to-material ratio is set to (3-7): 1, the ball milling rotation speed is set to 250-350rpm, and the forward and reverse rotation mode is adopted, namely, the ball milling tank rotates clockwise for 25-35min, then rotates anticlockwise for 25-35min after resting for 7-13min, and the process is repeated. The ball milling time is 15-50h.
Preferably, the ball-material ratio is set to be 5:1, the ball milling rotating speed is set to be 300rpm, and the ball milling is carried out repeatedly in a forward and reverse rotation mode, namely, the ball milling tank rotates clockwise for 30min firstly and then rotates anticlockwise for 30min after resting for 10 min. The ball milling time is 25-40h.
The high ball-to-material ratio can provide more collision opportunities, effectively crush and refine powder particles, ensure that the powder particles are fully mixed in the ball milling process, improve the uniformity of mixing, the high rotating speed can provide higher energy input, accelerate the crushing and mixing processes of the powder particles, ensure that the powder particles are uniformly dispersed in a ball milling tank, avoid local overheating and local aggregation, the positive and negative rotation modes can ensure that the powder particles are uniformly collided and sheared in different directions, improve the uniformity of mixing, ensure that the powder particles are fully refined in the longer ball milling time, improve the compactness of materials, ensure that the powder particles are fully mixed in the ball milling process, and improve the uniformity of mixing.
The arrangement ensures the efficient crushing and uniform mixing of powder particles, reduces agglomeration phenomenon, and improves the compactness, hardness, wear resistance, bending strength and electromagnetic shielding performance of the material.
Specifically, in step S22, the ball milling tank and the grinding balls are made of YG-6 hard alloy.
The high hardness and the wear resistance of the ball milling tank and the grinding balls are ensured by the arrangement, the generation of wear debris is avoided, the service life is prolonged, the production cost is reduced, meanwhile, the high toughness and the chemical stability of the YG-6 hard alloy ensure the high-efficiency crushing and uniform mixing in the ball milling process, the pollution of raw material powder is avoided, and the performance consistency of the material is improved.
Specifically, in step S23, in the ball milling and powder mixing process, absolute ethanol is selected as a ball milling medium, so as to improve the ball milling efficiency and prevent powder oxidation.
The absolute ethyl alcohol can form a protective film, and the protective film covers the surfaces of powder particles, so that the powder particles are further prevented from being oxidized, the lubricating effect can be further achieved, friction among the powder particles is reduced, the ball milling process is smoother, the ball milling efficiency is improved, meanwhile, the powder particles can be effectively dispersed, the agglomeration phenomenon is reduced, and the powder particles are fully mixed and refined in the ball milling process.
This setting can effectively improve ball-milling efficiency, prevents powder oxidation.
Specifically, in step S3, a graphite mold is used for pre-pressing, and the mixed powder is placed in the graphite mold for pre-pressing molding.
The thermal conductivity of the graphite can ensure the uniform distribution of temperature in the pre-pressing process, reduce the temperature gradient, avoid local overheating, improve the pre-pressing forming quality, ensure the stability and the repeatability of the pre-pressing process, improve the surface finish of a pre-pressing forming part and reduce the surface defects, and the chemical stability of the graphite can ensure that the die cannot chemically react with mixed powder, avoid introducing impurities and ensure the purity of raw material powder.
This setting make full use of graphite mould's heat conductivity and lubricity can improve the fashioned quality of pre-compaction, ensures temperature evenly distributed and reduces friction, avoids introducing impurity, ensures raw materials powder's purity, and graphite mould can design into complicated shape simultaneously, satisfies the shaping requirement of different products.
Specifically, in step S4, the SPS furnace is adopted for high-temperature high-pressure sintering treatment, the sintering pressure is 20-60MPa, the sintering temperature is 1000-1600 ℃, the heating speed is 40-60 ℃ per minute, and the sintering heat preservation time is 3-13 minutes.
Preferably, the sintering pressure is 30-45MPa, the sintering temperature is 1200-1400 ℃, the heating speed is 50 ℃ per minute, and the sintering heat preservation time is 5-10 minutes.
The rapid temperature rise can obviously reduce sintering time, reduce oxidation possibility, ensure purity of materials, ensure uniform temperature distribution of samples in the sintering process by uniformly heating an SPS furnace, avoid local overheating or supercooling, improve sintering quality, reduce porosity by closely contacting powder particles at high pressure, improve material compactness, improve mechanical property and electromagnetic shielding property of the materials, reduce sintering temperature, avoid grain growth caused by long-time high-temperature treatment, reduce adverse effect of high temperature on material property, and prolong service life of the materials.
The characteristics of rapid temperature rise, uniform heating, high-pressure sintering and short-time sintering of the SPS furnace can obviously improve the sintering efficiency, reduce the sintering time and improve the density and the performance of the material.
Example 1:
Ball milling mixing (high entropy alloy powder mass ratio 10%) is carried out by adopting WC ceramic powder with the diameter of 0.6 μm and AlCoCrFeNiCu high entropy alloy powder with the diameter of 10 μm (atomic ratio is 1:1:1:1:1). Ball milling process, wherein the ball material ratio is set to be 5:1, the ball milling rotating speed is set to be 300rpm, and the ball milling is carried out repeatedly by adopting a positive and negative rotation mode, namely, the ball milling tank rotates clockwise for 30min firstly and then rotates anticlockwise for 30min after resting for 10 min. The ball milling time is 40h. After the ball milling was completed, the mixed slurry was taken out and placed in a distillation flask, and absolute ethanol thereof was removed by means of a rotary evaporator to obtain a dry mixed powder.
Then pre-pressing treatment is carried out through a die, and then ultra-high temperature high pressure (SPS) sintering is carried out. Sintering pressure is 30MPa, sintering temperature is 1200 ℃, heating speed is 50 ℃ per minute, and sintering heat preservation time is 6 minutes. The density of the prepared WC-AlCoCrFeNiCu composite material reaches 99.75%, the Rockwell hardness is 93.5HRA, and the bending strength is 1900MPa.
Example 2
Ball milling mixing is carried out by adopting WC ceramic powder with the diameter of 0.8 mu m and AlCoCrFeNiCu mu m (the atomic ratio is 1:1:1:0.8:0.8) high-entropy alloy powder (the mass ratio of the high-entropy alloy powder is 2%). Ball milling process, wherein the ball material ratio is set to be 5:1, the ball milling rotating speed is set to be 300rpm, and the ball milling is carried out repeatedly by adopting a positive and negative rotation mode, namely, the ball milling tank rotates clockwise for 30min firstly and then rotates anticlockwise for 30min after resting for 10 min. The ball milling time was 25h. After the ball milling was completed, the mixed slurry was taken out and placed in a distillation flask, and absolute ethanol thereof was removed by means of a rotary evaporator to obtain a dry mixed powder.
Then pre-pressing treatment is carried out through a die, and then ultra-high temperature high pressure (SPS) sintering is carried out. Sintering pressure is 25MPa, sintering temperature is 1350 ℃, heating speed is 50 ℃ per minute, and sintering heat preservation time is 5 minutes. The density of the prepared WC-AlCoCrFeNiCu composite material reaches 99.53%, the Rockwell hardness is 94HRA, and the bending strength is 1400MPa.
Example 3
Ball milling mixing is carried out by adopting WC ceramic powder with the diameter of 0.6 μm and AlCoCrFeNiCu (the atomic ratio is 1:1:1:1:1) high-entropy alloy powder with the diameter of 15 μm (the mass ratio of the high-entropy alloy powder is 6%). Ball milling process, wherein the ball material ratio is set to be 5:1, the ball milling rotating speed is set to be 300rpm, and the ball milling is carried out repeatedly by adopting a positive and negative rotation mode, namely, the ball milling tank rotates clockwise for 30min firstly and then rotates anticlockwise for 30min after resting for 10 min. The ball milling time is 35h. After the ball milling was completed, the mixed slurry was taken out and placed in a distillation flask, and absolute ethanol thereof was removed by means of a rotary evaporator to obtain a dry mixed powder.
Then pre-pressing treatment is carried out through a die, and then ultra-high temperature high pressure (SPS) sintering is carried out. Sintering pressure is 40MPa, sintering temperature is 1400 ℃, heating speed is 50 ℃ per minute, and sintering heat preservation time is 10 minutes. The density of the prepared WC-AlCoCrFeNiCu composite material reaches 99.68%, the Rockwell hardness is 93.8HRA, and the bending strength is 1852MPa.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.