A method for producing a ceramic preform and a ceramic preform

Abstract

The application discloses a preparation method of a ceramic preform and the ceramic preform, and steps are as follows: at least two of Al2O3 powder, B4C powder and iron-based self-fluxing alloy powder are mixed to obtain uniformly mixed powder; the pretreated ceramic particles are placed on a laser cladding workbench, the mixed powder is synchronously sent into a molten pool, and the ceramic particles are metallized through laser cladding; the ceramic particles after laser cladding treatment are directly added into a mold without cooling, and then are placed into a device with heating and pressurizing functions together, are solidified after heating and pressurizing, are demolded, and the ceramic preform block is obtained; according to actual requirements of a workpiece, one or more ceramic preform blocks are fixedly placed in a casting cavity; then metal liquid is poured, and after cooling, the metal ceramic composite wear-resistant product is obtained after heat treatment and machining. The application realizes metallization of the ceramic particles itself, does not use a binder in the preparation process of the preform, does not additionally add active elements, is environment-friendly, and has a simple process.

Description

Technical Field

[0001] This invention belongs to the field of metal-based ceramic composite materials technology, and in particular relates to a method for preparing ceramic preforms and ceramic preforms. Background Technology

[0002] Metal-matrix ceramic composites, as a novel type of wear-resistant material, combine wear resistance and toughness. On one hand, they rely on the high hardness and stability of the ceramic particles to resist material wear; on the other hand, they rely on the strength and toughness of the metal matrix to protect the ceramic particles from impact. Their excellent comprehensive wear resistance is gradually becoming apparent in applications. Due to the superior wear resistance of metal-matrix ceramic composites and the increasing demand for wear-resistant metal-matrix composite parts, research on metal-matrix ceramic composites has been increasing in recent years.

[0003] In the preparation of metal-based ceramic composites, if ceramic particles that wet well with molten metal, such as WC ceramic particles, are selected, there are problems such as high cost and narrow applicability. If relatively inexpensive ceramic particles with high industrial maturity, such as ZTA ceramic particles, are selected, there are problems such as poor wettability with metal, and it is necessary to improve the wettability between metal and ceramic through surface modification or the addition of active elements to achieve the purpose of good metal-ceramic composite.

[0004] Chinese invention patent CN103641487A discloses a method for preparing and applying a ceramic preform. This method involves mixing a binder with ceramic particles, adding carbide powders such as silicon carbide and boron carbide, and filling the mixture into a mold to form a honeycomb-shaped porous ceramic preform. However, this method only solves the molding problem of the honeycomb-shaped ceramic preform and does not fundamentally achieve the metallization of the ceramic particles, nor can it prepare ceramic preforms with complex spatial structures. Chinese invention patent CN109706438A discloses a method for preparing surface-modified ZTA ceramic particle-reinforced iron-based composite materials. One method involves electroless plating of nickel and chromium onto the surface of ceramic particles to achieve metallization. However, simply plating nickel and chromium cannot fundamentally improve the wetting and bonding strength between ZTA ceramic particles and the metal substrate. Furthermore, electroless plating can only plate a limited variety of metal powders. Chinese invention patent CN103143699A discloses a metal-ceramic preform composite reinforced wear-resistant part and its preparation method. This method only solves the problem of the density of the ceramic preform making it difficult for the preform to collapse during casting, but it has not yet solved the problem of the wettability between ceramic particles and metal.

[0005] In summary, on the one hand, most existing ceramic preform preparation technologies involve mixing ceramic particles and active element powders with binders to form a coating layer on the surface of the ceramic particles that is well wetted by the molten metal, thereby improving the wettability between the metal and the ceramic. However, this method does not fundamentally achieve the metallization of the ceramic particles themselves and suffers from problems such as uneven coating of active elements and ceramic particles. On the other hand, some methods involve electroless plating to deposit low-melting-point alloy powders such as iron-based, nickel-based, or cobalt-based alloys onto the surface of ceramic particles to achieve metallization. However, electroless plating has a limited range of metal powders that can be plated, and it has limited effectiveness in addressing the bonding strength between the metal and the ceramic particles.

[0006] On the other hand, to improve the penetration of molten metal, most current research involves preparing ceramic particles into honeycomb-shaped ceramic preforms. However, honeycomb-shaped ceramic preforms require a high wall thickness; too thick a wall hinders penetration, while too thin a wall makes them prone to breakage during transportation. Furthermore, honeycomb-shaped ceramic preforms have limitations when preparing complex-shaped composite wear-resistant products. Therefore, thoroughly metallizing the ceramic particles themselves, preparing them into ceramic blocks, and then arranging these blocks in a mold cavity as needed to prepare various complex-shaped metal-ceramic composite wear-resistant parts, while simultaneously addressing the wettability issues between the ceramic particles and the metal matrix, and truly achieving a metallurgical bond between the ceramic and the molten metal, is of great significance for the fabrication and development of metal-based ceramic composite wear-resistant products. Summary of the Invention

[0007] To address the problems and shortcomings of the existing technology, this invention provides a method for preparing ceramic preforms and the ceramic preforms themselves. This method involves laser cladding to coat the surface of ceramic particles with a layer of active metal powder. Under high-temperature cladding conditions, the ceramic preforms are directly heated and pressurized to produce a ceramic preform with through holes. Then, the ceramic preforms are arranged in a mold cavity according to the shape of the casting, and molten metal is poured in to produce the desired metal-ceramic composite wear-resistant product. This preparation method achieves the metallization of the ceramic particles themselves. The prepared ceramic composite preforms do not require the use of binders, avoiding insufficient strength of the preform or defects in the composite process caused by improper use of binders. The manufacturing process is also more environmentally friendly. Furthermore, the preparation process of this ceramic preform does not require the addition of additional active elements, making the preform preparation process simpler.

[0008] This invention is achieved through a method for preparing ceramic preforms, with the following specific steps:

[0009] Step 1: Metallization of ceramic particles

[0010] Step 11: Pre-treat the ceramic particles;

[0011] Step 12: At least two of the Al2O3 powder, B4C powder and iron-based self-fluxing alloy powder are put into a ball mill and mixed to obtain a uniform mixed powder.

[0012] Step 13: Place the pretreated ceramic particles on the laser cladding stage, and simultaneously feed the mixed powder into the molten pool to achieve metallization of the ceramic particles through laser cladding.

[0013] Step 2: Fabrication of ceramic precast components

[0014] Step 21: The ceramic particles after laser cladding are added directly into the pre-made ceramic precast block mold without cooling.

[0015] Step 22: Place the laser-clad ceramic particles together with the ceramic precast block mold into a device with heating and pressurizing functions for heating and pressurizing curing.

[0016] Step 23: After curing, demold to obtain a ceramic precast block of a specific shape;

[0017] Step 3: Preparation of metal-based ceramic composite materials

[0018] Step 31: According to the actual requirements of the workpiece, fix one or more ceramic precast blocks in the casting cavity;

[0019] Step 32: Pour the molten metal into the casting cavity. After solidification and cooling, remove the composite material and then perform heat treatment and machining to obtain the desired metal-ceramic composite wear-resistant product.

[0020] Preferably, in step 11, the ceramic particles are one or a mixture of several of zirconium corundum, alumina, silicon nitride, titanium nitride, silicon carbide, boron carbide, titanium carbide, titanium boride, and tungsten carbide in any proportion; the particle size of the ceramic particles is 2 to 4.5 mm.

[0021] Preferably, in step 11, the pretreatment of the ceramic particles refers to placing the ceramic particles in a ball mill and ball milling them at a speed of 50-120 rpm, then ultrasonically cleaning them with acetone, and finally drying them for later use.

[0022] Preferably, in step 12, the particle size of the Al2O3 powder and B4C powder is 500-600 mesh, the particle size of the iron-based self-fluxing alloy powder Fe30 is 800-1000 mesh, and the Fe30 contains 0.7-0.8% C, 12-14% Cr, 28-30% Ni, and the balance Fe by weight percentage; the ball mill speed is 30-80 rpm, and the mixing time is 15-30 min.

[0023] Preferably, in step 13, the total amount of the mixed powder is 2 to 10% of the weight of the ceramic particles, wherein the weight of a single component of Al2O3 powder or B4C powder, or the mixture of both, does not exceed 3% of the weight of the ceramic particles.

[0024] The laser used for laser cladding is a CO2 laser, with a laser cladding power of 300–1000W, a spot diameter of 2–5 mm, and a scanning rate of 5–8 mm / s. Argon gas is used for protection during laser cladding.

[0025] Preferably, in step 21, the ceramic preform mold is a three-dimensional shape with a through hole, which can be a cube, cuboid, cylinder, regular hexagonal prism, etc.

[0026] Preferably, in step 22, when the device with heating and pressurizing function heats and pressurizes, it first raises the temperature at a rate of 0.5 to 2°C / min, raises the temperature to 1000 to 1150°C, holds the temperature for 0.5 to 1 hour, then applies a pressure of 30 to 50 kg, holds the pressure for 0.5 to 2 hours, and then releases the pressure.

[0027] Preferably, in step 23, the size of a single ceramic preform is 50-100mm, and the ceramic preform has through holes on each face, with the holes being circular, hexagonal, or other geometric shapes.

[0028] Preferably, in step 31, one or more ceramic preforms are fixedly placed in the casting cavity, with a gap of 6 to 12 mm between each ceramic preform, and are fixed through the through holes between the ceramic preforms.

[0029] Preferably, in step 32, the molten metal is high-chromium cast iron or high-alloy steel, the pouring temperature is controlled at 1500-1580℃, and the pouring speed is 6-12 kg / s.

[0030] The advantages and positive effects of this invention are:

[0031] 1. This invention uses laser cladding to clad a layer of mixed powder onto the surface of ceramic particles, thereby achieving the metallization of the ceramic particles, ensuring the wettability between the molten metal and the ceramic, and effectively realizing the metallurgical bonding between the ceramic particles and the high-temperature molten metal, resulting in a higher bonding strength.

[0032] 2. This invention prepares ceramic particles into a ceramic preform structure by heating and pressurizing, rather than a honeycomb ceramic preform structure. The preform can be in various shapes such as cube, cuboid, and regular hexagonal prism. When making metal-ceramic composite wear-resistant products, the ceramic preform can be arranged in the cavity according to the shape of the product, and complex-shaped metal-ceramic wear-resistant parts can be made.

[0033] 3. The ceramic preform prepared by the present invention has a through-hole structure, which on the one hand facilitates the fixing of the ceramic preform in the cavity and avoids the ceramic preform drifting during the pouring of molten metal. On the other hand, it can serve as an impregnation channel during the pouring of molten metal, which is more conducive to the impregnation of molten metal.

[0034] 4. In the process of preparing ceramic preforms, this invention does not require the use of any binders or the addition of any additional active elements, making the manufacturing process simpler and easier to operate. It avoids the collapse or reduction in strength of ceramic preforms caused by improper use of binders, and is also more environmentally friendly. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the process of laser cladding of ceramic particles with powder according to the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of the cuboid ceramic preform prepared in Embodiment 1 of the present invention;

[0037] Figure 3 This is a simplified diagram of the arrangement structure of the cuboid ceramic preform prepared in Embodiment 1 of the present invention within the cavity;

[0038] Figure 4 This is a schematic diagram of the structure of the cylindrical ceramic preform prepared in Embodiment 2 of the present invention;

[0039] Figure 5 This is a schematic diagram of the structure of the regular hexagonal prism-shaped ceramic preform prepared in Embodiment 3 of the present invention.

[0040] Among them, 11. Laser cladding stage; 12. Ceramic particles; 13. Coaxial powder transfer device; 14. Laser beam. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, and to further understand the invention's content, features, and effects, the following specific embodiments are provided to further illustrate the invention in detail. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0042] Example 1

[0043] This embodiment 1 provides a method for preparing a ceramic preform, the specific steps of which are as follows:

[0044] Step 1: Metallization of ceramic particles

[0045] Step 11: Place zirconia corundum ceramic particles with a particle size of 2-3 mm into a ball mill for ball milling. The ball mill speed is 50 rpm and the ball milling time is 1 hour. Then, ultrasonically clean with acetone and dry for later use.

[0046] Step 12: 600-mesh Al2O3 powder and 900-mesh Fe30 iron-based self-fluxing alloy powder are put into a ball mill for mixing. The weight ratio of Al2O3 powder to Fe30 powder is 2:3. The ball mill speed is 30 rpm and the ball milling time is 20 min to obtain a uniform mixed powder.

[0047] Step 13: Place the pretreated ceramic particles from Step 11 onto the laser cladding stage of the CO2 laser, and simultaneously feed the mixed powder from Step 12 into the molten pool. The weight of the mixed powder is 5% of the weight of the ceramic particles. Metallization of the ceramic particles is achieved through laser cladding. The laser power is 500W, the spot diameter is 3mm, and the scanning rate is 8mm / s.

[0048] Step 2: Fabrication of ceramic precast components

[0049] Step 21: The ceramic particles that have been laser-clad and metallized in step 13 are placed directly into a cuboid mold without cooling. The mold has a six-sided structure with circular holes.

[0050] Step 22: Place the ceramic particles from step 21, along with the mold, into the heating and pressurizing device. Heat the heating and pressurizing device at a rate of 1℃ / min until it reaches 1100℃. Hold the temperature for 0.5h. Then apply a pressure of 50kg and hold the pressure for 1h before releasing the pressure and cooling.

[0051] Step 23: After the ceramic preform from step 22 has cooled and been demolded, the product is obtained as shown in the figure. Figure 2 The rectangular ceramic precast block shown has dimensions of 100mm*60mm*50mm.

[0052] Step 3: Preparation of metal-based ceramic composite materials

[0053] Step 31: According to the actual requirements of the workpiece, place one or more rectangular ceramic preforms with through holes into the casting cavity, such as... Figure 3 As shown, use clips to fix the ceramic precast blocks through the through holes to ensure that the gap between the ceramic precast blocks is 10mm;

[0054] Step 32: Pour the molten high-chromium cast iron into the mold cavity at a pouring temperature of 1550℃. After solidification and cooling, remove the composite material and then perform heat treatment and machining to obtain the desired metal-ceramic composite wear-resistant product.

[0055] Example 2

[0056] This embodiment 2 provides a method for preparing a ceramic preform, the specific steps of which are as follows:

[0057] Step 1: Metallization of ceramic particles

[0058] Step 11: Place zirconium corundum ceramic particles and silicon nitride ceramic particles with a particle size of 3-4 mm into a ball mill for ball milling. The ball mill speed is 80 rpm and the ball milling time is 1.5 hours. Then, ultrasonically clean with acetone and dry for later use.

[0059] Step 12: Mix 500-mesh B4C powder and 800-mesh Fe30 iron-based self-fluxing alloy powder in a ball mill. The weight ratio of B4C powder to Fe30 powder is 2:5. The ball mill speed is 60 rpm and the ball milling time is 15 min to obtain a uniform mixed powder.

[0060] Step 13: Place the pre-treated ceramic particles from Step 11 onto the laser cladding stage of the CO2 laser, and simultaneously feed the mixed powder from Step 12 into the molten pool. The weight of the mixed powder is 7% of the weight of the ceramic particles. Metallization of the ceramic particles is achieved through laser cladding. The laser power is 750W, the spot diameter is 4mm, and the scanning rate is 6mm / s.

[0061] Step 2: Fabrication of ceramic precast components

[0062] Step 21: The ceramic particles that have been laser clad and metallized in step 13 are placed directly into a cylindrical mold without cooling. The mold has a circular through hole with a diameter of 12mm.

[0063] Step 22: Place the ceramic particles from step 21, along with the mold, into the heating and pressurizing device. Heat the heating and pressurizing device at a rate of 1.5℃ / min until it reaches 1050℃. Hold the temperature for 1 hour. Then apply a pressure of 40kg and hold the pressure for 1.5 hours before releasing the pressure and cooling.

[0064] Step 23: After the ceramic preform from step 22 has cooled and been demolded, the product is obtained as shown in the figure. Figure 4 The cylindrical ceramic precast block shown has a base diameter of 50mm and a height of 80mm.

[0065] Step 3: Preparation of metal-based ceramic composite materials

[0066] Step 31: According to the actual requirements of the workpiece, place one or more cylindrical ceramic preforms with through holes in the casting cavity, and fix the ceramic preforms with clips through the through holes to ensure that the gap between the ceramic preforms is 6mm.

[0067] Step 32: Pour the molten high-chromium cast iron into the mold cavity at a pouring temperature of 1520℃. After solidification and cooling, remove the composite material and then perform heat treatment and machining to obtain the desired metal-ceramic composite wear-resistant product.

[0068] Example 3

[0069] This embodiment 3 provides a method for preparing a ceramic preform, the specific steps of which are as follows:

[0070] Step 1: Metallization of ceramic particles

[0071] Step 11: Place zirconium corundum, silicon nitride and titanium carbide ceramic particles with a particle size of 3.5-4.5 mm into a ball mill for ball milling. The ball mill speed is 100 rpm and the ball milling time is 1.5 hours. Then, ultrasonically clean with acetone and dry for later use.

[0072] Step 12: 600-mesh Al2O3 powder, 600-mesh B4C powder and 1000-mesh Fe30 iron-based self-fluxing alloy powder are put into a ball mill for mixing. The weight ratio of Al2O3 powder, B4C powder and Fe30 powder is 1:1:6. The ball mill speed is 80 rpm and the ball milling time is 30 min to obtain a uniform mixed powder.

[0073] Step 13: Place the pretreated ceramic particles from Step 11 onto the laser cladding stage of the CO2 laser, and simultaneously feed the mixed powder from Step 12 into the molten pool. The weight of the mixed powder is 8% of the weight of the ceramic particles. Metallization of the ceramic particles is achieved through laser cladding. The laser power is 1000W, the spot diameter is 5mm, and the scanning rate is 7mm / s.

[0074] Step 2: Fabrication of ceramic precast components

[0075] Step 21: The ceramic particles that have been laser clad and metallized in step 13 are placed directly into a regular hexagonal prism mold without cooling. The mold has a structure with through holes on each opposite face, and the hole size is about 8mm.

[0076] Step 22: Place the ceramic particles from step 21, along with the mold, into the heating and pressurizing device. Heat the heating and pressurizing device at a rate of 2℃ / min until it reaches 1000℃. Hold the temperature for 1 hour. Then apply a pressure of 30kg and hold the pressure for 2 hours before releasing the pressure and cooling.

[0077] Step 23: After the ceramic preform from step 22 has cooled and been demolded, the product is obtained as shown in the figure. Figure 5 The ceramic precast block shown is in the shape of a regular hexagonal prism. The dimensions of the ceramic precast block are: the hexagonal sides of the top and bottom faces are 50mm long, and the height of the hexagonal prism is 100mm.

[0078] Step 3: Preparation of metal-based ceramic composite materials

[0079] Step 31: According to the actual requirements of the workpiece, place one or more regular hexagonal prism-shaped ceramic preforms with through holes into the casting cavity, and fix the ceramic preforms with clips through the through holes to ensure that the gap between the ceramic preforms is 8mm.

[0080] Step 32: Pour the molten high-chromium cast iron into the mold cavity at a pouring temperature of 1500℃. After solidification and cooling, remove the composite material and then perform heat treatment and machining to obtain the desired metal-ceramic composite wear-resistant product.

[0081] Volumetric wear tests were conducted on the metal-ceramic composite material preparation of Example 1, the honeycomb metal-ceramic composite material preparation of the existing patent technology (CN103641487A), and the wear-resistant white cast iron KmTBCr26 (GB / T8263-1999) preparation. The results are shown in Table 1 below.

[0082] Table 1 Results of Volumetric Wear Measurement

[0083]

[0084] As can be seen from the results in Table 1, under the same wear conditions, the volumetric wear of Example 1 of the present invention is 5.86 mm. 3 The wear percentage was 4.80%; the volumetric wear of the existing patented technology (CN103641487A) was 15.62 mm. 3 The wear percentage was 13.21%; the former's wear performance was significantly better than the latter.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a ceramic preform, characterized in that, The specific steps are as follows: Step 1: Metallization of ceramic particles Step 11: Pre-treat the ceramic particles; the particle size of the ceramic particles is 2~4.5mm; Step 12: At least two of the Al2O3 powder, B4C powder and iron-based self-fluxing alloy powder are put into a ball mill and mixed to obtain a uniform mixed powder. Step 13: Place the pretreated ceramic particles on the laser cladding stage, and simultaneously feed the mixed powder into the molten pool to achieve metallization of the ceramic particles through laser cladding; the spot diameter is 2~5mm. Step 2: Fabrication of ceramic precast components Step 21: The ceramic particles after laser cladding are added directly into the pre-made ceramic precast block mold without cooling, without adding any binder or additional active element powder. Step 22: Place the laser-clad ceramic particles together with the ceramic precast block mold into a device with heating and pressurizing functions for heating and pressurizing curing. Step 23: After curing, demold to obtain a ceramic precast block of a specific shape; Step 3: Preparation of metal-based ceramic composite materials Step 31: According to the actual requirements of the workpiece, fix one or more ceramic precast blocks in the casting cavity; Step 32: Pour the molten metal into the casting cavity. After solidification and cooling, remove the composite material and then perform heat treatment and machining to obtain the desired metal-ceramic composite wear-resistant product.

2. The method for preparing ceramic preforms according to claim 1, characterized in that, In step 11, the ceramic particles are one or a mixture of several of the following in any proportion: zirconium corundum, alumina, silicon nitride, titanium nitride, silicon carbide, boron carbide, titanium carbide, titanium boride, and tungsten carbide. The pretreatment of the ceramic particles refers to placing the ceramic particles in a ball mill and milling them at a speed of 50-120 rpm, then ultrasonically cleaning them with acetone, and finally drying them for later use.

3. The method for preparing ceramic preforms according to claim 1, characterized in that, In step 12, the particle size of the Al2O3 powder and B4C powder is 500-600 mesh, the particle size of the iron-based self-fluxing alloy powder Fe30 is 800-1000 mesh, and the Fe30 contains 0.7-0.8% C, 12-14% Cr, 28-30% Ni, and the balance Fe by weight percentage; the ball mill speed is 30-80 rpm, and the mixing time is 15-30 min.

4. The method for preparing ceramic preforms according to claim 1, characterized in that, In step 13, the total amount of the mixed powder is 2-10% of the weight of the ceramic particles, wherein the weight of any single component of Al2O3 powder or B4C powder, or the mixture of both, does not exceed 3% of the weight of the ceramic particles; The laser used for laser cladding is a CO2 laser, with a laser cladding power of 300~1000W and a scanning rate of 5~8mm / s. Argon gas is used for protection during laser cladding.

5. The method for preparing ceramic preforms according to claim 1, characterized in that, In step 21, the ceramic preform mold is a three-dimensional shape with a through hole.

6. The method for preparing ceramic preforms according to claim 1, characterized in that, In step 22, when the device with heating and pressurizing function heats and pressurizes, it first raises the temperature at a rate of 0.5~2℃ / min, raises the temperature to 1000~1150℃, holds the temperature for 0.5~1h, then applies a pressure of 30~50kg, holds the pressure for 0.5~2h, and then releases the pressure.

7. The method for preparing ceramic preforms according to claim 1, characterized in that, In step 23, the size of a single ceramic preform is 50~100mm, and each ceramic preform has a through hole on each side. The shape of the hole is circular, regular hexagonal or other geometric shape.

8. The method for preparing ceramic preforms according to claim 1, characterized in that, In step 31, one or more ceramic preforms are fixedly placed in the casting cavity, with a gap of 6-12mm between each ceramic preform, and are fixed through the through holes between the ceramic preforms.

9. The method for preparing ceramic preforms according to claim 1, characterized in that, In step 32, the molten metal is high-chromium cast iron or high-alloy steel, the pouring temperature is controlled at 1500~1580℃, and the pouring speed is 6~12kg / s.

10. A ceramic preform, characterized in that, The ceramic preform is prepared by the preparation method described in any one of claims 1 to 9.

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