Steel bond hard alloy cutter used under irradiation working condition and preparation method of steel bond hard alloy cutter

Abstract

The invention discloses a steel bond hard alloy cutter used under an irradiation working condition and a preparation method of the steel bond hard alloy cutter. The steel bond hard alloy cutter comprises the following materials: WC, M6C type carbide, submicron oxide particles and a steel substrate, and the contents of the M6C type carbide and the submicron oxide particles in the materials of the structure of the cutter from inside to outside are sequentially increased. Through step-by-step mixing of raw materials and controllable oxidation design, the steel bond hard alloy material provided by the invention comprises an inner-layer gradient structure and an outer-layer gradient structure. The inner layer material is composed of WC and a steel matrix, added rare earth metal elements are dissolved in the steel matrix in a solid mode, and reliable internal strength and toughness are provided for the cutter. Due to micro-oxidation in the controllable oxidation process, on one hand, rare earth elements absorb oxygen elements to form rare earth oxide particles, and on the other hand, a carbon-deficient area is formed on the surface, so that a large-size, high-hardness and high-wear-resistance M6C (Fe3W3C) phase is formed in the sintering process, and a high-hardness and high-wear-resistance outer layer structure is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy, and in particular relates to a steel-bonded carbide tool used in irradiation conditions and a preparation method thereof. Background Art

[0002] Nuclear energy is considered to be a sustainable clean energy that can replace fossil energy. It replaces the chemical energy of mineral fuels with fission energy. It does not produce air pollution in the process and does not aggravate the greenhouse effect. Nuclear fuel has high energy density, low fuel cost and stable cost. However, the related processing of the nuclear energy industry is accompanied by harsh working conditions such as mechanical load, chemical corrosion and radiation irradiation. Therefore, with the rapid development of the nuclear industry, higher and more stable requirements are put forward for industry-related service materials. Among them, the tool material determines the industrial production efficiency and the stability of related accessories of the nuclear industry to a certain extent. While enduring irradiation, it also needs to withstand high-speed impact and high-speed wear, which puts extremely high requirements on the comprehensive properties of the material such as strength, toughness and hardness.

[0003] Among the related machining tools, metal ceramics, cemented carbide, and high-speed steel are commonly used tool materials. Metal ceramics and cemented carbide tools have excellent hardness and wear resistance, but poor toughness; high-speed steel tools have good toughness, but the wear resistance of the material is far from that of cemented carbide. Faced with the heavy-load cutting common in the nuclear industry, metal ceramics and cemented carbide tools often fail quickly in the form of insufficient toughness and edge chipping, while high-speed steel has a relatively poor overall life due to its relatively poor wear resistance, which limits the overall project start-up rate and increases the project operation cost.

[0004] Faced with this problem, steel-bonded cemented carbide is a commonly used material choice in the nuclear industry. It is composed of a metal steel matrix bonding phase and WC and TiC ceramic hard phases. Therefore, it can combine the advantages of high-speed steel and cemented carbide. Through appropriate composition and heat treatment design, it can have a certain degree of good wear resistance and toughness. However, faced with harsh working conditions and gradually increasing life and stability requirements, the current steel-bonded cemented carbide still has problems: 1. Due to the relatively poor wettability between the steel matrix and WC and TiC, the strength and toughness of the material are still insufficient; 2. Considering that the material needs good strength and toughness, due to the limited proportion of ceramic hard phase, the wear resistance of the material is poor; 3. Heavy-duty tools are mostly large-sized. The production process of steel-bonded cemented carbide requires a forming agent, and the performance is sensitive to carbon content and porosity. The performance stability of large-sized products is poor; 4. The radiation resistance is insufficient, and the comprehensive performance is reduced after long-term work.

[0005] In summary, the insufficient performance of tool materials limits the high efficiency and high stability of nuclear industry production. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a steel-bonded cemented carbide tool for use under irradiation conditions and a preparation method thereof, in order to address the problems of insufficient hardness and wear resistance, poor toughness when bearing load and short service life of steel-bonded cemented carbide tools under special irradiation conditions in the prior art. The material is a tool material with high wear resistance and high toughness under irradiation environment. The tool has good radiation resistance, good wear resistance, strong impact resistance and long service life under this condition, and can improve the efficiency of the processing process and ensure processing stability.

[0007] The technical solution adopted to solve the technical problem of the present invention is to provide a steel-bonded carbide tool for use under irradiation conditions, wherein the materials thereof include: WC, M6C carbides, submicron oxide particles, and a steel matrix, and the contents of M6C carbides and submicron oxide particles in the material of the structure of the tool from the inside to the outside increase successively.

[0008] Preferably, the M6C type carbides are Fe3W3C and Fe3Mo3C produced by WC, Mo and iron matrix, and the submicron oxide particles are produced by the oxidation of rare earth elements.

[0009] Preferably, the steel-bonded carbide tool for use under irradiation conditions comprises: an inner layer structure and an outer layer structure arranged outside the inner layer structure, the material of the outer layer structure comprises WC, M6C carbide, submicron oxide particles, and a steel matrix, the material of the inner layer structure comprises WC and a steel matrix, the thickness of the inner layer structure is 10 to 500 mm, and the thickness of the outer layer structure is 2 to 3 mm.

[0010] Preferably, the raw material formula for preparing the cutting tool includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder and carbon black.

[0011] Preferably, the Fe powder is carbonyl iron powder;

[0012] The rare earth powder includes one or more of Y, La and Ce single substance powders.

[0013] Preferably, the Fresno particle sizes in the raw material powder are:

[0014] WC powder: 0.5~1μm, rare earth powder: 0.2~0.5μm, other metal powder: 2~5μm, carbon black particle size is -200 mesh~-400 mesh.

[0015] Preferably, the mass percentage of each raw material in the raw material formula for preparing the cutting tool is: WC powder accounts for 30-40%, Mo powder accounts for 0.5-2%, Cr powder accounts for 0.5-2%, Co powder accounts for 0.1-5%, Ni powder accounts for 0.1-4%, Mn powder accounts for 0.1-0.5%, rare earth powder accounts for 0.1-0.5%, carbon black accounts for 0.4-0.8%, and the rest is Fe powder.

[0016] Preferably, the mass percentage of each raw material in the raw material formula for preparing the cutting tool is: WC powder accounts for 30-35%, Mo powder accounts for 0.5-1%, Cr powder accounts for 0.5-1%, Co powder accounts for 2-4%, Ni powder accounts for 1-2%, Mn powder accounts for 0.1-0.3%, rare earth powder accounts for 0.1-0.3%, carbon black accounts for 0.5-0.7%, and the rest is Fe powder.

[0017] The present invention also provides a method for preparing the above-mentioned steel-bonded cemented carbide tool under irradiation conditions, comprising the following steps:

[0018] (1) mixing raw materials, wherein the raw material formula for preparing the cutting tool includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder, and carbon black to obtain a mixed material;

[0019] (2) pressing the mixed material to obtain a pressed blank;

[0020] (3) heating the pressed blank under a preset oxygen partial pressure for pre-oxidation;

[0021] (4) sintering under preset gas pressure conditions and preset temperature conditions to obtain a sintered blank;

[0022] (5) heating the sintered green body, applying uniaxial pressure, and creeping the green body to densify the sintered green body, thereby obtaining a hot pressed green body;

[0023] (6) The hot pressed blank is quenched and tempered to finally obtain a finished steel-bonded carbide tool.

[0024] Preferably, the step (1) is specifically to premix the raw material powders other than rare earth powder and Cr powder in a wet manner to obtain a premix, dry the premix, add Cr powder and rare earth powder, and perform final mixing using dry mixing technology under atmosphere protection to obtain a mixture.

[0025] Preferably, the wet premixing in step (1) is performed in a ball mill, the ball milling medium is alcohol, and argon is used to replace the air in the ball mill before ball milling;

[0026] After wet premixing, vacuum drying is adopted. Before drying, argon is used to replace the gas in the dryer and then vacuum is drawn. The drying temperature is 60-80°C. After drying, it is cooled to below 25°C and leaves the dryer.

[0027] Preferably, the step (2) is specifically to perform cold isostatic pressing on the mixed material to obtain a pressed blank.

[0028] Preferably, in step (2), the cold isostatic pressing pressure is 200 to 300 MPa, and the holding time is 10 to 20 minutes.

[0029] Preferably, the heating temperature in step (3) is 50-80° C., and the pre-oxidation time is 4-6 hours.

[0030] Preferably, the atmosphere of step (3) is a low oxygen partial pressure mixed gas of nitrogen and oxygen, wherein the oxygen content accounts for 3-5% by volume.

[0031] Preferably, in the step (4), a step-by-step heating process is adopted during the sintering process, and the temperature is kept at 120-150°C, 580-620°C, 780-820°C, 980-1020°C, and 1180-1220°C for 1-3 hours, and finally the temperature is raised to a maximum temperature of 1250°C to 1300°C and kept for 2-4 hours.

[0032] Preferably, in step (4), vacuum sintering is performed at 1180-1220°C, and the pressure of vacuum sintering is less than 10 -2 Pa;

[0033] Gas pressure sintering is used for heat preservation from 1180 to 1220°C to the highest temperature. The gas used in the gas pressure sintering process is argon gas and the pressure is 5 to 10 MPa.

[0034] Preferably, during the high temperature creep in step (5), the temperature is 1000-1200°C, the uniaxial pressure is 3-8 MPa, the time is 5-10 h, the gas used is argon or nitrogen atmosphere, and the final thickness deformation is controlled to be less than 0.2 mm.

[0035] Preferably, in the step (6), the quenching heating temperature is 1000°C to 1150°C, the quenching holding time is 60 to 120 min, the quenching is carried out in any one of a salt bath, an inert gas atmosphere, and a vacuum atmosphere, and the quenching cooling is carried out by oil quenching or gas quenching; the tempering temperature is 120 to 200°C, the tempering time is 1 to 3 h, and the steel is naturally cooled to room temperature after tempering.

[0036] Large-size products refer to those whose shortest side is greater than 60mm.

[0037] Preferably, in step (6), for large-sized products, the shortest side of which is greater than 100 mm, a cryogenic treatment is added before tempering, the cryogenic temperature is -180°C to -50°C, and the cryogenic time is 60 to 240 min.

[0038] Tool performance data in the present invention:

[0039] The outer layer structure is a controllable oxide layer with a hardness of HRC65-67 and a fracture toughness of 30-50 MPa·m1 / 2.

[0040] Inner layer structure hardness HRC59~62, fracture toughness 70~90MPa·m1 / 2, bending strength 3200~4000MPa, impact toughness 15~18J / cm 2 .

[0041] The test methods used above are as follows: hardness test HRC, GB / T3849.1-2015 (hard alloy Rockwell hardness test), three-point bending GB / T3851-2015 (hard alloy transverse fracture strength determination method), impact toughness GB / T1817-2017 (hard alloy room temperature impact toughness test method), GB / T 33819-2017 hard alloy Babbitt toughness test.

[0042] The present invention provides a steel-bonded carbide tool for use under irradiation conditions and a preparation method thereof, which can produce the following technical effects:

[0043] (1) Through the step-by-step mixing of raw materials and controlled oxidation design, the steel-bonded cemented carbide material provided by the present invention comprises an inner and outer layer gradient structure. The inner layer material is composed of WC and a steel matrix, and the added rare earth metal elements are dissolved in the steel matrix, providing reliable internal strength and toughness for the tool. Due to the micro-oxidation of the outer layer material during the controlled oxidation process, on the one hand, the rare earth elements absorb oxygen elements to form rare earth oxide particles, and on the other hand, a carbon-deficient area is formed on the surface, thereby forming a large-sized, high-hardness, and high-wear-resistant M6C (Fe3W3C) phase during the sintering process, and obtaining a high-hardness, high-wear-resistant outer layer structure.

[0044] (2) In the preparation method provided by the present invention, through the design of raw material particle size distribution and molding process, no molding agent is added in the entire material molding process, which can effectively avoid the problems of long degreasing time, product cracking, local differences in carbon content, etc. caused by the difficulty in removing the molding agent during the sintering process, shorten the product sintering time, improve the product production efficiency and product performance stability, and avoid the limitation of large size of the product.

[0045] (3) In order to achieve full density of the material and high bonding strength to WC particles, the patent adopts enhanced gas pressure sintering and high creep deformation and low deformation to strengthen the material. In these processes, the absolute volume change of the material is not large, avoiding the segregation of submicron WC and the damage to the surface organization during large deformation, thereby ensuring the reliability of the unique internal and external structure and material performance.

[0046] (4) Through controlled oxidation, the rare earth element oxides formed externally can pin the defects caused by radiation during the irradiation process, preventing them from aggregating and growing at the grain boundaries, thereby ensuring the long-term performance stability of the material under irradiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a SEM picture of the outer structure of the tool in Example 2 of the present invention;

[0048] Figure 2 This is a SEM picture of the inner layer structure of the tool in Example 2 of the present invention. DETAILED DESCRIPTION

[0049] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific implementation methods and drawings.

[0050] Example 1

[0051] This embodiment provides a steel-bonded carbide tool for use under irradiation conditions, wherein the materials thereof include: WC, M6C carbides, submicron oxide particles, and a steel matrix, wherein the contents of M6C carbides and submicron oxide particles in the material of the tool structure from the inside to the outside increase successively.

[0052] This embodiment also provides a method for preparing the steel-bonded cemented carbide tool under irradiation conditions, comprising the following steps:

[0053] (1) mixing raw materials, wherein the raw material formula for preparing the cutting tool includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder, and carbon black to obtain a mixed material;

[0054] (2) pressing the mixed material to obtain a pressed blank;

[0055] (3) heating the pressed blank under a preset oxygen partial pressure for pre-oxidation;

[0056] (4) sintering under preset gas pressure conditions and preset temperature conditions to obtain a sintered blank;

[0057] (5) heating the sintered green body, applying uniaxial pressure, and creeping the green body to densify the sintered green body, thereby obtaining a hot pressed green body;

[0058] (6) The hot pressed blank is quenched and tempered to finally obtain a finished steel-bonded carbide tool.

[0059] This embodiment provides a steel-bonded carbide tool for use under irradiation conditions and a preparation method thereof, which can produce the following technical effects:

[0060] Through step-by-step mixing of raw materials and controlled oxidation design, the steel-bonded cemented carbide material provided in this embodiment includes an inner and outer layer gradient structure. The inner layer material is composed of WC and a steel matrix, and the added rare earth metal elements are solid-dissolved in the steel matrix, providing reliable internal strength and toughness for the tool. Due to micro-oxidation in the controlled oxidation process of the outer layer material, on the one hand, the rare earth elements absorb oxygen elements to form rare earth oxide particles, and on the other hand, carbon-deficient areas are formed on the surface, thereby forming a large-sized, high-hardness, and high-wear-resistant M6C (Fe3W3C) phase during the sintering process, and obtaining a high-hardness, high-wear-resistant outer layer structure.

[0061] Through controlled oxidation, the rare earth element oxides formed externally can pin the defects caused by radiation during the irradiation process, preventing them from aggregating and growing at the grain boundaries, thereby ensuring the long-term performance stability of the material in an irradiated environment.

[0062] Example 2

[0063] This embodiment provides a steel-bonded carbide tool for use under irradiation conditions, wherein the materials thereof include: WC, M6C carbides, submicron oxide particles, and a steel matrix, wherein the contents of M6C carbides and submicron oxide particles in the material of the tool structure from the inside to the outside increase successively.

[0064] Preferably, the M6C type carbides are Fe3W3C and Fe3Mo3C produced by WC, Mo and iron matrix, and the submicron oxide particles are produced by the oxidation of rare earth elements.

[0065] Preferably, the steel-bonded carbide tool used under irradiation conditions comprises: an inner layer structure and an outer layer structure arranged outside the inner layer structure, the materials of the outer structure include WC, M6C carbide, submicron oxide particles, and a steel matrix, the materials of the inner layer structure include WC and a steel matrix, and according to actual tool requirements, the thickness of the inner layer structure is 10 to 500 mm, and the thickness of the wear-resistant outer layer structure in the material surface gradient structure is 2 to 3 mm.

[0066] Preferably, the raw material formula for preparing the cutting tool includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder and carbon black.

[0067] Preferably, the Fe powder is carbonyl iron powder;

[0068] The rare earth powder includes one or more of Y, La and Ce single substance powders.

[0069] Preferably, the Fresno particle sizes in the raw material powder are:

[0070] WC powder: 0.5~1μm, rare earth powder: 0.2~0.5μm, other metal powder: 2~5μm, carbon black particle size is -200 mesh~-400 mesh. Only by adopting such particle size matching and mixing technology can the mixture be pressed and formed without forming agent.

[0071] Preferably, the mass percentage of each raw material in the raw material formula for preparing the cutting tool is: WC powder accounts for 30-40%, Mo powder accounts for 0.5-2%, Cr powder accounts for 0.5-2%, Co powder accounts for 0.1-5%, Ni powder accounts for 0.1-4%, Mn powder accounts for 0.1-0.5%, rare earth powder accounts for 0.1-0.5%, carbon black accounts for 0.4-0.8%, and the rest is Fe powder.

[0072] Preferably, the mass percentage of each raw material in the raw material formula for preparing the cutting tool is: WC powder accounts for 30-35%, Mo powder accounts for 0.5-1%, Cr powder accounts for 0.5-1%, Co powder accounts for 2-4%, Ni powder accounts for 1-2%, Mn powder accounts for 0.1-0.3%, rare earth powder accounts for 0.1-0.3%, carbon black accounts for 0.5-0.7%, and the rest is Fe powder.

[0073] Ultrafine WC in the raw material provides the material with excellent hardness and wear resistance, but excessive addition will lead to a decrease in the toughness of the material. Co and Ni can improve the toughness and strength of the material by improving the wettability of the steel matrix to the WC wear-resistant phase, but too much Co will lead to excessive hardness increase and reduced toughness, while too much Ni will lead to too low hardness. Mo and Mn mainly play the role of improving the hardenability of the steel matrix. Mn can also promote sintering densification to a certain extent, but excessive addition of Mo will lead to the in-situ generation of Mo carbides, connecting the carbides and causing a decrease in toughness. Too low Mn will cause sintering volatilization and a decrease in the density and mechanical properties of the material. Cr provides the material with certain corrosion resistance. Rare earth powder is mainly used to improve the toughness and wettability of the metal phase in the inner layer, and to generate oxides in situ in the outer layer to strengthen the steel matrix and improve the radiation resistance of the material. Excessive addition will also affect the density and mechanical properties of the outer wear-resistant layer.

[0074] This embodiment also provides a method for preparing the steel-bonded cemented carbide tool for use under irradiation conditions and corrosion conditions, comprising the following steps:

[0075] (1) mixing raw materials, wherein the raw material formula for preparing the cutting tool includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder, and carbon black to obtain a mixed material;

[0076] (2) pressing the mixed material to obtain a pressed blank;

[0077] (3) heating the pressed blank under a preset oxygen partial pressure in a low oxygen partial pressure container, performing pre-oxidation, wherein the pre-oxidation is a controlled oxidation, and obtaining a pre-oxidized pressed blank after cooling;

[0078] (4) placing the pre-oxidized compact prepared in step (3) in a sintering furnace, sintering under preset gas pressure conditions and preset temperature conditions, and obtaining a sintered compact after cooling after sintering;

[0079] (5) High temperature creep densification: the sintered green body prepared in step (4) is placed in a high temperature environment, heated, and subjected to a certain uniaxial pressure to perform high temperature creep to densify the sintered green body, and then cooled to obtain a hot pressed green body after keeping it for a period of time;

[0080] (6) The hot pressed blank prepared in step (5) is quenched under certain conditions, and then tempered at a certain temperature and time after quenching to finally obtain a finished steel-bonded cemented carbide tool.

[0081] Preferably, the step (1) is specifically to wet premix the other raw material powders except rare earth powder and Cr powder according to a ratio to obtain a premix, and after drying the premix, Cr powder, rare earth powder and other easily oxidizable powders are added in proportion, and finally mixed by dry mixing technology under atmosphere protection to obtain a mixture.

[0082] Preferably, the wet premixing in step (1) is performed in a ball mill, the ball milling medium is alcohol, and argon is used to replace the air in the ball mill before ball milling to prevent the mixed powder from being excessively oxidized;

[0083] After wet premixing, vacuum drying is adopted. Before drying, argon is used to replace the gas in the dryer and then vacuum is drawn. The drying temperature is 60-80℃. The drying time is determined according to the specific alcohol content. During the drying cooling process, the outer wall of the dryer is cooled by chilled water. After drying, it is cooled to below 25℃ and then leaves the dryer.

[0084] The wet premixing technology can adopt the planetary ball mill, drum ball mill and the like which are commonly used in the industry.

[0085] Further optimization, considering the production efficiency, the premixing technology is preferably drum ball milling.

[0086] Preferably, the ball milling time is 72 to 96 hours, the ball-to-material ratio is (3 to 6):1, and the ball milling speed is 80 to 150 rpm.

[0087] The purpose of multiple mixing is to ensure that the mixed powder has high sintering activity while preventing easily oxidized powders such as Cr powder and rare earth metals from being oxidized by ball milling medium alcohol and gas during the drying process, resulting in the sintering process being unable to be dense and the internal material having poor mechanical properties.

[0088] Preferably, the dry mixing technology can use a double motion mixer, a vertical plowshare mixer or a horizontal plowshare mixer. Since the powder generates heat during the mixing process, argon is used to replace the air in the mixer before mixing, and the air tightness of the mixer cavity is ensured to prevent oxidation of easily oxidizable powders such as Cr powder and rare earth metals. Further preferably, the mixing is suspended for 1 hour every 4 hours during the dry mixing process to ensure that the mixture is not overheated. After the mixing is completed, the outer wall of the mixer is cooled with chilled water and cooled to below 25°C before leaving the mixer.

[0089] Preferably, the step (2) is specifically to perform cold isostatic pressing on the mixed material to obtain a pressed blank.

[0090] In powder metallurgy production, the key factor limiting the size and performance stability of large-sized products is the removal of the forming agent. If the size is too large, the forming agent is difficult to remove, which will cause pores or residual carbon. Therefore, there is a contradiction between powder metallurgy formability and the removal of the forming agent. This patent has achieved a significant improvement in the pressing performance by designing the raw material particle size and ball milling parameters. Through the particle size matching and the preparation scheme of the mixture, the pressing of the mixture can be carried out in the absence of a forming agent. Therefore, there is no need to consider the removal of the forming agent during the subsequent sintering process, which improves the stability of the material performance. The material properties of steel-bonded cemented carbide are highly correlated with the carbon content. In conventional technology, the forming agent inside large-sized steel-bonded cemented carbide is difficult to remove, requiring a lot of degreasing time, and is prone to residual carbonization of the forming agent, causing local carbon content fluctuations in the material and deterioration of performance. Therefore, the presence of the forming agent limits the size and performance stability of the steel-bonded alloy.

[0091] Preferably, the cold isostatic pressing pressure in step (2) is 200-300 MPa, and the holding time is 10-20 minutes. During the pressing process, it is necessary to ensure that the pressed blank has sufficient strength and density uniformity. Since the mixture does not contain a molding agent, only cold isostatic pressing can be used for blanking. In addition, the blank needs to reach a relatively high density and reduce gas channels to avoid oxidation of the internal material during the subsequent controlled oxidation process.

[0092] Preferably, the heating temperature in step (3) is 50-80° C., and the pre-oxidation time is 4-6 hours.

[0093] Preferably, the atmosphere of step (3) is a low oxygen partial pressure mixed gas of nitrogen and oxygen, wherein the oxygen content accounts for 3-5% by volume.

[0094] Because the diffusion of oxygen takes time, the degree of oxidation is controlled by controlling the oxygen partial pressure, temperature and time. This step is to make the surface area of ​​the compact controlled by oxidation, so as to obtain a gradient structure during the sintering process. On the one hand, during the sintering process, rare earth metals and other elements will absorb oxygen to form fine oxides, improving the radiation resistance of the material. On the other hand, the steel matrix is ​​properly oxidized and can be reduced by the added carbon black during the sintering process, thereby constructing a carbon-deficient area and further forming M6C-type carbides to increase the surface hardness and wear resistance of the material.

[0095] Preferably, after the heating controlled oxidation is completed and the container is cooled to room temperature, air is introduced into the container and allowed to stand for 6 hours before the container is opened and the controlled oxidation compact is taken out.

[0096] Preferably, in the step (4), a step-by-step heating process is adopted during the sintering process, and the temperature is kept at 120-150°C, 580-620°C, 780-820°C, 980-1020°C, and 1180-1220°C for 1-3 hours, and finally the temperature is raised to a maximum temperature of 1250°C to 1300°C and kept for 2-4 hours.

[0097] The 120-150℃ platform heat preservation can remove the moisture in the green compact. The 580-620℃, 780-820℃, and 980-1020℃ heat preservation platforms can allow the added carbon black to react with the adsorbed oxygen in the metal powder and ceramic powder to form CO reducing gas to further reduce the trace oxidation on the surface of the powder, exposing the internal fresh surface to promote further densification. The 1180-1220℃ and highest temperature heat preservation are conducive to the completion of the final sintering shrinkage and obtain a high-density sintered green compact.

[0098] Preferably, in step (4), vacuum sintering is performed at 1180-1220°C, and the vacuum pump is kept in operation, and the pressure of vacuum sintering is less than 10 -2 Pa;

[0099] Gas pressure sintering is used for heat preservation from 1180 to 1220°C to the highest temperature. The gas used in the gas pressure sintering process is argon gas and the pressure is 5 to 10 MPa.

[0100] During the sintering process, due to the low carbon content in the surface pre-oxidation layer, WC reacts with the Fe matrix at high temperature to in-situ generate large M6C-type ceramic particles, which improves the wear resistance of the outer layer.

[0101] The use of vacuum before 1180-1220℃ is to fully expel water vapor, oxygen and other low-melting-point impurities through evaporation and carbon-oxygen reaction during the sintering process, thereby reducing the oxygen content of the material and enhancing the bonding force between WC and the metal phase. The subsequent gas pressure sintering is to strengthen the sintering and improve the sintered density and mechanical properties of the material.

[0102] Preferably, during the high temperature creep in step (5), the temperature is 1000-1200°C, the uniaxial pressure is 3-8 MPa, the time is 5-10 h, the gas used is argon or nitrogen atmosphere, and the final thickness deformation is controlled to be less than 0.2 mm.

[0103] In order to further improve the density of the material, close the internal pores of the material, and avoid the destruction of the inner and outer layer structures of the material during thermal deformation, and also avoid the uneven distribution of WC with the plastic flow of the metal phase, high-temperature creep is used to improve the density of the material. However, hot processing methods with large deformation such as forging are prone to process defects during the process, and will cause the surface wear-resistant structure to be destroyed. In addition, submicron WC particles will flow with the metal phase, causing local segregation of the ceramic phase and bringing instability in performance.

[0104] The high temperature creep process can be carried out using equipment such as a hot press furnace or a bell furnace.

[0105] Preferably, in the step (6), the heating temperature of the quenching is 1000°C to 1150°C, the quenching holding time is 60 to 120 minutes depending on the product size, the quenching is carried out in any one of a salt bath, an inert gas atmosphere, and a vacuum atmosphere, and the quenching cooling is carried out by oil quenching or gas quenching; the tempering temperature is 120 to 200°C, the tempering time is 1 to 3 hours, and the product is naturally cooled to room temperature after tempering.

[0106] Preferably, in step (6), for large-sized products, the shortest side of which is greater than 100 mm, a cryogenic treatment is added before tempering, the cryogenic temperature is -180°C to -50°C, and the cryogenic time is 60 to 240 min.

[0107] Preferably, the machining plan is determined according to the final tool use shape and working conditions to ensure that the outer wear-resistant layer is not damaged and the machining is performed. Usually, rough machining is performed before heat treatment, when the material has slightly lower wear resistance and is easy to process, and fine machining is performed after heat treatment to the final state.

[0108] The present invention provides a steel-bonded carbide tool for use under irradiation conditions, wherein the surface of the material has a microstructure with a gradient structure, and the gradient structure is mainly composed of an inner structure with a high toughness layer and an outer structure with a high wear-resistant layer. The inner layer maintains toughness to support the material from breaking and fragmenting during impact, while the outer structure has strong wear resistance during the use of the tool, maintains the dimensional stability of the tool and provides a considerable lifespan. The gradient structure of the material is obtained by controllably oxidizing the pressed blank, so that the bonding force between the inner and outer layer structures is good, thereby giving the tool material the characteristics of both high wear resistance and high impact resistance. In addition, in order to ensure that the material has good radiation resistance, the microstructure of the material has dispersed rare earth oxides, which can pin the defects caused by radiation and cannot gather and grow at the grain boundaries, thereby ensuring the stability of the material under irradiation. Under the combined effect of these advantages, compared with existing steel-bonded carbide tools, it has better performance and more outstanding stability.

[0109] The present invention provides a steel-bonded carbide tool for use under irradiation conditions. The performance difference between the inner and outer layer structures of the material is mainly due to the different microstructures and phase compositions of the inner and outer layer structures after special treatment in the preparation process. The microstructure of the outer layer structure mainly includes WC, M6C carbides (Fe3W3C, Fe3Mo3C, etc. produced by WC, Mo and iron matrix), submicron oxide particles (rare earth elements produced in controlled oxidation), and steel matrix, and the inner layer structure mainly includes WC and steel matrix.

[0110] Specifically, this embodiment provides a steel-bonded carbide tool for use under irradiation conditions, the materials of which include: WC, M6C carbide, submicron oxide particles, and a steel matrix. The contents of M6C carbide and submicron oxide particles in the material of the tool structure from the inside to the outside increase successively.

[0111] Specifically, in this embodiment, the M6C type carbides are Fe3W3C and Fe3Mo3C produced by WC, Mo and iron matrix, and the submicron oxide particles are produced by the oxidation of rare earth elements.

[0112] Specifically, the steel-bonded carbide tool used under irradiation conditions in this embodiment includes: an inner layer structure and an outer layer structure arranged outside the inner layer structure, the material of the outer structure includes WC, M6C carbide, submicron oxide particles, and a steel matrix, the material of the inner layer structure includes WC and a steel matrix, the thickness of the inner layer structure is 250 mm, and the thickness of the outer layer structure is 3 mm.

[0113] Specifically, the raw material formula for preparing the cutting tool in this embodiment includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder, and carbon black.

[0114] Specifically, in this embodiment, the Fe powder is carbonyl iron powder;

[0115] The rare earth powder includes Y and La single substance powders (mass ratio is 1:1).

[0116] Specifically, the Fresno particle sizes of the raw material powders in this embodiment are:

[0117] WC powder: 1μm, rare earth powder: 0.4μm, other metal powder: 4μm, carbon black particle size is -200 mesh.

[0118] Specifically, the mass percentage of each raw material in the raw material formula for preparing the cutting tool in this embodiment is: WC powder accounts for 30%, Mo powder accounts for 0.5%, Cr powder accounts for 2%, Co powder accounts for 5%, Ni powder accounts for 2%, Mn powder accounts for 0.3%, rare earth powder accounts for 0.2%, carbon black accounts for 0.4%, and the rest is Fe powder.

[0119] Specifically, this embodiment provides a method for preparing the steel-bonded cemented carbide tool under irradiation conditions, comprising the following steps:

[0120] (1) The raw material formula for preparing the cutting tool includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder, and carbon black. The raw material powders other than the rare earth powder and Cr powder are wet premixed. The wet premixing is performed by mixing in a ball mill to obtain a premixed material. The ball milling medium is alcohol. Argon gas is used to replace the air in the ball mill before ball milling.

[0121] After wet premixing, vacuum drying is adopted. Before drying, argon is used to replace the gas in the dryer and then vacuum is drawn. The drying temperature is 80°C. After drying, it is cooled to below 25°C and leaves the dryer. After the premix is ​​dried, Cr powder and rare earth powder are added, and dry mixing technology is used for final mixing under atmosphere protection to obtain a mixed material.

[0122] (2) The mixed material is subjected to cold isostatic pressing at a pressure of 200 MPa and a holding time of 10 minutes to obtain a pressed blank.

[0123] (3) The pressed blank is heated at 70° C. The pre-oxidation time is 6 hours. The atmosphere is a low oxygen partial pressure mixed gas of nitrogen and oxygen, in which the oxygen content is 5% by volume. The blank is heated at a preset oxygen partial pressure for pre-oxidation.

[0124] (4) Sintering is performed under preset gas pressure and temperature conditions. During the sintering process, a step-by-step heating process is used. The temperature is kept at 120°C, 620°C, 820°C, 980°C, and 1180°C for 3 hours. Vacuum sintering is performed before 1180-1220°C. The gas pressure of vacuum sintering is less than 10 -2Pa; finally the temperature is raised to a maximum temperature of 1300°C, kept at that temperature for 3 hours, and then gas pressure sintering is performed at 1180-1220°C to the maximum temperature. The gas used in the gas pressure sintering process is argon gas and the pressure is 5 MPa to obtain a sintered blank.

[0125] (5) The sintered blank is heated and subjected to uniaxial pressure to creep. During high-temperature creep, the temperature is 1100°C, the uniaxial pressure is 3 MPa, the time is 5 h, and the gas is argon or nitrogen atmosphere. The final thickness deformation is controlled to be less than 0.2 mm, so that the sintered blank is densified to obtain a hot pressed blank.

[0126] (6) The hot pressed blank is quenched at a heating temperature of 1150°C and a quenching holding time of 90 min in a vacuum atmosphere and cooled by oil quenching; tempered at a tempering temperature of 120°C and a tempering time of 2 h. After tempering, the blank is naturally cooled to room temperature. For large-sized products, a deep cooling treatment is added before tempering. The deep cooling temperature is -180°C and the deep cooling time is 60 min. Finally, a finished steel-bonded carbide tool is obtained.

[0127] The cutter in this embodiment has good impact resistance, good wear resistance and long service life under this working condition.

[0128] Tool performance data in this embodiment:

[0129] The outer layer structure is a controllable oxide layer with a hardness of HRC65 and a fracture toughness of 48MPa·m1 / 2.

[0130] The inner layer structure has a hardness of HRC59, fracture toughness of 88MPa·m1 / 2, bending strength of 3200MPa, and impact toughness of 16J / cm2.

[0131] The test methods used above are as follows: hardness test HRC, GB / T3849.1-2015 (hard alloy Rockwell hardness test), three-point bending GB / T3851-2015 (hard alloy transverse fracture strength determination method), impact toughness GB / T1817-2017 (hard alloy room temperature impact toughness test method), GB / T 33819-2017 hard alloy Babbitt toughness test.

[0132] like Figure 1 This is the SEM picture of the outer structure of the tool. Figure 2 This is a SEM picture of the inner structure of the tool. The scanning electron microscope used is FEIQuanta 250FEG.

[0133] This embodiment provides a steel-bonded carbide tool for use under irradiation conditions and a preparation method thereof, which can produce the following technical effects:

[0134] (1) Through the step-by-step mixing of raw materials and controlled oxidation design, the steel-bonded cemented carbide material provided in this embodiment includes an inner and outer layer gradient structure. The inner layer material is composed of WC and a steel matrix, and the added rare earth metal elements are solid-dissolved in the steel matrix, providing reliable internal strength and toughness for the tool. Due to the micro-oxidation of the outer layer material during the controlled oxidation process, on the one hand, the rare earth elements absorb oxygen elements to form rare earth oxide particles, and on the other hand, a carbon-deficient area is formed on the surface, thereby forming a large-sized, high-hardness, and high-wear-resistant M6C (Fe3W3C) phase during the sintering process, and obtaining a high-hardness, high-wear-resistant outer layer structure.

[0135] (2) In the preparation method provided in this embodiment, through the design of raw material particle size distribution and molding process, no molding agent is added in the entire material molding process, which can effectively avoid the problems of long degreasing time, product cracking, local differences in carbon content, etc. caused by the difficulty in removing the molding agent during the sintering process, shorten the product sintering time, improve the product production efficiency and product performance stability, and avoid the limitation of large size of the product.

[0136] (3) In order to achieve full density of the material and high bonding strength to WC particles, the patent adopts enhanced gas pressure sintering and high creep deformation and low deformation to strengthen the material. In these processes, the absolute volume change of the material is not large, avoiding the segregation of submicron WC and the damage to the surface organization during large deformation, thereby ensuring the reliability of the unique internal and external structure and material performance.

[0137] (4) Through controlled oxidation, the rare earth element oxides formed externally can pin the defects caused by radiation during the irradiation process, preventing them from aggregating and growing at the grain boundaries, thereby ensuring the long-term performance stability of the material under irradiation.

[0138] Example 3

[0139] This embodiment provides a steel-bonded carbide tool for use under irradiation conditions. The difference from Example 2 is that its materials include: WC, M6C carbide, submicron oxide particles, and a steel matrix. The content of M6C carbide and submicron oxide particles in the material of the tool structure increases from the inside to the outside.

[0140] Specifically, in this embodiment, the M6C type carbides are Fe3W3C and Fe3Mo3C produced by WC, Mo and iron matrix, and the submicron oxide particles are produced by the oxidation of rare earth elements.

[0141] Specifically, the steel-bonded carbide tool used under irradiation conditions in this embodiment includes: an inner layer structure and an outer layer structure arranged outside the inner layer structure, the material of the outer structure includes WC, M6C carbide, submicron oxide particles, and a steel matrix, the material of the inner layer structure includes WC and a steel matrix, the thickness of the inner layer structure is 10 mm, and the thickness of the outer layer structure is 2.5 mm.

[0142] Specifically, the raw material formula for preparing the cutting tool in this embodiment includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder, and carbon black.

[0143] Specifically, in this embodiment, the Fe powder is carbonyl iron powder;

[0144] The rare earth powder includes Ce single substance powder.

[0145] Specifically, the Fresno particle sizes of the raw material powders in this embodiment are:

[0146] WC powder: 0.8μm, rare earth powder: 0.2μm, other metal powder: 5μm, carbon black particle size is -200 mesh.

[0147] Specifically, the mass percentage of each raw material in the raw material formula for preparing the cutting tool in this embodiment is: WC powder accounts for 35%, Mo powder accounts for 0.8%, Cr powder accounts for 0.5%, Co powder accounts for 4%, Ni powder accounts for 4%, Mn powder accounts for 0.1%, rare earth powder accounts for 0.5%, carbon black accounts for 0.8%, and the rest is Fe powder.

[0148] Specifically, this embodiment provides a method for preparing a steel-bonded cemented carbide tool under irradiation conditions, which is different from that in Embodiment 2 in that it includes the following steps:

[0149] (1) The raw material formula for preparing the cutting tool includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder, and carbon black. The raw material powders other than the rare earth powder and Cr powder are wet premixed. The wet premixing is performed by mixing in a ball mill to obtain a premixed material. The ball milling medium is alcohol. Argon gas is used to replace the air in the ball mill before ball milling.

[0150] After wet premixing, vacuum drying is adopted. Before drying, argon is used to replace the gas in the dryer and then vacuum is drawn. The drying temperature is 70°C. After drying, it is cooled to below 25°C and leaves the dryer. After the premix is ​​dried, Cr powder and rare earth powder are added, and dry mixing technology is used for final mixing under atmosphere protection to obtain a mixed material.

[0151] (2) The mixed material is subjected to cold isostatic pressing at a pressure of 250 MPa and a holding time of 20 minutes to obtain a pressed blank.

[0152] (3) The pressed blank is heated at 80° C. The pre-oxidation time is 4 h. The atmosphere is a low oxygen partial pressure mixed gas of nitrogen and oxygen, in which the oxygen content is 3% by volume. The blank is heated at a preset oxygen partial pressure for pre-oxidation.

[0153] (4) Sintering is performed under preset gas pressure and temperature conditions. During the sintering process, a step-by-step heating process is used. The temperature is kept at 150°C, 600°C, 780°C, 1020°C, and 1200°C for 2 hours. Vacuum sintering is performed before 1200°C. The gas pressure of vacuum sintering is less than 10 -2 Pa; finally the temperature is raised to a maximum temperature of 1250°C, kept at this temperature for 2 hours, and then gas pressure sintering is performed from 1200°C to the maximum temperature. The gas used in the gas pressure sintering process is argon gas and the pressure is 8 MPa to obtain a sintered blank.

[0154] (5) The sintered blank is heated and subjected to uniaxial pressure to creep. During high-temperature creep, the temperature is 1000°C, the uniaxial pressure is 8 MPa, the time is 8 h, and the gas atmosphere is argon or nitrogen. The final thickness deformation is controlled to be less than 0.2 mm, so that the sintered blank is densified to obtain a hot pressed blank.

[0155] (6) The hot pressed blank is quenched at a heating temperature of 1100°C and a quenching holding time of 120 min in an inert gas atmosphere and cooled by gas quenching; tempered at a tempering temperature of 170°C and a tempering time of 1 h. After tempering, the blank is naturally cooled to room temperature. For large-sized products, a deep cooling treatment is added before tempering. The deep cooling temperature is -100°C and the deep cooling time is 150 min. Finally, a finished steel-bonded carbide tool is obtained.

[0156] Tool performance data in this embodiment:

[0157] The outer layer structure is a controllable oxide layer with a hardness of HRC66 and a fracture toughness of 42MPa·m1 / 2.

[0158] Inner layer structure hardness HRC61, fracture toughness 83MPa·m1 / 2, bending strength 3760MPa, impact toughness 17J / cm 2 .

[0159] This embodiment provides a steel-bonded carbide tool for use under irradiation conditions and a preparation method thereof, which can produce the following technical effects:

[0160] (1) Through the step-by-step mixing of raw materials and controlled oxidation design, the steel-bonded cemented carbide material provided in this embodiment includes an inner and outer layer gradient structure. The inner layer material is composed of WC and a steel matrix, and the added rare earth metal elements are solid-dissolved in the steel matrix, providing reliable internal strength and toughness for the tool. Due to the micro-oxidation of the outer layer material during the controlled oxidation process, on the one hand, the rare earth elements absorb oxygen elements to form rare earth oxide particles, and on the other hand, a carbon-deficient area is formed on the surface, thereby forming a large-sized, high-hardness, and high-wear-resistant M6C (Fe3W3C) phase during the sintering process, and obtaining a high-hardness, high-wear-resistant outer layer structure.

[0161] (2) In the preparation method provided in this embodiment, through the design of raw material particle size distribution and molding process, no molding agent is added in the entire material molding process, which can effectively avoid the problems of long degreasing time, product cracking, local differences in carbon content, etc. caused by the difficulty in removing the molding agent during the sintering process, shorten the product sintering time, improve the product production efficiency and product performance stability, and avoid the limitation of large size of the product.

[0162] (3) In order to achieve full density of the material and high bonding strength to WC particles, the patent adopts enhanced gas pressure sintering and high creep deformation and low deformation to strengthen the material. In these processes, the absolute volume change of the material is not large, avoiding the segregation of submicron WC and the damage to the surface organization during large deformation, thereby ensuring the reliability of the unique internal and external structure and material performance.

[0163] (4) Through controlled oxidation, the rare earth element oxides formed externally can pin the defects caused by radiation during the irradiation process, preventing them from aggregating and growing at the grain boundaries, thereby ensuring the long-term performance stability of the material under irradiation.

[0164] Example 4

[0165] This embodiment provides a steel-bonded carbide tool for use under irradiation conditions. The difference from Embodiment 2 is that its materials include: WC, M6C carbide, submicron oxide particles, and a steel matrix. The contents of M6C carbide and submicron oxide particles in the material of the structure of the tool from the inside to the outside increase successively.

[0166] Specifically, in this embodiment, the M6C type carbides are Fe3W3C and Fe3Mo3C produced by WC, Mo and iron matrix, and the submicron oxide particles are produced by the oxidation of rare earth elements.

[0167] Specifically, the steel-bonded carbide tool used under irradiation conditions in this embodiment includes: an inner layer structure and an outer layer structure arranged outside the inner layer structure, the material of the outer structure includes WC, M6C carbide, submicron oxide particles, and a steel matrix, the material of the inner layer structure includes WC and a steel matrix, the thickness of the inner layer structure is 500 mm, and the thickness of the outer layer structure is 2 mm.

[0168] Specifically, the raw material formula for preparing the cutting tool in this embodiment includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder, and carbon black.

[0169] Specifically, in this embodiment, the Fe powder is carbonyl iron powder;

[0170] The rare earth powder includes Y.

[0171] Specifically, the Fresno particle sizes of the raw material powders in this embodiment are:

[0172] WC powder: 0.5μm, rare earth powder: 0.5μm, other metal powder: 2μm, carbon black particle size is -200 mesh.

[0173] Specifically, the mass percentage of each raw material in the raw material formula for preparing the cutting tool in this embodiment is: WC powder accounts for 40%, Mo powder accounts for 2%, Cr powder accounts for 1%, Co powder accounts for 2%, Ni powder accounts for 0.1%, Mn powder accounts for 0.2%, rare earth powder accounts for 0.1%, carbon black accounts for 0.6%, and the rest is Fe powder.

[0174] Specifically, this embodiment provides a method for preparing a steel-bonded cemented carbide tool under irradiation conditions, which is different from that in Embodiment 2 in that it includes the following steps:

[0175] (1) The raw material formula for preparing the cutting tool includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder, and carbon black. The raw material powders other than the rare earth powder and Cr powder are wet premixed. The wet premixing is performed by mixing in a ball mill to obtain a premixed material. The ball milling medium is alcohol. Argon gas is used to replace the air in the ball mill before ball milling.

[0176] After wet premixing, vacuum drying is adopted. Before drying, argon is used to replace the gas in the dryer and then vacuum is drawn. The drying temperature is 60°C. After drying, it is cooled to below 25°C and leaves the dryer. After the premix is ​​dried, Cr powder and rare earth powder are added, and dry mixing technology is used for final mixing under atmosphere protection to obtain a mixed material.

[0177] (2) The mixed material is subjected to cold isostatic pressing at a pressure of 300 MPa and a holding time of 15 minutes to obtain a pressed blank.

[0178] (3) The pressed blank is heated at a temperature of 50° C. and a pre-oxidation time of 5 h. The atmosphere is a low oxygen partial pressure mixed gas of nitrogen and oxygen, in which the oxygen content is 4% by volume. The pressed blank is heated at a preset oxygen partial pressure for pre-oxidation.

[0179] (4) Sintering is performed under preset gas pressure and temperature conditions. During the sintering process, a step-by-step heating process is used. The temperature is kept at 130°C, 580°C, 800°C, 1000°C, and 1220°C for 1 hour. Vacuum sintering is performed before 1180-1220°C. The gas pressure of vacuum sintering is less than 10 -2 Pa; finally the temperature is raised to a maximum temperature of 1280°C, kept at that temperature for 4 hours, and then gas pressure sintering is performed at 1180-1220°C to the maximum temperature. The gas used in the gas pressure sintering process is argon gas with a pressure of 10 MPa to obtain a sintered blank.

[0180] (5) The sintered blank is heated and subjected to uniaxial pressure to creep. During high-temperature creep, the temperature is 1200°C, the uniaxial pressure is 5 MPa, the time is 10 h, and the gas atmosphere is argon or nitrogen. The final thickness deformation is controlled to be less than 0.2 mm, so that the sintered blank is densified to obtain a hot pressed blank.

[0181] (6) The hot pressed blank is quenched at a heating temperature of 1000°C and a quenching holding time of 60 min in a salt bath and cooled with oil; tempered at a tempering temperature of 200°C and a tempering time of 3 h, and naturally cooled to room temperature after tempering. For large-sized products, a deep cooling treatment is added before tempering, and the deep cooling temperature is -50°C and the deep cooling time is 240 min. Finally, a finished steel-bonded carbide tool is obtained.

[0182] Tool performance data in this embodiment:

[0183] The outer layer structure is a controllable oxide layer with a hardness of HRC67 and a fracture toughness of 31MPa·m1 / 2.

[0184] Inner layer structure hardness HRC62, fracture toughness 72MPa·m1 / 2, bending strength 3200MPa, impact toughness 15J / cm 2 .

[0185] This embodiment provides a steel-bonded carbide tool for use under irradiation conditions and a preparation method thereof, which can produce the following technical effects:

[0186] (1) Through the step-by-step mixing of raw materials and controlled oxidation design, the steel-bonded cemented carbide material provided in this embodiment includes an inner and outer layer gradient structure. The inner layer material is composed of WC and a steel matrix, and the added rare earth metal elements are solid-dissolved in the steel matrix, providing reliable internal strength and toughness for the tool. Due to the micro-oxidation of the outer layer material during the controlled oxidation process, on the one hand, the rare earth elements absorb oxygen elements to form rare earth oxide particles, and on the other hand, a carbon-deficient area is formed on the surface, thereby forming a large-sized, high-hardness, and high-wear-resistant M6C (Fe3W3C) phase during the sintering process, and obtaining a high-hardness, high-wear-resistant outer layer structure.

[0187] (2) In the preparation method provided in this embodiment, through the design of raw material particle size distribution and molding process, no molding agent is added in the entire material molding process, which can effectively avoid the problems of long degreasing time, product cracking, local differences in carbon content, etc. caused by the difficulty in removing the molding agent during the sintering process, shorten the product sintering time, improve the product production efficiency and product performance stability, and avoid the limitation of large size of the product.

[0188] (3) In order to achieve full density of the material and high bonding strength to WC particles, the patent adopts enhanced gas pressure sintering and high creep deformation and low deformation to strengthen the material. In these processes, the absolute volume change of the material is not large, avoiding the segregation of submicron WC and the damage to the surface organization during large deformation, thereby ensuring the reliability of the unique internal and external structure and material performance.

[0189] (4) Through controlled oxidation, the rare earth element oxides formed externally can pin the defects caused by radiation during the irradiation process, preventing them from aggregating and growing at the grain boundaries, thereby ensuring the long-term performance stability of the material under irradiation.

[0190] Example 5

[0191] This embodiment provides a steel-bonded carbide tool for use under irradiation conditions, which differs from the embodiment 2 in that:

[0192] In the raw material formula for preparing the cutting tool in this embodiment, the mass percentage of each raw material is: WC powder accounts for 32%, Mo powder accounts for 1%, Cr powder accounts for 0.8%, Co powder accounts for 0.1%, Ni powder accounts for 1.5%, Mn powder accounts for 0.5%, rare earth powder accounts for 0.3%, carbon black accounts for 0.7%, and the rest is Fe powder.

[0193] This embodiment provides a method for preparing a steel-bonded cemented carbide tool under irradiation conditions, which is different from the method in Embodiment 2 in that:

[0194] The raw material formulas for preparing the cutting tools in this embodiment are different.

[0195] Tool performance data in this embodiment:

[0196] The outer layer structure is a controllable oxide layer with a hardness of HRC65 and a fracture toughness of 48MPa·m1 / 2.

[0197] Inner layer structure hardness HRC59, fracture toughness 88MPa·m1 / 2, bending strength 3800MPa, impact toughness 17J / cm 2 .

[0198] The present invention provides a steel-bonded carbide tool for use under irradiation conditions and a preparation method thereof, which can produce the following technical effects:

[0199] (1) Through the step-by-step mixing of raw materials and controlled oxidation design, the steel-bonded cemented carbide material provided by the present invention comprises an inner and outer layer gradient structure. The inner layer material is composed of WC and a steel matrix, and the added rare earth metal elements are dissolved in the steel matrix, providing reliable internal strength and toughness for the tool. Due to the micro-oxidation of the outer layer material during the controlled oxidation process, on the one hand, the rare earth elements absorb oxygen elements to form rare earth oxide particles, and on the other hand, a carbon-deficient area is formed on the surface, thereby forming a large-sized, high-hardness, and high-wear-resistant M6C (Fe3W3C) phase during the sintering process, and obtaining a high-hardness, high-wear-resistant outer layer structure.

[0200] (2) In the preparation method provided by the present invention, through the design of raw material particle size distribution and molding process, no molding agent is added in the entire material molding process, which can effectively avoid the problems of long degreasing time, product cracking, local differences in carbon content, etc. caused by the difficulty in removing the molding agent during the sintering process, shorten the product sintering time, improve the product production efficiency and product performance stability, and avoid the limitation of large size of the product.

[0201] (3) In order to achieve full density of the material and high bonding strength to WC particles, the patent adopts enhanced gas pressure sintering and high creep deformation and low deformation to strengthen the material. In these processes, the absolute volume change of the material is not large, avoiding the segregation of submicron WC and the damage to the surface organization during large deformation, thereby ensuring the reliability of the unique internal and external structure and material performance.

[0202] (4) Through controlled oxidation, the rare earth element oxides formed externally can pin the defects caused by radiation during the irradiation process, preventing them from aggregating and growing at the grain boundaries, thereby ensuring the long-term performance stability of the material under irradiation.

[0203] Example 6

[0204] This embodiment provides a steel-bonded carbide tool for use under irradiation conditions, which differs from Embodiment 2 in that a controlled oxidation process is not used.

[0205] This embodiment provides a method for preparing the steel-bonded cemented carbide cutting tool under irradiation conditions, which is different from the method in Example 2 in that a controlled oxidation process is not used.

[0206] The raw material formulas for preparing the cutting tools in this embodiment are different.

[0207] Tool performance data in this embodiment:

[0208] The inner and outer layers are consistent, with structural hardness HRC59, fracture toughness 88MPa·m1 / 2, bending strength 3200MPa, and impact toughness 16J / cm 2 The material hardness and wear resistance are insufficient, and the service life is limited.

[0209] The present invention provides a steel-bonded carbide tool for use under irradiation conditions and a preparation method thereof, which can produce the following technical effects:

[0210] (1) Through the step-by-step mixing of raw materials and controlled oxidation design, the steel-bonded cemented carbide material provided by the present invention comprises an inner and outer layer gradient structure. The inner layer material is composed of WC and a steel matrix, and the added rare earth metal elements are dissolved in the steel matrix, providing reliable internal strength and toughness for the tool. Due to the micro-oxidation of the outer layer material during the controlled oxidation process, on the one hand, the rare earth elements absorb oxygen elements to form rare earth oxide particles, and on the other hand, a carbon-deficient area is formed on the surface, thereby forming a large-sized, high-hardness, and high-wear-resistant M6C (Fe3W3C) phase during the sintering process, and obtaining a high-hardness, high-wear-resistant outer layer structure.

[0211] (2) In the preparation method provided by the present invention, through the design of raw material particle size distribution and molding process, no molding agent is added in the entire material molding process, which can effectively avoid the problems of long degreasing time, product cracking, local differences in carbon content, etc. caused by the difficulty in removing the molding agent during the sintering process, shorten the product sintering time, improve the product production efficiency and product performance stability, and avoid the limitation of large size of the product.

[0212] (3) In order to achieve full density of the material and high bonding strength to WC particles, the patent adopts enhanced gas pressure sintering and high creep deformation and low deformation to strengthen the material. In these processes, the absolute volume change of the material is not large, avoiding the segregation of submicron WC and the damage to the surface organization during large deformation, thereby ensuring the reliability of the unique internal and external structure and material performance.

[0213] (4) Through controlled oxidation, the rare earth element oxides formed externally can pin the defects caused by radiation during the irradiation process, preventing them from aggregating and growing at the grain boundaries, thereby ensuring the long-term performance stability of the material under irradiation.

[0214] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A steel-bonded carbide tool for use under irradiation conditions, characterized in that: Its materials include: WC, M6C carbide, submicron oxide particles, and a steel matrix. The contents of M6C carbide and submicron oxide particles in the materials of the tool structure from the inside to the outside increase in sequence.

2. The steel-bonded carbide tool for use under irradiation conditions according to claim 1, characterized in that: M6C type carbides are Fe3W3C and Fe3Mo3C produced by WC, Mo and iron matrix, and submicron oxide particles are produced by rare earth elements during oxidation.

3. The steel-bonded carbide tool for use under irradiation conditions according to claim 1 or 2, characterized in that: include: The inner layer structure and the outer layer structure arranged outside the inner layer structure, the materials of the outer structure include WC, M6C type carbide, submicron oxide particles, and a steel matrix, the materials of the inner layer structure include WC and a steel matrix, the thickness of the inner layer structure is 10 to 500 mm, and the thickness of the outer layer structure is 2 to 3 mm.

4. The steel-bonded carbide tool for use under irradiation conditions according to claim 1, characterized in that: The raw material formula for preparing the cutting tool includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder and carbon black.

5. The steel-bonded carbide tool for use under irradiation conditions according to claim 4, characterized in that: Fe powder is carbonyl iron powder; The rare earth powder includes one or more of Y, La and Ce single substance powders.

6. The steel-bonded carbide tool for use under irradiation conditions according to claim 4, characterized in that: The Fresno particle sizes of the raw material powders are: WC powder: 0.5~1μm, rare earth powder: 0.2~0.5μm, other metal powder: 2~5μm, carbon black particle size is -200 mesh~-400 mesh.

7. The steel-bonded carbide tool for use under irradiation conditions according to claim 4, characterized in that: The mass percentage of each raw material in the raw material formula for preparing the cutting tool is: WC powder accounts for 30-40%, Mo powder accounts for 0.5-2%, Cr powder accounts for 0.5-2%, Co powder accounts for 0.1-5%, Ni powder accounts for 0.1-4%, Mn powder accounts for 0.1-0.5%, rare earth powder accounts for 0.1-0.5%, carbon black accounts for 0.4-0.8%, and the rest is Fe powder.

8. The steel-bonded carbide tool for use under irradiation conditions according to claim 7, characterized in that: The mass percentage of each raw material in the raw material formula for preparing the cutting tool is: WC powder accounts for 30-35%, Mo powder accounts for 0.5-1%, Cr powder accounts for 0.5-1%, Co powder accounts for 2-4%, Ni powder accounts for 1-2%, Mn powder accounts for 0.1-0.3%, rare earth powder accounts for 0.1-0.3%, carbon black accounts for 0.5-0.7%, and the rest is Fe powder.

9. A method for preparing a steel-bonded carbide tool for use under irradiation conditions as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: (1) mixing raw materials, wherein the raw material formula for preparing the cutting tool includes: WC powder, Mo powder, Cr powder, Co powder, Ni powder, Mn powder, rare earth powder, Fe powder, and carbon black to obtain a mixed material; (2) pressing the mixed material to obtain a pressed blank; (3) heating the pressed blank under a preset oxygen partial pressure for pre-oxidation; (4) sintering under preset gas pressure conditions and preset temperature conditions to obtain a sintered blank; (5) heating the sintered green body, applying uniaxial pressure, and creeping the green body to densify the sintered green body, thereby obtaining a hot pressed green body; (6) The hot pressed blank is quenched and tempered to finally obtain a finished steel-bonded carbide tool.

10. The method for preparing a steel-bonded carbide tool for use under irradiation conditions according to claim 9, characterized in that: The step (1) specifically comprises premixing the raw material powders other than rare earth powder and Cr powder in a wet manner to obtain a premix, drying the premix, adding Cr powder and rare earth powder, and finally mixing the premix by dry mixing technology under atmosphere protection to obtain a mixture.

11. The method for preparing a steel-bonded carbide tool for use under irradiation conditions according to claim 10, characterized in that: In the step (1), the wet premixing is performed in a ball mill, the ball milling medium is alcohol, and argon is used to replace the air in the ball mill before ball milling; After wet premixing, vacuum drying is adopted. Before drying, argon is used to replace the gas in the dryer and then vacuum is drawn. The drying temperature is 60-80°C. After drying, it is cooled to below 25°C and leaves the dryer.

12. The method for preparing a steel-bonded carbide tool for use under irradiation conditions according to claim 9, characterized in that: The step (2) specifically involves cold isostatic pressing the mixed material to obtain a pressed blank.

13. The method for preparing a steel-bonded carbide tool for use under irradiation conditions according to claim 12, characterized in that: In the step (2), the cold isostatic pressing pressure is 200 to 300 MPa, and the holding time is 10 to 20 minutes.

14. The method for preparing a steel-bonded carbide tool for use under irradiation conditions according to claim 9, characterized in that: The heating temperature of step (3) is 50-80° C., and the pre-oxidation time is 4-6 hours.

15. The method for preparing a steel-bonded carbide cutting tool for use under irradiation conditions according to claim 9, characterized in that: The atmosphere of step (3) is a low oxygen partial pressure mixed gas of nitrogen and oxygen, wherein the oxygen content accounts for 3-5% by volume.

16. The method for preparing a steel-bonded carbide tool for use under irradiation conditions according to claim 9, characterized in that: In the step (4), a step-by-step heating process is used during the sintering process, and the temperature is kept at 120-150°C, 580-620°C, 780-820°C, 980-1020°C, and 1180-1220°C for 1-3 hours, and finally the temperature is raised to a maximum temperature of 1250°C to 1300°C and kept for 2-4 hours.

17. The method for preparing a steel-bonded carbide tool for use under irradiation conditions according to claim 16, characterized in that: In the step (4), vacuum sintering is performed at 1180-1220°C, and the pressure of the vacuum sintering is less than 10 -2 Pa; Gas pressure sintering is used for heat preservation from 1180 to 1220°C to the highest temperature. The gas used in the gas pressure sintering process is argon gas and the pressure is 5 to 10 MPa.

18. The method for preparing a steel-bonded carbide cutting tool for use under irradiation conditions according to claim 9, characterized in that: During the high temperature creep in step (5), the temperature is 1000-1200° C., the uniaxial pressure is 3-8 MPa, the time is 5-10 h, and the gas used is argon or nitrogen atmosphere.

19. The method for preparing a steel-bonded carbide cutting tool for use under irradiation conditions according to claim 9, characterized in that: In the step (6), the heating temperature of quenching is 1000°C to 1150°C, the quenching holding time is 60 to 120 minutes, the quenching is carried out in any one of a salt bath, an inert gas atmosphere, and a vacuum atmosphere, and the cooling of the quenching is carried out by oil quenching or gas quenching; the tempering temperature is 120 to 200°C, the tempering time is 1 to 3 hours, and the steel is naturally cooled to room temperature after tempering.

20. The method for preparing a steel-bonded carbide cutting tool for use under irradiation conditions according to claim 9, characterized in that: In the step (6), for large-sized products, a cryogenic treatment is added before tempering, the cryogenic temperature is -180°C to -50°C, and the cryogenic time is 60 to 240 minutes.

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