A process for the preparation of a metal-diamond composite by pressure infiltration

Abstract

This invention provides a pressure infiltration process for preparing metal-diamond composite materials, belonging to the technical field of metal-diamond composite materials. The process includes steps such as preparing wax molds, preparing plaster molds, raw material assembly, preparing the metal-diamond composite material, and post-processing of the metal-diamond composite material. This invention utilizes plaster molds instead of graphite molds and graphite crucibles instead of quartz crucibles, which not only simplifies the preparation process and improves production efficiency but also significantly reduces material production costs and enables the production of complex-shaped components. Furthermore, the metal-diamond composite material of this invention has a dense structure and uniform thickness, enabling mass production of components through wax mold arrays or wax tree assembly, demonstrating good application prospects and certain economic advantages.

Description

Technical Field

[0001] This invention relates to the field of metal-diamond composite materials technology, and more particularly to a pressure impregnation preparation process for metal-diamond composite materials. Background Technology

[0002] Metal-diamond composites are a new generation of high-performance thermally conductive composite materials formed by using dispersed diamond particles as the thermally conductive matrix and metal as a binder. As high-performance thermally conductive materials, thermal conductivity and coefficient of thermal expansion are two key indicators for evaluating metal-diamond composites. In recent years, this type of thermally conductive material has entered the industrialization stage due to the increasingly demanding heat dissipation requirements of electronic devices, and substantial progress has been made in improving thermal conductivity and controlling the coefficient of thermal expansion.

[0003] Common manufacturing processes for metal-diamond composites include pressure infiltration and powder sintering. Pressure infiltration produces metal-diamond composites with advantages such as dense structure, high diamond volume fraction, good thermal conductivity, and an adjustable coefficient of thermal expansion based on the diamond volume fraction. However, it also suffers from high mold costs, difficulty in demolding, and easy crucible wear, which reduces production efficiency and increases production costs.

[0004] Furthermore, in the pressure infiltration method, a combination of graphite molds and quartz crucibles is generally used to form diamond composite materials. However, metal-diamond composite materials produced by graphite molds are prone to carbon-carbon bonding between diamond powder and graphite molds during high-temperature preparation, making it difficult to demold the finished product. The molds need to be thoroughly and destructively ground, and the grinding process is time-consuming and labor-intensive. Both graphite molds and quartz crucibles are disposable consumables, which further increases the process cost of metal-diamond composite materials. Summary of the Invention

[0005] To overcome the above problems, this invention proposes a low-cost, high-efficiency, simple process for preparing metal-diamond composite materials by pressure impregnation, which can produce irregularly shaped parts.

[0006] The pressure impregnation preparation process of the metal-diamond composite material of the present invention includes the following steps:

[0007] S1. Preparing the wax model:

[0008] A wax model is prepared according to the shape of the metal-diamond composite material, and a riser is set on the wax model;

[0009] S2. Preparation of plaster mold:

[0010] After the gypsum powder for casting is mixed evenly with water, a gypsum fluid is obtained. After the gypsum fluid is defoamed, it is poured into a wax mold container to cover the wax mold. The riser of the wax mold is exposed on the surface of the gypsum. After the gypsum has solidified, the wax is removed, and then it is fired and cooled in the furnace to obtain a hollow gypsum mold. During the preparation of the gypsum mold, the preparation process and its parameters are strictly controlled to ensure that the outer wall of the gypsum mold fits tightly against the inner wall of the crucible and that the gypsum mold has good mechanical properties.

[0011] S3, Raw Material Assembly:

[0012] Diamond powder is filled into the cavity inside the plaster mold through the riser and compacted by vibration to ensure the density of the powder filling. The plaster mold is then placed into a graphite crucible with the riser facing upwards. Then, metal or alloy material is placed into the crucible and positioned above the riser of the plaster mold to obtain the assembly. The gap between the outer wall of the plaster mold and the inner wall of the graphite crucible should be as small as possible to ensure good air permeability during vacuuming and to prevent the mold from floating after the metal or alloy material melts.

[0013] S4. Preparation of metal-diamond composite materials:

[0014] The assembly is placed in a pressure infiltration furnace. After the furnace is sealed, a vacuum is drawn to ensure that the air between the diamond powder particles in the plaster mold is fully removed. Then, the metal or alloy material is heated until it melts. At the same time, the plaster and the diamond powder inside are also heated, so that the molten metal or alloy material is evenly spread on the surface of the plaster mold and seals the gap between the plaster mold and the crucible. After the metal or alloy material is fully melted and evenly spread, inert high-pressure gas is introduced to force the liquid metal or alloy material into the gap between the diamond particles along the riser of the plaster mold to achieve material composite. After the furnace is kept warm, the heating is stopped to allow the metal or alloy material to solidify and cool with the furnace.

[0015] S5. Post-processing of metal-diamond composite materials:

[0016] After cooling, the composite material is removed and the plaster mold is removed. After the riser is cut off, a metal-diamond composite material is obtained. The removed plaster mold is recycled, dried, crushed and other processes, and can be reused as a mold.

[0017] Furthermore, in S1, the wax model is prepared by wax injection molding, 3D printing molding, or wax block carving, and during the wax model making process, the shrinkage caused by casting is considered and appropriate compensation and verification are performed.

[0018] Furthermore, the weight ratio of gypsum powder to water in S2 is 100:30.

[0019] Furthermore, in S2, the dewaxing temperature is 150℃ and the holding time is 60-180 minutes, with the specific holding time depending on the size of the wax mold.

[0020] Furthermore, in S2, the calcination temperature is 750℃-900℃, and the calcination time is 2-4 hours. The specific calcination time and temperature can be determined by the gypsum brand.

[0021] Furthermore, in S2, the calcination adopts a stepped heating process, specifically: after dewaxing, the temperature is raised to 400℃ and held for 1.5h, then raised to 780℃ and held for 1.5h, then raised to 900℃ and held for 1h, and then naturally cooled to room temperature, with each stage of heating time ≤30min.

[0022] Furthermore, in S3, the metal is a metal block or metal powder, and the alloy material is an alloy block or alloy powder.

[0023] Furthermore, in step S3, the volume ratio of diamond powder to metal or alloy material during loading is 100:40, and the particle size of the diamond is 60-70 mesh. The thermal conductivity and coefficient of thermal expansion of the composite material can be controlled by controlling the diamond particle size.

[0024] Furthermore, in step S3, a draft angle of 1° to 2° is reserved between the plaster mold and the graphite crucible to facilitate mold removal.

[0025] Furthermore, in step S4, the heating temperature is 150-200°C higher than the melting point of the metal or alloy, and the holding time is 5-10 minutes.

[0026] Furthermore, S5 also includes a polishing or plating process.

[0027] This invention produces a standard plaster mold for metal-diamond composite materials by plaster casting followed by high-temperature dewaxing and plaster calcination, achieving a perfect replacement for traditional graphite molds. Simultaneously, the use of a reusable graphite crucible as a pressure impregnation container, in conjunction with the plaster mold, solves the cost problem associated with disposable quartz crucibles. Furthermore, because plaster molds have good air permeability, and the pressure impregnation process requires ensuring airtightness in areas other than the mold riser, a tight fit between the plaster mold and the crucible is necessary. This ensures that the molten metal or alloy material is effectively spread on the upper surface of the mold to guarantee the vacuum seal of the diamond powder inside the mold. This ensures a pressure difference between the gaps between the diamond powder and the subsequently introduced inert gas, allowing the molten metal or alloy material to effectively impregnate into the diamond gaps.

[0028] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0029] (1) The present invention can realize the preparation of thin metal-diamond composite materials and can meet the requirements of efficient and precise preparation of complex irregular components such as tube shell and heat dissipation array, avoiding the pain point problem of diamond composite materials in subsequent cutting and grinding.

[0030] (2) The metal-diamond composite material prepared by the present invention has a dense structure and uniform thickness, and can achieve mass production of components by arranging wax mold arrays or wax trees, and realize the integrated molding of components such as tube shells for electronic packaging.

[0031] (3) The present invention replaces the traditional graphite mold and quartz crucible with gypsum mold and graphite crucible, which can realize the reuse of mold and crucible. This not only simplifies the preparation process and improves production efficiency, but also significantly reduces the production cost of materials. It has good application prospects and great economic advantages. Attached Figure Description

[0032] The present invention will be further described below with reference to the accompanying drawings.

[0033] Figure 1 This is a flow chart of the pressure impregnation process for preparing the metal-diamond composite material of the present invention.

[0034] Figure 2 The wax model (left) and the silver-diamond composite material irregular part (right) are from specific embodiment 1. Detailed Implementation

[0035] The technical solution provided by the present invention will be further described below with reference to the embodiments.

[0036] Example 1

[0037] A pressure impregnation process for preparing silver-diamond composite materials, comprising the following steps:

[0038] S1. Preparation of wax model: Based on the shape of the silver-diamond composite material, a wax model is prepared using 3D printing technology, and risers are set on the wax model;

[0039] S2. Preparation of plaster mold: Plaster powder for casting is mixed with water at a weight ratio of 100:30 to obtain plaster fluid. After removing bubbles, the plaster fluid is poured into a wax mold container to cover the wax mold, with the wax mold riser exposed above the plaster surface. After the plaster has solidified, it is dewaxed at 150℃ for 60 minutes. After dewaxing, a stepped heating process is used for calcination and furnace cooling to obtain a hollow plaster mold. During the preparation of the plaster mold, the preparation process and its parameters are strictly controlled to ensure that the outer wall of the plaster mold fits tightly against the inner wall of the crucible and that the plaster mold has good mechanical properties. The stepped heating process for calcination is as follows: after dewaxing, the temperature is increased to 400℃ at 10℃ / min and held for 1.5 hours; then increased to 780℃ at 19℃ / min and held for 1.5 hours; then increased to 900℃ at 6℃ / min and held for 1 hour; and then naturally cooled to room temperature.

[0040] S3. Raw material assembly: Fill 100g of diamond powder into the cavity inside the plaster mold through the riser and vibrate to ensure the compactness of the powder filling. Place the plaster mold into the graphite crucible with the riser facing upwards. Then, place 120g of pure silver ingot into the crucible and position it above the riser of the plaster mold to obtain the assembly. The gap between the outer wall of the mold and the inner wall of the graphite crucible should be as small as possible to ensure good air permeability during vacuuming and to prevent the mold from floating after the metal material melts. Leave a 2° draft angle between the plaster mold and the graphite crucible for easy mold removal.

[0041] Preparation of S4 silver-diamond composite materials:

[0042] The assembly is placed in a pressure infiltration furnace. After the furnace is sealed, a vacuum is drawn to ensure that the air between the diamond powder particles in the plaster mold is fully removed. Then, it is heated to 1100°C until the pure silver melts. At the same time, the plaster and the diamond powder inside are also heated, so that the molten pure silver is evenly spread on the surface of the plaster mold and seals the gap between the plaster mold and the crucible. After the pure silver is fully melted and evenly spread, inert high-pressure gas is introduced to force the liquid silver metal through the riser of the plaster mold into the gap between the diamond particles to achieve material composite. The furnace is kept at a certain temperature for 8 minutes and then heating is stopped to allow the silver to solidify and cool with the furnace.

[0043] Post-processing of S5, silver-diamond composite materials:

[0044] After cooling, the composite material is removed and the plaster mold is taken out. After the riser is cut off, it is polished to obtain the silver-diamond composite material.

[0045] Example 2

[0046] Same as Example 1, except that:

[0047] The alloy used in S3 is a copper-zirconium alloy, in which the weight ratio of zirconium is 1.5%. 100g of diamond powder is filled into the cavity inside the plaster mold through the riser and compacted to ensure the density of the powder filling. The plaster mold is placed in the graphite crucible with the riser facing upward. Then, 102g of copper-zirconium alloy block is placed in the crucible and positioned above the riser of the plaster mold to obtain the assembly. The gap between the outer wall of the mold and the inner wall of the graphite crucible should be as small as possible to ensure good air permeability during vacuuming and to prevent the mold from floating after the metal material melts. A 2° draft angle is reserved between the plaster mold and the graphite crucible for easy mold removal.

[0048] The heating and melting temperature of S4 is 1150℃, the holding time after composite is 15min, and then it is cooled with the furnace.

[0049] Finally, a copper-zirconium alloy-diamond composite material was prepared.

[0050] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A pressure infiltration process for preparing a metal-diamond composite material, characterized in that, Includes the following steps: S1. Preparation of wax model: Prepare a wax model according to the shape of the metal-diamond composite material and set risers on the wax model; S2. Preparation of plaster mold: After uniformly mixing the casting plaster powder with water, the plaster fluid is obtained. After removing the bubbles from the plaster fluid, it is poured into a wax mold container to cover the wax mold. The wax mold riser position is exposed on the plaster surface. After the plaster solidifies, it is dewaxed. After dewaxing, it is fired and cooled with the furnace to obtain a hollow plaster mold. S3. Raw material assembly: Fill the gypsum mold cavity with diamond powder through the riser and compact it. Place the gypsum mold into a reusable graphite crucible with the riser facing upwards. Then place the metal material into the crucible and position it above the riser of the gypsum mold to obtain the assembly. The gap between the outer wall of the gypsum mold and the inner wall of the graphite crucible should be as small as possible. The volume ratio of diamond powder to metal material during loading is 100:

40. The particle size of the diamond is 60-70 mesh. S4. Preparation of metal-diamond composite material: The assembly is placed in a pressure infiltration furnace. After the furnace is sealed, a vacuum is drawn, and then the metal material is heated until it melts. At the same time, the gypsum and the internal diamond powder are heated so that the molten metal material is evenly spread on the surface of the gypsum mold and the gap between the gypsum mold and the crucible is sealed. After the metal material is fully melted and evenly spread on the gypsum mold, inert high-pressure gas is introduced to press the liquid metal material into the gap between the diamond particles along the riser of the gypsum mold to achieve material composite. After the furnace is kept warm, the heating is stopped to allow the metal material to solidify and cool with the furnace. S5. Post-processing of metal-diamond composite materials: After cooling, the composite material is removed and the plaster mold is removed. After cutting off the riser, the metal-diamond composite material is obtained.

2. The pressure infiltration process for preparing a metal-diamond composite material according to claim 1, characterized in that, In S1, the wax model is prepared by wax injection molding, 3D printing molding, or wax block carving. During the wax model making process, the shrinkage caused by casting is considered and appropriate compensation and verification are performed.

3. The pressure infiltration process for preparing a metal-diamond composite material according to claim 1, characterized in that, In S2, the weight ratio of gypsum powder to water is 100:

30.

4. The pressure infiltration process for preparing a metal-diamond composite material according to claim 1, characterized in that, In step S2, the dewaxing temperature is 150℃ and the holding time is 60-180 min.

5. The pressure infiltration process for preparing a metal-diamond composite material according to claim 1, characterized in that, In S2, the calcination temperature is 750℃-900℃, and the calcination time is 2-4 h.

6. The pressure infiltration process for preparing a metal-diamond composite material according to claim 1, characterized in that, In S2, the calcination adopts a stepped heating process, specifically: after dewaxing, the temperature is raised to 400℃ and held for 1.5 h, then raised to 780℃ and held for 1.5 h, then raised to 900℃ and held for 1 h, and then naturally cooled to room temperature. The heating time for each stage is ≤30 min.

7. The pressure infiltration process for preparing a metal-diamond composite material according to claim 1, characterized in that, In step S3, a draft angle of 1° to 2° is reserved between the plaster mold and the graphite crucible to facilitate mold removal.

8. The pressure infiltration process for preparing a metal-diamond composite material according to claim 1, characterized in that, In step S4, the heating temperature is 150-200°C higher than the melting point of the metal material, and the holding time is 5-10 minutes.

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