Submicron crystal ceramic-based composite material as well as preparation method and application thereof

Abstract

The invention provides a submicron crystal ceramic-based composite material and a preparation method and application thereof, the preparation method comprises the following steps: coating at least two metal layers on the surface of a ceramic-based presintered body, and then sequentially carrying out vacuum sintering and hot isostatic pressing sintering to obtain the submicron crystal ceramic-based composite material, the relative density of the ceramic-based pre-sintered body is 80%-92%, and the average grain size of the ceramic-based pre-sintered body is 0.6 [mu] m or less; according to the method, the surface of the ceramic-based presintered body is coated with at least two metal layers, so that the ceramic-based composite material is sintered to be compact at a lower temperature, and the contradiction that the sintering densification is promoted by a higher temperature but the grain growth is caused and the grain growth is inhibited by a lower temperature but the sintering is not compact is solved; the average grain size of the submicron grain ceramic matrix composite material is smaller than 1 micron, and the relative density of the submicron grain ceramic matrix composite material is higher than 99.8%. In addition, vacuum sintering and hot isostatic pressing sintering are not limited by the shape and size of the product, and batch production can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic-based composite materials, and relates to a submicron-crystalline ceramic-based composite material and a preparation method and application thereof. Background Art

[0002] Ceramic-based composite materials such as carbide-based, nitride-based, boride-based and oxide-based have good wear resistance and are widely used in the preparation of molds, cutting tools and wear-resistant parts, but the intrinsic brittleness of ceramic-based composite materials limits their application range to some extent. The strength and toughness of ceramic-based composite materials increase with the decrease of grain size, and other mechanical properties will not be significantly reduced. For polycrystalline composite materials, those with an average grain size less than 0.1μm are called nanocrystalline materials, those with an average grain size of 0.1μm to 1μm are called submicron crystalline materials, and those with an average grain size of 1μm to 100μm are called micron crystalline materials. However, the average grain size of ceramic-based composite materials prepared by existing technologies is generally above 2μm, and it is difficult to obtain submicron crystalline ceramic-based composite materials.

[0003] The addition of grain inhibitors can effectively inhibit the grain growth in ceramic matrix composites, but the addition of grain inhibitors will have an adverse effect on the performance of ceramic matrix composites; however, if the amount of grain inhibitor added is reduced, the effect of inhibiting grain growth will be affected.

[0004] Lowering the sintering temperature and shortening the sintering time can also inhibit grain growth, but it will bring about the problem of non-dense sintering. In order to achieve the purpose of inhibiting grain growth and sintering densely, the existing technology adopts hot pressing sintering method and spark plasma sintering method, but the conductivity of most ceramic materials is poor, which affects the sintering effect. In addition, the above method assists external pressure during sintering, which is beneficial to improve the sintering density, and the sintering temperature and sintering time can also be appropriately reduced and reduced, which is beneficial to inhibit grain growth; however, the production efficiency of the above method is low; and the biggest drawback of the above method is that it can only prepare products with relatively simple shapes, and the product size is limited.

[0005] Hot isostatic pressing (HIP) uses gas pressure to sinter products. It is not limited by the shape of the product, can achieve mass production, and can promote densification at a relatively low temperature. However, before HIP sintering, the pre-sintered body needs to have a relative density of more than 93%. In other words, it is necessary to ensure that the interior of the pre-sintered body is a closed pore, so as to prevent high-pressure gas from entering the interior of the pre-sintered body during HIP sintering to ensure sintering density. However, when the pre-sintered body has a relative density of more than 93%, the sintering temperature of the pre-sintered body needs to be increased, resulting in grain growth.

[0006] It can be seen that the existing technology has a contradiction that higher temperature promotes sintering densification but causes grain growth, and lower temperature inhibits grain growth but the sintering is not dense. How to obtain dense submicron-crystalline ceramic-based composite materials and achieve mass production requirements without being restricted by product shape and size is a problem that needs to be urgently solved in this field. Summary of the invention

[0007] The purpose of the present invention is to provide a submicron-crystalline ceramic-based composite material and a preparation method and application thereof, so as to solve the contradiction in the prior art that higher temperatures promote sintering densification but cause grain growth, and lower temperatures inhibit grain growth but cause sintering to be non-densified, thereby obtaining a dense submicron-crystalline ceramic-based composite material.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a submicron-crystalline ceramic-based composite material, the preparation method comprising the following steps:

[0010] At least two metal layers are coated on the surface of the ceramic-based pre-sintered body, and then vacuum sintering and hot isostatic pressing sintering are performed in sequence to obtain the submicron-crystalline ceramic-based composite material.

[0011] The relative density of the ceramic-based pre-sintered body is 80% to 92%, and the average grain size of the ceramic-based pre-sintered body is less than 0.6 μm.

[0012] The melting point of the outermost metal layer of the at least two metal layers is T m2 Higher than the melting point T of the innermost metal layer m1 And the vacuum sintering temperature T1.

[0013] The melting point of the innermost metal layer is T m1 The temperature is 0°C to 20°C lower than the vacuum sintering temperature T1.

[0014] In the at least two metal layers, the melting point of each metal layer is higher than the hot isostatic pressing sintering temperature T2.

[0015] The preparation method provided by the present invention covers at least two metal layers on the surface of a ceramic-based pre-sintered body, melts the innermost metal layer through vacuum sintering, forms a dense metal sealing layer on the surface of the ceramic-based pre-sintered body, and then performs hot isostatic pressing sintering at a relatively low temperature below the melting point of the innermost metal layer, thereby maintaining the innermost metal layer in a solid state and having good plasticity, which can not only prevent high-pressure gas from entering the ceramic-based pre-sintered body, but also transfer the pressure to the pre-sintered body evenly and well, thereby ensuring the densification of the submicron-crystalline ceramic-based composite material and effectively inhibiting the growth of grains. That is, by coating the surface of the ceramic-based pre-sintered body with at least two metal layers, the submicron-crystalline ceramic-based composite material can be sintered and densified at a relatively low temperature, thereby solving the contradiction between higher temperature promoting sintering densification but causing grain growth and lower temperature inhibiting grain growth but sintering not being dense. Ultimately, a submicron-crystalline ceramic-based composite material with an average grain size of submicron level (less than 1 μm) and a relative density higher than 99.8% can be obtained; in addition, vacuum sintering and hot isostatic pressing sintering are not limited by product shape and size, and can achieve mass production.

[0016] The present invention does not specifically limit the specific shape and preparation method of the ceramic-based pre-sintered body, as long as its relative density is between 80% and 92% and the average grain size is below 0.6 μm. The relative density of the ceramic-based pre-sintered body refers to the ratio of the density of the ceramic-based pre-sintered body to the theoretical density of the submicron-crystalline ceramic-based composite material.

[0017] The innermost metal layer of the present invention refers to the metal layer closest to the ceramic-based pre-sintered body among at least two metal layers; the outermost metal layer refers to the metal layer farthest from the ceramic-based pre-sintered body among at least two metal layers.

[0018] Preferably, the melting point of the innermost metal layer is m1 1430℃ to 1852℃.

[0019] Preferably, the material of the innermost metal layer includes any one of Ni, Co, Fe, Ti or Zr, or a combination of at least two of them.

[0020] Preferably, the material of the outermost metal layer includes any one of Ti, Zr, Mo, Nb or Ta, or a combination of at least two of them.

[0021] Preferably, the thickness of the innermost metal layer is 0.1 mm to 0.5 mm.

[0022] Preferably, the thickness of the outermost metal layer is 0.1 mm to 0.3 mm.

[0023] Preferably, the vacuum sintering temperature T1 is 1430°C to 1872°C.

[0024] Preferably, the holding time of the vacuum sintering is 0.5h to 1h.

[0025] Preferably, the vacuum sintering is carried out at a pressure of 10 -3 Pa is carried out below.

[0026] Preferably, the hot isostatic pressing sintering is performed in an inert atmosphere.

[0027] Preferably, the hot isostatic pressing sintering pressure is 150 MPa to 300 MPa.

[0028] Preferably, the hot isostatic pressing sintering temperature T2 is higher than the melting point T m1 Low 10℃ to 50℃.

[0029] Preferably, the hot isostatic pressing sintering temperature T2 is 1380°C to 1842°C.

[0030] Preferably, the holding time of the hot isostatic pressing sintering is 1 h to 3 h.

[0031] Preferably, the method for preparing the ceramic-based pre-sintered body comprises powder mixing, molding, degreasing and vacuum pre-sintering performed in sequence.

[0032] Preferably, the vacuum pre-sintering temperature T3 is 1400°C to 1910°C.

[0033] Preferably, the holding time of the vacuum pre-sintering is 1 h to 3 h.

[0034] Preferably, the vacuum pre-sintering is performed at a pressure below 30 Pa.

[0035] Preferably, in terms of volume percentage, the raw materials for preparing the submicron-crystalline oxide ceramic-based composite material include: more than 50 vol% of oxide ceramic matrix, less than 49.5 vol% of additives, and less than 0.5 vol% of sintering aids.

[0036] Preferably, in terms of volume percentage, the raw materials for preparing the submicron crystalline nitride ceramic-based composite material include: more than 50 vol% of nitride ceramic matrix, less than 49.5 vol% of additives and less than 0.5 vol% of sintering aids.

[0037] Preferably, in terms of volume percentage, the raw materials for preparing the submicron-crystalline boride ceramic-based composite material include: more than 50 vol% of a boride ceramic matrix, less than 49.5 vol% of an additive, and less than 0.5 vol% of a sintering aid.

[0038] Preferably, in terms of volume percentage, the raw materials for preparing the submicron-crystalline carbide ceramic-based composite material include: more than 50 vol% of a carbide ceramic matrix, less than 49.5 vol% of an additive, and less than 0.5 vol% of a sintering aid.

[0039] In a second aspect, the present invention provides a submicron crystalline ceramic-based composite material, wherein the submicron crystalline ceramic-based composite material is prepared by the preparation method described in the first aspect.

[0040] The submicron-crystalline ceramic-based composite material has an average grain size of less than 1 μm and a relative density of higher than 99.8%.

[0041] In a third aspect, the present invention provides an application of a submicron-crystalline ceramic-based composite material, wherein the submicron-crystalline ceramic-based composite material is used to prepare molds, cutting tools or wear-resistant parts.

[0042] The submicron-crystalline ceramic-based composite material is prepared by the preparation method described in the first aspect, or is the submicron-crystalline ceramic-based composite material described in the second aspect.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The preparation method provided by the present invention realizes the sintering and densification of submicron-crystalline ceramic-based composite materials at a relatively low temperature by coating at least two metal layers on the surface of the ceramic-based pre-sintered body, thereby resolving the contradiction between higher temperatures promoting sintering and densification but causing grain growth and lower temperatures inhibiting grain growth but sintering without densification. Ultimately, a submicron-crystalline ceramic-based composite material with an average grain size of submicron level (less than 1 μm) and a relative density higher than 99.8% can be obtained; in addition, vacuum sintering and hot isostatic pressing sintering are not limited by product shape and size, and can achieve mass production.

[0045] (2) The submicron-crystalline ceramic-based composite material prepared by the present invention has an average grain size of submicron level (less than 1 μm) and a relative density higher than 99.8%. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0047] A certain embodiment of the present invention provides a method for preparing a submicron-crystalline ceramic-based composite material, the preparation method comprising the following steps:

[0048] At least two metal layers are coated on the surface of the ceramic-based pre-sintered body, and then vacuum sintering and hot isostatic pressing sintering are performed in sequence to obtain the submicron-crystalline ceramic-based composite material.

[0049] The relative density of the ceramic-based pre-sintered body is 80% to 92%, and the average grain size of the ceramic-based pre-sintered body is less than 0.6 μm.

[0050] The melting point of the outermost metal layer of the at least two metal layers is T m2 Higher than the melting point T of the innermost metal layer m1 And the vacuum sintering temperature T1.

[0051] The melting point of the innermost metal layer is T m1 The temperature is 0°C to 20°C lower than the vacuum sintering temperature T1.

[0052] In the at least two metal layers, the melting point of each metal layer is higher than the hot isostatic pressing sintering temperature T2.

[0053] The preparation method provided by the present invention covers at least two metal layers on the surface of a ceramic-based pre-sintered body, melts the innermost metal layer through vacuum sintering, forms a dense metal sealing layer on the surface of the ceramic-based pre-sintered body, and then performs hot isostatic pressing sintering at a relatively low temperature below the melting point of the innermost metal layer, thereby maintaining the innermost metal layer in a solid state and having good plasticity, which not only prevents high-pressure gas from entering the ceramic-based pre-sintered body, but also transmits the pressure to the pre-sintered body evenly and well, thereby ensuring the densification of the submicron-crystalline ceramic-based composite material, and effectively inhibiting the growth of the grain size. That is, by coating the surface of the ceramic-based pre-sintered body with at least two metal layers, the submicron-crystalline ceramic-based composite material can be sintered and densified at a relatively low temperature, thereby solving the contradiction between higher temperature promoting sintering densification but causing grain growth and lower temperature inhibiting grain growth but sintering not being dense. Ultimately, a submicron-crystalline ceramic-based composite material with an average grain size of submicron level (less than 1 μm) and a relative density higher than 99.8% can be obtained; in addition, vacuum sintering and hot isostatic pressing sintering are not limited by product shape and size, and can achieve mass production.

[0054] The present invention does not specifically limit the specific shape and preparation method of the ceramic-based pre-sintered body, as long as its relative density is between 80% and 92% and the average grain size is below 0.6 μm. The relative density of the ceramic-based pre-sintered body refers to the ratio of the density of the ceramic-based pre-sintered body to the theoretical density of the submicron-crystalline ceramic-based composite material.

[0055] The innermost metal layer of the present invention refers to the metal layer closest to the ceramic-based pre-sintered body among at least two metal layers; the outermost metal layer refers to the metal layer farthest from the ceramic-based pre-sintered body among at least two metal layers.

[0056] In the preparation method provided by the present invention, the average grain size of the ceramic-based pre-sintered body is less than 0.6 μm, and the relative density is 80% to 92%, for example, it can be 80%, 85%, 88%, 90% or 92%, but is not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable.

[0057] In some embodiments, the melting point of the innermost metal layer is m1 The temperature is 1430°C to 1852°C, for example, 1430°C, 1450°C, 1500°C, 1600°C, 1700°C, 1800°C, 1830°C or 1852°C, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. In order to facilitate the at least two metal layers to cover the ceramic-based pre-sintered body of any shape, the material of the at least two metal layers has good room temperature plasticity.

[0058] In some embodiments, the material of the innermost metal layer includes any one of Ni (melting point 1455°C), Co (melting point 1495°C), Fe (melting point 1538°C), Ti (melting point 1668°C) or Zr (melting point 1852°C) or a combination of at least two of them, and typical but non-limiting combinations include a combination of Ni and Co, a combination of Ni and Fe, a combination of Fe and Ti, a combination of Ni, Co and Fe, a combination of Co, Fe and Ti, or a combination of Ni, Co, Fe and Ti. The combination includes a simple mixture of at least two metals, or an alloy including at least two metal elements.

[0059] In the preparation method provided by the present invention, the melting point of the outermost metal layer is T m2 Higher than the melting point T of the innermost metal layer m1 During the entire preparation method, the outermost metal layer always remains solid, thereby preventing the remaining metal layers from being lost due to gravity during vacuum sintering and hot isostatic pressing, thereby ensuring the complete coating effect of the inner metal layer on the ceramic-based pre-sintered body.

[0060] In some embodiments, the material of the outermost metal layer includes any one of Ti (melting point 1668°C), Zr (melting point 1852°C), Mo (melting point 2623°C), Nb (melting point 2468°C) or Ta (melting point 2996°C) or a combination of at least two of them, and typical but non-limiting combinations include a combination of Ti and Zr, a combination of Zr and Mo, a combination of Mo and Nb, a combination of Nb and Ta, a combination of Ti, Zr, Mo and Nb, a combination of Zr, Mo, Nb and Ta, or a combination of Ti, Zr, Mo, Nb and Ta. The combination includes a simple mixture of at least two metals, or an alloy including at least two metal elements.

[0061] The method of coating the surface of the ceramic-based pre-sintered body with at least two metal layers in the present invention is a conventional coating method, as long as the non-airtight coating of the metal layer on the surface of the ceramic-based pre-sintered body can be achieved.

[0062] Exemplarily, the method of coating the innermost metal layer on the surface of the ceramic-based pre-sintered body includes spraying or metal thin-walled part sheathing.

[0063] In some embodiments, when coating the innermost metal layer, the spraying method includes: uniformly spraying a slurry containing coating metal powder on the surface of the ceramic-based pre-sintered body, and forming the innermost metal coating layer after drying.

[0064] In certain embodiments, when coating the innermost metal layer, the method of sleeve installation of metal thin-walled parts includes: preparing the metal to be coated into multiple thin-walled parts that are consistent with the appearance of the ceramic-based pre-sintered body, and the multiple thin-walled parts are combined and sleeved and tightly attached to the surface of the ceramic-based pre-sintered body. The interfaces of the multiple thin-walled parts are connected by nesting to form the innermost metal coating layer.

[0065] Exemplarily, the method of coating the outermost metal layer includes sleeve coating of a thin-walled metal member.

[0066] In certain embodiments, when coating the outermost metal layer, the method of sleeve installation of metal thin-walled parts includes: preparing the metal to be coated into multiple thin-walled parts that are consistent with the appearance of the ceramic-based pre-sintered body coated with the inner metal layer, the multiple thin-walled parts are combined and sleeved and tightly attached to the outer surface of the ceramic-based pre-sintered body coated with the inner metal layer, and the interfaces of the multiple thin-walled parts are connected by nesting to form the outermost metal coating layer.

[0067] The present invention uses at least two metal layers to coat the ceramic-based pre-sintered body, wherein the thickness of the innermost metal layer is too thin, resulting in insufficient sealing, which easily causes the high-pressure gas to diffuse into the ceramic-based pre-sintered body during hot isostatic pressing, resulting in loose sintering, but too thick will result in high processing costs; wherein the thickness of the outermost metal layer is too thin, resulting in reduced protection, and at the same time, due to the need to subsequently process and remove the metal layer, too thick will also result in high processing costs. Therefore, in order to achieve a good protective effect, it is necessary to optimize the thickness of the innermost metal layer and the thickness of the outermost metal layer.

[0068] In some embodiments, the thickness of the innermost metal layer is 0.1 mm to 0.5 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm or 0.5 mm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0069] In some embodiments, the thickness of the outermost metal layer is 0.1 mm to 0.3 mm, for example, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm or 0.3 mm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0070] The total thickness of the at least two metal layers is related to the number of metal layers. The present invention only needs to control the thickness of the innermost metal layer and the thickness of the outermost metal layer.

[0071] In the present invention, during vacuum sintering, the vacuum sintering temperature T1 must be equal to or greater than the melting point T m1 , that is, the innermost metal layer needs to be melted so that the ceramic-based pre-sintered body can be completely sealed; but it is necessary to avoid further increase in the grain size of the ceramic-based pre-sintered body, so the temperature of vacuum sintering cannot be too high; in addition, before the innermost metal layer is melted and sealed, various reactions in the ceramic-based pre-sintered body that are not conducive to sintering and are easy to form gas must be completed, otherwise these gases cannot be discharged out of the ceramic-based pre-sintered body, and are sealed in the pre-sintered body to form pores, resulting in hot isostatic pressing sintering. The above pores cannot be eliminated, and the performance of the final product deteriorates. Therefore, it is necessary to optimize the temperature of vacuum sintering.

[0072] In some embodiments, the vacuum sintering temperature is 1430°C to 1872°C, for example, it can be 1430°C, 1450°C, 1500°C, 1600°C, 1700°C, 1800°C or 1872°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0073] In some embodiments, the holding time of the vacuum sintering is 0.5h to 1h, for example, 0.5h, 0.6h, 0.8h, 0.9h or 1h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0074] In some embodiments, the vacuum sintering is carried out at a pressure of 10 -3 Pa to avoid the gases generated by the reaction being sealed in the ceramic-based pre-sintered body.

[0075] In certain embodiments, the hot isostatic pressing sintering is performed in an inert atmosphere.

[0076] The gas used in the inert atmosphere includes inert gases such as nitrogen and / or argon.

[0077] In some embodiments, the hot isostatic pressing sintering pressure is 150 MPa to 300 MPa, for example, 150 MPa, 180 MPa, 200 MPa, 240 MPa, 250 MPa, 280 MPa or 300 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0078] In the present invention, under the premise of sintering the ceramic-based pre-sintered body to a dense state, the lower the hot isostatic pressing sintering temperature, the more conducive it is to inhibiting grain growth.

[0079] In some embodiments, the hot isostatic pressing sintering temperature T2 is higher than the melting point T m1 10°C to 50°C lower, for example, 10°C, 20°C, 30°C, 40°C or 50°C, but not limited to the listed values, and the remaining values ​​not listed in the numerical range are also applicable. Within this temperature range, the innermost metal layer can be kept in a solid sealed state during hot isostatic pressing sintering, reducing its diffusion ability under high pressure, and can further prevent high-pressure gas from diffusing into the ceramic-based pre-sintered body; moreover, within this temperature range, it can maintain good plasticity, thereby ensuring that the pressure can be effectively transmitted to the pre-sintered body and promoting its densification.

[0080] In some embodiments, the hot isostatic pressing sintering temperature T2 is 1380°C to 1842°C, for example, it can be 1380°C, 1400°C, 1500°C, 1600°C, 1700°C, 1800°C, 1820°C or 1842°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0081] In some embodiments, the holding time of the hot isostatic pressing sintering is 1 h to 3 h, for example, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0082] In some embodiments, the method for preparing the ceramic-based pre-sintered body comprises powder mixing, molding, degreasing and vacuum pre-sintering in sequence.

[0083] In certain embodiments, the mixed powder is ball-milled according to the component formula of the submicron-crystalline ceramic-based composite material to obtain uniformly mixed powder.

[0084] In some embodiments, the ball milling mixing includes: placing the formulated raw material powder in a ball mill, injecting anhydrous ethanol into the ball mill, and ball milling mixing in a protective atmosphere for more than 24 hours to obtain a uniformly mixed mixed powder with an average particle size of no more than 0.3 μm.

[0085] In some embodiments, the material of the grinding balls used in the ball milling mixture includes zirconium oxide, aluminum oxide, silicon carbide, silicon nitride or cemented carbide, and the mass ratio of the grinding balls to the raw material powder is 2:1 to 8:1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1 or 8:1, but is not limited to the listed values, and the remaining values ​​not listed in the numerical range are also applicable.

[0086] In some embodiments, the molding includes at least one of molding, cold isostatic pressing, extrusion molding, injection molding or 3D printing. The present invention does not specifically limit the molding method, as long as a molded body of a desired shape can be obtained. When the desired shape cannot be obtained by one-step molding, the molding also includes cutting.

[0087] In certain embodiments, the degreasing is inert gas negative pressure degreasing or hydrogen positive pressure degreasing.

[0088] In some embodiments, if the shape of the molded body after degreasing is inconsistent with the shape of the target product, cutting processing is performed after degreasing.

[0089] In the present invention, in order to obtain a ceramic-based pre-sintered body with a relative density of 80% to 92% and an average grain size of less than 0.6 μm, the vacuum pre-sintering temperature T3 is crucial. If the vacuum pre-sintering temperature T3 is too low, the grains of the obtained ceramic-based pre-sintered body will not grow excessively, and the grain size is relatively small, but the relative density of the ceramic-based pre-sintered body is less than 80%, and there are many pores, resulting in low strength of the ceramic-based pre-sintered body, leading to the following two unfavorable results: (1) Due to the low strength of the ceramic-based pre-sintered body, it is not conducive to the operation of coating the metal layer on its surface, and the pre-sintered body is easily damaged; (2) Due to the large number of pores, during the subsequent vacuum sintering, the metal liquid phase formed after the innermost metal layer is melted is easy to diffuse along the pores to the inside of the ceramic-based pre-sintered body, resulting in too deep a diffusion depth, thereby affecting the surface quality of the submicron-crystalline ceramic-based composite material obtained in the end; if the vacuum pre-sintering temperature is too high, although the relative density of the ceramic-based pre-sintered body can be improved, submicron-sized grains cannot be obtained.

[0090] In some embodiments, the vacuum pre-sintering temperature T3 is 1400°C to 1910°C, for example, it can be 1400°C, 1500°C, 1600°C, 1700°C, 1800°C, 1850°C or 1910°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0091] In some embodiments, the holding time of the vacuum pre-sintering is 1 h to 3 h, for example, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0092] In some embodiments, the vacuum pre-sintering is performed at a pressure below 30 Pa.

[0093] In some embodiments, the submicron crystalline ceramic-based composite material includes any one of a submicron crystalline oxide ceramic-based composite material, a submicron crystalline nitride ceramic-based composite material, a submicron crystalline boride ceramic-based composite material, or a submicron crystalline carbide ceramic-based composite material.

[0094] In some embodiments, the raw materials for preparing the submicron-crystalline oxide ceramic-based composite material include, by volume percentage: more than 50 vol% of oxide ceramic matrix, less than 49.5 vol% of additives, and less than 0.5 vol% of sintering aids.

[0095] In some embodiments, the oxide ceramic matrix includes any one of Al2O3, ZrO2 or SiO2, or a combination of at least two thereof.

[0096] In some embodiments, the additive includes any one of WC, Cr3C2, VC, ZrC, TiC, TiCN, Mo2C, TaC, NbC, SiC, B4C, ZrB, ZrB2, TiB, TiB2, WB, W2B, W2B5, CrB, SiAlON, BN, AlN, ZrN, TiN, MgO, rare earth metal oxides or rare earth metal borides, or a combination of at least two of them.

[0097] In certain embodiments, the sintering aid includes any one of Co, Ni, Fe or Ti, or a combination of at least two thereof.

[0098] In some embodiments, the raw materials for preparing the submicron crystalline nitride ceramic-based composite material include, by volume percentage: more than 50 vol% of a nitride ceramic matrix, less than 49.5 vol% of an additive, and less than 0.5 vol% of a sintering aid.

[0099] In some embodiments, the nitride ceramic matrix includes any one of SiAlON, BN, AlN or TiN, or a combination of at least two thereof.

[0100] In some embodiments, the additive includes any one of WC, Cr3C2, VC, ZrC, TiC, TiCN, Mo2C, TaC, NbC, SiC, B4C, ZrB, ZrB2, TiB, TiB2, WB, W2B, W2B5, CrB, ZrN, TiN, Al2O3, ZrO2, MgO, SiO2, rare earth metal oxides or rare earth metal borides, or a combination of at least two of them.

[0101] In certain embodiments, the sintering aid includes any one of Co, Ni, Fe, Ti, C or B, or a combination of at least two thereof.

[0102] In certain embodiments, the raw materials for preparing the submicron-crystalline boride ceramic-based composite material include, by volume percentage: more than 50 vol% of a boride ceramic matrix, less than 49.5 vol% of an additive, and less than 0.5 vol% of a sintering aid.

[0103] In certain embodiments, the boride ceramic matrix includes ZrB2 and / or TiB2.

[0104] In some embodiments, the additive includes any one of WC, Cr3C2, VC, ZrC, TiC, TiCN, Mo2C, TaC, NbC, SiC, B4C, ZrB, TiB, WB, W2B, W2B5, CrB, SiAlON, BN, AlN, ZrN, TiN, Al2O3, ZrO2, MgO, SiO2, rare earth metal oxides or rare earth metal borides, or a combination of at least two of them.

[0105] In certain embodiments, the sintering aid includes any one of Co, Ni, Fe, Ti, C or B, or a combination of at least two thereof.

[0106] In certain embodiments, the raw materials for preparing the submicron-crystalline carbide ceramic-based composite material include, by volume percentage: more than 50 vol% of a carbide ceramic matrix, less than 49.5 vol% of an additive, and less than 0.5 vol% of a sintering aid.

[0107] In certain embodiments, the carbide ceramic matrix includes any one of TiCN, TiC, ZrC, SiC or B4C, or a combination of at least two thereof.

[0108] In some embodiments, the additive includes any one of WC, Cr3C2, VC, Mo2C, TaC, NbC, SiC whiskers, ZrB, ZrB2, TiB, TiB2, WB, W2B, W2B5, CrB, SiAlON, BN, AlN, ZrN, TiN, Al2O3, ZrO2, MgO, SiO2, rare earth metal oxides or rare earth metal borides, or a combination of at least two of them.

[0109] In certain embodiments, the sintering aid includes any one of Co, Ni, Fe, Ti, C or B, or a combination of at least two thereof.

[0110] A certain embodiment of the present invention provides a submicron crystalline ceramic-based composite material, and the submicron crystalline ceramic-based composite material is prepared by the preparation method described in any embodiment.

[0111] The submicron-crystalline ceramic-based composite material has an average grain size of less than 1 μm and a relative density of higher than 99.8%.

[0112] A certain embodiment of the present invention provides an application of a submicron-crystalline ceramic-based composite material, wherein the submicron-crystalline ceramic-based composite material is used to prepare a mold, a cutting tool or a wear-resistant part.

[0113] The submicron-crystalline ceramic-based composite material is prepared by the preparation method described in any embodiment, or is the submicron-crystalline ceramic-based composite material described in any embodiment.

[0114] Preparation of pre-sintered body

[0115] Preparation Example 1

[0116] This preparation example provides a method for preparing a ceramic-based pre-sintered body. In terms of volume percentage, the raw material powder of the ceramic-based pre-sintered body includes 70 vol% Al2O3, 22 vol% SiC w whiskers, 5.5 vol% MgO and 2.5 vol% Y2O3, the preparation method comprising the following steps:

[0117] (1) In a nitrogen atmosphere, the raw material powder is placed in a ball mill, and alumina grinding balls and anhydrous ethanol are used for ball milling and mixing for 24 hours, so that the average particle size of the obtained mixed powder is less than 0.3 μm; wherein the mass ratio of the grinding balls to the raw material powder is 2:1;

[0118] (2) cold isostatic pressing at a pressure of 200 MPa to obtain a molded body;

[0119] (3) The first degreasing stage, the second degreasing stage, the third degreasing stage and the fourth degreasing stage are performed in sequence. The first degreasing stage, the second degreasing stage and the third degreasing stage are performed in an argon atmosphere at a pressure of 400 Pa:

[0120] First degreasing stage: over 3 hours, the temperature is evenly raised from room temperature (25°C) to 120°C;

[0121] Second degreasing stage: After 6 hours, the temperature is evenly increased from 120℃ to 360℃;

[0122] The third degreasing stage: 360℃ for 3h;

[0123] Fourth degreasing stage: stop filling with argon and evacuate to a pressure below 30Pa, raise the temperature evenly from 360℃ to 650℃, and keep it warm for 1h;

[0124] (4) Under the condition of a pressure below 30 Pa, vacuum pre-sintering is carried out at a temperature T3 of 1480°C for 2 hours (holding time) to obtain a pre-sintered body with a relative density of 84%.

[0125] In Preparation Example 2, Preparation Example 3, Comparative Preparation Example 1 and Comparative Preparation Example 2 shown in Table 1, except that the parameter conditions of vacuum pre-sintering are different from those of Preparation Example 1, the rest are the same as Preparation Example 1.

[0126] Table 1. Test parameters and test results of each preparation example and comparative preparation example

[0127]

[0128] Preparation Example 4

[0129] This preparation example provides a method for preparing a ceramic-based pre-sintered body. In terms of volume percentage, the raw material powder of the ceramic-based pre-sintered body includes 97.4 vol% SiAlON, 1.3 vol% Y2O3, 0.7 vol% La2O3 and 0.6 vol% CeO2;

[0130] In the preparation method, except that the vacuum pre-sintering temperature T3 is 1700° C., the rest is the same as that of Preparation Example 1.

[0131] The relative density of the calcined body obtained in this preparation example is 86%, and the average grain size is 0.543 μm.

[0132] Preparation Example 5

[0133] This preparation example provides a method for preparing a ceramic-based pre-sintered body. In terms of volume percentage, the raw material powder of the ceramic-based pre-sintered body includes 93.5 vol% TiCN, 4 vol% WC, 2 vol% ZrC, 0.3 vol% Cr3C2 and 0.2 vol% VC;

[0134] In the preparation method, except that the vacuum pre-sintering temperature T3 is 1840° C., the rest is the same as that of Preparation Example 1.

[0135] The relative density of the calcined body obtained in this preparation example is 86%, and the average grain size is 0.513 μm.

[0136] Preparation Example 6

[0137] This preparation example provides a method for preparing a ceramic-based pre-sintered body. In terms of volume percentage, the raw material powder of the ceramic-based pre-sintered body includes 75 vol% TiB2, 20 vol% B4C, 2.5 vol% SiC, 2 vol% Mo2C and 0.5 vol% B;

[0138] In the preparation method, except that the vacuum pre-sintering temperature T3 is 1880° C., the rest is the same as that of Preparation Example 1.

[0139] The relative density of the calcined body obtained in this preparation example is 82%, and the average grain size is 0.525 μm.

[0140] Example 1-1

[0141] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material, the preparation method comprising the following steps:

[0142] (a) Two metal layers are coated on the surface of the ceramic-based pre-sintered body; wherein the material of the innermost metal layer is nickel (melting point T m1 1455℃), thickness 0.3mm; the material of the outermost metal layer is titanium (melting point T m2 1668℃), thickness is 0.2mm;

[0143] The coating method of the innermost metal layer is spray coating; the coating method of the outermost metal layer is metal thin-walled parts sleeve method;

[0144] The ceramic-based pre-sintered body is the ceramic-based pre-sintered body provided in Preparation Example 1;

[0145] (b) At a pressure of 10 -3 Under the condition of less than Pa, vacuum sintering is carried out, the vacuum sintering temperature T1 is 1455℃, and the holding time is 1h;

[0146] (c) Hot isostatic pressing sintering was carried out in an argon atmosphere with a pressure of 170 MPa, a temperature T2 of 1420°C, and a holding time of 1.5 h to obtain a submicron-crystalline ceramic-based composite material.

[0147] The submicron-crystalline ceramic-based composite material obtained in this embodiment is completely sintered and dense, with a relative density of 100%, and an average grain size of 0.834 μm.

[0148] Example 1-2

[0149] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material, which is the same as that of Embodiment 1-1 except that the vacuum sintering temperature T1 is 1475° C. and the holding time is 0.5 h.

[0150] Compared with Example 1-1, the vacuum sintering temperature is increased in this example, but due to the reduction of the holding time, the submicron-crystalline ceramic-based composite material obtained in this example is completely sintered and dense, with a relative density of 100%, and the average grain size is slightly increased to 0.848 μm.

[0151] Examples 1-3

[0152] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material, which is the same as that of Embodiment 1-1 except that the hot isostatic pressing sintering temperature T2 is 1445° C. and the holding time is 1 h.

[0153] Compared with Example 1-1, the hot isostatic pressing sintering temperature is increased in this example, and the obtained submicron-crystalline ceramic-based composite material is completely sintered and dense, with a relative density of 100%, and the average size of the grains is slightly increased to 0.841 μm.

[0154] Examples 1-4

[0155] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material, which is the same as that of Embodiment 1-1 except that the hot isostatic pressing sintering temperature T2 is 1405° C. and the holding time is 3 h.

[0156] Compared with Example 1-1, this example reduces the hot isostatic pressing sintering temperature and increases the holding time. The sintering density of the submicron-crystalline ceramic-based composite material obtained in this example is slightly poor, and the relative density reaches 99.91%, but the average grain size is slightly reduced to 0.822μm.

[0157] Examples 1-5

[0158] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material, which is the same as that of Embodiment 1-1 except that the hot isostatic pressing sintering temperature T2 is 1390°C.

[0159] Compared with Examples 1-4, since the hot isostatic pressing sintering temperature is further reduced in this example, the density of the submicron-crystalline ceramic-based composite material obtained in this example is further reduced, and the relative density reaches 99.82%, and the average grain size is further reduced to 0.816 μm.

[0160] Example 2

[0161] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material. Except that the ceramic-based pre-sintered body is the ceramic-based pre-sintered body provided in Preparation Example 2, the rest is the same as that of Embodiment 1-1.

[0162] Compared with Example 1-1, the relative density of the ceramic-based pre-sintered body in this embodiment is reduced, resulting in a slight diffusion of the molten liquid phase along the pores on the surface of the ceramic-based pre-sintered body during vacuum sintering after the innermost metal layer melts, and the surface quality of the obtained submicron-crystalline ceramic-based composite material is slightly poor. However, due to the reduction in the temperature of vacuum pre-sintering, the average grain size of the ceramic-based pre-sintered body is finer. Under the subsequent vacuum sintering and hot isostatic pressing sintering processes that are the same as those in Example 1-1, the obtained submicron-crystalline ceramic-based composite material is also completely dense, and the relative density reaches 100%. Due to the increase in pores, the distance for the mutual diffusion, migration and growth of the grains during sintering is relatively increased, thereby increasing the energy of grain growth. Therefore, the average grain size of the obtained submicron-crystalline ceramic-based composite material is also finer than that of Example 1-1, reaching 0.797μm.

[0163] Example 3

[0164] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material. Except that the pre-sintered body is the pre-sintered body provided in Preparation Example 3, the rest is the same as that of Embodiment 1-1.

[0165] Compared with Example 1-1, the ceramic-based pre-sintered body provided by Preparation Example 3 in this embodiment is obviously increased by the temperature of vacuum pre-sintering, and the relative density of the ceramic-based pre-sintered body provided by Preparation Example 3 is increased to 92%, and the average size of the grains is also grown to 0.596μm. Under the subsequent vacuum sintering and hot isostatic pressing sintering processes that are the same as those in Example 1-1, the obtained submicron-crystalline ceramic-based composite material is also completely dense, with a relative density of 100%, but the average size of the grains is increased to 0.968μm.

[0166] Example 4

[0167] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material, the preparation method comprising the following steps:

[0168] (a) Two metal layers are coated on the surface of the ceramic-based pre-sintered body; wherein the material of the innermost metal layer is titanium (melting point T m1 1668℃), thickness 0.3mm; the material of the outermost metal layer is molybdenum (melting point T m2 2623℃), thickness is 0.2mm;

[0169] The coating method of the innermost metal layer is spray coating; the coating method of the outermost metal layer is metal thin-walled parts sleeve method;

[0170] The ceramic-based pre-sintered body is the ceramic-based pre-sintered body provided in Preparation Example 4;

[0171] (b) At a pressure of 10 -3Vacuum sintering was carried out under the condition of less than Pa, the vacuum sintering temperature T1 was 1668℃, and the holding time was 0.5h;

[0172] (c) Hot isostatic pressing sintering was carried out in an argon atmosphere with a pressure of 200 MPa, a temperature T2 of 1630°C and a holding time of 1.5 h to obtain a submicron-crystalline ceramic-based composite material.

[0173] The submicron-crystalline ceramic-based composite material obtained in this embodiment is completely sintered and dense, with a relative density of 100%, and an average grain size of 0.849 μm.

[0174] Example 5

[0175] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material, the preparation method comprising the following steps:

[0176] (a) Two metal layers are coated on the surface of the ceramic-based pre-sintered body; wherein the material of the innermost metal layer is zirconium-titanium alloy (melting point T m1 1800℃), thickness 0.3mm; the material of the outermost metal layer is molybdenum (melting point T m2 2623℃), thickness is 0.2mm;

[0177] The coating method of the innermost metal layer is spray coating; the coating method of the outermost metal layer is metal thin-walled parts sleeve method;

[0178] The ceramic-based pre-sintered body is the ceramic-based pre-sintered body provided in Preparation Example 5;

[0179] (b) At a pressure of 10 -3 Vacuum sintering is carried out under the condition of less than Pa, the vacuum sintering temperature T1 is 1800℃, and the holding time is 0.5h;

[0180] (c) Hot isostatic pressing sintering was carried out in an argon atmosphere with a pressure of 170 MPa, a temperature T2 of 1760°C, and a holding time of 1.5 h to obtain a submicron-crystalline ceramic-based composite material.

[0181] The submicron-crystalline ceramic-based composite material obtained in this embodiment is completely sintered and dense, with a relative density of 100%, and an average grain size of 0.783 μm.

[0182] Example 6

[0183] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material, the preparation method comprising the following steps:

[0184] (a) Two metal layers are coated on the surface of the ceramic-based pre-sintered body; wherein the material of the innermost metal layer is zirconium (melting point T m11852℃), thickness 0.3mm; the material of the outermost metal layer is molybdenum (melting point T m2 2623℃), thickness is 0.2mm;

[0185] The ceramic-based pre-sintered body is the ceramic-based pre-sintered body provided in Preparation Example 6;

[0186] (b) At a pressure of 10 -3 Vacuum sintering was carried out under the condition of less than Pa, the vacuum sintering temperature T1 was 1852℃, and the holding time was 0.5h;

[0187] (c) Hot isostatic pressing sintering was carried out in an argon atmosphere with a pressure of 150 MPa, a temperature T2 of 1820°C, and a holding time of 1.5 h to obtain a submicron-crystalline ceramic-based composite material.

[0188] The submicron-crystalline ceramic-based composite material obtained in this embodiment is completely sintered and dense, with a relative density of 100%, and an average grain size of 0.802 μm.

[0189] Example 7

[0190] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material, the preparation method comprising the following steps:

[0191] (a) Two metal layers are coated on the surface of the ceramic-based pre-sintered body; wherein the material of the innermost metal layer is a zirconium-cobalt alloy (melting point T m1 1668℃), thickness 0.1mm; the material of the outermost metal layer is niobium (melting point T m2 2468℃), thickness is 0.1mm;

[0192] The coating method of the innermost metal layer is spray coating; the coating method of the outermost metal layer is metal thin-walled parts sleeve method;

[0193] The ceramic-based pre-sintered body is the ceramic-based pre-sintered body provided in Preparation Example 4;

[0194] (b) At a pressure of 10 -3 Under the condition of less than Pa, vacuum sintering is carried out, the vacuum sintering temperature T1 is 1668℃, and the holding time is 0.5h;

[0195] (c) Hot isostatic pressing sintering was carried out in an argon atmosphere with a pressure of 200 MPa, a temperature T2 of 1630°C and a holding time of 1.5 h to obtain a submicron-crystalline ceramic-based composite material.

[0196] Example 8

[0197] This embodiment provides a method for preparing a submicron-crystalline ceramic-based composite material, the preparation method comprising the following steps:

[0198] (a) Two metal layers are coated on the surface of the ceramic-based pre-sintered body; wherein the material of the innermost metal layer is titanium (melting point T m1 1668℃), thickness 0.5mm; the material of the outermost metal layer is tantalum (melting point T m2 2996℃), thickness is 0.3mm;

[0199] The coating method of the innermost metal layer is spray coating; the coating method of the outermost metal layer is metal thin-walled parts sleeve method;

[0200] The ceramic-based pre-sintered body is the ceramic-based pre-sintered body provided in Preparation Example 4;

[0201] (b) At a pressure of 10 -3 Vacuum sintering was carried out under the condition of less than Pa, the vacuum sintering temperature T1 was 1668℃, and the holding time was 0.5h;

[0202] (c) Hot isostatic pressing sintering was carried out in an argon atmosphere with a pressure of 200 MPa, a temperature T2 of 1630°C, and a holding time of 1.5 h to obtain a submicron-crystalline ceramic-based composite material.

[0203] Comparative Example 1

[0204] This comparative example provides a method for preparing a submicron-crystalline ceramic-based composite material. Except that the ceramic-based pre-sintered body is the ceramic-based pre-sintered body provided in Comparative Preparation Example 1, the rest is the same as Example 1-1.

[0205] In this comparative example, due to the high temperature of vacuum pre-sintering, the relative density of the ceramic-based pre-sintered body reaches 93%, and the average grain size of the ceramic-based pre-sintered body also increases to 0.621 μm. Then, during the subsequent vacuum sintering and hot isostatic pressing, the sintered body is completely sintered and dense, and the relative density of the sintered body reaches 100%, but the grains further grow to 1.272 μm.

[0206] Comparative Example 2

[0207] This comparative example provides a method for preparing a submicron-crystalline ceramic-based composite material. Except that the ceramic-based pre-sintered body is the ceramic-based pre-sintered body provided in Comparative Preparation Example 2, the rest is the same as Example 1-1.

[0208] Since the relative density of the ceramic-based pre-sintered body of this comparative example is relatively low, at 69%, it is all open pores. On the one hand, the strength of the ceramic-based pre-sintered body is relatively low, and it is easy to cause damage to its edges and corners when further operating and processing the ceramic-based pre-sintered body. On the other hand, when vacuum sintering, the molten metal liquid phase diffuses deeper into the interior of the ceramic-based pre-sintered body along the pores, causing the material of the submicron-crystalline ceramic-based composite material to change, and it cannot meet the application requirements of molds, cutting tools or wear-resistant parts.

[0209] Comparative Example 3

[0210] This comparative example provides a method for preparing a submicron-crystalline ceramic-based composite material, which is the same as Example 1-1 except that only a metal nickel layer with a thickness of 0.3 mm is coated on the surface of the ceramic-based pre-sintered body.

[0211] In this comparative example, since only one layer of metal nickel is coated, during vacuum sintering, the molten nickel liquid flows to the lower part of the product under the action of gravity, resulting in the upper part of the product not being well sealed, and the subsequent hot isostatic pressing sintering cannot sinter the product densely.

[0212] Comparative Example 4

[0213] This comparative example provides a method for preparing a submicron-crystalline ceramic-based composite material, which is the same as Example 1-1 except that only a metal titanium layer with a thickness of 0.3 mm is coated on the surface of the ceramic-based pre-sintered body.

[0214] In this comparative example, since only one layer of metal titanium is coated, the temperature during vacuum sintering is lower than the melting point of the titanium layer and it cannot be melted, resulting in the inability to seal the pre-sintered body by melting sealing, resulting in the inability to sinter the product densely.

[0215] Comparative Example 5

[0216] This comparative example provides a method for preparing a submicron-crystalline ceramic-based composite material, which is the same as Example 1-1 except that the vacuum sintering temperature T1 is 1485°C.

[0217] Since the temperature of vacuum sintering is much higher than the melting point of the innermost metal nickel layer, on the one hand, the diffusion capacity of the molten metal nickel liquid phase increases rapidly, resulting in an increase in the depth of its diffusion along the pores into the ceramic-based pre-sintered body, and the surface quality of the obtained submicron-crystalline ceramic-based composite material decreases; on the other hand, the increase in the temperature of vacuum sintering leads to grain growth, and the average grain size of the final submicron-crystalline ceramic-based composite material reaches 1.114μm.

[0218] Comparative Example 6

[0219] This comparative example provides a method for preparing a submicron-crystalline ceramic-based composite material, which is the same as Example 1-1 except that the hot isostatic pressing sintering temperature T2 is 1455°C.

[0220] Compared with Example 1-1, since the temperature of hot isostatic pressing sintering is increased to the melting point of the innermost metal layer, the innermost metal layer does not remain in a solid phase during hot isostatic pressing sintering, but melts. Under the action of pressure, the molten liquid phase rapidly diffuses along the pores of the ceramic-based pre-sintered body into the interior, resulting in an increase in the nickel metal content in the organizational structure of the submicron-crystalline ceramic-based composite material obtained after sintering at a certain depth from the surface. Within this depth range, the performance of the submicron-crystalline ceramic-based composite material is sharply reduced, and cannot meet the application requirements of molds, cutting tools or wear-resistant parts.

[0221] The average grain size and relative density of the submicron-crystalline ceramic-based composite materials obtained in the above examples and comparative examples are shown in Table 2 and Table 3, wherein the average grain size is measured by scanning electron microscopy (SEM), and the relative density is measured by Archimedes drainage method. The relative density of the obtained submicron-crystalline ceramic-based composite material refers to the ratio of the density of the obtained material to its theoretical density.

[0222] Table 2. Experimental parameters of various embodiments and comparative examples

[0223]

[0224]

[0225] Table 3. Test results of various embodiments and comparative examples

[0226]

[0227]

[0228] In summary, the preparation method provided by the present invention achieves sintering and densifying the submicron-crystalline ceramic-based composite material at a relatively low temperature by coating at least two metal layers on the surface of the ceramic-based pre-sintered body, thereby solving the contradiction between higher temperature promoting sintering and densification but causing grain growth and lower temperature inhibiting grain growth but sintering is not dense, and ultimately a submicron-crystalline ceramic-based composite material with an average grain size of submicron level (less than 1 μm) and a relative density higher than 99.8% can be obtained; in addition, vacuum sintering and hot isostatic pressing sintering are not limited by shape and size, and mass production can be achieved; the submicron-crystalline ceramic-based composite material prepared by the present invention has an average grain size of submicron level and a relative density higher than 99.8%.

[0229] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a submicron-crystalline ceramic-based composite material, characterized in that: The preparation method comprises the following steps: Coating at least two metal layers on the surface of the ceramic-based pre-sintered body, and then sequentially performing vacuum sintering and hot isostatic pressing sintering to obtain the submicron-crystalline ceramic-based composite material; The relative density of the ceramic-based pre-sintered body is 80% to 92%, and the average grain size of the ceramic-based pre-sintered body is less than 0.6 μm; The melting point of the outermost metal layer of the at least two metal layers is T m2 Higher than the melting point T of the innermost metal layer m1 and the vacuum sintering temperature T1; The melting point of the innermost metal layer is T m1 0°C to 20°C lower than the vacuum sintering temperature T1; In the at least two metal layers, the melting point of each metal layer is higher than the hot isostatic pressing sintering temperature T2.

2. The preparation method according to claim 1, characterized in that: The melting point of the innermost metal layer is T m1 1430℃ to 1852℃; Preferably, the material of the innermost metal layer includes any one of Ni, Co, Fe, Ti or Zr, or a combination of at least two thereof; Preferably, the material of the outermost metal layer includes any one of Ti, Zr, Mo, Nb or Ta, or a combination of at least two of them.

3. The preparation method according to claim 1 or 2, characterized in that: The thickness of the innermost metal layer is 0.1 mm to 0.5 mm; Preferably, the thickness of the outermost metal layer is 0.1 mm to 0.3 mm.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The vacuum sintering temperature T1 is 1430°C to 1872°C; Preferably, the holding time of the vacuum sintering is 0.5h to 1h; Preferably, the vacuum sintering is carried out at a pressure of 10 -3 Pa is carried out below.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The hot isostatic pressing sintering is carried out in an inert atmosphere; Preferably, the hot isostatic pressing sintering pressure is 150 MPa to 300 MPa; Preferably, the hot isostatic pressing sintering temperature T2 is higher than the melting point T m1 Low 10℃ to 50℃; Preferably, the hot isostatic pressing sintering temperature T2 is 1380° C. to 1842° C.; Preferably, the holding time of the hot isostatic pressing sintering is 1 h to 3 h.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The preparation method of the ceramic-based pre-sintered body comprises powder mixing, molding, degreasing and vacuum pre-sintering in sequence; Preferably, the vacuum pre-sintering temperature T3 is 1400° C. to 1910° C.; Preferably, the holding time of the vacuum pre-sintering is 1h to 3h; Preferably, the vacuum pre-sintering is performed at a pressure below 30 Pa.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The submicron crystalline ceramic-based composite material includes any one of a submicron crystalline oxide ceramic-based composite material, a submicron crystalline nitride ceramic-based composite material, a submicron crystalline boride ceramic-based composite material or a submicron crystalline carbide ceramic-based composite material.

8. The preparation method according to claim 7, characterized in that: The raw materials for preparing the submicron-crystalline oxide ceramic matrix composite material include, in volume percentage, more than 50 vol% of an oxide ceramic matrix, less than 49.5 vol% of an additive, and less than 0.5 vol% of a sintering aid; Preferably, the raw materials for preparing the submicron crystalline nitride ceramic matrix composite material include, by volume percentage: more than 50 vol% of nitride ceramic matrix, less than 49.5 vol% of additives and less than 0.5 vol% of sintering aid; Preferably, the raw materials for preparing the submicron-crystalline boride ceramic-based composite material include, by volume percentage: more than 50 vol% of a boride ceramic matrix, less than 49.5 vol% of an additive, and less than 0.5 vol% of a sintering aid; Preferably, in terms of volume percentage, the raw materials for preparing the submicron-crystalline carbide ceramic-based composite material include: more than 50 vol% of a carbide ceramic matrix, less than 49.5 vol% of an additive, and less than 0.5 vol% of a sintering aid.

9. A submicron-crystalline ceramic-based composite material, characterized in that: The submicron-crystalline ceramic-based composite material is prepared by the preparation method according to any one of claims 1 to 8; The submicron-crystalline ceramic-based composite material has an average grain size of less than 1 μm and a relative density of more than 99.8%.

10. An application of a submicron-crystalline ceramic-based composite material, characterized in that: The submicron-crystalline ceramic-based composite material is used to prepare molds, cutting tools or wear-resistant parts; The submicron-crystalline ceramic-based composite material is prepared by the preparation method described in any one of claims 1 to 8, or is the submicron-crystalline ceramic-based composite material described in claim 9.

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